Ling, Joanne Soon Ning (2023) Comparative study of virgin and acid washed activated carbons for adsorption treatment of textile wastewater. Final Year Project, UTAR.
Abstract
The production of textiles produces large volume of wastewater containing dyes, salts and heavy metals. The wastewater requires treatment before it can be recycled or discharged to any receiving water bodies. Adsorption is one of the commonly used methods to treat textile wastewater. It involves the binding of adsorbates that are present in the solution to the surface of the adsorbent used. In this study, the effectiveness of using virgin and acid washed activated carbons for adsorption to treat textile wastewater was investigated and compared. Four commercial activated carbons (ACs) include virgin coconut shell granular activated carbon (GAC), acid washed coconut shell GAC, virgin palm kernel shell GAC and acid washed palm kernel shell GAC were used as the adsorbents. Their surface morphologies were analysed using scanning electron microscopy (SEM). From the SEM images, it was observed that the virgin ACs had more porous structures while acid washed ACs showed collapsed structures with little pores. Following that, real textile wastewater was used to carry out batch adsorption to investigate the effect of retention time (20, 40, 60, 80, 100, 120 minutes) and pH (6, 7, 8, 9) on the removal efficiency of COD, colour, hardness, conductivity and turbidity. From the batch adsorption experiments, the removal performances of acid washed ACs were slightly better than that of virgin ACs. However, since virgin ACs were more economical than acid washed ACs, virgin ACs were selected for further adsorption study on the effect of pH. Overall, the optimum retention time and pH were 60 minutes and pH 7, respectively. Based on the effect of pH experiment, virgin coconut shell AC showed better colour removal efficiency than virgin palm kernel shell AC. Therefore, virgin coconut shell AC was used to carry out breakpoint analysis in a continuous system. A breakthrough time of 230 minutes was obtained. Lastly, a final set of batch experiment using both virgin ACs to treat two different textile wastewater samples was carried out, followed by a complete water quality test. In short, this study concludes that adsorption using commercial ACs made of virgin palm kernel shell and virgin coconut shell is feasible to treat textile wastewater.
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