Azo Dye Removal from Aqueous Solution by Powder Graphite: Investigation of Parameter Effects and Optimization by Box-Behnken Design

Abstract

Industrial wastewaters containing dyes comprise organics that are difficult to biodegrade and when they are discharged to receiving bodies, they cause serious impacts on environment. Therefore, this wastewater requires advanced treatment besides conventional ones. Adsorption is accepted one of the favorable processes, which can be applied integrative to conventional systems during the treatment of this wastewater. In addition to the effectiveness of the materials to be utilized in the adsorption process, their cost and availability are also very important factors. In this study, the efficiency of environmentally friendly, cost-effective powdered graphite was investigated in the removal of diazo type dye (Direct Red 243) from aqueous solution by adsorption. For this purpose, Response Surface Method was applied via Box-Behnken Design and the most effective parameters were investigated in dye adsorption with graphite. Also, the morphology of the graphite before and after adsorption was scanned by Scanning Electron Microscopy. Adsorption study was carried out in batch mode and pH (2-10), adsorbent amount (0.1-1.5 g) and time (15-65 min) were designated as experimental parameters. It has been observed that the most effective parameter in color removal of dye was pH and at low values of this parameters the higher efficiencies were obtained. Additionally, it was observed that the increase in the amount of adsorbent increased the efficiency, and time had no significant effect besides two parameters. Almost complete decolorization (98%) was acquired at pH 2 with 1.5 g adsorbent for 40 min of study. As a result of the study, even it is not improved with further applications, graphite can be effective for anionic dye color removal under acidic conditions by its pristine form.