Treatment of petroleum wastewater using synthesised haematite (α-Fe2O3) photocatalyst and optimisation with response surface methodology

Abstract

ABSTRACT Haematite (α-Fe2O3) photocatalyst (HPC) has been synthesised by a modified solution combustion method. The prepared catalyst was characterised with a Scanning Electron Microscopy (SEM) and X-ray Diffractometer (XRD). Catalyst characterisation confirmed its composition and phase, but it also showed a slight lack in uniformity and crystallinity due to uncontrolled combustion caused by the modifications made to the preparation procedure. The photocatalyst was tested for the removal of pollutants present in the petroleum refinery wastewater (PRW) under UV-A lamp solar irradiation. A central composite design (CCD) with response surface methodology (RSM) was employed for optimisation of the model. The PRW treatment achieved a marked improvement in biodegradability, raising the biological oxygen demand (BOD)/chemical oxygen demand (COD) ratio from 0.074 to 0.604 in 90 min and percentage COD removal was 90.85% at a catalyst concentration of 5 g/L, pH 7.5 and hydrogen peroxide (H2O2)/COD ratio of 1 mg/mg. RSM optimisation predicted a maximum theoretical BOD/COD ratio of 0.661 and percentage COD removal of 94.73% at a catalyst concentration of 1.494 g/L, pH 7.5 and hydrogen peroxide (H2O2)/COD ratio of 1 mg/mg.