Photocatalytic Degradation of Crude Oil-Contaminated Water Using Rice Husk-Supported Titanium Dioxide Nanocomposite

Abstract

Oil spills constitute one of the most devastating forms of environmental pollution, causing profound and long-lasting damage to ecosystems and aquatic life. This issue is particularly acute in oil-producing regions such as Rivers State, Nigeria, where frequent incidents pose significant challenges to environmental management, underscoring the urgent need for effective, affordable, and sustainable remediation strategies. Among various sorbents, agricultural wastes have gained prominence for oil spill cleanup owing to their biodegradability, low cost, and abundant availability. This study investigates the batch photocatalytic degradation of crude oil-contaminated water using acid-modified biochar derived from rice husk and loaded with titanium dioxide (TiO₂). The morphological and chemical modifications significantly enhanced the adsorbent's hydrophobicity and porosity, thereby improving its affinity for oil adsorption, as confirmed by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analyses. These techniques revealed the presence of key functional groups, including O–H bonds, carboxylic OH, C=O in aldehydes, and Si–O–Si in siloxanes, along with favorable crystalline structures. Parametric studies, optimized via Box-Behnken design, identified the highest removal efficiency of 97.85% under conditions of 5 mg/L TiO₂ loading, pH 6, and 90 minutes residence time. Removal efficiency increased with higher adsorbent dosage and contact time/illumination duration, while decreasing with higher initial oil concentration and pH. Experimental data exhibited excellent fit to the Langmuir isotherm model and pseudo-second-order kinetics, indicating monolayer adsorption on homogeneous surfaces. Comparative evaluation with other agro-based adsorbents underscored the superior performance of the TiO₂-loaded modified rice husk biochar. The material demonstrates exceptional potential as a low-cost, regenerable, and eco-friendly adsorbent for effective oil spill remediation, offering a sustainable solution aligned with circular economy principles through valorization of agricultural waste.