**7. Experimental details**

Additional used chemicals (benzalkonium chloride 50 wt.% aqueous solution (AlkBzMe2NCl), Aliquat 336 (A336), hexadecyltrimethylammonium chloride (AlkMe3NCl), diclofenac sodium salt (NaDCF, 98%+, Mr = 303.21), flufenamic acid (FLUFA, 98% + Mr = 281.23), Mordant Blue 9 (MB9, purity, 50% Mr = 551.28), and octan-1-ol, etc.) were purchased from Sigma-Aldrich, Czech Republic.

Powdered active carbon (PAC) Silcarbon CW20 (specific area 1300 m2 /g) was obtained from Brenntag Co. Granular active carbon (GAC) Hydraffin CC8x30 (specific area 1000 m<sup>2</sup> /g) was purchased from Donau Carbon GmbH & Co.

Demineralized water was used for the preparation of the used aqueous solutions.

### **7.1 Preparation of used stock solutions**

25 mM aqueous diclofenac stock solution was obtained by a dissolution of 8.0 g of NaDCF in 1 liter of water; the pH of the stock solution was 8.7. Aqueous 10 mM stock sol. of NaFLUFA was obtained by a dissolution of 2.81 g of flufenamic acid in 12 mM aqueous NaOH (pH = 10.3). Aqueous 25 mM stock sol. of NaFLUFA was obtained by a dissolution of 7 g of flufenamic acid in 30 mM aqueous NaOH (pH = 10.3). Aqueous 10 mM solution of MB9 was obtained by a dissolution of 11.0 g of MB9 (50% purity) in 1 liter of water (pH = 8.2).

### **7.2 Preparation of the mixtures of A336 with aqueous 50% AlkBzMe2NCl**

Solution 3/2 A336/50% aq. AlkBzMe2NCl.

30 g of Aliquat 336 was dissolved in 20 g (21 mL) of 50 wt. % aqueous AlkBzMe2NCl under stirring.

Solution 2/3 A336/50% aq. AlkBzMe2NCl.

20 g of Aliquat 336 was dissolved in 30 g (32 mL) of 50 wt. % aqueous AlkBzMe2NCl under stirring.

### **7.3 Preparation of ex situ modified biochar**

Modified biocharAlkBzMe2NCl was prepared by impregnation of biochar (20 g) using 5 wt.% aqueous AlkBzMe2NCl (100 mL) under vigorous stirring at 500 rpm overnight, subsequent filtration, filter cake washing with 400 mL of water, and drying of washed filter cake at 105°C to a constant weight.

### **7.4 Applied analyses**

A Hach DR2800 (Austria) VIS spectrophotometer was employed for the absorbance measurements using 1 cm glass cuvettes. The concentrations of MB9 and R4N.MB9 were determined by measuring at the maximum absorbance (Amax) [7, 8].

Concentration of NaDCF and NaFLUFA was determined by voltammetric determination at carbon paste electrode in situ modified by AlkMe3NCl cetyltrimethylammonium bromide (CTAB) [21]. Electrochemical measurements were carried

**259**

**Figure 13.**

*Application of Biochar for Treating the Water Contaminated with Polar Halogenated…*

out using an AUTOLAB analyzer (model PGSTAT-128 N; Autolab/Metrohm, the Netherlands/Switzerland), coupled with the three-electrode cell incorporating the working carbon paste electrode (CPE), containing the hand- homogenized carbon paste containing 0.5 g graphite powder (product "CR-5"; Maziva, Czech Republic) and 0.3 mL paraffin oil (Uvasol® grade; Merck, USA). This paste mixture was then manually filled into a piston-driven electrode body. The remaining electrodes were a Ag/AgCl/3.5 M KCl reference and a platinum auxiliary electrode (both from

