166-Reduction of Cr (VI) in Electroplating Wastewater and Investigation on the Sorptive Removal by WBAP.

Abstract

Chromium (VI) that exists in many industrial wastewaters is considered highly toxic. The aim of the present investigation was to study the reduction of Cr (VI) to Cr (III) and then removing it with the help of Weathered Basalt Andesite Products (WBAP). Reduction of the Cr (VI) to Cr (III) by Hydrazinium Sulfate (HS) was investigated. The influence of hydronium ion concentration, contact time, HS dosage, and temperature has been tested in batch runs. The process was found to be acid, temperature and concentration dependent. The suitability of WBAP as a potential sorbent was assessed for the removal of Cr (III) following batch mode of operation. The effect of various parameters such as hydroniuni ion concentration, shaking time, sorbent dose, initial metal ion concentration, and temperature on the removal of Cr (III) from aqueous solution was studied. Thermodynamic parameters (AH°, AS°, and AG°) for the sorption process were evaluated. Analysis of sorption results obtained showed that the sorption pattern followed the Freundlich, Langmuir, and DubininKaganer-Radushkevich isotherms. The process follows Pseudo second order rate and surface diffusion is identified as the predominating mechanism. The sorption process was shown to be reversible by the recovery of sorbed Cr (III) upon extraction with 0.5 M HNO3. The sorbent before and after sorption, was characterized by FTIR, X-ray diffraction, SEM, TEM, and TGA methods. An increase in crystallanity after sorption of chromium was observed. An industrial effluent was successfully treated with the same sorbent.