Comparison of FeCl3 and leucaena seeds FeCl3 extract coagulation performance to treat synthetic Congo red wastewater

Abstract

In this study we compared utilization of FeCl3 extracted leucaena protein and FeCl3 to treat synthetic Congo red wastewater. The extraction was done at leucaena seeds kernel to 0.5 M FeCl3 solution ratio 1:20 with various initial extraction pH (2 to 9). It was observed that pH 2 gave the highest protein concentration of 1.7 mg eq BSA/mL, compared to other pH. The extract obtained at this condition was further used in the coagulation study. At various initial coagulation pH (2 to 10), the highest Congo red removal was observed at initial coagulation pH 6. This result indicated that FeCl3 was the active coagulating agent despite of the presence of leucaena extract, with charge neutralization coagulation mechanism. Variation of coagulant dosage was done from 4 to 44 mL/L. At dosage 4 to 12 mL/L, low color removal was observed due to insufficient coagulant to neutralize Congo red molecules. Over addition of coagulant also lowered the coagulation efficient, and increased the sludge volume due to colloid re-stabilization phenomenon. The best Congo red removal was observed at coagulant dosage 20mL/L FeCl3 – leucaena extract combination with color removal of 95% with 9 mL/L sludge volume, slightly higher compared to FeCl3 only. Based on this result, it could be concluded that FeCl3 could act effectively as coagulant without the presence of leucaena extract.