It was confirmed that the anodic oxidation of NaDCF at the CPE gives rise to a well-developed signal with a peak potential of about +0.6 V vs. Ag/AgCl/3.5 M KCl (further denoted as "ref.") and anodic oxidation of NaFLUFA at the CPE gives rise to a well-developed signal with a peak potential of about +0.78 V vs. ref. Almost identical responses for measurements with differential pulse and square-wave voltammetry (DPV and SWV, respectively) have indicated that the reaction of interest is not kinetically controlled and hence suitable for (electro)analytical purposes. Therefore, measurements of all water samples were performed using DPV. It was also found that the most favorable response could be obtained in neutral media, whereas more alkaline solutions had already caused a decrease of the first peak and the total disappearance of the second one. Thus, pH 7.0 was definitely set as optimal; therefore, phosphate buffer (PBS) at pH 7.0 was used for all measurements. Because the respective measurements had not sensitive response, electrochemical measurements were extended to the effect of a modifier on a possible enhancement of the response. Such a modification is very simple as it can be realized in situ; i.e., by adding a small amount of surfactant directly to the sample analyzed. This can be exemplarily illustrated in **Figure 13**, portraying the effect of CTAB that had

*The main oxidation peak of NaDCF and the effect of the presence of cetyltrimethylammonium bromide* 

*(CTAB) surfactant in the solution and phosphate buffer baseline (PBS) [19].*

*DOI: http://dx.doi.org/10.5772/intechopen.92760*

Metrohm).

*Application of Biochar for Treating the Water Contaminated with Polar Halogenated… DOI: http://dx.doi.org/10.5772/intechopen.92760*

out using an AUTOLAB analyzer (model PGSTAT-128 N; Autolab/Metrohm, the Netherlands/Switzerland), coupled with the three-electrode cell incorporating the working carbon paste electrode (CPE), containing the hand- homogenized carbon paste containing 0.5 g graphite powder (product "CR-5"; Maziva, Czech Republic) and 0.3 mL paraffin oil (Uvasol® grade; Merck, USA). This paste mixture was then manually filled into a piston-driven electrode body. The remaining electrodes were a Ag/AgCl/3.5 M KCl reference and a platinum auxiliary electrode (both from Metrohm).

It was confirmed that the anodic oxidation of NaDCF at the CPE gives rise to a well-developed signal with a peak potential of about +0.6 V vs. Ag/AgCl/3.5 M KCl (further denoted as "ref.") and anodic oxidation of NaFLUFA at the CPE gives rise to a well-developed signal with a peak potential of about +0.78 V vs. ref. Almost identical responses for measurements with differential pulse and square-wave voltammetry (DPV and SWV, respectively) have indicated that the reaction of interest is not kinetically controlled and hence suitable for (electro)analytical purposes. Therefore, measurements of all water samples were performed using DPV. It was also found that the most favorable response could be obtained in neutral media, whereas more alkaline solutions had already caused a decrease of the first peak and the total disappearance of the second one. Thus, pH 7.0 was definitely set as optimal; therefore, phosphate buffer (PBS) at pH 7.0 was used for all measurements.

Because the respective measurements had not sensitive response, electrochemical measurements were extended to the effect of a modifier on a possible enhancement of the response. Such a modification is very simple as it can be realized in situ; i.e., by adding a small amount of surfactant directly to the sample analyzed. This can be exemplarily illustrated in **Figure 13**, portraying the effect of CTAB that had

### **Figure 13.**

*The main oxidation peak of NaDCF and the effect of the presence of cetyltrimethylammonium bromide (CTAB) surfactant in the solution and phosphate buffer baseline (PBS) [19].*

*Applications of Biochar for Environmental Safety*

**7. Experimental details**

(specific area 1000 m2

**7.1 Preparation of used stock solutions**

11.0 g of MB9 (50% purity) in 1 liter of water (pH = 8.2).

drying of washed filter cake at 105°C to a constant weight.

Solution 3/2 A336/50% aq. AlkBzMe2NCl.

Solution 2/3 A336/50% aq. AlkBzMe2NCl.

