**3. Results and discussion**

In recent years [28, 29], PUFs immobilizing some ion pairing reagents have received considerable attention for selective separation, determination and / or chemical speciation of trace and ultra trace metal ions. The non-selective sorption characteristic of the PUFs has been rendered and became more selective by controlling the experimental conditions e.g. pH, ionic strength, etc. Preliminary investigation has shown that, on shaking unloaded PUFs and PQ+.Cl immobilized PUFs with aqueous solutions containing bismuth (III) ions , KI (10%w/v) and H2SO4 (0.5 mol L-1), considerable amount of bismuth (III) species were retained onto PQ+.Cl treated PUFs in a very short time compared to the untreated PUFs ones. Thus, in subsequent work, detailed study on the application of PQ+.Cl immobilized PUFS for retention of various bismuth (III & V) species to assign the most probable kinetic model, sorption isotherm models, mechanism and thermodynamic characteristics of retention of bismuth (III) from the test aqueous solutions.

#### **3.1. Retention profile of bismuth (III) from the aqueous solution onto PUFs**

Bismuth (ІІІ) forms an orange – yellow colored tetraiodobismuthate(III) complex, [BiI4]- [32] in aqueous solutions containing sulfuric acid (0.5 mole L-1) and an excess of KI (10%w/v). Thus, the sorption profile of aqueous solutions containing bismuth (ІІІ) at different pH by PQ+.Cl loaded foams was critically studied after shaking for 1h at room temperature. After equilibrium, the amount of bismuth (ІІІ) in the aqueous phase was determined spectrophotometrically [32]. The results are shown in Fig. 2. The %E and Kd of bismuth (ІІІ) sorption onto the PUFs markedly decreased on increasing solution pH and maximum uptake was achieved at pH zero. At pH >1, the sorption of bismuth (III) by PQ+.Cl treated PUFs towards bismuth (III) decreased markedly (Fig.2). This behavior is most likely attributed to the deprotonation of the ether oxygen (-CH2 – O– CH2 –) and/or urethane nitrogen (- NH– CO–**)** of PUFs, instability, hydrolysis, or incomplete extraction of the produced ternary complex ion associate of PQ+.[BiI4]-. on/ in the PUFs sorbent.

**Figure 2.** Effect of pH on the sorption percentage of bismuth (III) from aqueous solutions containing KI (10 % m/v) - H2SO4 (2.0 mol L-1) onto PQ+ .Cl immobilized PUFs (0.1 ± 0.002 g) at 25 ± 0.10C**.**

The retention of bismuth (ІІІ) at low pH of aqueous media is most likely attributed to sorbent membranes. The pKa values of protonation of oxygen atom of ether group (\_ CH2\_ OH+\_ CH2\_) foam and nitrogen atom of the amide group (- N+H2 - COO-) foam are \_ 3 and \_ 6, respectively [32]. Thus, in extraction media containing H2SO4 (0.50 mole L-1) and KI, the complexed species of bismuth [BiI4]- are easily retained onto the protonated ether group of the PUFs than amide group of PUFs sorbent. The stability constants of the binding sites of the PUFs with [BiI4]- were calculated using the Scatchard equation [33]:

$$\frac{n}{\lfloor Bi \rfloor} = \text{ } \text{K} \text{(ni } -n \text{)}\tag{2}$$

and n is given by the equation:

286 Polyurethane

*2.4.2. Analysis of total bismuth in wastewater* 

then recovered and analyzed as described above.

*2.4.3. Analysis of total bismuth in seawater* 

samples onto PQ+.Cl-

passed through PQ+.Cl-

and PQ+.Cl-

PQ+.Cl-

retained onto PQ+.Cl-

**3. Results and discussion** 

Wastewater samples (1.0 L) were collected and filtered through a 0.45 μm membrane filter (Milex, Millipore Corporation). The test solution was digested with nitric acid (10 mL, 3.0. mol L-1) and hydrogen peroxide (10 mL, 10% v/v), boiled for 5 min and spiked with different amounts (0.05- 0.5 μg ) of bismuth (ІІІ) in presence of an excess of KI (10% w/v). After

packed columns at 5 mL min-1 flow rate. The concentration of bismuth in the effluent solution was determined by ICP - MS. The retained bismuth (III) species on the PUFs were

The general procedure for the extraction and recovery of bismuth (III) ions from seawater

samples were filtered through 0.45 μm membrane filter, adjusted to pH zero with H2SO4 (0.5 mol L-1) in the presence of KI (0.1%w/v) and ascorbic acid. The sample solution was then

at 5 mL min.-1 The retained bismuth(III) species were then recovered and analyzed as

In recent years [28, 29], PUFs immobilizing some ion pairing reagents have received considerable attention for selective separation, determination and / or chemical speciation of trace and ultra trace metal ions. The non-selective sorption characteristic of the PUFs has been rendered and became more selective by controlling the experimental conditions e.g. pH, ionic strength, etc. Preliminary investigation has shown that, on shaking unloaded PUFs

(10%w/v) and H2SO4 (0.5 mol L-1), considerable amount of bismuth (III) species were

PUFS for retention of various bismuth (III & V) species to assign the most probable kinetic model, sorption isotherm models, mechanism and thermodynamic characteristics of

**3.1. Retention profile of bismuth (III) from the aqueous solution onto PUFs** 

Bismuth (ІІІ) forms an orange – yellow colored tetraiodobismuthate(III) complex, [BiI4]-

in aqueous solutions containing sulfuric acid (0.5 mole L-1) and an excess of KI (10%w/v). Thus, the sorption profile of aqueous solutions containing bismuth (ІІІ) at different pH by

equilibrium, the amount of bismuth (ІІІ) in the aqueous phase was determined spectrophotometrically [32]. The results are shown in Fig. 2. The %E and Kd of bismuth (ІІІ)

loaded foams was critically studied after shaking for 1h at room temperature. After

ones. Thus, in subsequent work, detailed study on the application of PQ+.Cl-

retention of bismuth (III) from the test aqueous solutions.

immobilized PUFs with aqueous solutions containing bismuth (III) ions , KI

treated PUFs in a very short time compared to the untreated PUFs

described above. The recovered bismuth (III) ions were then determined by ICP-OES.

impregnated PUFs was performed as follow: A 100 mL of water

impregnated PUFs (1.0 ± 0.001 g) packed column (10 cm x 1.0 cm i.d.)

loaded PUFs

immobilized

[32]

centrifugation for 5 min, the sample solutions were percolated through PQ+.Cl-

$$m = \frac{weight \text{ of bismuth bound to foam (g)}}{weight \text{ of beam (g)}} \tag{3}$$

where, K = stability constant of bismuth (III) on PUF, ni = maximum concentration of sorbed bismuth (III) by the available sites onto the PUFs, and [Bi] is the equilibrium concentration of bismuth (III) in solution (mol L-1). The plot of n /[Bi] versus *n* is shown in Fig. 3. The curvature of the Scatchard plot demonstrated that more than one class of complex species of

bismuth (III) has been formed and each complex has its own unique formation constant. The stability constants log K1 and log K2 for the sorbed species derived from the respective slopes were 5.56 ± 0.2 and 4.82 ± 0.5, respectively. The values of n1 and n2 calculated from the plot were found equal 0.038 ± 0.005 and 0.078 ± 0.01 mol g-1, respectively. The values of the stability constants (log K1 and log K2) indicated that, the sorption of bismuth (III) species took place readily on site K1 that most likely belong to the ether group. The fact that, ether group has a stability greater than the amide group (site K2) as reported [32]. Moreover, the high values of K1 and K2 indicated that, both bonding sites of PUFs are highly active towards [BiI4]- species in good agreement with the data reported involving the extraction of the bulky anion [BiI4] by methyl isobutyl ketone and other solvents that posses ether linkages in their structures e.g. diethyl ether and isopropyl ether [34]. Based on these data and the results reported on the retention of AuCl4 and CdI4 by PUFs [29, 34], a sorption mechanism involving a weak base anion ion exchanger and/ solvent extraction of [BiI4] aq by the protonated ether oxygen or urethane nitrogen linkages of the PUFs as a ternary complex ion associate is most likely proceeded as follows:

Ether group, PUF:

$$\text{(-CH-}\text{-O-CH-}\text{)}\text{ foam} + \text{H}^+ \quad \leftrightarrow \quad \text{(-CH-}\text{-HO}\text{-}\text{-CH-}\text{)}\text{\_{\text{\textquotedblleft}}}\tag{4}$$

Fast, Selective Removal and Determination of Total Bismuth (III) and (V) in Water by Procaine Hydrochloride Immobilized Polyurethane Foam Packed Column Prior to Inductively Coupled… 289

loaded PUFs was studied. Bismuth (ІІІ) sorption onto the PUFs sorbent

immobilized PUFs was fast and reached equilibrium within 60 min of

immobilized PUFs as in the case of common ion exchange resins [19] and the

(D= 6.17 x 104 mL g-1) compared to the unloaded PUFs (3.05 x 103 mL g-1) due to the formation of the ion associate ([(PQ+). (BiI4)] –foam on/in treated PUFs. Thus, the solution pH was adjusted at pH 0.0 – 1.0 and PQ+.Cl-1 treated PUFs was used as a proper sorbent in the

The influence of the plasticizer e.g. tri-n-octylamine (TOA, 0.5 -2.0 %v/v) and tri-n-butylphosphate (TBP,0.01%v/v) on the retention of bismuth (ІІІ) from the aqueous solutions onto

increased (D = 6.6 X 104 mL g-1) in presence of TOA (1% v/v). The formation of the co ternary

The influence of shaking time (0 \_\_ 60 min) on the uptake of bismuth (ІІІ) from the aqueous acidic media at pH zero was investigated. The sorption of bismuth (III) ions onto TOA

shaking time. This conclusion was supported by calculation of the half-life time (t1/2) of bismuth (III) sorption from the aqueous solutions onto the solid sorbents PUFs. The values of t1/2 calculated from the plots of -log C/ C0 versus time for bismuth (III) sorption onto PUFs, where C0 and C are the original and final concentration of bismuth(III) ions in the test aqueous solution, respectively . The value of t1/2 was found 2.32 0.04 min in agreement with t1/2 value reported earlier [19]. Thus, gel diffusion is not only the rate-controlling step

intraparticle diffusion step where, the more rapid one controls the overall rate of transport.

