Optimization of cyanide adsorption from cassava wastewater using phosphoric acid-functionalized activated carbons derived from livestock keratin waste via in-situ and ex-situ activation routes

This study introduces cow hoof as a novel biomass for producing activated carbon aimed at cyanide removal from cassava wastewater. It uniquely evaluates how in-situ and ex-situ activation methods impact the cyanide adsorption capacity of the synthesized activated carbons. The effects of impregnation ratio, carbonization temperature, and carbonization time on the cyanide adsorption capacity of cow hoof-derived activated carbons (ACs) produced via these activation methods were investigated using Response Surface Methodology (RSM). Functional and morphological characterizations revealed that both ACs possess highly porous surfaces with well-developed adsorption-active functional groups. The high correlation coefficients of the derived models (R² of 0.9681 for in-situ and 0.9961 for ex-situ activation) demonstrate the models' accuracy in predicting the activation process. Optimization results indicated that the in-situ-derived AC achieved a maximum cyanide adsorption capacity of 92.67% at an impregnation ratio of 1.676 g/g, a carbonization temperature of 707 °C, and a carbonization time of 175 minutes. The ex-situ-derived AC achieved a comparable adsorption capacity of 93.12% at an impregnation ratio of 1.526 g/g, an activation temperature of 655 °C, and an activation time of 162 minutes. Given the marginal difference in adsorption capacities, both activation methods are effective, but the ex-situ activation method is preferable as it produced AC with comparable cyanide adsorption capacity while requiring a shorter activation time and lower activation temperature than the in-situ method. This results in reduced energy consumption and faster processing, making the ex-situ method a more efficient and cost-effective option for producing high-performance activated carbon for cyanide removal.