Biosorption Studies of Cr(VI) Ions from Electroplating Wastewater by Walnut Shell Powder

Abstract

Biosorption of Cr(VI) ions from aqueous solutions and electroplating wastewater by walnut shell powder has been investigated in a batch biosorption process. The biosorption of Cr(VI) ions was found to be dependent pH, initial chromiu m ion concentrations, biosorbent dose, contact time and temperature. The experimental equilib riu m biosorption data were analy zed by Lang muir, Freundlich, and Temkin isotherm models. The Lang muir model gave a better fit than the Freundlich and Temkin models. The maximu m biosorption capacity calculated from the Langmu ir isotherm was 138.89 mg/g at optimu m conditions. The kinetic studies indicated that the biosorption process of the chromiu m ions fo llo wed well pseudo-second-order model. The negative values of ∆G o (-3.51 kJ/ mo l) and positive value of ∆H o (12.95 kJ/ mol) revealed that the biosorption process was spontaneous and endothermic. Biosorption process was successfully applied to the treatment of an electroplating wastewater sample, where the concentration of chro miu m (VI) ions, organic materials and COD were effectively reduced. According to the sorption capacity, walnut shell powder considered as an effective, low cost, and environmentally friendly biosorbent for the removal of Cr(VI) ions fro m aqueous solution and electroplating wastewater.