Photo-Fenton mineralization of synthetic apple-juice wastewater

The mineralization of a synthetic wastewater containing apple juice using a homogeneous photo-Fenton oxidation process was evaluated as an alternative to or a rapid pretreatment step for conventional anaerobic digestion with the aim of considerably reducing the total treatment time. The mineralization process was found to follow pseudo-first-order kinetics. Experimental kinetic constants were fitted using neural networks (NNs) with a 90% confidence level. At the selected operation conditions ([H2O2] = 5800 ppm, [Fe(II)] = 40 ppm, pH = 4.2 and temperature = 26 °C), 91% mineralization was achieved in 40 min when treating a synthetic wastewater with 700 ppm of the total organic carbon (TOC). This process can be performed without modifying the natural pH of the wastewater with consequent savings for reagents and a technical simplification of the process. In total, 6.7 mol of H2O2 was consumed per each mol of total organic carbon removed from solution. Finally, the mineralization mechanism was also studied.