Synthesis of Magnetite Coated Oleic Acid: Sequestration of Toluene and Xylene from Aqueous Solution and Cost Analysis

Abstract

Toluene and xylene are carcinogenic and toxic compounds, and their presence in excessive amounts in the environment has an adverse impact on water quality, thus affecting public health. In this study, magnetite coated oleic acid, (MNP-OA) nanocomposite was synthesized, characterized and applied as an effective nano-adsorbent for the efficient removal of toluene and xylene from aqueous solutions. Magnetite nanoparticles were coated with oleic acid via the microwave method and characterized using BET surface area, XPS, SEM-EDX and pHpzc analysis. Batch adsorption studies were performed to optimize operating parameters including solution pH, adsorbent dose, contact time, and initial concentration. The impact of hydrophobic coating on the kinetics, equilibrium, and the mechanism of toluene and xylene uptake were determined. Characterization confirmed the surface coating of magnetite with oleic acid which evidenced from the additional oxygenated functional groups such as hydroxyl and carboxylic groups. The morphological analysis showed spherically shaped magnetite nanoparticles. Maximum adsorption capacity of 133.57 mg/g for toluene and 161.01 mg/g for xylene were attained at solution pH of 8, adsorbent dose of 0.1 g and concentration of 100 mg/dm3 at 298 K. The pseudo-second-order and Langmuir models best explained the kinetics and adsorption isotherm, respectively. The thermodynamic parameters, including Gibbs free energy, enthalpy change, and entropy change of adsorption indicated that the adsorption process was endothermic and spontaneous in nature. The MNP-OA nanocomposites can be applied as a reusable, cost-effective, and efficient adsorbent for toluene and xylene remediation and could be considered for other volatile organic compounds in future application.