(122b) Effective Decolorization of Wastewater By Chemically Activated Biochar

Water is the most valuable gift from nature on the earth for sustaining our healthy life. However, the modernization of industries caused significant environmental damage, mainly through the discharge of industrial wastewater, which severely affected the water resource and its purity. The textile industries are identified as the most significant polluting source that continuously harms the environment out of all the industrial sectors. As consumer demand escalates for textile products, the textile industries and associated wastewater have increased proportionally. Each year, the global yield of about 0.7 million tons of dye in 10,000 different variations, and 2-50% of that are dumped as untreated polluted water. This dye contained waste effluent through industrial application discharged into the environment, which has a negative impact on flora, fauna, and human beings. It involves a decrease in sunlight penetration on the water surface, which interrupt the photosynthesis activity of aquatic plants. Furthermore, it is also responsible for various issues, such as cancer, genetic mutation, nausea, vomiting, and many more. In particular, Malachite Green (MG), a typical cationic dye, has been widely utilized in industries for dyeing silk, cotton, wool, leather, paper, and jute. It is also used in fish farming to cure fungal and bacterial infections. However, the residual dyes present in the effluent, even in small amount, can harm the ecosystem and causes health risks to society. MG affects the reproductive system and immunity due to its properties of genotoxicity and carcinogenic. Various techniques have been adopted to address these problems and eliminate the harmful effects. These include solvent extraction, co-precipitation, flocculation, ion exchange, adsorption, and membrane separation. Different studies from past decades have indicated that the adsorption process is one of the most effective techniques to treat dye molecules from polluted water due to its simple operation with higher removal efficacy, availability of the adsorbent, and cost-effectiveness. This study aimed to synthesize the bio-adsorbent for MG dye treatment. For the fabrication of the adsorbent, carpentry waste sawdust was employed as carbonaceous material, and for chemical activation, ZnCl₂ was utilized. Several analytical techniques were employed to study the physicochemical characteristics (i.e., XRD, FTIR, and FESEM/EDX). Moreover, a batch-scale decolorization experiment was carried out to study the effect of initial pH, adsorbent amount, and interaction time. The maximum removal of MG dye (99.03%) was achieved at a pH of 9.5. The experimental adsorption kinetic data of MG dye followed the pseudo-second-order model. Furthermore, the dye removal efficiency of the adsorbent was 80.86% obtained at its pH, which was increased by 1.5 times after chemical activation. Overall, these results implied the adsorption potential for successful uptake of effluent from textile industries where the released dye is of similar electropositive nature as that of MG dye.