Adsorption of chromium by brewers spent grain -g- poly (acrylic acid-co-acryl amide) from electroplating effluent

Abstract

Toxic metal ions have lethal effects on all forms of life and these metal ions could enter the food chain when untreated waste effluents are discharged into the environment. In recent years, the use of low-cost adsorbent materials has been widely investigated in search of replacement for the costly methods that are currently used for removing these toxic metal ions from waste streams. In this study, the remediation of chromium ions from electroplating effluent was studied under static conditions using a copolymer material that was derived by grafting polyacrylic acid and polyacrylamide onto the cellulosic backbone of brewers spent grain (BSG). Batch experiments were carried-out using effluents with different concentrations of chromium ions, specifically 25, 50, 75, 100 and 125 mg/L. The results revealed that the optimum sorption of chromium occurs at pH 3.0 and absorbent-adsorbate contact time of 1.5 h gave maximum adsorption regardless of the metal ion concentration in the effluent. The kinetic data fit the pseudo-second order reaction model, suggesting that chemosorption was the rate limiting step for the sorption of chromium ions onto BSG-g-poly (acrylic acid –co- acryl amide). The isotherm studies showed that the Langmuir model gave the best fit to the experimental data, with qmax value of 15.58 mg/g after 5 h of effluent contact with the absorbent material. The results obtained in this study have shown that BSG-g- poly (acrylic acid –co- acryl amide) has a lot of potentials for application as an alternative adsorbent material for the remediation of chromium ions from electroplating waste streams. Key words: Adsorption, chromium, electroplating, effluent, brewers spent grain, studies.