The sorbed bismuth (III) species onto PUFs sorbent was subjected to Weber–Morris model

 qt = Rd (t)1/2 (8) where, Rd is the rate constant of intraparticle transport in μ mole g-1 min-1/2 and qt is the sorbed Bi (ІІІ) concentration (μ mole g-1) at time t. The plot of qt *vs.* time ( Fig 4) was linear

PUFs sorbents was linear up to 10 ± 1.1 min and deviate on increasing shaking time. The rate

stage of extraction [34, 35]. The values of Rd computed from the two distinct slopes of Weber – Morris plots (Fig.4) for bismuth(III) retention by the solid sorbent were found equal 3.076 ± 1.01 and 0.653 m mole g-1 with correlation coefficient (R2) of 0.989 and 0.995, respectively. The observed change in the slope of the linear plot (Fig.4) is most likely attributed to the different pore size [34, 35]. Thus, intra-particle diffusion step is most likely the rate

aq species is high and decreased on increasing shaking time. Thus, the

aq onto the used solid sorbent is film diffusion at the early

(R2= 0.989) at the initial stage of bismuth (III) uptake by TOA plasticized PQ+ .Cl-

immobilized PUFs showed high retention

in acidic media may account for the

immobilized PUFs sorbent depends on film and

 **-TOA loaded PUFs** 

loaded

The distribution ratio of bismuth (III) onto PQ+.Cl-

complex ion associates TOA+.BiI4 – and PO+. BiI4 -

kinetic of bismuth (III) sorption by PQ+ .Cl-

**3.2. Kinetic behavior of bismuth (ІІІ) sorption onto PQ+ .Cl-**

subsequent work.

observed increase.

plasticized PQ+ .Cl-

for PQ+ .Cl-

of diffusion of [BiI4]-

determining step.

rate of the retention step of [BiI4]-

[35]:

the PQ+ .Cl-

 (\_ CH2\_ HO +\_\_ CH2\_) foam + [BiI4] aq [\_ CH2\_ HO +\_\_ CH2\_]. [BiI4]- foam (5)

Urethane group, PUF:

$$\text{(-NH-}\text{-COO-}\text{)}\_{\text{fan}} + \text{H}^+ \quad \leftrightarrow \qquad \text{(-NH-}\text{-COO-}\text{)}\_{\text{fan}}\tag{6}$$

$$\text{(}-\text{N}^\*\text{H}\text{z}-\text{COO-}\text{)}\text{\_{bam}} + \text{[BiId}\text{]\_{aq}} \qquad \leftrightarrow \qquad \text{[-N}^\*\text{H}\text{z}-\text{COO-}\text{]}\text{\_{c}[\text{BiId}]\_{bam}}\tag{7}$$

**Figure 3.** Scatchard plot for the binding of [BiI4]- species by PQ+ .Cl immobilized PUF (0.1 ± 0.002 g) from aqueous media containing KI (10 % m/v) - H2SO4 (0.5 mol L-1) at 25 ± 0.10C**.**

The distribution ratio of bismuth (III) onto PQ+.Cl immobilized PUFs showed high retention (D= 6.17 x 104 mL g-1) compared to the unloaded PUFs (3.05 x 103 mL g-1) due to the formation of the ion associate ([(PQ+). (BiI4)] –foam on/in treated PUFs. Thus, the solution pH was adjusted at pH 0.0 – 1.0 and PQ+.Cl-1 treated PUFs was used as a proper sorbent in the subsequent work.

288 Polyurethane

bismuth (III) has been formed and each complex has its own unique formation constant. The stability constants log K1 and log K2 for the sorbed species derived from the respective slopes were 5.56 ± 0.2 and 4.82 ± 0.5, respectively. The values of n1 and n2 calculated from the plot were found equal 0.038 ± 0.005 and 0.078 ± 0.01 mol g-1, respectively. The values of the stability constants (log K1 and log K2) indicated that, the sorption of bismuth (III) species took place readily on site K1 that most likely belong to the ether group. The fact that, ether group has a stability greater than the amide group (site K2) as reported [32]. Moreover, the high values of K1 and K2 indicated that, both bonding sites of PUFs are highly active towards [BiI4]- species in good agreement with the data reported involving the extraction of the bulky anion [BiI4] by methyl isobutyl ketone and other solvents that posses ether linkages in their structures e.g. diethyl ether and isopropyl ether [34]. Based on these data

mechanism involving a weak base anion ion exchanger and/ solvent extraction of [BiI4]-

the protonated ether oxygen or urethane nitrogen linkages of the PUFs as a ternary complex

and CdI4-

(\_ CH2\_ O\_ CH2\_) foam + H+ (\_ CH2\_ HO +\_\_ CH2\_) foam (4)

(- NH - COO- ) foam + H+ (--NH+2\_COO-)foam (6)

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 **n (mol / g)**

aq [-N+H2 \_\_ COO- ] .[BiI4]-

aq [\_ CH2\_ HO +\_\_ CH2\_]. [BiI4]- foam (5)

immobilized PUF (0.1 ± 0.002 g)

by PUFs [29, 34], a sorption

aq by

foam (7)

and the results reported on the retention of AuCl4-

ion associate is most likely proceeded as follows:

(\_ CH2\_ HO +\_\_ CH2\_) foam + [BiI4]-

( \_\_ N+H2 \_\_ COO- )foam + [BiI4]-

0

5000

**n/[Bi] (L/m**

 **ol)** 10000

15000

**Figure 3.** Scatchard plot for the binding of [BiI4]- species by PQ+ .Cl-

from aqueous media containing KI (10 % m/v) - H2SO4 (0.5 mol L-1) at 25 ± 0.10C**.**

Ether group, PUF:

Urethane group, PUF:

The influence of the plasticizer e.g. tri-n-octylamine (TOA, 0.5 -2.0 %v/v) and tri-n-butylphosphate (TBP,0.01%v/v) on the retention of bismuth (ІІІ) from the aqueous solutions onto the PQ+ .Cl loaded PUFs was studied. Bismuth (ІІІ) sorption onto the PUFs sorbent increased (D = 6.6 X 104 mL g-1) in presence of TOA (1% v/v). The formation of the co ternary complex ion associates TOA+.BiI4 – and PO+. BiI4 in acidic media may account for the observed increase.

#### **3.2. Kinetic behavior of bismuth (ІІІ) sorption onto PQ+ .Cl- -TOA loaded PUFs**

The influence of shaking time (0 \_\_ 60 min) on the uptake of bismuth (ІІІ) from the aqueous acidic media at pH zero was investigated. The sorption of bismuth (III) ions onto TOA plasticized PQ+ .Cl immobilized PUFs was fast and reached equilibrium within 60 min of shaking time. This conclusion was supported by calculation of the half-life time (t1/2) of bismuth (III) sorption from the aqueous solutions onto the solid sorbents PUFs. The values of t1/2 calculated from the plots of -log C/ C0 versus time for bismuth (III) sorption onto PUFs, where C0 and C are the original and final concentration of bismuth(III) ions in the test aqueous solution, respectively . The value of t1/2 was found 2.32 0.04 min in agreement with t1/2 value reported earlier [19]. Thus, gel diffusion is not only the rate-controlling step for PQ+ .Cl immobilized PUFs as in the case of common ion exchange resins [19] and the kinetic of bismuth (III) sorption by PQ+ .Cl immobilized PUFs sorbent depends on film and intraparticle diffusion step where, the more rapid one controls the overall rate of transport.

