The Kinetics and Thermodynamics studies of the biosorption of Chromium (III) ions from aqueous solution using groundnut husk

Abstract

The biosorption of Cr (III) ions from aqueous solutions by groundnut husk, a low-cost biosorbent was studied on a laboratory scale batch experiments. The effects of pH, contact time, particle size, biosorbent dosage and temperature on the adsorption of Cr (III) ions were investigated. Determination of Chromium ion concentration in solution was done using Atomic Absorption Spectrophotometer (AAS). The results show that the removal mechanism is predominantly by chemisorption and it is dependent on the physical and chemical characteristics of the biosorbent material. From the initial concentration of 0.5 mM, optimum Cr (III) ions removal was obtained at pH of 4, particle size of 0.15 nm, contact time of 180 minutes and biosorbent dosage of 50 mg, with the highest biosorption efficiency of 81.15 %. The biosorption process was best described by the BET adsorption isotherm with R2 value 0.9814 indicating multiplayer adsorption. Analysis of the experimental data revealed that the biosorption of Cr (III) ions from aqueous solution by groundnut husk is a spontaneous process with a ?Go value of -24.38 kJmol-1 at 298 K and follow the pseudo second order kinetics with a rate constant of 0.0151 min-1. The results indicate that groundnut husk can be employed as a low cost alternative to commercial adsorbents in the removal of Cr (III) ions from wastewater.