## 2 Materials and Methods
### pH Buffering Capacity of Amendments and Soil Determination  
pH buffering capacity of the amendments and soil were determined using titration method [26]. Titration curves were plotted by adding incremental mmol H\({}^{+}\) kg\({}^{-1}\) samples in water. The ratio of 1:2.5 sample:water (w:v) was used for soil alone, B1, B2, and B3, whereas 1:5 sample:water (w:v) ratio was used for CLB because of the high water absorption capacity of CLB. For each titration, 10 g of soil, B1, B2, and B3 were weighed into 100 mL plastic vials using a digital weighing balance after which 25 mL of distilled water were added. A 5 g of CLB was weighed into a 100 mL plastic vial using a digital weighing balance after which 25 mL of distilled water were added. All the samples were in triplicate. For each sample, 1 mL of 0.05 M CaCl\({}_{2}\) was added to minimize variations in ionic strength. A 0.2 mL of toluene was added to inhibit microbial activities [27]. The suspension was shaken for 15 min at 180 rpm using an orbital shaker and equilibrated for seven days at 25 \({}^{\circ}\)C because it takes approximately three to six days for the suspension to equilibrate [27; 28; 29]. \begin{table}
\begin{tabular}{l l l l l} \hline
**Isotherm** & **Nonlinear Form** & **Linear Form** & **Plot** & **Variables** \\ \hline Langmuir-1 & & \(\frac{\mathrm{C_{e}}}{\mathrm{q_{e}}}=\frac{\mathrm{C_{e}}}{\mathrm{q_{n}}}+ \frac{1}{\mathrm{K_{t}}\mathrm{q_{n}}}\) & \(\frac{\mathrm{C_{e}}}{\mathrm{q_{e}}}\) vs. \(\mathrm{C_{e}}\) & \(\mathrm{K_{L}}=\frac{\mathrm{slope}}{\mathrm{interp}}\) \\   Langmuir-2 & & \(\mathrm{q_{e}}=\frac{\mathrm{q_{e}}\mathrm{K_{t}}\mathrm{C_{e}}}{\mathrm{1+K_{ t}}\mathrm{C_{e}}}\) & \(\frac{1}{\mathrm{q_{e}}}\) & \(\frac{\mathrm{1}}{\mathrm{q_{e}}}\) vs. \(\mathrm{\frac{1}{\mathrm{C_{e}}}}\) & \(\mathrm{K_{L}}=\frac{\mathrm{interp}}{\mathrm{slope}}\) \\   Langmuir-3 & & \(\mathrm{q_{e}}=\frac{\mathrm{q_{m}}-\left(\frac{1}{\mathrm{K_{t}}}\right) \mathrm{\frac{3}{C_{e}}}}{\mathrm{q_{e}}}\) & \(\mathrm{q_{e}}\) vs. \(\mathrm{\frac{3}{C_{e}}}\) & \(\mathrm{q_{m}}=\frac{\mathrm{interp}}{\mathrm{interp}}\) \\   Langmuir-4 & & \(\mathrm{\frac{q_{e}}}{\mathrm{C_{e}}}=\mathrm{K_{t}}\mathrm{Q_{m}}-\mathrm{K_{t}} \mathrm{Q_{e}}\) & \(\mathrm{\frac{q_{e}}{\mathrm{C_{e}}}}\) vs. \(\mathrm{q_{e}}\) & \(\mathrm{K_{L}}=-\mathrm{slope}\) \\   [PERSON] & \(\mathrm{q_{e}}=\mathrm{K_{F}}\mathrm{C_{e}^{\frac{1}{2}}}\) & \(\mathrm{\log}\!\left(\mathrm{q_{e}}\right)=\mathrm{\log}\!\left(\mathrm{K_{F}} \right)+\mathrm{\frac{1}{n}\log\!\left(\mathrm{C_{e}}\right)}\) & \(\mathrm{\log}\!\left(\mathrm{q_{e}}\right)\mathrm{vs.}\ \mathrm{\log}\!\left(\mathrm{C_{e}}\right)\) & \(\mathrm{K_{F}}=\mathrm{\mathrm{antilog}}\!\left(\mathrm{intercept}\right)\) \\  & \(\mathrm{q_{e}}=\mathrm{B_{T}}\mathrm{ln}\left(\mathrm{K_{T}}\mathrm{C_{e}}\right)\) & \(\mathrm{q_{e}}=\mathrm{B_{T}}\mathrm{ln}\ \mathrm{K_{T}}+\mathrm{B_{T}}\mathrm{ln}\ \mathrm{C_{e}}\) & \(\mathrm{q_{e}}\) vs. \(\mathrm{ln}\mathrm{C_{e}}\) & \(\mathrm{K_{T}}=\mathrm{\mathrm{exp}}\!\left(\frac{\mathrm{intercept}}{\mathrm{B_{T }}}\right)\) \\  & & & & \\  & & & & \\ \end{tabular}
\end{table} 
Table 3: List of adsorption isotherms models used in this study and their nonlinear and linear forms. At seven days of equilibration, the initial pH of the suspensions was determined using a digital pH meter (SevenEasy pH, Mettler-Toledo GmbH, Switzerland). A 0.1 M NaOH was added to the samples with very low initial pH (pH less than 5.5) using Eppendorf pipette. This was also done to reduce suspension effect [26]. A 0.1 M HCl was used on the samples with slightly acidic to basic initial pH (pH higher than 6). In all of the samples, 1, 2, 3, 4, 6, 8, and 10 mL of 0.1 M HCl or 0.1 M NaOH were used. After addition of 0.1 M HCl or 0.1 M NaOH, the suspensions were stirred thoroughly using a glass rod for 10 s after which pH of the suspensions were determined using a digital pH meter.