Modeling and Optimization of Oil Adsorption from Wastewater Using an Amorphous Carbon Thin Film Fabricated from Wood Sawdust Waste Modified with Palmitic Acid

Abstract

Economic, reusable and renewable adsorbents are prepared by surface functionalization of wood sawdust (WD) based amorphous carbon thin film (ACTF) using long-chain palmitic fatty acid (PAC). The prepared adsorbents were characterized by FTIR, HR-TEM, SEM, and N2 physisorption (BET) techniques. The WD-PAC and ACTF-PAC materials reflect a good gasoline and condensate oil adsorption capacity (q e , mg.g−1) from wastewater with high kinetics rates within 2–4 h contact time. Kinetic adsorption was found to behave as a pseudo-second kinetic model and controlled by a diffusion mechanism with an exothermic nature. The initial oil adsorption rates, h O (mg.g−1.h−1) for gasoline and condensate oil were 72.5–109.9 mg.g−1.h−1 and 322.6–384.6 mg.g−1.h−1, respectively, by WD-PAC and ACTF-PAC. Equilibrium data reflected favorable fit with multiple Langmuir-Freundlich isotherm model and the maximum monolayer q e,calc (mg.g−1) was calculated respectively as 363.3 and 447.4 mg.g−1 for condensate oil using WD-PAC and ACTF-PAC. Response surface methodology (RSM) was successfully utilized to optimize and simulate four statistical quadratic polynomial models to predict the oil uptake by the prepared adsorbents. The quality of the models was judged by analysis of variance (ANOVA) at 95% confidence limit (p < 0.05). The quadratic interaction effects between adsorbent dose (2.5–7.5 g.L−1) and initial oil concentrations (0.1–2.5 g.L−1) by ACTF-PAC shows no significant effect (p-value of 0.198 and 0.687), indicating the improvement of the hydrophobic surface characteristics after functionalization. In addition, the WD-PAC and ACTF-PAC adsorbents proved to be a potential candidate for oil contamination prevention and/or recovery even after ten cycles.