Cyanide removal from cassava wastewater onto H3PO4 activated periwinkle shell carbon

Abstract

The continuous generation of waste resulting from the industrial activities of humans has significantly been on the rise, especially liquid wastes emanating from cassava processing mills, which is a major cause for concern in developing countries. This study focused on the preparation of H3PO4 activated periwinkle carbon (APSC) and use in the removal of cyanide in cassava wastewater. The influence of variables such as pH, adsorbent dosage, contact time, and different cyanide concentrations was investigated in batch procedures. Results from the batch studies reveal a strong pH-dependent adsorption process with optimum cyanide removal occurring at pH 8. An equilibrium time of 80 min and adsorbent dosage of 3.0 g gave the highest percentage of cyanide adsorbed at 83.93%. The Pseudo-first-order, Pseudo-second-order, and Elovich kinetic models were used for the analysis of experimental data while equilibrium data analysis using Langmuir, Freundlich, and Redlich–Peterson was carried out to determine the best-fit isotherm model. The Coefficient of determination (r2), Sum of square error (SSE), and Chi-square (chi^{2}) were used to estimate the error deviations between the predicted and the experimental models using nonlinear regression analysis to determine models that best explain the adsorption process. Kinetic data fitted well to the Elovich and Pseudo-second-order kinetic model which implies chemisorption as the dominant adsorption process. The Redlich–Peterson and Langmuir model best describes the adsorption process suggesting mono-layer adsorption with the monolayer adsorption capacity of APSC found to be 2.856 mg.g−1.