## 3 Results
### Simultaneous Sorption of Heavy Metals  
Heavy metals spiked simultaneously in the contaminant solution were tested for understanding their sorption behavior. Figure 3 shows variation of sorption coefficient of Cd + Ni and Ni + Pb for different initial concentrations. Similar graphs for Pb + Cd and Ni + Cd + Pb are given in the Supplementary Material (Figure S3). It can be observed from the Figure 3 that simultaneous sorption of heavy metals on raw soils was comparatively less than that for the treated soil and maximum sorption of heavy metals were found taking place on soil treated with E2. Sorption of Cd dominated Ni in raw soil, that is 2.0968 mg/g of Cd and 1.8862 mg/g of Ni was sorbed on the raw red soil sample and the solution pH was 6.21 whereas 4.8215 mg/g and 4.3166 mg/g Cd and Ni respectively were sorbed on red soil treated by E2 while the pH was 7.11 both the results shown here are of initial concentration of 100 mg/L. Sorption coefficients of Cd and Ni for raw black soil were 2.4861 mg/g and 2.4689 mg/g (pH 5.91) respectively and after treatment with E2 sorption increased to 6.8419 mg/g and 5.4178 mg/g (pH 6.14) respectively. Figure 3a,b shows the variation of sorption coefficients for different initial concentrations  
Figure 2: Sorption coefficients at different dilution ratios for (**a**) for Cd and (**b**) for Ni. for the soil samples treated with E1, E2 and E3 and spiked with Cd + Ni and Ni + Pb respectively, similar graphs for Pb + Cd and Ni + Cd + Pb are shown in Supplementary Materials (Figure S3a,b). Pb adsorption in Figure 3b along Ni is plotted for varying initial concentrations, simultaneous sorption of Ni + Pb on soils also depicted appreciable results after treatment, initially sorption of Ni and Pb were 1.6325 mg/g and 1.2088 mg/g for raw red soil and for black soil 2.8631 mg/g and 2.5611 mg/g respectively at 100 mg/L initial concentration, solution pH for raw red and black soils were 5.86 and 5.37 respectively. Sorption coefficient at initial concentration of 100 mg/L for soils treated with E2 were 3.8288 mg/g (Ni) and 4.2109 mg/g (Pb) for red soil and 6.8241 mg/g (Ni) and 5.8057 mg/g (Pb), while the pH values of the contaminant solutions were to 6.33 and 6.21 respectively for red soil and black soil. Sorption coefficients for different dilution ratios are plotted in Figure 4 simultaneous sorption of Cd and Ni showed sorption coefficient of 3.7145 mg/g for Cd and that for Ni was 3.5014 mg/g for raw red soil (pH 6.64), whereas sorption of Cd was 5.2036 mg/g and for Ni it was 5.2910 mg/g for raw black soil (pH 6.83), at dilution ratio of 1:100. Sorption of Cd and Ni improved for both soils after treatment \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Heavy Metal**} & \multirow{2}{*}{**Soil**} & \multirow{2}{*}{**Sorption**} & \multirow{2}{*}{\(\pm\)**SD**} & \multirow{2}{*}{\(\pm\)**SD**} & \multirow{2}{*}{\(\pm\)**SD**} \\  & & & & **Raw Soil** & & **E2 Treatment** \\ \hline \multirow{4}{*}{Initial concentration (100 mg/L)} & \multirow{2}{*}{Cd} & Red Soil & 1.3520 & & 5.4236 & \\ \cline{3-6}  & & Black Soil & 2.4524 & & 5.8519 & \\ \cline{3-6}  & & Red Soil & 1.5131 & & 7.0838 & 0.8893 \\ \cline{3-6}  & & Black Soil & 1.8754 & & 7.6874 & \\ \cline{3-6}  & & Red Soil & 1.5476 & & 5.6925 & \\ \cline{3-6}  & & Black Soil & 1.8140 & & 6.6741 & \\ \hline \multirow{4}{*}{Dilution Ratio (1:100)} & \multirow{2}{*}{Cd} & Red Soil & 3.3564 & & 6.5830 & \\ \cline{3-6}  & & Black Soil & 4.7110 & & 6.6487 & \\ \cline{3-6}  & & Red Soil & 3.5297 & 1.3352 & 10.0817 & 3.1039 \\ \cline{3-6}  & & Black Soil & 6.7370 & & 15.0400 & \\ \cline{3-6}  & & Red Soil & 3.6910 & & 8.7716 & \\ \cline{3-6}  & & Black Soil & 5.5038 & & 9.4015 & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Sorption coefficients of untreated soils and treated with E2 with corresponding SD values. Figure 3: Sorption coefficient of heavy metals spiked simultaneously for different initial concentrations, (**a**) combination of Cd + Ni (**b**) combination of Ni + Pb.