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

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.