The sorbed bismuth (III) species onto PUFs sorbent was subjected to Weber–Morris model [35]:

$$\mathbf{q}\_l = \mathbf{R}d\_l(\mathbf{t})^{1/2} \tag{8}$$

where, Rd is the rate constant of intraparticle transport in μ mole g-1 min-1/2 and qt is the sorbed Bi (ІІІ) concentration (μ mole g-1) at time t. The plot of qt *vs.* time ( Fig 4) was linear (R2= 0.989) at the initial stage of bismuth (III) uptake by TOA plasticized PQ+ .Cl loaded PUFs sorbents was linear up to 10 ± 1.1 min and deviate on increasing shaking time. The rate of diffusion of [BiI4] aq species is high and decreased on increasing shaking time. Thus, the rate of the retention step of [BiI4] aq onto the used solid sorbent is film diffusion at the early stage of extraction [34, 35]. The values of Rd computed from the two distinct slopes of Weber – Morris plots (Fig.4) for bismuth(III) retention by the solid sorbent were found equal 3.076 ± 1.01 and 0.653 m mole g-1 with correlation coefficient (R2) of 0.989 and 0.995, respectively. The observed change in the slope of the linear plot (Fig.4) is most likely attributed to the different pore size [34, 35]. Thus, intra-particle diffusion step is most likely the rate determining step.

**Figure 4.** Weber – Morris plot of sorbed bismuth (ІІІ) onto PQ+ .Cl immobilized PUFs *vs.* square root of time. Conditions: Aqueous solution (100 mL) containing KI (10 % m/v) and H2SO4 (0.5 mol L-1), foam doze = (0.1 ± 0.002 g and 25 ± 0.10C**.**

The retention step of the [BiI4] species onto the loaded PUFs at 25 ± 1 0C was subjected to Lagergren model [28]:

$$\log|\text{(qe-qt)}| = \log q\_{\text{e}} - \frac{\text{K}\_{\text{Lager}}}{2.303} \text{ t} \tag{9}$$

Fast, Selective Removal and Determination of Total Bismuth (III) and (V) in Water by Procaine Hydrochloride Immobilized Polyurethane Foam Packed Column Prior to Inductively Coupled… 291

Bhatt

e

C - C - C

*<sup>C</sup>* ,

*o*


and TOA loaded PUFs.

BT - 0.4977 - 2.303 lo g (1- F) (11)

treated sorbents. Thus, the uptake of [BiI4]-

PUFs towards bismuth

in

The sorption data was also subjected to Bhattacharya- Venkobachar kinetic model [36].

( t )

where, 0 t ( )

where, KBhatt = overall rate constant (min – 1 ), t = time (min), Ct= concentration of the bismuth (III) at time t in μg mL-1, Ce= concentration of Bi (ІІІ) at equilibrium in μg mL-1. The plot of log (1-U(t)) *vs.* time was linear (Fig.6) with R2= 0.987. The computed value of KBhatt (0.143 ± 0.002 min-1) from Fig. 6 was found close to the value of KLager (0.132 ± 0.033 min-1) providing an additional indication of first order kinetic of bismuth (ІІІ) retention towards PQ+ .Cl-

**Figure 6.** Bhattacharya**-**Venkobachar plot of bismuth (ІІІ) retention from aqueous media containing KI

0 5 10 15 20 25 **Time, min** 

The value of BT, which is a mathematical function (F) of the ratio of the fraction sorbed (qt) at time t and at equilibrium (qe) in μ mole g -1 i.e. F= qt / qe calculated for each value of F

(III) species was linear( R2 = 0.990) up to 35 min ( Fig. 7) . The straight line does not pass through the origin indicating that, particle diffusion mechanism is not only responsible for

onto the employed sorbents is most likely involved three steps: i- bulk transport of [BiI4]-

solution, ii- film transfer involving diffusion of [BiI4]- within the pore volume of TOA

treated PUFs and/ or along the wall surface to the active sorption sites of

(10 % m/v) - H2SO4 (0.5 mol L-1) at 25 ± 0.10C onto the PQ+ .Cl-

The plot of Bt versus time at 25 ± 1 0C for TOA plasticized PQ+ .Cl-

sorption onto the PQ+ .Cl-

employing Reichenburg equation [36].




**log (1 - Ut)**


0

the kinetic of [BiI4]-

plasticized PQ+ .Cl-

*t*

*U*

loaded PUFs sorbent.

where, qe is the amount of [BiI4] sorbed at equilibrium per unit mass of PUFs sorbent (μmoles g-1) ; KLager is the first order overall rate constant for the retention process per min and t is the time in min . The plot of log (qe – qt) *vs.* time (Fig.5) was linear. The computed value of KLager was 0.132 ± 0.033 min-1 (R2= 0.979) confirming the first order kinetic model of sorption of [BiI4] species onto the solid sorbent [29]. The influence of adsorbate concentration was investigated and the results indicated that, the value of KLager increased on increasing adsorbate concentration confirming the first order kinetic nature of the retention process and the formation of monolayer species of [BiI4] onto the surface of the used adsorbent [26, 29].

**Figure 5.** Lagergren plot of bismuth (III) uptake onto PQ+ .Cl- PUFs from aqueous solutions containing KI (10 % m/v) - H2SO4 (2.0 mol L-1) *vs.* time at 25 ± 0.10C**.** ]

The sorption data was also subjected to Bhattacharya- Venkobachar kinetic model [36].

290 Polyurethane

**Figure 4.** Weber – Morris plot of sorbed bismuth (ІІІ) onto PQ+ .Cl-

0

5

**qt**

10

doze = (0.1 ± 0.002 g and 25 ± 0.10C**.**

The retention step of the [BiI4]-

where, qe is the amount of [BiI4]-

formation of monolayer species of [BiI4]-




**log(qe - qt)**

0

0.5

1

**Figure 5.** Lagergren plot of bismuth (III) uptake onto PQ+ .Cl-

KI (10 % m/v) - H2SO4 (2.0 mol L-1) *vs.* time at 25 ± 0.10C**.** ]

Lagergren model [28]:

time. Conditions: Aqueous solution (100 mL) containing KI (10 % m/v) and H2SO4 (0.5 mol L-1), foam

0246

**Time, min1/2**

g-1) ; KLager is the first order overall rate constant for the retention process per min and t is the time in min . The plot of log (qe – qt) *vs.* time (Fig.5) was linear. The computed value of KLager was 0.132 ± 0.033 min-1 (R2= 0.979) confirming the first order kinetic model of sorption of [BiI4] species onto the solid sorbent [29]. The influence of adsorbate concentration was investigated and the results indicated that, the value of KLager increased on increasing adsorbate concentration confirming the first order kinetic nature of the retention process and the

0 5 10 15 20 25 30 35

immobilized PUFs *vs.* square root of

species onto the loaded PUFs at 25 ± 1 0C was subjected to

Lager e t <sup>e</sup><sup>K</sup> log (q - q ) log q t 2.303 (9)

sorbed at equilibrium per unit mass of PUFs sorbent (μmoles

onto the surface of the used adsorbent [26, 29].

**Time, min**

PUFs from aqueous solutions containing

$$
\log\left(1\text{--U}\_{(t)}\right) = \frac{\text{--K}\cdot\text{Bhttt}}{\text{--}\,\text{2.303}}\,\text{t}\tag{10}
$$

$$
\text{where, }\,\text{U}(t) = \begin{array}{c}\text{Co}\cdot\text{-Cl}\,\\ \text{Co}\cdot\text{-Cl}\_{2}\end{array}\,\text{'}
$$

where, KBhatt = overall rate constant (min – 1 ), t = time (min), Ct= concentration of the bismuth (III) at time t in μg mL-1, Ce= concentration of Bi (ІІІ) at equilibrium in μg mL-1. The plot of log (1-U(t)) *vs.* time was linear (Fig.6) with R2= 0.987. The computed value of KBhatt (0.143 ± 0.002 min-1) from Fig. 6 was found close to the value of KLager (0.132 ± 0.033 min-1) providing an additional indication of first order kinetic of bismuth (ІІІ) retention towards PQ+ .Clloaded PUFs sorbent.

**Figure 6.** Bhattacharya**-**Venkobachar plot of bismuth (ІІІ) retention from aqueous media containing KI (10 % m/v) - H2SO4 (0.5 mol L-1) at 25 ± 0.10C onto the PQ+ .Cl and TOA loaded PUFs.

The value of BT, which is a mathematical function (F) of the ratio of the fraction sorbed (qt) at time t and at equilibrium (qe) in μ mole g -1 i.e. F= qt / qe calculated for each value of F employing Reichenburg equation [36].

$$\text{BT} = -0.4977 \text{--} 2.303 \log \text{ (1- F)} \tag{11}$$

The plot of Bt versus time at 25 ± 1 0C for TOA plasticized PQ+ .Cl- PUFs towards bismuth (III) species was linear( R2 = 0.990) up to 35 min ( Fig. 7) . The straight line does not pass through the origin indicating that, particle diffusion mechanism is not only responsible for the kinetic of [BiI4] sorption onto the PQ+ .Cl treated sorbents. Thus, the uptake of [BiI4] onto the employed sorbents is most likely involved three steps: i- bulk transport of [BiI4] in solution, ii- film transfer involving diffusion of [BiI4]- within the pore volume of TOA plasticized PQ+ .Cl treated PUFs and/ or along the wall surface to the active sorption sites of the sorbent and finally iii- formation of the complex ion associate of the formula [\_ CH2\_ HO +\_\_ CH2\_]. [BiI4]- Foam or [\_+NH2 \_\_ COO- ]. [BiI4]- Foam. Therefore, the actual sorption of [BiI4]- onto the interior surface of PUFs was rapid and hence particle diffusion mechanism is not the rate determining step in the sorption process. Thus, film and intraparticle transport might be the two main steps controlling the sorption step. Hence, "solvent extraction" and/or "weak base anion ion exchanger" mechanism is not only the most probable participating mechanism and some other processes e.g. surface area and specific sites on the PUFs are most likely involved simultaneously in bismuth (III) retention [37].

