The removal of turbidity and toxic metals in the AMD using a combination of saw dust, bentonite clay and synthetic CaMg.2(OH)2

Abstract

Sets of experiments were conducted using 200 mL of synthetic acid mine drainage(AMD) into five 500 mL glass beaker, dosed with varying quantities of bentonite clay, saw dust and CaMg.2(OH)2 respectively and as a flocculent (bentonite clay, saw dust and CaMg.2(OH)2), mixed at 250 and 100 rpm for 2 and 10 mns respectively. The samples settled for 1 hour after which the pH, conductivity, turbidity, dissolved oxygen, oxidation reduction potential and toxic metals were measured. The turbidity removal of treated AMD samples treated with a flocculent (0–23 NTU) is lower compared to that of the samples treated with bentonite clay and saw dust (27–32 NTU). Results show 100% removal of Ni, moderate percentage removal of Fe and slightly lower percentage of Cu in treated AMD using a flocculent. Turbidity removal in treated AMD using a flocculent is higher compared to that of the samples treated with bentonite clay, saw dust or CaMg.2(OH)2. Treated AMD using flocculent has low Ca, Mg, Cl− and SO42− content (>84.8%). The SEM micrograph of the sludge of the sample with a combination of 1.5 bentonite clay, 1.5 g saw dust and 20 mL 0.025 M CaMg.2(OH)2 dosage shows optimal sorption of turbid materials.

Efficiency of a flocculent consisting of bentonite clay and fly ash for the removal of pollutants in AMD

“…Figures 2 and 3 represent adsorption isotherm applying Langmuir and Freundlich models for Cu, Zn, Co and Pb respectively. Based on the limited graphs required, it was decided to represent those four toxic metals as they are classified as some of the metals which are toxic to aquatic life (Ntwampe 2021b). Adsorption behaviour of flocculent-C using Langmuir model could also not be predicted due to the lack of fitness the experimental data, and that was substantiated by low R 2 for Cu, Zn, Co and Pb (i.e.…”