An effective way for the simultaneous valorization and treatment of olive mill wastewater by means of a photocatalytic process

This work hereby illustrates how to valorize olive mill wastewater (OMW) with a photocatalytic process able to produce hydrogen and simultaneously break down the polluting load of this waste. To achieve this objective, a comparison between the performances of commercial TiO2 and home-made sol–gel TiO2 on olive mill wastewater was first carried out. The hydrogen production and the ability of the catalyst to remove the organic matter present in wastewater were considered, with particular attention to the best combination (in terms of processing time and experimental phase sequence) between the anoxic phase (for the hydrogen production) and the oxidative phase (for the degradation of the organic residue). Once the best combination was identified, the photocatalyst in powder form was transferred on the surface of polystyrene pellets in order to make the catalyst easily separable and recyclable. The photocatalytic activity tests demonstrated that the proposed photocatalyst showed very good stability after ten reuse cycles, even in the presence of real OMW (with dilution 1:70), assuring a hydrogen production of about 16954 μmol/L. During the tests, the liquid samples were analyzed also with UHPLC technique that evidenced the phenol degradation and the presence of only hydroquinone as by-product.