Fast, Selective Removal and Determination of Total Bismuth (III) and (V) in Water by Procaine Hydrochloride Immobilized Polyurethane Foam Packed Column Prior to Inductively Coupled… 293

*Fe* (14)

species onto the sorbents is an

loaded PUFs was also subjected to Vant

loaded

*<sup>H</sup>* (15)

1 *C Fe <sup>K</sup>*

Plot of ln KC *vs.* 1000/T (K-1) for bismuth (ІІІ) retention was linear (Fig. 8) over the wide range of temperature range (293- 323 K). The value of KC decreased on increasing

exothermic process [21, 22]**.** The numerical values of ΔH, ΔS, and ΔG calculated from the slope and intercept of the linear plot Fig. 8 were -18.72± 1.01 kJ mol-1 , 54.57± 0.5 J mol-1 K-1

**Figure 8.** Plot of ln KC *vs.* 1000/T (K-1) of bismuth (III) sorption from aqueous media containing KI (10 %

3.05 3.1 3.15 3.2 3.25 3.3 3.35 3.4 3.45 **1000/T**

> log K C <sup>d</sup> 2.30 RT

where, C is a constant. Vant - Hoff plot of log Kd *vs.* 1000/T (K-1) of bismuth (ІІІ) uptake from

PUFs sorbent was linear (Fig. 9). The value of ΔH calculated from the slope of Fig. 9 was - 20.1 ± 1.1 kJ mol-1 in good agreement with the values evaluated from equations 12 and 13. The ΔS of activation were lower than TΔS at all temperature. Thus, the retention step is

The negative value of ΔH and the data of D and KC reflected the exothermic behavior of bismuth (ІІІ) uptake by the employed solid PUFs and non-electrostatics bonding formation between the adsorbent and the adsorbate. The positive value of ΔS proved that, bismuth (III) uptake are organized onto the used sorbent in a more random fashion and may also

the test aqueous media of KI (10 % m/v) - H2SO4 (0.5 mol L-1) onto plasticized PQ+.Cl-

treated PUFs.

and -2.46 ± 0.1 kJ mol-1 (at 298 K), respectively with a correlation factor of 0.998**.** 

temperature, revealing that, the retention process of [BiI4]-

m/v) - H2SO4 (0.5 mol L-1) onto PQ+ .Cl-

0

5

10

**\_R lnKc X103**

15

20

entropy controlled at the activation state.

Hoff model:

The retention of bismuth (IIII) by plasticized PQ+.Cl-

**Figure 7.** Reichenburg plot of bismuth (ІІІ) retention from aqueous media containing KI (10 % m/v) - H2SO4 (0.5 mol L-1) at 25 ± 0.10C onto PQ+ .Cl loaded PUFs.

#### **3.3. Thermodynamic characteristics of bismuth (ІІІ) retention onto plasticized PQ+.Cl loaded PUFs**

Bismuth (ІІІ) retention onto TOA plasticized PQ+.Cl- PUFs was studied over a wide range of temperature (293-353 K) to determine the nature of bismuth (III) retention onto solid sorbent at the established experimental conditions. The thermodynamic parameters (ΔH, ΔS, and ΔG) were evaluated using the equations:

$$
\ln K\_{\mathcal{E}} = \frac{-\Delta H}{RT} + \frac{\Delta S}{R} \tag{12}
$$

$$
\Delta G = \Delta H - T\Delta S \tag{13}
$$

where, ΔH, ΔS, ΔG, and T are the enthalpy, entropy, Gibbs free energy changes and temperature in Kelvin, respectively and R is the gas constant (≈ 8.3 J K-1 mol-1). KC is the equilibrium constant depending on the fractional attainment (Fe) of the sorption process. The values of KC of bismuth (ІІІ) retention from the test aqueous solutions at equilibrium onto the plasticized PQ+.Cl- PUFs were calculated using the equation:

Fast, Selective Removal and Determination of Total Bismuth (III) and (V) in Water by Procaine Hydrochloride Immobilized Polyurethane Foam Packed Column Prior to Inductively Coupled… 293

$$\text{Kc} = \frac{\text{Fe}}{1 - \text{Fe}} \tag{14}$$

Plot of ln KC *vs.* 1000/T (K-1) for bismuth (ІІІ) retention was linear (Fig. 8) over the wide range of temperature range (293- 323 K). The value of KC decreased on increasing temperature, revealing that, the retention process of [BiI4] species onto the sorbents is an exothermic process [21, 22]**.** The numerical values of ΔH, ΔS, and ΔG calculated from the slope and intercept of the linear plot Fig. 8 were -18.72± 1.01 kJ mol-1 , 54.57± 0.5 J mol-1 K-1 and -2.46 ± 0.1 kJ mol-1 (at 298 K), respectively with a correlation factor of 0.998**.** 

292 Polyurethane

+\_\_ CH2\_]. [BiI4]-

Foam or [\_+NH2 \_\_ COO-

involved simultaneously in bismuth (III) retention [37].

H2SO4 (0.5 mol L-1) at 25 ± 0.10C onto PQ+ .Cl-

0

2

**Bt**

4

ΔG) were evaluated using the equations:

Bismuth (ІІІ) retention onto TOA plasticized PQ+.Cl-

 **loaded PUFs** 

onto the plasticized PQ+.Cl-

**PQ+.Cl-**

the sorbent and finally iii- formation of the complex ion associate of the formula [\_ CH2\_ HO

the interior surface of PUFs was rapid and hence particle diffusion mechanism is not the rate determining step in the sorption process. Thus, film and intraparticle transport might be the two main steps controlling the sorption step. Hence, "solvent extraction" and/or "weak base anion ion exchanger" mechanism is not only the most probable participating mechanism and some other processes e.g. surface area and specific sites on the PUFs are most likely

**Figure 7.** Reichenburg plot of bismuth (ІІІ) retention from aqueous media containing KI (10 % m/v) -

**3.3. Thermodynamic characteristics of bismuth (ІІІ) retention onto plasticized** 

loaded PUFs.

0 10 20 30 40

**Time, min**

temperature (293-353 K) to determine the nature of bismuth (III) retention onto solid sorbent at the established experimental conditions. The thermodynamic parameters (ΔH, ΔS, and

> ln *<sup>c</sup> H S <sup>K</sup> RT R*

where, ΔH, ΔS, ΔG, and T are the enthalpy, entropy, Gibbs free energy changes and temperature in Kelvin, respectively and R is the gas constant (≈ 8.3 J K-1 mol-1). KC is the equilibrium constant depending on the fractional attainment (Fe) of the sorption process. The values of KC of bismuth (ІІІ) retention from the test aqueous solutions at equilibrium

PUFs were calculated using the equation:

Foam. Therefore, the actual sorption of [BiI4]- onto

PUFs was studied over a wide range of

(12)

*G H TS* (13)

]. [BiI4]-

**Figure 8.** Plot of ln KC *vs.* 1000/T (K-1) of bismuth (III) sorption from aqueous media containing KI (10 % m/v) - H2SO4 (0.5 mol L-1) onto PQ+ .Cl treated PUFs.

The retention of bismuth (IIII) by plasticized PQ+.Cl loaded PUFs was also subjected to Vant Hoff model:

$$\text{Log } \text{Kd} = \frac{-\Delta H}{2.30 \text{ RT}} \text{ + } \text{C} \tag{15}$$

where, C is a constant. Vant - Hoff plot of log Kd *vs.* 1000/T (K-1) of bismuth (ІІІ) uptake from the test aqueous media of KI (10 % m/v) - H2SO4 (0.5 mol L-1) onto plasticized PQ+.Cl loaded PUFs sorbent was linear (Fig. 9). The value of ΔH calculated from the slope of Fig. 9 was - 20.1 ± 1.1 kJ mol-1 in good agreement with the values evaluated from equations 12 and 13. The ΔS of activation were lower than TΔS at all temperature. Thus, the retention step is entropy controlled at the activation state.

The negative value of ΔH and the data of D and KC reflected the exothermic behavior of bismuth (ІІІ) uptake by the employed solid PUFs and non-electrostatics bonding formation between the adsorbent and the adsorbate. The positive value of ΔS proved that, bismuth (III) uptake are organized onto the used sorbent in a more random fashion and may also

indicative of moderated sorption step of the complex ion associate of [BiI4]- and ordering of ionic charges without a compensatory disordering of the sorbed ion associate onto the used sorbents. The sorption process involves a decrease in free energy, where ΔH is expected to be negative as confirmed above. Moreover, on raising the temperature, the physical structure of the PUFs membrane may be changing, and affecting the strength of intermolecular interactions between the membrane of PUFs sorbent and the [BiI4] species. Thus, high temperature may make the membrane matrix become more unstructured and affect the ability of the polar segments to engage in stable hydrogen bonding with [BiI4] species, which would result in a lower extraction. The negative of ΔG at 295 K implies the spontaneous and physical sorption nature of bismuth (III) retention onto PUFs. The decrease in ΔG on decreasing temperature confirms the spontaneous nature of sorption step of bismuth (III) is more favorable at low temperature. The energy of urethane nitrogen and/or ether oxygen sites of the PUFs provided by raising the temperature minimizes the interaction between the active sites of PUFs and the complex ion associates of bismuth (ІІІ) ions resulting low sorption via "Solvent extraction" [38]. These results encouraged the use of the reagent loaded PUFs in packed column mode for collection, and sequential determination of bismuth (III) and (V) in water samples.

