An innovative method to remove phenols from olive mill wastewater using heterogeneous modified polyacrylonitrile (PAN) catalyst

ABSTRACT Phenolic compounds contained in olive oil mill wastewater (OMW) cause environmental issues when left untreated. A novel heterogeneous surface functionalised nanocoated polyacrylonitrile (PAN) mesh used as a Fentons' catalyst acting with hydrogen peroxide gave 70–100% phenol reduction and an average total organic carbon (TOC) reduction of 64.7% when seven phenols as described below were individually treated (100 mg/L phenolic, 500 mg/L H2O2, 12 g catalyst, 20 °C). As a mixture of seven phenols (100 mg/L of each, 12 g catalyst, 3,500 mg/L H2O2), such as trans-cinnamic acid, p-coumaric acid, caffeic acid, vanillic acid, ferulic acid, tyrosol and hydroxytyrosol, there was 77.5% phenol and 43.9% TOC reduction. The addition of UVc light (100 mg/L phenolic, 500 mg/L H2O2, 12 g catalyst, 20 °C, UV flux 2.66 mW/cm2) significantly improved the degradation of the initial phenolic concentration by 98% in the individual treatments. A pH of 3 and a temperature of 30 °C were found to be the most effective and efficient. The fresh and regenerated catalysts were both recycled over 10 cycles before deactivation which shows promise for continuous flow and scale-up for use as an OMW treatment.