**7.3 Preparation of ex situ modified biochar**

AlkBzMe2NCl under stirring.

AlkBzMe2NCl under stirring.

**7.4 Applied analyses**

Republic.

efficiency comparable with commercial active carbons containing at least twice higher specific area as biochar. These obtained results agree with the information by Xi et al. [20] which observed that the surface area of the used sorbent by the coaction of R4NX does not play a major role in sorption of anionic contaminants.

Additional used chemicals (benzalkonium chloride 50 wt.% aqueous solution (AlkBzMe2NCl), Aliquat 336 (A336), hexadecyltrimethylammonium chloride (AlkMe3NCl), diclofenac sodium salt (NaDCF, 98%+, Mr = 303.21), flufenamic acid (FLUFA, 98% + Mr = 281.23), Mordant Blue 9 (MB9, purity, 50% Mr = 551.28), and octan-1-ol, etc.) were purchased from Sigma-Aldrich, Czech

Powdered active carbon (PAC) Silcarbon CW20 (specific area 1300 m2

**7.2 Preparation of the mixtures of A336 with aqueous 50% AlkBzMe2NCl**

30 g of Aliquat 336 was dissolved in 20 g (21 mL) of 50 wt. % aqueous

20 g of Aliquat 336 was dissolved in 30 g (32 mL) of 50 wt. % aqueous

Modified biocharAlkBzMe2NCl was prepared by impregnation of biochar (20 g) using 5 wt.% aqueous AlkBzMe2NCl (100 mL) under vigorous stirring at 500 rpm overnight, subsequent filtration, filter cake washing with 400 mL of water, and

A Hach DR2800 (Austria) VIS spectrophotometer was employed for the absorbance measurements using 1 cm glass cuvettes. The concentrations of MB9 and R4N.MB9 were determined by measuring at the maximum absorbance (Amax) [7, 8]. Concentration of NaDCF and NaFLUFA was determined by voltammetric determination at carbon paste electrode in situ modified by AlkMe3NCl cetyltrimethylammonium bromide (CTAB) [21]. Electrochemical measurements were carried

obtained from Brenntag Co. Granular active carbon (GAC) Hydraffin CC8x30

Demineralized water was used for the preparation of the used aqueous solutions.

25 mM aqueous diclofenac stock solution was obtained by a dissolution of 8.0 g of NaDCF in 1 liter of water; the pH of the stock solution was 8.7. Aqueous 10 mM stock sol. of NaFLUFA was obtained by a dissolution of 2.81 g of flufenamic acid in 12 mM aqueous NaOH (pH = 10.3). Aqueous 25 mM stock sol. of NaFLUFA was obtained by a dissolution of 7 g of flufenamic acid in 30 mM aqueous NaOH (pH = 10.3). Aqueous 10 mM solution of MB9 was obtained by a dissolution of

/g) was purchased from Donau Carbon GmbH & Co.

/g) was

**258**

**Figure 14.**

*The main oxidation peak of NaFLUFA and the effect of the presence of cetyltrimethylammonium bromide (CTAB) surfactant in the solution and phosphate buffer baseline (PBS).*

been found the most effective for this function among all the surfactants tested. The observed benefit of CTAB was attributed to the (pre)treatment of CPE by means of "erosion effect." The same modifier effect was observed for NaFLUFA, as could be seen in **Figure 14**.

Typical experimental and instrumental conditions of NaDCF and NaFLUFA voltammetric determination (DPV) had included the following parameters: supporting electrolyte 0.1 M PBS + 0.1 mM CTAB, potential scan from +0.2 to 1.2 V vs. ref., and scan rate of 50 mV/s.