Fast, Selective Removal and Determination of Total Bismuth (III) and (V) in Water by Procaine Hydrochloride Immobilized Polyurethane Foam Packed Column Prior to Inductively Coupled… 295

loaded PUFs compared to other onium cations. Thus, the

immobilized PUFs as calculated

loaded PUFs sorbent from aqueous KI (10%w/v) -H2SO4 (1.0 mol L-1)

loaded PUFs sorbent is given in Fig. 11. The most favorable values of Kd of

ammonium bromide or procaine hydrochloride was tested for the separation of bismuth (III) from aqueous iodide aqueous media. The results revealed considerable retention of

retention profile of bismuth (III) over a wide range of equilibrium concentrations of bismuth

solutions was investigated. The amount of [BiI4] – retained onto the PUFs at low or moderate bismuth (III) concentration varied linearly with the amount of bismuth (III) remained in the test aqueous solution (Fig. 10).The equilibrium was approached only from the direction of [BiI4]- species-rich aqueous phase confirming a first- order sorption behavior [39]. The

from the sorption isotherm (Fig.10) was 40.0 ± 1.10 mg g-1. The plot of distribution coefficient (Kd) of bismuth (ІІІ) sorption between the aqueous solution H2SO4 (0.5 mol L-1) and KI (10%

bismuth (ІІІ) sorption onto PUFs sorbent were also obtained from more diluted aqueous solutions (Fig. 11). The Kd values decreased on increasing the concentration of bismuth (ІІІ) ions in the aqueous phase and the PUFs membranes became more saturated with the

**Figure 10.** Sorption isotherm of bismuth (ІІІ) from aqueous solution of H2SO4 (0.5 mol L-1) and KI (10%

0 5 10 15 20

mg Bi L-1

bismuth (III) onto PQ+ .Cl-

sorption capacity of bismuth (III) species towards PQ+.Cl-

(III) ions onto PQ+ .Cl-

w/v) and PQ+.Cl-

retained [BiI4]-

w/v onto the PQ+. Cl-

0

10

20

m g B i g-1

30

40

50

immobilized PUFs.

species.

**Figure 9.** Vant - Hoff plot of log Kd *vs.* 1000/T (K-1) of bismuth (ІІІ) retention from aqueous media containing KI (10 % m/v) - H2SO4 (0.5 mol L-1) onto PQ+ .Cl loaded PUFs.

#### **3.4. Sorption isotherms of bismuth (ІІІ) onto PQ+ .Cl loaded PUFs sorbents**

The development of a suitable preconcentration and/ or separation procedures for determination of trace concentrations of bismuth (III) in water is becoming increasingly important. PUFs physically immobilized with a series of quaternary ammonium ion pairireagents e.g. tetraphenyl phosponium chloride, amiloride hydrochloride, tetraheptyl ammonium bromide or procaine hydrochloride was tested for the separation of bismuth (III) from aqueous iodide aqueous media. The results revealed considerable retention of bismuth (III) onto PQ+ .Cl loaded PUFs compared to other onium cations. Thus, the retention profile of bismuth (III) over a wide range of equilibrium concentrations of bismuth (III) ions onto PQ+ .Cl loaded PUFs sorbent from aqueous KI (10%w/v) -H2SO4 (1.0 mol L-1) solutions was investigated. The amount of [BiI4] – retained onto the PUFs at low or moderate bismuth (III) concentration varied linearly with the amount of bismuth (III) remained in the test aqueous solution (Fig. 10).The equilibrium was approached only from the direction of [BiI4]- species-rich aqueous phase confirming a first- order sorption behavior [39]. The sorption capacity of bismuth (III) species towards PQ+.Cl immobilized PUFs as calculated from the sorption isotherm (Fig.10) was 40.0 ± 1.10 mg g-1. The plot of distribution coefficient (Kd) of bismuth (ІІІ) sorption between the aqueous solution H2SO4 (0.5 mol L-1) and KI (10% w/v) and PQ+.Cl loaded PUFs sorbent is given in Fig. 11. The most favorable values of Kd of bismuth (ІІІ) sorption onto PUFs sorbent were also obtained from more diluted aqueous solutions (Fig. 11). The Kd values decreased on increasing the concentration of bismuth (ІІІ) ions in the aqueous phase and the PUFs membranes became more saturated with the retained [BiI4] species.

294 Polyurethane

indicative of moderated sorption step of the complex ion associate of [BiI4]- and ordering of ionic charges without a compensatory disordering of the sorbed ion associate onto the used sorbents. The sorption process involves a decrease in free energy, where ΔH is expected to be negative as confirmed above. Moreover, on raising the temperature, the physical structure of the PUFs membrane may be changing, and affecting the strength of

Thus, high temperature may make the membrane matrix become more unstructured and affect the ability of the polar segments to engage in stable hydrogen bonding with [BiI4] species, which would result in a lower extraction. The negative of ΔG at 295 K implies the spontaneous and physical sorption nature of bismuth (III) retention onto PUFs. The decrease in ΔG on decreasing temperature confirms the spontaneous nature of sorption step of bismuth (III) is more favorable at low temperature. The energy of urethane nitrogen and/or ether oxygen sites of the PUFs provided by raising the temperature minimizes the interaction between the active sites of PUFs and the complex ion associates of bismuth (ІІІ) ions resulting low sorption via "Solvent extraction" [38]. These results encouraged the use of the reagent loaded PUFs in packed column mode for collection, and sequential

species.

intermolecular interactions between the membrane of PUFs sorbent and the [BiI4]-

**Figure 9.** Vant - Hoff plot of log Kd *vs.* 1000/T (K-1) of bismuth (ІІІ) retention from aqueous media

The development of a suitable preconcentration and/ or separation procedures for determination of trace concentrations of bismuth (III) in water is becoming increasingly important. PUFs physically immobilized with a series of quaternary ammonium ion pairireagents e.g. tetraphenyl phosponium chloride, amiloride hydrochloride, tetraheptyl

3 3.2 3.4 3.6 **1000/T**

loaded PUFs.

 **loaded PUFs sorbents** 

determination of bismuth (III) and (V) in water samples.

containing KI (10 % m/v) - H2SO4 (0.5 mol L-1) onto PQ+ .Cl-

2.2

2.4

**log Kd**

2.6

2.8

**3.4. Sorption isotherms of bismuth (ІІІ) onto PQ+ .Cl-**

**Figure 10.** Sorption isotherm of bismuth (ІІІ) from aqueous solution of H2SO4 (0.5 mol L-1) and KI (10% w/v onto the PQ+. Cl immobilized PUFs.

**Figure 11.** Plot of the distribution coefficient (Kd) of bismuth (ІІІ) sorption between the aqueous solution H2SO4 (0.5 mol L-1) and KI (10% w/v) and PQ+.Cl loaded PUFs

Sorption of bismuth (ІІІ) onto PUFs sorbent was subjected to Langmuir isotherm model expressed in the following linear form [40]:

$$\frac{\mathbf{C}\_{\text{e}}}{\mathbf{C}\_{\text{ads}}} = \frac{1}{Qb} + \frac{\mathbf{C}\_{\text{e}}}{\mathbf{Q}} \tag{16}$$

Fast, Selective Removal and Determination of Total Bismuth (III) and (V) in Water by Procaine Hydrochloride Immobilized Polyurethane Foam Packed Column Prior to Inductively Coupled… 297

where, KDR is the maximum amount of bismuth (ІІІ) retained, β is a constant related to the energy transfer of the solute from the bulk solution to the sorbent and Є is Polanyi potential

ε2 = RT ln (1+1/Ce) (18)

**Figure 12.** Langmuir sorption isotherm of bismuth (ІІІ) uptake from aqueous solution onto PQ+.Cl-

PUFs indicating that, the D-R model is obeyed for bismuth (ІІІ) sorption over the entire concentration range . The values of β and KDR computed from the slope and intercept were found 0.33 ± 0.01 mol2 KJ-2 and 171 ± 2.01 μ mol g-1, respectively. Assuming that, the surface of PUFs is heterogonous and an approximation to Langmuir isotherm model is chosen as a local isotherm for all sites that are energetically equivalent, the quantity β can be related to the mean of free energy (E) of the transfer of one mole of solute from infinity to the surface

0 5 10 15

**Ce**

1 2

(19)

*E*

immobilized

The plot of ln Cads versus Є2 was linear with R2 = 0.986 (Fig. 13) for the PQ+ .Cl-

of PUFs. The E value is expressed by the following equation:

which is given by the following equation:

loaded PUFs at optimum conditions.

