Performance Evaluation of Fixed Bed of Nano Calcium Oxide Synthesized from a Gastropod Shell (Achatina achatind) in Hexavalent Chromium Abstraction from Aqua System

摘要

The shell of a gastropod (Achatina Achatina) was used as a precursor for the synthesis of nano calcium oxide (NC) via the sol-gel technique. The NC was characterized and the performance evaluation in chromium (Cr) (VI) abstraction was assessed in a fixed bed. The operating characteristics of the NC-Cr (VI) system were analysed with the mass transfer model and the mass transfer zone parameters were found to fluctuate with changes in the initial Cr (VI) concentration. The evaluation of the equilibrium data, generated from the fixed bed studies, showed that the sorption of Cr (VI) occurred via monolayer adsorption mechanism, and the monolayer sorption capacity was 833.33 mg/g. Different kinetic models (i.e., Adams-Bohart, Thomas, Wolborska, and Yoon-Nelson models) were applied to experimental data to predict the breakthrough curves and to determine the parameters of the column useful for process design. The kinetic analysis showed that the Yoon and Nelson model had the best fitting of the experimental data. The data obtained for Cr (VI) removal, when the NC bed height was optimized, were well described by bed depth service time model.