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Interest has grown in the modification of titanium dioxide with graphene to improve the photocatalytic behaviour. In this work, titanium dioxide–reduced graphene oxide (TiO 2 –RGO) composites were synthesised by the photocatalytic reduction of exfoliated graphene oxide (GO) by TiO 2 (Evonik P25) under UV irradiation in the presence of methanol as a hole acceptor. The composite materials were characterised using high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Raman and XPS analysis provided evidence that GO was converted to RGO by photocatalytic reduction. The TiO 2 –RGO composites were compared to TiO 2 in suspension reactors for the disinfection of water contaminated with Escherichia coli and Fusarium solani spores under real sunlight. Very rapid water disinfection was observed with both E. coli and F. solani spores. An enhancement in the rate of inactivation of E. coli was observed with the TiO 2 –RGO composite compared to P25 alone. The rate of inactivation of F. solani spores was similar for both the TiO 2 –RGO and P25. When the major part of the solar UVA was cut-off ( λ > 380 nm) using a methacrylate screen, there was a marked increase in the time required for inactivation of E. coli with P25 but no change in the inactivation rate for the TiO 2 –RGO. There is evidence of singlet oxygen production with visible light excitation of the TiO 2 –RGO composites which would lead to E. coli inactivation. [ABSTRACT FROM AUTHOR]

[Display omitted] • TiO 2 -rGO at the solar assisted photodegradation of complex mixing of pesticides. • Best photocatalytic performances with oxygen, regardless of the water matrix. • H 2 O 2 has not improved the final photocatalytic efficiency in any case. • P25-rGO promoted the photo-oxidation of the complex pesticides mix studied. • HBK-rGO presented excellent solar photoefficiency with 200 μg L-1 of pesticides. New titania-reduced graphene oxide (TiO 2 -rGO) nanocomposites have been studied to assess their application in the solar assisted photodegradation of a complex mixing of pesticides (pyrimethanil, isoproturon, alachlor and methomyl) at solar pilot plant, opening the opportunity to extend the use of these hybrid photocatalysts to complex wastewater effluents. TiO 2 -rGO nanocomposites were prepared by hydrothermal method from two commercial TiO 2 , Hombikat UV-100 (HBK) and Aeroxide® P25 (P25). The effect of two different water matrices (simulated and natural) on TiO 2 -rGO solar photoefficiency with two pesticides concentrations (5 mg·L−1 and 200 μg·L−1), and the additional use of an electron scavenging as oxidant agent, such as hydrogen peroxide in a comparison with oxygen from air, has been studied in compound parabolic collectors (CPC) photoreactors. Best photocatalytic performances were always found with oxygen over both TiO 2 -rGO nanocomposites, regardless of the water matrix employed. The use of H 2 O 2 as oxidant agent has not improved the final photocatalytic efficiency in any case. The generation of secondary highly reactive species in the reaction media from reaction of SO 4 ●- /HO radicals, and the more negatively surface charge with low S BET of P25-rGO nanocomposite, besides its lower hydrodynamic size with lower particle aggregation in the reaction conditions, have been responsible to promote the photo-oxidation of the complex pesticides mix studied. Finally, HBK TiO 2 -reduced graphene oxide (HBK-rGO) nanocomposite has presented excellent solar photoefficiency in the photodegradation of 200 μg·L−1 of each pesticide with the oxygen form air, especially under natural water matrix, because of its large negatively charge surface area where probably recombination of electrons and holes is prevented. [ABSTRACT FROM AUTHOR]

Agricultural wastewater is characterized by high organic matter and traces of organic pollutants. Effluents from the agro-food industry in particular are a potentially high environmental risk which requires appropriate, comprehensive treatment. This study evaluated the treatment of real wastewater from an agro-food processing plant by an Immobilized Biomass Reactor working in batch and continuous operating modes. Organic matter oxidation and the removal of reference organic pollutants were analyzed. Finally, the efficiency of a photocatalytic tertiary treatment with supported TiO 2 for the IBR effluent containing persistent microcontaminants was also studied. After the combined treatment, imazalil and thiabendazole were completely removed and over 90% of acetamiprid had been eliminated, but only with the additional contribution of hydrogen peroxide as an electron acceptor. [ABSTRACT FROM AUTHOR]

Highlights: [•] Immobilized photocatalyst based on TiO2 on glass spheres was successfully applied for ECs removal. [•] Regeneration with H2O2/UV or calcination are the most efficient methods to recover photoactivity. [•] F-, S- and Cl-containing compounds are preferentially adsorbed and easily removed from titania acid sites. [•] Compounds containing amine and amide groups are resistant to the photodegradation. [ABSTRACT FROM AUTHOR]