*3.2.1 Type of beads of CFA1 only with PMEs*

In these column studies, the raw PMEs samples were passed through 75 g of CFA1 only beads within the column. The flow rates of Q = 0.78–0.89 mL/min, empty bed contact time (a measure of the time during which water to be treated is in contact with CFA beads in a contact column), EBCT = 125 min with an operation time t = 12–24 h. During this operational period, almost 5–13 bed volumes of PMEs were treated in fixed bed column. **Figure 3** shows the physical properties of PMEs and fixed bed column. At the end of each column study, the apparent color ratio of C/C0 reached up to 0.546, which corresponded to 45.4% apparent color removal.

*3.2.2 Types of CFA beads of CFA2 + Lime and CFA2 + CFA1 with PMEs*

In these column studies, the raw PMEs sample were passed through 50 75 g of CFA2 + Lime (Mass Ratio of CFA2 to Lime = 4:1) and CFA2 + CFA1 beads with a


**Table 3.**

*Summary of the finalized cost-effective binders and a Total of five (5) types of CFA beads produced.*

#### **Figure 2.**

*The five (5) types of CFA beads produced from the three (3) CFA samples (from left to right: 1 CFA3 + 2 CFA1; 1 CFA2 + 2 CFA1; 4 CFA3 + 1 Lime; 4 CFA2 + 1 Lime; and CFA1. Note: the numbers of 1, 2, and 4 are referred to mass ratios).*

*Immobilization of Powdered Coal Fly Ashes (CFAs) into CFA Beads and Column Studies… DOI: http://dx.doi.org/10.5772/intechopen.94293*

#### **Figure 3.**

*Breakthrough of color column experiments using three different PME and CFA1 only beads. Experimental setup: Initial color concentration: PME1: 182; PME2: 834 and PME3: 968 (mg/L Pt-Co); bed height: 51 61 cm; flow rate: 0.78 0.89 mL/min; at room temperature.*

#### **Figure 4.**

*Breakthrough of color column experiments using three different PMEs, CFA2 and additive materials CFA beads. Experimental setup: initial color concentration: PME1: 182; PME2: 834 and PME3: 968 (mg/L Pt-Co); bed height: 56 63 cm; flow rate: 0.72 0.96 mL.*

height of 562–660 mm in the column, respectively. The flow rates of Q = 0.72– 0.97 mL/min, EBCT = 125 min with an operation time t = 24 h. **Figure 4** shows the physical properties of PMEs and fixed bed column. During this operational period, almost 6–12 bed volumes of PMEs were treated in fixed bed column. At the end of each column study, the apparent color ratio of C/C0 reached up to 0.27, which corresponded to 73% apparent color removal. The curve of CFA2 + Lime - PME1 shows a different characteristic compare with others. Color might be added due to leaching out of chemicals from the CFA beads and breakdown some chemical reagents present in PME1.

#### *3.2.3 Type of CFA beads of CFA3 + Lime and CFA3 + CFA1 with PMEs*

In these column studies, the raw PMEs sample was passed through 50 75 g of CFA3 + Lime, and CFA3 + CFA1 beads with a height of 582–645 mm in the column, respectively. The flow rates of Q = 0.75–0.96 mL/min, EBCT = 125 min with an operation time t = 24 h. **Figure 5** shows the physical properties of PMEs and fixed bed column. During this operational period, almost 6–14 bed volumes of PMEs were treated in fixed bed column. At the end of each column study, the apparent color ratio of C/C0 reached up to 0.473, which corresponded to 52.7% apparent color removal.

#### **Figure 5.**

*Breakthrough of color column experiments using three different PME and CFA3 and additive materials CFA beads. Experimental setup: initial color concentration: PME1: 182; PME2: 834 and PME3: 968 (mg/L Pt-Co); bed height: 58* � *65 cm; flow rate: 0.75* � *0.96.*

#### **3.3 Modeling of breakthrough curves from column studies**

#### *3.3.1 Adams-Bohart model*

The Adams-Bohart model is typically applied to check the dynamic behavior of the column which describes the relationship between *Ct <sup>C</sup>*<sup>0</sup> and t in a continuous fixedbed column system. This model is eminent to predict the initial phase of the breakthrough curve. The linear equation is expressed as:

$$\ln\left(\frac{\mathbf{C}\_t}{\mathbf{C}\_0}\right) = \mathbf{K}\_{AB} \times \mathbf{C}\_0 \times t - \mathbf{K}\_{AB} \times \mathbf{N}\_0 \times \left(\frac{Z}{U\_0}\right) \tag{6}$$

