Photo-Fenton process for removal of polycyclic aromatic hydrocarbons from hazardous waste landfill leachate

Polycyclic aromatic hydrocarbons (PAHs) are the toxic and persistent micro-pollutants recalcitrant to biodegradation. Photo-Fenton process is a commonly adopted advanced oxidation process. Advanced oxidation processes generate highly reactive hydroxyl radicals (OH·) which completely mineralise the organic contaminants. This study aims to find the efficiency of photo-Fenton oxidation process in the removal of PAHs and COD from landfill leachate, and investigate its effect on 16 PAHs according to their number of aromatic rings. Experiments were designed using central composite design, a module of response surface methodology (RSM) in the Design-Expert software. pH, Fe2+ concentration, H2O2 concentration, reaction time and UV intensity were the five experimental variables which were optimised and modeled successfully. The statistical analysis proved that all the variables have significant effect on the model. The value of R2 (0.94) showed a high reliability in the estimation of chemical oxygen demand and polycyclic aromatic hydrocarbons removal efficiency. Optimum experimental conditions of pH 6.5, Fe2+ 1.1 g/L, H2O2 concentration 5.5 g/L, reaction time 40 min and UV intensity 13.5 W resulted in the maximum chemical oxygen demand and polycyclic aromatic hydrocarbons removal efficiency of 84.43% and 92.54%, respectively. Validation was carried out by conducting additional set of experiments, and the small gap between observed and predicted values confirmed that central composite design is the effective tool to optimise the photo-Fenton oxidation process in the degradation of chemical oxygen demand and polycyclic aromatic hydrocarbons.