Removal of Cd2+, Cr3+, Cu2+, Hg2+, Pb2+ and Zn2+ cations and AsO4(3-) anions from aqueous solutions by mixed clay from Tundulu in Malawi and characterisation of the clay

Abstract

Water and wastewater studies in Malawi have revealed very high levels of heavy metals in most streams and other water bodies particularly within urban areas. The metals are produced and released during industrial and agricultural activities, and also in vehicular emissions. These metals may pose serious threats to both human health and the environment. This study investigated the potential of mixed clay, obtained from the Tundulu area, in removing, Cd 2+, Cr3+, Cu2+, Hg2+, Pb2+ and Zn 2+ cations and AsO 43-anions from aqueous solutions using batch equilibrium technique. Qualitative mineralogical characterisa tion of the clay revealed that the clay contains illite, distorted kaolinite, mixed layer minerals and non-clay mineral carbonate fluoroapatite. pH pzc for the raw clay, as determined by potentiometric titrations, was 9.66 while pH pzc of pretreated clay was 9.63. Pretreatment of the clay involved removal of carbonates, iron oxides and organic matter. Initial total metal concentra tions ranged from 3 to 5 mg/ℓ.

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