Where, *C*<sup>0</sup> and *Ct* are denoted as the color concentration (mg/L Pt-Co) of influent and effluent of column system; *KAB* represents the kinetic constant (L/mg. min); *N*<sup>0</sup> is the saturation concentration (mg/L); Z is denoted as bed depth of the fixed-bed column and *U*<sup>0</sup> stands for superficial velocity (cm/min). By plotting ln *Ct C*<sup>0</sup> vs. *<sup>t</sup>*, *<sup>N</sup>*<sup>0</sup> is obtained from the intercept and *KAB* can be calculated from slope of the graph.

The column studies experimental data obtained from the five different combinations of CFA beads with PME1 were used for linear regression analysis and their corresponding parameters kinetic constant *KAB* and saturation constant *N*<sup>0</sup> were obtained along with the correlation coefficient *R*<sup>2</sup> given in (Eq. (6)). The model is shown in **Figure 6**. At initial color concentration, *C*<sup>0</sup> = 182 mg/L, the *R*<sup>2</sup> value of Adams-Bohart model for different combinations were varied in a range of 0.54– 0.80. Under the similar condition, this model corresponding parameters kinetic constant *KAB* values were varied 2.20–4.40 (10�<sup>6</sup> L/mg.min), and N0 = 10.23–0.78 (10<sup>3</sup> mg/L) respectively.

The column studies experimental data obtained from the four different combinations of CFA beads with PME2 were used for linear regression analysis and their corresponding parameters kinetic constant *KAB* and saturation constant *N*<sup>0</sup> were obtained along with the correlation coefficient *R*<sup>2</sup> given in (Eq. (6)). The model is shown in **Figure 7**. At initial color concentration, *C*<sup>0</sup> = 834 mg/L, the *R*<sup>2</sup> value of Adams-Bohart model for different combinations varied in a range of 0.70–0.94.

*Immobilization of Powdered Coal Fly Ashes (CFAs) into CFA Beads and Column Studies… DOI: http://dx.doi.org/10.5772/intechopen.94293*

**Figure 6.** *Application of the Adams-Bohart model to the experimental data from column study for PME1.*

**Figure 7.** *Application of the Adams-Bohart model to the column study experimental data for PME2.*

Under the similar condition, this model's corresponding parameters kinetic constant *KAB* values was varied 1.68–4.68 (10�<sup>3</sup> L/mg.min). N0 = 12.63–4.23 (10<sup>3</sup> mg/L) respectively.

The column studies experimental data obtained from the four different combinations of CFA beads with PME3 were used for linear regression analysis and their corresponding parameters kinetic constant *KAB* and saturation constant *N*<sup>0</sup> were obtained along with the correlation coefficient *R*<sup>2</sup> given in (Eq. (6)). The model was shown in **Figure 8**. At initial color concentration, *C*<sup>0</sup> = 968 mg/L, the *R*<sup>2</sup> value of Adams-Bohart model for different combinations varied in a range of 0.67–0.85. Under the similar condition, this model's corresponding parameters kinetic constant *KAB* values was varied 1.14–3.2 (10�<sup>3</sup> L/mg.min). N0 = 55.22–16.06 (10<sup>3</sup> mg/L) respectively.

#### *3.3.2 Thomas model*

Thomas model is one of the widely used models in fixed-bed continuous column operation. This model based on three assumptions: i) follows Langmuir Isotherm model; ii) obeys the second order reversible reaction kinetics; and iii) there is no axial depression of the adsorbent. The linear equation is expressed as follows

**Figure 8.** *Application of the Adams-Bohart model to the column study experimental data for PME3.*

$$\ln\left(\frac{C\_0}{C\_t} - 1\right) = \frac{K\_{Th} \times q\_0 \times M}{Q} - K\_{Th} \times C\_0 \times t \tag{7}$$

Where, *C*<sup>0</sup> and *Ct* are denoted as the color concentration (mg/L Pt-Co) of influent and effluent of column system; *KTh* stands for Thomas rate constant (L/(min.mg)); *q*<sup>0</sup> is the maximum color adsorption capacity for CFA beads (mg/g), M is the mass of CFA beads (g), Q is the flow rate (mL/min). By plotting ln *<sup>C</sup>*<sup>0</sup> *Ct* � 1 versus t, Thomas rate constant *KTh* can be obtained from the slope and *q*<sup>0</sup> can be calculated from the interception of the plot.

