Efficient mercury sequestration from wastewaters using palm kernel and coconut shell derived biochars

Abstract

Elevated mercury (Hg) concentrations in water bodies caused by illegal artisanal gold mining in Ghana is a serious health concern given the toxicity of Hg. As an ecofriendly cost-effective solution for removing Hg from these water bodies, we synthesized biochars using palm kernel (PB) and coconut shells (CB), which are dominant biomass wastes in Ghana. The biochars were sulfurized (SPB, SCB) and fabricated into polysulfone-based beads for Hg(II) sorption. The Hg(II) concentration, contact time, sorbent mass, and solution pH were investigated and were found to be influential on the sorption of Hg(II) from aqueous solution. The sulfurized biochars showed a faster Hg(II) removal (within 1h) compared to the pristine biochars. Sorption tests conducted using natural riverine water samples confirmed the potential use of the biochars, with SPB and SCB showing higher efficiencies than pristine PB and CB. The fabricated beads exhibited 70–90% efficiency in Hg(II) removal from 1.0 mg L−1 Hg solution and the sorption capacity was below 0.1 mg g−1, which we attribute to the mass of biochar used for the beads. The Hg(II) sorption mechanisms of PB and CB from spectroscopic analyses suggest that the biochars synthesized in this study can be used to treat Hg polluted waters and suitable for large-scale applications in natural water bodies.