0

0.2

**C**

**e / C**

**ads**

0.4

0.6

where, Ce is the equilibrium concentration (μg mL-1) of bismuth (ІІІ) in the test solution, Cads is the amount of bismuth (III) retained onto PUFs per unit mass. The Langmuir parameter *Q* and *b* related to the maximum adsorption capacity of solute per unite mass of adsorbent required for monolayer coverage of the surface and the equilibrium constant related to the binding energy of solute sorption that is independent of temperature, respectively. The plot of Ce/Cads *vs.* Ce over the entire range of bismuth (ІІІ) concentration was linear (Fig.12) with correlation coefficient of, R2= 0.998 indicating adsorption of the analyte by PQ+ .Cl treated PUFs sorbents followed Langmuir model. The calculated values of *Q* and *b* from the slope and intercept of the linear plot (Fig.12) were 0.21 ± 0.01 m mol g-1 and 5.6 ± 0.20 x 105 L mol-1, respectively.

Dubinin - Radushkevich (D - R) isotherm model [41] is postulated within the adsorption space close to the adsorbent surface. The D-R model is expressed by the following equation:

$$\text{In }\mathsf{Cads} = \mathsf{In}\,\mathsf{Kɔlɔ} - \,\beta\,\,\mathrm{a}^2\tag{17}$$

where, KDR is the maximum amount of bismuth (ІІІ) retained, β is a constant related to the energy transfer of the solute from the bulk solution to the sorbent and Є is Polanyi potential which is given by the following equation:

296 Polyurethane

**Figure 11.** Plot of the distribution coefficient (Kd) of bismuth (ІІІ) sorption between the aqueous

*e ads C*

coefficient of, R2= 0.998 indicating adsorption of the analyte by PQ+ .Cl-

ads DR <sup>2</sup> ln C ln K

*C Qb*

Sorption of bismuth (ІІІ) onto PUFs sorbent was subjected to Langmuir isotherm model

where, Ce is the equilibrium concentration (μg mL-1) of bismuth (ІІІ) in the test solution, Cads is the amount of bismuth (III) retained onto PUFs per unit mass. The Langmuir parameter *Q* and *b* related to the maximum adsorption capacity of solute per unite mass of adsorbent required for monolayer coverage of the surface and the equilibrium constant related to the binding energy of solute sorption that is independent of temperature, respectively. The plot of Ce/Cads *vs.* Ce over the entire range of bismuth (ІІІ) concentration was linear (Fig.12) with correlation

followed Langmuir model. The calculated values of *Q* and *b* from the slope and intercept of the linear plot (Fig.12) were 0.21 ± 0.01 m mol g-1 and 5.6 ± 0.20 x 105 L mol-1, respectively.

Dubinin - Radushkevich (D - R) isotherm model [41] is postulated within the adsorption space close to the adsorbent surface. The D-R model is expressed by the following equation:

> 

1 Ce Q

0 10 20 30 40 50

**Bismuth, µg mL-1**

loaded PUFs

(16)

treated PUFs sorbents

(17)

solution H2SO4 (0.5 mol L-1) and KI (10% w/v) and PQ+.Cl-

expressed in the following linear form [40]:

5

6

**log K**

**d**

7

$$
\varepsilon^2 = \text{RT} \, \text{ln} \, (1 + 1/\text{Ce}) \tag{18}
$$

**Figure 12.** Langmuir sorption isotherm of bismuth (ІІІ) uptake from aqueous solution onto PQ+.Clloaded PUFs at optimum conditions.

The plot of ln Cads versus Є2 was linear with R2 = 0.986 (Fig. 13) for the PQ+ .Cl immobilized PUFs indicating that, the D-R model is obeyed for bismuth (ІІІ) sorption over the entire concentration range . The values of β and KDR computed from the slope and intercept were found 0.33 ± 0.01 mol2 KJ-2 and 171 ± 2.01 μ mol g-1, respectively. Assuming that, the surface of PUFs is heterogonous and an approximation to Langmuir isotherm model is chosen as a local isotherm for all sites that are energetically equivalent, the quantity β can be related to the mean of free energy (E) of the transfer of one mole of solute from infinity to the surface of PUFs. The E value is expressed by the following equation:

$$E = \frac{1}{\sqrt{-2\beta}}\tag{19}$$

The value of E was found 1.23 ± 0.07 KJmol-1 for the PQ+.Cl loaded foam. Based on these results, the values of *Q* and *b* and the data reported [42, 43], a dual sorption sorption mechanism involving absorption related to "weak – base anion ion exchange" and an added component for "surface adsorption" is the most probable mechanism for the uptake of bismuth (ІІІ) by the used PUFs. This model can be expressed by the equation:

$$\mathbf{C}\_{r} = \mathbf{C}\_{abs} + \mathbf{C}\_{ads} = \mathbf{D}\mathbf{C}\_{aq} + \frac{\mathbf{SK}\iota\mathbf{C}\_{aq}}{\mathbf{1} + \mathbf{K}\iota\mathbf{C}\_{aq}} \tag{20}$$

Fast, Selective Removal and Determination of Total Bismuth (III) and (V) in Water by Procaine Hydrochloride Immobilized Polyurethane Foam Packed Column Prior to Inductively Coupled… 299

Bismuth (ІІІ) found,

μg L-1

**Table 2.** Recovery percentage (%) of bismuth (ІІІ) ions from deionized water by the developed PUFs

The proposed PUFs packed columns was also tested for collection and recovery of bismuth (V) species (< 5 μg L-1) from aqueous solutions after reduction to bismuth (ІІІ). A series of reducing agents e.g. H2S, Na2SO3, and KI was tested and satisfactory results were achieved using KI. Thus, in the subsequent work, KI was selected as a proper reducing agent for bismuth (V) to bismuth (III) species. Reduction of bismuth (V) to bismuth (ІІІ) was found

PUFs packed column following the described procedures of bismuth (III) retention. The results are summarized in Table 3. An acceptable recovery percentage of Bismuth (V) in the range 94.0 ± 2.1 – 95.0 ± 3.5 was achieved. The proposed PUFs packed column was also tested for chemical speciation and determination of total bismuth (III) and (V) species in their mixtures. An aqueous solution of bismuth (III) and (V) was first analyzed according to the described procedure for bismuth (V). Another aliquot portion was also adjusted to pH 3 – 4 and shaken with Na-DDTC for 2-3 min and extracted with chloroform (5.0 mL) as Bi (DDTC)3 [33]. The remaining aqueous solution of bismuth (V) was reduced to bismuth (III) with KI (10%w/v) - H2SO4 (0.5 mol L-1) and percolated through the PQ+.Cl- loaded PUFs column. The retained bismuth species were then recovered and finally analyzed following the recommended procedures of bismuth (III) retention. The signal intensity of ICP- OES of the first aliquot (I1) is a measure of the sum of bismuth (III) and (V) ions in the mixture, while the net signal intensity of the second aliquot (I2) is a measure of bismuth (V) ions. The difference (I1-I2) of the net signal intensity is a measure of bismuth (III) ions in the binary mixture. Alternatively, bismuth (ІІІ) as Bi(DDTC)3 in the methylisobutyl ketone phase was stripped to the aqueous phase by HNO3 (1 mol L-1) and analyzed by ICP-OES The results are given in Table 4. An acceptable recovery percentage in the 92.5 ± 3.01\_\_ 104.3 ± 4.5% of

100 98.5 98.0 ± 1.5 50 52 104 ± 2.3 10 10.2 101 ± 1.1

loaded PUFs.

Recovery, % \*

species. The solutions were then percolated through

measurements of bismuth in the effluent indicated complete uptake of bismuth (III). A series of eluting agents e.g. NH4NO3, HClO4 and HNO3 (1-5. mol L-1) was tested for complete elution of the retained bismuth (III). An acceptable recovery (96.0 ± 2.1) of bismuth (III) was achieved using HNO3 (10 mL, 3 mol L-1) at 2 mL min-1 flow rate. Therefore, HNO3 (3 mol L-1) was selected as a proper eluting agent for bismuth (III) from the packed columns. With HNO3, reproducibility data even at ultra trace concentrations (0.5 ng mL-1) of bismuth (ІІІ) were successfully achieved. The data of pre concentration and recovery of various concentrations of bismuth (III) are summarized in Table 2. A recovery percentage in the range 98.0 ± 1.5 \_ 104.2 ±

2.3 was achieved confirming the performance of the developed of PQ+.Cl-

Bismuth (ІІІ) taken,

\* Average (n=5) ± relative standard deviation.

fast, simple and also form a stable [BiI4]-

bismuth (ІІІ) and (V) ions was achieved.

μg L-1

packed columns

where, Cr and Caq are the concentrations of bismuth (III) retained onto the PUFs and the aqueous solution at equilibrium, respectively. Cabs and Cads are the concentrations of the absorbed and adsorbed bismuth (ІІІ) species onto the PUFs at equilibrium, respectively and S and KL are the saturation parameters for the Langmuir adsorption model.

