Adsorption of heavy metals by agroforestry waste derived activated carbons applied to aqueous solutions

Abstract

Activated carbons prepared from macadamia nut shells, baobab shells, pigeon pea husks, rice husks, Moringa oleifera husks, and marula stones were investigated for their abilities to adsorb Pb(II), Zn(II), Cu(II), Ni(II), Fe(II), Mn(II), Hg(II), Cr(III), As(III) and Cd(II) from aqueous solutions. Batch adsorption experiments were conducted at pH values of 4, 5 and 6. Metal ion adsorption generally increased as the pH was increased from 4 to 6. Percentage adsorption values were above 60% for adsorption of Hg(II) by all the activated carbons at pH 6. The adsorption of Pb(II) by carbons from Baobab shells, pigeon pea husks, Moringa oleifera husks and Marula stones was at least 22% higher than that of the commercial carbons used for comparison. Carbons derived from pigeon pea husks and baobab shells showed better metal ion adsorption compared to the other carbons and were used to determine the effects of initial metal concentration, contact time and adsorbent quantity on metal adsorption. The metal ion adsorption data fitted the Langmuir adsorption model.

Keywords: Agroforestry, wastes, activated, carbon, adsorption, metals

African Journal of Biotechnology, Vol 13(14), 1579-1587