Removal Of Chromium (Vi) From Aqueous Solution Using Natural Bentonite From Ledi Area, Afar Region, Ethiopia

Abstract

In this study natural bentonite obtained from Ledi area, Affar regional state was investigated as adsorbent for removal of Cr (VI) from aqueous solution since. It was readily available, reusable and cost effective. 100g of bentonite weighted, dried in oven at 120 0c for 4 hours, cooled, crushed and ground. It was characterized by XRD and AAS for complete silicate analysis. The study was employed with 250µm particle size and by varying working parameters such as pH (1, 3, 5), adsorbent dose (1g, 2 g, 3 g, 4 g), initial concentration (20 (mg/L), 40 (mg/L), 60 (mg/L), 80 (mg/L), 90 (mg/L), 120 (mg/L), 150 (mg/L), 180 (mg/L)and contact time (30 min, 60 min, 90 min , 150 min, 180 min) have been studied at room temperature. Adsorbent efficiency was Optimum at pH = 3, dose 1g, initial concentration 60 (mg/L) and contact time 120min were obtained. To determine adsorption effiecy Ledi area bentonite real sample was adjusted at optimized working parameters. The mechanism and characteristics of parameters adsorption were analyzed by six different isotherm models. Temkin adsorption isotherm fit experimental data. From Langmuir model it was identified that adsorption was favorable, from freundlich model adsorption was normal and from D- R isotherm adsorption is physical. The maximum adsorption was found to be 1.94 (mg/g) and kinetic adsorption process was studied by pseudo first, pseudo second, intraparticle diffusion and Elovich equations. The result showed pseudo first order fit experimental result and it reveals as adsorption is physical. The result of thermodynamic parameter shows that adsorption is feasible since ∆G0 is negative. The concentration of chromium discharged to Mojo River from Hora tannery was 305.6 (mg/L). The efficiency of bentonite to remove Cr (VI) from real sample was examined at optimized condition 0.049 mg/L. It was identified that adsorption efficiency of Ledi area bentonite is low.