**Figure 13.** Dubinin-Radushkevich (D-R) sorption of bismuth (ІІІ) extraction from aqueous solution onto PQ+.Cl loaded PUFs at the optimum conditions

#### **3.5. Chromatographic behavior of bismuth (ІІІ) sorption**

The membrane like structures, the excellent hydrodynamic and aerodynamic properties of PUFs sorbent [42, 43], kinetics, capacity and the sorption characteristics of bismuth (III) retention towards plasticized PQ+.Cl- PUFs sorbent [39] encouraged the use of the sorbent in packed column for quantitative retention of bismuth (III) from the test aqueous iodide solution. Thus, the test solutions (1.0 L) of the deionized water containing KI (10% w/v) - H2SO4 (1.0 mol L-1) was spiked with various trace concentrations (5 -100 μg L-1) of bismuth (III) and percolated through the PUFs packed columns at 5 mL min-1 flow rate. ICP-OES measurements of bismuth in the effluent indicated complete uptake of bismuth (III). A series of eluting agents e.g. NH4NO3, HClO4 and HNO3 (1-5. mol L-1) was tested for complete elution of the retained bismuth (III). An acceptable recovery (96.0 ± 2.1) of bismuth (III) was achieved using HNO3 (10 mL, 3 mol L-1) at 2 mL min-1 flow rate. Therefore, HNO3 (3 mol L-1) was selected as a proper eluting agent for bismuth (III) from the packed columns. With HNO3, reproducibility data even at ultra trace concentrations (0.5 ng mL-1) of bismuth (ІІІ) were successfully achieved. The data of pre concentration and recovery of various concentrations of bismuth (III) are summarized in Table 2. A recovery percentage in the range 98.0 ± 1.5 \_ 104.2 ± 2.3 was achieved confirming the performance of the developed of PQ+.Cl loaded PUFs.


\* Average (n=5) ± relative standard deviation.

298 Polyurethane

PQ+.Cl-

loaded PUFs at the optimum conditions

0

0.5

1

1.5

**ln Cads**

2

2.5

3

3.5

**3.5. Chromatographic behavior of bismuth (ІІІ) sorption** 

The value of E was found 1.23 ± 0.07 KJmol-1 for the PQ+.Cl-

results, the values of *Q* and *b* and the data reported [42, 43], a dual sorption sorption mechanism involving absorption related to "weak – base anion ion exchange" and an added component for "surface adsorption" is the most probable mechanism for the uptake of

*L aq r abs ads aq*

where, Cr and Caq are the concentrations of bismuth (III) retained onto the PUFs and the aqueous solution at equilibrium, respectively. Cabs and Cads are the concentrations of the absorbed and adsorbed bismuth (ІІІ) species onto the PUFs at equilibrium, respectively and

**Figure 13.** Dubinin-Radushkevich (D-R) sorption of bismuth (ІІІ) extraction from aqueous solution onto

**є 2 X 10<sup>7</sup>**

0 2 4 6 810

The membrane like structures, the excellent hydrodynamic and aerodynamic properties of PUFs sorbent [42, 43], kinetics, capacity and the sorption characteristics of bismuth (III) retention towards plasticized PQ+.Cl- PUFs sorbent [39] encouraged the use of the sorbent in packed column for quantitative retention of bismuth (III) from the test aqueous iodide solution. Thus, the test solutions (1.0 L) of the deionized water containing KI (10% w/v) - H2SO4 (1.0 mol L-1) was spiked with various trace concentrations (5 -100 μg L-1) of bismuth (III) and percolated through the PUFs packed columns at 5 mL min-1 flow rate. ICP-OES

*SK C C C C DC*

1

*L aq*

*K C*

bismuth (ІІІ) by the used PUFs. This model can be expressed by the equation:

S and KL are the saturation parameters for the Langmuir adsorption model.

loaded foam. Based on these

(20)

**Table 2.** Recovery percentage (%) of bismuth (ІІІ) ions from deionized water by the developed PUFs packed columns

The proposed PUFs packed columns was also tested for collection and recovery of bismuth (V) species (< 5 μg L-1) from aqueous solutions after reduction to bismuth (ІІІ). A series of reducing agents e.g. H2S, Na2SO3, and KI was tested and satisfactory results were achieved using KI. Thus, in the subsequent work, KI was selected as a proper reducing agent for bismuth (V) to bismuth (III) species. Reduction of bismuth (V) to bismuth (ІІІ) was found fast, simple and also form a stable [BiI4] species. The solutions were then percolated through PUFs packed column following the described procedures of bismuth (III) retention. The results are summarized in Table 3. An acceptable recovery percentage of Bismuth (V) in the range 94.0 ± 2.1 – 95.0 ± 3.5 was achieved. The proposed PUFs packed column was also tested for chemical speciation and determination of total bismuth (III) and (V) species in their mixtures. An aqueous solution of bismuth (III) and (V) was first analyzed according to the described procedure for bismuth (V). Another aliquot portion was also adjusted to pH 3 – 4 and shaken with Na-DDTC for 2-3 min and extracted with chloroform (5.0 mL) as Bi (DDTC)3 [33]. The remaining aqueous solution of bismuth (V) was reduced to bismuth (III) with KI (10%w/v) - H2SO4 (0.5 mol L-1) and percolated through the PQ+.Cl- loaded PUFs column. The retained bismuth species were then recovered and finally analyzed following the recommended procedures of bismuth (III) retention. The signal intensity of ICP- OES of the first aliquot (I1) is a measure of the sum of bismuth (III) and (V) ions in the mixture, while the net signal intensity of the second aliquot (I2) is a measure of bismuth (V) ions. The difference (I1-I2) of the net signal intensity is a measure of bismuth (III) ions in the binary mixture. Alternatively, bismuth (ІІІ) as Bi(DDTC)3 in the methylisobutyl ketone phase was stripped to the aqueous phase by HNO3 (1 mol L-1) and analyzed by ICP-OES The results are given in Table 4. An acceptable recovery percentage in the 92.5 ± 3.01\_\_ 104.3 ± 4.5% of bismuth (ІІІ) and (V) ions was achieved.


Fast, Selective Removal and Determination of Total Bismuth (III) and (V) in Water by Procaine Hydrochloride Immobilized Polyurethane Foam Packed Column Prior to Inductively Coupled… 301

0 20 40 60 80

**Volume of eluting agent.**

0 500 1000 1500 2000

Feed volume, mL

loaded PUFs packed column using

loaded packed column at

**Figure 14.** Chromatogram of bismuth (ІІІ) recovery from PQ+.Cl-

0

30

**% R** 60

90

nitric acid (5 mol L-1) as eluting agent at flow rate of 2.5 mL min-1.

**Figure 15.** Breakthrough capacity curve for bismuth retention onto PQ+.Cl-

the optimum conditions.

0

50

100 - %

 E 100

\*Average recovery of five measurements ± relative standard deviation.

**Table 3.** Recovery (%) of bismuth (V) ions from deionized water by PUFs packed columns


\* Average recovery of five measurements ± relative standard deviation.

**Table 4.** Recovery (%) of total bismuth (ІІІ) and (V) in their mixture from aqueous media

## **3.6. Capacity of the PQ+.Cl- immobilized PUFs**

The developed method was assessed by comparing the capacity of the used sorbent towards bismuth (III) sorption with most of the reported solid sorbents e.g. 2, 5- di- mercapto-1, 3, 4 thiadiazol loaded on Silica gel [44] and amionophosphonic dithio-carbamate functionalized polyacrylonitrile [45]. The capacity of the used PQ+.Cl- loaded PUFs sorbent (40.0 ± 1.10 mg g-1) towards bismuth (III) retention was found far better than the data reported by other solid sorbents e.g. 2, 5- dimercapto-1, 3, 4-thiadiazol loaded on Silica gel (3.5 mg g-1) [44] and amionophosphonic dithiocarbamate functionalized poly acrylonitrile (15.5 mg g-1) [45] and some other solid sorbents.5

#### **3.7. Analytical performance of the immobilized PUFs packed column**

The performance of the PUFs packed column was described in terms of the number (N) and the height equivalent to the theoretical plate (HETP). Thus, aqueous solution (1.0 L) containing bismuth (ІІІ) at concentration of 100 μg L-1 at the optimum experimental conditions was percolated through the PUFs packed columns (1.0 ±0.001 g) at 5 mL min-1 flow rate. Complete retention of [BiI4]- was achieved as indicated from the analysis of bismuth in the effluent solution using ICP-MS. The retained bismuth (ІІІ) species were then eluted with HNO3 (10 mL, 3 mol L-1) and a series of fractions (2.0 mL) of eluent solution at 2.0 mL min-1 were then collected and analyzed by ICP –OES. The calculated values of N and HETP values from the chromatogram method (Fig. 14) using Gluenkauf equation [14] were equal to 90 ± 3.02 and 0.11± 0.02mm, respectively. The values of N and HETP were also computed from the breakthrough capacity curve (Fig. 15) by percolating aqueous solution (2.0 L) containing bismuth (ІІІ) at 100 μgL-1 under the experimental conditions through PQ+.Cl loaded PUFs column at 5 mL min-1 flow rate of. The critical and breakthrough capacities [42, 45] calculated from Fig.15 were 1.95 ± 0.1 and 31.25 ± 1.02 mg g-1, respectively. These HETP (97 ± 4) and N (0.13 ± 0.02 mm) values are in good agreement with the values obtaioned from the chromatogram method.

