Application of cassava peels activated carbon in the treatment of oil refinery wastewater - A comparative analysis

Abstract

A comparative analysis of the efficiency of activated carbon produced from fermented cassava peels (CPB), unfermented cassava peels (CPA) and commercial grade activated carbon (CAC) in the treatment of refinery wastewater was carried out. CPB was found to be 8% and 18% more efficient when compared to CPA and CAC in the removal of COD, and 14% and 3% better than CAC and CPA respectively in the removal of BOD5. The removal efficiency of Pb2+ by CPB was 100% compared to 95% and 57% by CPA and CAC while 96% of phenol was removed by CPB against 93% and 83% by CPA and CAC respectively. This better performance of CPB over CPA and CAC is not unconnected with its higher pH resulting from the removal of cyanide from the peels during the fermentation process. However, despite the high phenol removal efficiency by CPB, the concentration of phenol in the treated effluent does not meet the environmental guidelines for disposal. It is therefore, recommended that a two-stage CPB adsorption column arranged in series is necessary to treat refinery wastewater efficiently if it is desired to totally remove phenol from the effluent or reduce the concentration to 0.005 mg/l allowed by the Federal environmental protection agency (FEPA). The equilibrium adsorption test conducted showed that the Freundlich isotherm is a better fit for the adsorption of phenol by the three activated carbons with correlation coefficients (R2) of 0.9364, 0.9383 and 0.9541 for CAC, CPA and CPB respectively. CPB was found to be a better adsorbent as it has the highest adsorptive capacity as evidenced from its better Freundlich exponent.