Elemental composition of the extracted leachate was analyzed to deduce the concentration of Al and Fe which are necessary for the coagulation process. Table 2 shows concentrations of Al and Fe of filtered leachate in mg/L measured by AAS. Al concentration was higher in the range of 9.7–35.7 mg/g of WTS compared to 3.1–5.4 mg/g of WTS for Fe. As aforementioned, this is because the sludge used was collected from a processing plant that uses an Al-based coagulant which will inherently increase the Al content of the sludge. Since a high concentration of reactants increases the rate of a chemical reaction (Sodiqovna 2020), high Al concentration in WTS resulted in its high rate of extraction compared to Fe which was at a lower concentration.
Al and Fe concentrations in leachate
| . | Al Conc. (mg/g of WTS) . | Fe Conc. (mg/g of WTS) . | ||||
|---|---|---|---|---|---|---|
| Solid loading (g/100 mL H2SO4) . | 3 . | 5 . | 10 . | 3 . | 5 . | 10 . |
| H2SO4 Conc. (N) | ||||||
| 2 | 34.0 (1,019) | 26.8 (1,339) | 14.0 (1,402) | 5.0 (148.7) | 3.9 (194.4) | 3.1 (312.6) |
| 2.5 | 35.5 (1,066) | 28.1 (1,404) | 9.7 (971) | 5.4 (161.0) | 3.8 (189.1) | 3.2 (316.9) |
| 3 | 35.4 (1,063) | 35.7 (1,785) | 12.2 (1,215) | 4.7 (142.4) | 4.5 (224.8) | 3.1 (314.3) |
| . | Al Conc. (mg/g of WTS) . | Fe Conc. (mg/g of WTS) . | ||||
|---|---|---|---|---|---|---|
| Solid loading (g/100 mL H2SO4) . | 3 . | 5 . | 10 . | 3 . | 5 . | 10 . |
| H2SO4 Conc. (N) | ||||||
| 2 | 34.0 (1,019) | 26.8 (1,339) | 14.0 (1,402) | 5.0 (148.7) | 3.9 (194.4) | 3.1 (312.6) |
| 2.5 | 35.5 (1,066) | 28.1 (1,404) | 9.7 (971) | 5.4 (161.0) | 3.8 (189.1) | 3.2 (316.9) |
| 3 | 35.4 (1,063) | 35.7 (1,785) | 12.2 (1,215) | 4.7 (142.4) | 4.5 (224.8) | 3.1 (314.3) |
Note: Actual solution concentrations (mg/L) are indicated in brackets. Figures in bold represent the aluminum and iron concentrations of the chosen coagulant.