Modification of Coal Fly Ash with Dithizone for Adsorption of Ni(II) Metal Ion

Abstract

Adsorption of Ni(II) ion onto adsorbent of dithizone-immobilized coal fly ash (IFA) has been investigated in batch experiments. The activated coal fly ash (AFA) and its dithizone modification were characterized by FT-IR and XRD. Several parameters influencing the adsorption of Ni (II) ions on both adsorbents including effect of pH, adsorbent dosage, contact time and initial concentration on the efficiency of the adsorption of Ni (II) ion were investigated. The optimum condition of Ni(II) adsorption was found at pH 4, adsorbent dosage of 0.02 g, contact time of 60 min and initial Ni (II) ion concentration of 80 mg L–1. The adsorption kinetics of Ni(II) ions on AFA is best described by a pseudo first-order kinetic model while that on IFA follows a pseudo-second-order kinetic model. The adsorption isotherm of Ni(II) on both adsorbents follows the Langmuir model. Kinetics and adsorption isotherm studies suggest that the capacity and affinity of the IFA in adsorbing Ni(II) ions are significantly improved compared to those of AFA, suggesting the role of dithizone in the adsorption of Ni (II) by forming chelate complexation as proved by the results of sequential desorption.