Photocatalytic Treatment of Olive Oil Mill Wastewater Using TiO2 and Fe2O3 Nanomaterials

The olive oil industry produces a highly complex wastewater, known as olive oil mill wastewater (OOMW), which represents a relevant environmental problem for the Mediterranean region. Several physicochemical, biological and combined treatments have been tested to deal with this industrial externality but none was totally effective in reducing its toxicity for species inhabiting the receiving freshwater systems. Within this framework, nanotechnology appears as a promising research area, offering new approaches for the treatment of wastewaters based on the enhanced physical and chemical properties of nanomaterials (NMs). In this context, this work aimed to investigate the treatability of OOMW through several treatments involving advanced oxidation processes plus the use of two nanomaterials as catalysts (UV/H2O2, UV/TiO2, UV/Fe2O3, UV/TiO2/H2O2 and UV/Fe2O3/H2O2). The concentrations of the catalyst and of the oxidant agent were also investigated. The results obtained showed that photodegradation treatments combining TiO2 or Fe2O3 NMs with H2O2 were the most efficient. Regarding the OOMW toxicity to Vibrio fischeri, it was significantly reduced with the following treatments: UV/TiO2/H2O2 and UV/Fe2O3/H2O2. However, the highest reduction recorded for this parameter was obtained in the treatment with UV/H2O2. The use of NMs combined with H2O2 showed a great potential for removing phenols from OOMW, which have been pointed out as the major toxic compounds of this wastewater.