New porous adsorbents based on natural polymers for treatment of motor oil contaminated wastewaters

Abstract

This study aims to develop efficient adsorptive materials for retaining used 5w40 motor oil using xanthan (XG), xanthan esterified with acrylic acid (XGAC), Lignoboost lignin (LB), and LB esterified with oleic and stearic acids. The adsorption capacities of these materials were systematically evaluated, revealing a hierarchical efficacy with XG exhibiting the highest performance (60.16 g/g), followed by XGAC/LB (59.92 g/g) and XGAC (55.79 g/g). These capacities were correlated with the materials' surface area and morphology. Additionally, accelerated weathering studies assessed the degradation process of the adsorptive materials over time, revealing that all of them undergo significant structural changes, which suggests potential pathways for environmentally friendly disposal. Kinetic studies indicated that the experimental data fit well with the pseudo-second-order (PSO) model. The high correlation coefficient values for the PSO model (0.9318–0.9998) confirmed its suitability for describing the kinetics of oil sorption. FTIR spectra of the used motor oil-loaded materials confirmed the physical nature of the adsorption process, involving interactions such as hydrogen bonding, van der Waals forces, and π–π interactions. SEM analysis demonstrated that materials with larger pore sizes showed less efficient oil adsorption despite having high porosity, highlighting the importance of optimal pore size distribution for effective adsorption.