Removal of Hexavalent Chromium from Synthetic and Armament Engineering Industry Waste Water by Using Activated Carbon-Graphene Oxide Composite

Abstract

Nowadays, developing cost effective, and non-hazardous materials for the removal of toxic heavy metals discharged from industrial wastewater is one of the major challenging problem of the world particularly, developing countries. Among the different toxic heavy metals, Hexavalent chromium (Cr (VI)) is one of the most known toxic heavy metal and serious environmental concerns due to its long persistence in the environment and highly deadly nature in living organisms discharged from electroplating process, painting, tannery, and metal work industries. Hence, this study mainly focuses on the synthesis of activated carbon from corncob, sawdust and bamboo, and activated carbon-graphene oxide composite (BAC/GO) for the application of Cr (VI) adsorption. The most effective AC was synthesized from bamboo. Furthermore, the bamboo activated carbon combined with electrochemically exfoliated graphene oxide was synthesized to increase the adsorption efficiency of activated carbon prepared from bamboo. The synthesized materials were characterized using different techniques i.e. UV-Vis spectrophotometer, FTIR, XRD, TGA, DLS, BET, and SEM- EDX. The results confirmed that the developed activated carbon and composite successfully synthesized. From the single effect study the highest adsorption efficiency of bamboo activated carbon was 99.18% at the optimum process conditions of adsorption factors. Additionally, the kinetics of the adsorption was well-fitted to pseudo-second order (R2 =0.9998) and the corresponding rate constants were obtained. The isotherm of adsorption of corncob activated carbon, sawdust activated carbon, bamboo activated carbon, and BAC/GO composite was well-fitted to freundlich isotherm (R2 = 0.9835, 0.9733, 0.9634, and 0.9755, respectively) than Langmuir isotherm. The developed model‟s validation and interaction effects between process parameters were investigated by Box Behnken Design and the maximum Cr (VI) adsorption efficiency (99.34%) was attained at PH (2), adsorbent dose (2.5mg/L), initial Cr (VI) ion concentration (12.5mg/L), and contact time (90 min). Also at this optimum operating conditions the adsorption efficiency of corncob activated carbon, sawdust activated carbon and bamboo activated carbon were examined and the obtained result was (90.5%, 94.8%, and 98.95%), respectively. Moreover, the Cr (VI) adsorption efficiency of BAC/GO composite was investigated using real Armament engineering industrial wastewater and the obtained adsorption efficiency was (99.85 %). Generally, this study demonstrates that the developed BAC/GO composite was synthesized from waste and it has excellent adsorption capacity, easy to prepare and use, cost effective and non-hazardous than corncob activated carbon, sawdust activated carbon and bamboo activated carbon.