Fabrication, characterisation and application of Poly Allyl Amine Hydrochloride / Poly Styrene Sulphonate/Zinc Oxide (PAH/(PSS/ZnO)n bilayers in the removal of pollutants from oil refinery waste water

Abstract

ABSTRACT The application of nanomaterials in the oil and gas industry has been widely studied in the past few years, and polymeric nano thin films have become an area of interest among researchers. In this work, multilayer nano thin films were fabricated using poly(ally lamine hydrochloride) (PAH), zinc oxide (ZnO) and poly(styrene sulphonate sodium salt) (PSS) on glass template by Layer-by-Layer (L-b-L) technique and its potential application for the photo degradation of oil refinery wastewater have been reported. The L-b-L fabrication of the thin film was carried out at an assembly pH of 8.0. The morphological characterisation and elemental composition of the fabricated thin films were studied using Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Analysis (SEM – EDX). Chemical bond and surface functional groups were identified using Fourier Transform Infrared Spectroscopy (FTIR). SEM characterisation depicted the uniform deposition of ZnO particles in the polyelectrolyte matrix. The outcome of the FTIR analysis is justified by the presence of strong C=C bonds favouring the strength of bilayer deposition. A comparative study on the degradation efficiency was carried out using oil refinery effluents for the photo degradation of ZnO/PSS/PAH thin films and suspension form of ZnO by varying the process parameters such as number of bilayers and contact time. The ZnO/Polyelectrolyte multilayer thin films performed extremely well in reducing the chemical oxygen demand (COD) and Total Organic carbon (TOC) to the standards. A maximum COD removal efficiency of 80.1% was obtained at conditions where PAH/(PSS, ZnO)5 bilayers were used at pH 7.2 with a contact time of 120 minutes. The total organic carbon removal was around 55% under optimum conditions of pH 7.2 and PAH/(PSS, ZnO)5 at 120 minutes. This study illustrates that immobilised zinc oxide nanoparticles can effectively remove pollutants from oily wastewater and the process seems to be attractive in the environmental applications.