A comparative study of electrocoagulation and chitosan biosorption for the treatment of oil refinery wastewater

Abstract

Water quality is being impacted by the rapid expansion in industrialization, particularly in the oil and gas industry. Improper treatment of industrial wastewater exacerbates the problem. Chemical coagulation has been the most widely used technology in treating oily wastewater; nevertheless, electrocoagulation (EC) has been employed effectively to some extent, with different metals serving as electrodes. On the other hand, valorising seafood waste through bioconversion into biosorbents offers the promise of an environmentally benign wastewater treatment method. This study compares the performance of electrocoagulation using aluminium electrodes with that of adsorption using chitosan derived from oyster shells as the adsorbent. It aims to address effluent from refineries while also tackling waste beneficiation. Biosorbent characterization involved analyzing functional groups, which was confirmed using Fourier-Transform Infrared (FTIR) spectroscopy. The crystal structure, surface morphology, and elemental composition of the produced chitosan were examined using Scanning Electron Microscopy (SEM) combined with Energy-Dispersive X-ray (EDX) analysis, respectively. The adsorption process study was conducted through the use of empirical adsorption models. The Langmuir isotherm was shown to have the greatest fit for equilibrium data, whereas the pseudo 2nd order model provided the best fit for kinetic data. When removing Chemical Oxygen Demand (COD), colour, and phenols, the biosorbent chitosan achieved removal rates of 88.2%, 87.5%, and 88.9%, respectively. The optimal conditions were found to be at the dosage of 15 g, a reaction time of 90 minutes, a speed of 250 rpm, and a settling time of 15 minutes. Double-blade aluminium electrodes have proven to be highly effective for the electrocoagulation process, achieving reductions of 91.41% in COD, 96.77% in colour, and 94.53% in phenols. This performance was attained by maintaining a configuration with double-blade electrodes, an electrolysis time of 80 minutes, and a magnetic stirrer speed of 250 rpm, resulting in excellent electrocoagulation results. The results of this research showed that the EC is the fastest and best technique, although the performance of the biosorbent chitosan is good and should be further evaluated.