Polydimethylsiloxane-carbon nanotubes-based hydrophobic sponge for treatment of palm oil mill effluents with enhanced reusability

Abstract

Improper treatment and discharge of palm oil mill effluents (POME) into the water bodies have become one of the leading causes of aqueous contamination due to the release of a large volume of POME into the environment. This study reports the development of poly(dimethylsiloxane) (PDMS) and carbon nanotubes (CNTs) supported sorbent material to reduce the oil and grease (O&G) content of POME. The morphology and chemical properties of the prepared material were characterized using SEM-EDX, FTIR, Raman spectroscopy, XRD, TGA, water contact angle, and pH point of zero charge (pHPZC) analysis. CNT-PDMS optimal O&G removal capacity has been determined using batch experiments with varying parameters, including CNT wt%, contact time, pH, and initial POME concentration. The introduction of CNT significantly improves the oil sorption capacity almost three times as compared to pure PDMS. The maximum sorption capacity achieved was 658.09 ± 7.21 mg/g with the O&G removal of 84% within 8 min using initial POME concentration (1:20) and at room temperature. The study shows that the O&G sorption process using PDMS and CNT-PDMS-0.8 followed the pseudo-second-order kinetic model. Moreover, the adsorption isotherms study revealed that the adsorption process can be described by the Freundlich isotherm model based on the R2 values of 0.98075 and 0.99981 for PDMS and CNT-PDMS-0.8, respectively. Furthermore, the composites also show excellent reusability, retaining high O&G sorption and removal even after the tenth cycle.