Bismuth (V) added μg L-1 Bismuth (V) found, μg L-1 Recovery,% 100 95 ± 1.5 95.0± 3.5 250 235 ± 50 94.0 ± 2.1

Total bismuth found μg L Recovery,% \* Bismuth ( -1 ІІІ) and (V) taken, μg L-1

The developed method was assessed by comparing the capacity of the used sorbent towards bismuth (III) sorption with most of the reported solid sorbents e.g. 2, 5- di- mercapto-1, 3, 4 thiadiazol loaded on Silica gel [44] and amionophosphonic dithio-carbamate functionalized polyacrylonitrile [45]. The capacity of the used PQ+.Cl- loaded PUFs sorbent (40.0 ± 1.10 mg g-1) towards bismuth (III) retention was found far better than the data reported by other solid sorbents e.g. 2, 5- dimercapto-1, 3, 4-thiadiazol loaded on Silica gel (3.5 mg g-1) [44] and amionophosphonic dithiocarbamate functionalized poly acrylonitrile (15.5 mg g-1) [45] and

The performance of the PUFs packed column was described in terms of the number (N) and the height equivalent to the theoretical plate (HETP). Thus, aqueous solution (1.0 L) containing bismuth (ІІІ) at concentration of 100 μg L-1 at the optimum experimental conditions was percolated through the PUFs packed columns (1.0 ±0.001 g) at 5 mL min-1 flow rate. Complete retention of [BiI4]- was achieved as indicated from the analysis of bismuth in the effluent solution using ICP-MS. The retained bismuth (ІІІ) species were then eluted with HNO3 (10 mL, 3 mol L-1) and a series of fractions (2.0 mL) of eluent solution at 2.0 mL min-1 were then collected and analyzed by ICP –OES. The calculated values of N and HETP values from the chromatogram method (Fig. 14) using Gluenkauf equation [14] were equal to 90 ± 3.02 and 0.11± 0.02mm, respectively. The values of N and HETP were also computed from the breakthrough capacity curve (Fig. 15) by percolating aqueous solution (2.0 L) containing bismuth (ІІІ) at 100 μgL-1 under the experimental conditions through

 loaded PUFs column at 5 mL min-1 flow rate of. The critical and breakthrough capacities [42, 45] calculated from Fig.15 were 1.95 ± 0.1 and 31.25 ± 1.02 mg g-1, respectively. These HETP (97 ± 4) and N (0.13 ± 0.02 mm) values are in good agreement with the values

20 25 47 ± 3.5 104 ± 4.5 25 100 118± 5 94.4 ± 2.9 10 10 18.5± 1.5 92.5 ± 3.01

**Table 4.** Recovery (%) of total bismuth (ІІІ) and (V) in their mixture from aqueous media

**3.7. Analytical performance of the immobilized PUFs packed column** 

**Table 3.** Recovery (%) of bismuth (V) ions from deionized water by PUFs packed columns

\*Average recovery of five measurements ± relative standard deviation.

\* Average recovery of five measurements ± relative standard deviation.

**3.6. Capacity of the PQ+.Cl- immobilized PUFs** 

Bi (ІІІ) Bi (V)

some other solid sorbents.5

obtaioned from the chromatogram method.

PQ+.Cl-

**Figure 14.** Chromatogram of bismuth (ІІІ) recovery from PQ+.Cl loaded PUFs packed column using nitric acid (5 mol L-1) as eluting agent at flow rate of 2.5 mL min-1.

**Figure 15.** Breakthrough capacity curve for bismuth retention onto PQ+.Cl loaded packed column at the optimum conditions.

#### **3.8. Figure of merits of the PQ+.Cl- immobilize PUFs packed column**

The LOD, LOQ, enrichment and sensitivity factors and relative standard deviation, (RSD) under the optimized conditions were determined. The plot of signal intensity of ICP- OES (I) versus bismuth (III) concentration (C) has the regression equation:

$$\text{I} = 4.19 \times 10^{\circ} \text{C (ng L}^{\cdot}\text{)} + 12.96 \text{ (r=0.9995)} \tag{21}$$

Fast, Selective Removal and Determination of Total Bismuth (III) and (V) in Water by Procaine Hydrochloride Immobilized Polyurethane Foam Packed Column Prior to Inductively Coupled… 303

from a sample volume of 100 mL at the optimum conditions was studied. The tolerance limits (w/w) less than ± 5% change in percentage uptake of bismuth was taken as free from interference. The tested ions except Pb2+ did not cause any significant reduction on the percentage (96 -102 ± 2%) of bismuth (III) sorption. Lead ions were found to interfere at higher concentrations (> 0.5 mg/ 100 mL sample solution). Thus, it can be concluded that, the method could applied for the separation and / or determination of bismuth (III) and bismuth

The validation of the developed method was performed using the certified reference materials (CRM-TMDW). Good agreement between the concentration measured by the proposed method (8.9 ± 0.9 μgL-1) and the certified value (10.0 ± 0.1 μgL-1) of the total bismuth was achieved confirming the accuracy of the method for trace analysis of bismuth

The method was also applied for the determination of bismuth in wastewater samples (1.0 L) after digestion and percolation through the PUFs packed columns as described. Complete retention of bismuth was achieved as indicated from the ICP-MS analysis of bismuth in the

analyzed by ICP-OES. Various concentrations of bismuth (III) were spiked also onto the tested wastewater samples and analyzed (Table 6). Bismuth (ІІІ) determined by the method and that expected (Table 6) in the tested water samples revealed good recovery percentage

**Table 6.** Recovery study applied to the analysis of bismuth in wastewater by the developed method

Bismuth (ІІІ) found, (μg L Recovery, %\* -1 Bismuth (ІІІ) added, (μg L ) -1)

0.30 0.40 ± 0.01 108.1 ±2.7 0.5 0.61 ±0.02 107.01 ±3.5

\_ 0.07 \_

**Table 7.** Recovery test for bismuth in sea water by the developed method

The selectivity of the procedure was further tested for the analysis of bismuth in Red sea water at the coastal area of Jeddah City, Saudi Arabia following the standard addition. as described..The results are summarized in Table 7. An acceptable recovery percentage of 107.01 ±3.5 -108.1 ±2.7 was achieved confirming the selectivity, accuracy and validation of the method.

(98.4± 2.3 – 104 .3 ± 2.8 %) confirming the accuracy and validation of the method.

(μg L-1)

50 75 104.3 ±2.8 100 120.5 98.4±2.3

\_ 22 \_

\* Average recovery of five replicates ± relative standard deviation.

\* Average recovery of five replicates ± relative standard deviation

species were recovered with HNO3 (10 mL, 3.0 mol L-1) and

Bismuth (ІІІ) found, Recovery, %\*

(V) after reduction of the latter to trivalence.

**3.10. Analytical applications** 

in complex matrices.

effluent. The retained [BiI4]-

Bismuth (ІІІ) added,

(μgL-1)

According to IUPAC [46, 47], the LOD = *3Sy/x*/*b* and LOD = *10Sy/x*/*b* were 0.9 and 3.01 ngL-1, respectively (V sample = 100 mL) where, Sy/x is the standard deviation of *y*- residual and *b* is the slope of the calibration plot [46]. The LOD of the developed method is much better than direct measurement by ICP – OES (5.0 μg mL-1). The enrichment factor (Fc = Vs,b /Ve,v) was defined as the ratio between the volume of analyte sample (Vs,b = 1000 mL) before preconcentration and the eluent volume (Ve,v) after retention and recovery. An average value of Fc of 100 was achieved. The sensitivity factor (the ratio of the slope of the preconcentrated samples to that obtained without preconcentration) was 33.3. The RSD of the method for the determination of standard bismuth (III) solution (50 μg L-1) was ± 2.5% (n= 5) confirming the precision of the method. The figure of merits of the developed method were compared satisfactorily to the reported methods e.g. ICP-OES [45], spectrophotometric [47] and electrochemical [49 -51] (Table 5) in water confirming the sensitivity and applicability of the proposed method. The LOD of the method could be improved to lower values by prior pre concentration of bismuth (III) species from large sample volumes of water (>1.0L). Thus, the method is simple and reliable compared to other methods [50 -52].


#### ng L**-1**

**Table 5.** Figure of merits of the developed and some of the reported SPE coupled with spectrochemcal and electrochemical techniques for bismuth determination in water

#### **3.9. Interference study**

The influence of diverse ions relevant to wastewater e.g. alkali and alkali earth metal ions Ca2+, Mg2+, Cl- , Zn2+, Mn2+, Cu2+, Hg2+, Fe2+, Fe3+, Pb2+, Al3+, Ni2+, Co2+ and nitrate at various concentrations (0.5 -1.0 mg/ 100 mL sample solution) on the sorption of 10 μg bismuth (ІІІ) from a sample volume of 100 mL at the optimum conditions was studied. The tolerance limits (w/w) less than ± 5% change in percentage uptake of bismuth was taken as free from interference. The tested ions except Pb2+ did not cause any significant reduction on the percentage (96 -102 ± 2%) of bismuth (III) sorption. Lead ions were found to interfere at higher concentrations (> 0.5 mg/ 100 mL sample solution). Thus, it can be concluded that, the method could applied for the separation and / or determination of bismuth (III) and bismuth (V) after reduction of the latter to trivalence.