The experimental data obtained from the three selected combinations of three types of CFA beads with PME1 column studies were used for linear regression analysis and their corresponding Thomas rate constant *KTh* and maximum color adsorption capacity *<sup>q</sup>*<sup>0</sup> were calculated along with the correlation coefficient *<sup>R</sup>*<sup>2</sup> given in (Eq. (7)). The model is shown in **Figure 9**. At initial color concentration *C*<sup>0</sup> = 182 mg/L, the *R*<sup>2</sup> value of Thomas model for different combination varied in a range of 0.54–0.79. The Thomas rate constants were calculated for different combinations and were 6.593, 14.286 and 5.495 (x10�<sup>6</sup> L/min.mg) for the CFA2 + CFA1, CFA3 + CFA1 and CFA1 only beads, respectively. The maximum color adsorption capacity *q*<sup>0</sup> was obtained from the plot and their values were in a range of 0.31– 1.72 mg/g. On the other hand, the color adsorption capacities after 20 hours' operation of pump started were obtained and they varied in a range of 0.72–1.67 mg/g, which

**Figure 9.** *Application of Thomas model to the column study experimental data for PME1.*

#### *Immobilization of Powdered Coal Fly Ashes (CFAs) into CFA Beads and Column Studies… DOI: http://dx.doi.org/10.5772/intechopen.94293*

were very close to the range of the Thomas model adsorption capacities. However, these values were very low compared with the results from the batch studies. For the CFA beads (Class "F" type CFA + binder), the maximum color removal capacity increased with decreased the volumetric flow rate of column operation.

The experimental data obtained from the five selected combinations of CFA beads with PME2 column studies were used for linear regression analysis and their corresponding Thomas rate constant *KTh* and maximum color adsorption capacity *<sup>q</sup>*<sup>0</sup> were calculated along with the correlation coefficient *<sup>R</sup>*<sup>2</sup> given in (Eq. (7)). The model is shown in **Figure 10**. At initial color concentration *C*<sup>0</sup> = 834 mg/L, the *R*<sup>2</sup> value of Thomas model for different combination varied in a range of 0.71 to 0.97. Thomas rate constants were calculated for different combinations and were 3.36, 2.64, 9.71, 2.16 and 3.16 (x 10<sup>6</sup> L/min.mg) for the CFA3 + Lime, CFA3 + CFA1, CFA1 only, CFA2 + Lime, CFA2 + CFA1 beads, respectively. The maximum color adsorption capacity *q*<sup>0</sup> was obtained from the plot and their values were in a range of 3.65 to 14.02 mg/g. On the other hand, the color adsorption capacities after 20 hours' operation of pump started were obtained and they varied in a range of 4.04–12.95 mg/g which were very close to the range of the Thomas model adsorption capacities. However, these values were quite high compared with the results from the batch studies. For the CFA beads (Class "F" type CFA + binder), the maximum color removal capacity increased with decreased the volumetric flow rate of column operation.

The experimental data obtained from the four selected combinations of CFA beads with PME3 were used for linear regression analysis and their corresponding Thomas rate constant *KTh* and maximum color adsorption capacity *q*<sup>0</sup> were calculated along with the correlation coefficient *R*<sup>2</sup> shown in (Eq. (7)). The model is shown in **Figure 11**. At initial color concentration *C*0: 968 mg/L, *R*<sup>2</sup> value of Thomas model for different combination were varied in between 0.76 to 0.85. Thomas rate constant were calculated for different combination 23.1, 1.86, 1.76 and 35.71 (*x*10<sup>6</sup> L/min.mg). The maximum color adsorption capacity *q*<sup>0</sup> was obtained from the plot and their values were varied in between 0.8 28.23 mg/g. Where, color adsorption capacity after 20 hours' operation of pump started were obtained and their value varied in a range of 4.4 12.71 mg/g that had some difference with Thomas model constant values. Again, these values were quite high compared with the batch studies results. For the CFA beads (Class "F" type CFA + binder), the maximum color removal capacity increased with decreased the volumetric flow rate of column operation.

**Figure 10.** *Application of Thomas model to the column study experimental data for PME2.*

**Figure 11.** *Application of Thomas model to the column study experimental data for PME3.*
