Sequestration of Heavy Metals From Coal Wash Water Using Biochar From Pyrolysis of Morula Shells

Abstract

Biomass is a source of low-cost adsorbents used in the removal of contaminants. In this study, shells from an indigenous tree in Southern Africa called Morula were pyrolyzed to produce biochar that was used to sequester heavy metals from coal wash water. The produced biochar was activated using hydrochloric acid (HCl) and parameters such as the cation exchange capacity (CEC), point of zero charge (pHzc), elemental composition, mineral composition, proximate analysis and surface functional groups were determined. Batch adsorption experiments were carried out at 150 rpm for 60 min and 25 ºC at different metal ion concentrations and adsorbent dosages. The metal ions of interest were Zn, Ni and Fe and it was found that Fe recorded higher removals for both raw and activated biochar. Generally higher removals were noticed for both raw and activated at lower dosages (0.2 – 1.0 g/100 mL) and lower metal ion concentration (between 40 and 60 ppm) while lower removals were found at higher dosages (1 – 5 g/100 mL) and higher metal ion concentrations (between 400 – 600 ppm).