QUANTITATIVE ADSORPTON OF SELECTED HEAVY METALS FROM AQUEOUS SOLUTION USING LOCALLY AVAILABLE CLAY

Abstract

This study aims to examine the potential of natural,calcined and chemically modified clay soil from Ethiopia ,Oromia Region, West Hararghe Zone, Oda Bultum Woreda, Sakata Village as an effective adsorbent material for the removal of heavy metal ions (copper(Cu),lead (Pb) and nickel (Ni)) from aqueous solutions. The clay was mined, separated from dirt, washed; sun-dried and grinded and sieved to100 mm. The modification of the sized samples were done by two physico-chemical methods; thermal activation at temperature of 300°C and acid activation by hydrochloric acid at concentrations of 3 M. The modified and unmodified samples were characterized using Fourier transform infrared (FTIR) spectroscopy. Batch sorption was employed to determine the effect of pH, metal concentration, sorbent dose and contact time on the removal of Pb (II), Cu (II) and Ni (II) ions from solution by the adsorbents. Optimum operating conditions of pH 4.0 ( Cu(II) and Pb(II) )and pH 7.0 for Ni(II), metal ions concentration of 80 mg/l Pb(II) and 20 mg/l ( Cu(II) and Ni(II) ) , contact time of 120 min for Pb(II) and Cu(II) and 90 min for Ni(II) and adsorbent dose of 0.4 g for all adsorbent were obtained. The adsorption efficiency were found to be 96.01, 94.62 and 93.63 % of Pb(II), 98.96, 98.36 and 90.72 % of Cu(II) and 73.43, 73.43 and 65.17 % Ni(II), for acid activated, thermally activated and raw samples respectively. The equilibrium data were analyzed using Langmuir and Furdrich adsorption isotherms. Results of the equilibrium analysis showed that the adsorption of heavy metals onto acid modified, thermally activated and raw samples best fitted both Langmuir and Furdrich adsorption isotherm model. The kinetic data were analyzed using the pseudo-first order and pseudo-second order. The analysis revealed that the adsorption process followed pseudo second order model for all metal ions. Acid-modified clay showed a higher adsorption capacity than the calcined and unmodified ones for all metal ions. This study has confirmed the potential role of natural and modified clay in wastewater treatment processes as a cheap, environment-friendly and safe natural adsorbent material.