Screening of Fe–BEA catalysts for wet hydrogen peroxide oxidation of crude olive mill wastewater under mild conditions

Abstract

A series of Fe–BEA catalysts, differing in the amount of iron have been characterized by XRD, BET surface area, UV–vis spectroscopy and chemical analysis. The zeolite samples have been tested as heterogeneous catalysts for the wet hydrogen peroxide oxidation of crude olive mill wastewaters (OMW) under very mild conditions (at 28°C and atmospheric pressure). All experiments were performed on a laboratory scale set-up.BSE-1/3 catalyst with a moderate Fe content (Fe/Al=1.19) showed the best results in terms of catalytic activity and loss of active species into the aqueous solutions. The stability of Fe species has been shown to be strongly dependent on the Fe environment into the zeolite framework.Over the selected catalyst, application of catalytic procedure on diluted OMW solution permitted high removal efficiencies of pollutants. The process produces a removal capacity of 28% of total organic carbon (TOC), 40% of total phenols, 30% of chemical oxygen demand (COD) and 59% of colour, just after 12h. 5-Day biochemical oxygen demand (BOD5), and toxicity towards the bioluminescent bacteria Vibrio fischeri were selected to follow the performance of this process in terms of reducing the ecotoxicity of OMW. Results showed an increase in the biodegradability of the treated sample and a decrease of the microtoxicity from 100% to 70% load towards V. fischeri.Occurrence of small catalyst deactivation by carbonaeous during the oxidation reaction was observed through scanning electron microscopy (SEM) and elemental analysis.