### **7.5 Sorption experiments**

Sorption experiments were carried out in a magnetically, at 400 rpm, stirred 250 mL round-bottomed flasks at 25°C using Starfish equipment installed on an electromagnetic stirrer Heidolph-Hei-Standart with a temperature sensor Pt1000. The appropriate quantity of biochar was added to 100 mL of synthetic wastewater (possibly after the addition of R4NCl(s)). In performed kinetic experiments (**Figures 2**, **3**, **5**, **6**, and **8**), the initial concentration of NaDCF in synthetic wastewater was 25 mM (8 g NaDCF/L and pH = 8.7), the concentration of FLUFA in synthetic wastewater was 10 mM NaFLUFA in 12 mM NaOH (2.81 g FLUFA/L and pH = 10.3), and the concentration of MB9 was 10 mM (5.5 g MB9/L). In a subsequent comparative study for the construction of adsorption isotherms (**Figures 10–12**), the concentrations of contaminants in starting aqueous solutions were 0.25–8 g NaDCF /L, 0.25–7 g -FLUFA/L, and 0.5–5 g MB9/L (for additional information see the text and Figures and Tables in the previous chapters). Stirred suspensions were immediately filtered and analyzed after an appropriate time period.

**261**

**Author details**

with R4N+

QK1910056.

**Acknowledgements**

Barbora Kamenická1

Prague, Czech Republic

, Pavel Matějíček1

Technology, University of Pardubice, Czech Republic

\*Address all correspondence to: tomas.weidlich@upce.cz

provided the original work is properly cited.

, Tomáš Weidlich1

1 Institute of Environmental and Chemical Engineering, Faculty of Chemical

3 Department of Power Engineering, Faculty of Environmental Technology, University of Chemistry and Technology, Prague, Prague, Czech Republic

2 Institute of Chemical Process Fundamentals of the Czech Academy of Sciences,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\* and Michael Pohořelý2,3

*Application of Biochar for Treating the Water Contaminated with Polar Halogenated…*

Experiments dealing with log POW determination were performed using the same apparatus. An aqueous solution containing 1 mmol of studied contaminant was introduced to the round-bottomed flask (in case of studying log POW of ion pairs, 1 mmol of R4NCl per mmol of -COONa or -SO3Na group bound in contaminant was added subsequently); the total volume of aqueous phase was adjusted to 100 mL with water saturated with octan-1-ol, and the mixture was fulfilled using 100 mL of octan-1-ol. The prepared two-phase mixture was agitated at 400 rpm overnight, and the immiscible phases were separated in a separatory funnel, and a concentration of the tested chlorinated aromatic acid sodium salt or their ion pair

in the aqueous phase was analyzed using VIS spectroscopy in the case

of MB9 and R4N.MB9. In the case of NaDCF or R4N.DCF, the concentration in the

This work was funded by the Faculty of Chemical Technology, University of Pardubice, within the financial support for the excellent team (Chemical Technology Group), Specific university research—grant No. A1\_FTOP\_2020\_001, and by the Ministry of Agriculture of the Czech Republic—project QK1820175 and

aqueous phase was analyzed using voltammetric determination.

*DOI: http://dx.doi.org/10.5772/intechopen.92760*

*Application of Biochar for Treating the Water Contaminated with Polar Halogenated… DOI: http://dx.doi.org/10.5772/intechopen.92760*

Experiments dealing with log POW determination were performed using the same apparatus. An aqueous solution containing 1 mmol of studied contaminant was introduced to the round-bottomed flask (in case of studying log POW of ion pairs, 1 mmol of R4NCl per mmol of -COONa or -SO3Na group bound in contaminant was added subsequently); the total volume of aqueous phase was adjusted to 100 mL with water saturated with octan-1-ol, and the mixture was fulfilled using 100 mL of octan-1-ol. The prepared two-phase mixture was agitated at 400 rpm overnight, and the immiscible phases were separated in a separatory funnel, and a concentration of the tested chlorinated aromatic acid sodium salt or their ion pair with R4N+ in the aqueous phase was analyzed using VIS spectroscopy in the case of MB9 and R4N.MB9. In the case of NaDCF or R4N.DCF, the concentration in the aqueous phase was analyzed using voltammetric determination.
