This work has been carried out to check the ability of three biowastes, viz. corn cob ash (CCA), mango stone ash (MSA) and orange peel powder (OPP), to remove Ni(II) ions from aqueous solution. The surface environment of the adsorbents was characterized by Fourier transformation infrared spectroscopy and scanning electron microscopy (SEM) analysis which showed that these adsorbents contain favorable organic groups, such as, amido, amino, hydroxyls, carboxyl groups, etc., on their surface and have uniform characteristics in their surface morphology. The particle sizes for the three screened biowastes were found to be in the range of 1.5–4, 0.7–4.5 and 15–35 μm for CCA, MSA and OPP, respectively, as revealed by SEM. The effect of different system variables, viz. adsorbent dose, initial metal ion concentration and pH, were studied. Both Langmuir and Freundlich adsorption models were suitable for describing the sorption of Ni(II) on all three adsorbents used. The maximum sorption capacities of CCA, OPP and MSA used in this study were 107.4, 14.0, and 26.6 mg/g, respectively, for Ni(II) ions at optimum adsorbent dose.
Keywords: adsorption, biowastes, Ni(II)