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 beakers, 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 mins 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 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. HIGHLIGHTS Study utilises waste material.; Treatment conducted without pH adjustment.; Study removes total pollutants.; Study utilises unprocessed reagents.; Study utilises synthetic CaMg.2(OH)2 coagulant.;

Keywords

• amd
• dosage
• flocculent
• mixed
• ph
• settled