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This work reports a study on the reactivity of polymeric carbon nitride (PCN) and PCN-H2O2 adduct samples for sunlight photocatalytic selective oxidation reactions. The characterization of these materials was reported in a previous paper where the reactivity towards the partial oxidation of 5-hydroxymethylfurfural (HMF) was studied by using two different laboratory scale photoreactors; one irradiated by UV lamps and the other one by natural sunlight. In the present study it has been confirmed the effectiveness of these C3N4 based materials for the selective partial oxidation of HMF to FDC (2,5-furandicarboxaldehyde) in aqueous medium in a pilot plant photoreactor irradiated by natural sunlight. The reactivity results and, in particular, the selectivity to FDC formation have been very encouraging, mostly by considering that the reaction was carried out in water. Moreover, they are comparable with those obtained in the laboratory scale photoreactors irradiated by both UV lamps and natural sunlight. Interestingly, the pristine PCN sample has shown a higher HMF conversion with respect to that of the PCN-H2O2 adduct, but the last one is more selective to the FDC formation. A kinetic study indicates that the pseudo-first-order rate constant of HMF oxidation is higher in the case of pristine photocatalyst and that the equilibrium adsorption constants of HMF is higher in the case of PCN-H2O2 adduct catalyst. Finally, the partial oxidation of two aromatic alcohols, i.e. benzyl alcohol (BA) and 4-methoxy benzyl alcohol (4-MBA) to benzaldehyde (BAL) and 4-methoxy benzaldehyde (4-MBAL), respectively, has also been studied.

The degradation of a mixture of four pharmaceutical compounds (atenolol, hydrochlorothiazide, ofloxacin and trimethoprim) in distilled water and in a synthetic solution simulating a typical secondary effluent from a municipal wastewater treatment plant by ozonation, solar TiO2-photocatalytic oxidation and a sequence of both methods has been investigated. Degradation by ozone led to the complete removal of the selected emerging compounds (EC) but an accumulation of ozonation by-products (e.g., phenolic intermediates and carboxylic acids) in solution was observed. The presence of ozone-consuming substances in the synthetic effluent had not a negative impact on the removal of the pharmaceuticals but on their mineralization (TOC removal

The photocatalytic degradation in distilled water of 15 selected emerging contaminants (ECs) has been evaluated in a solar pilot compound parabolic collector (CPC) plant by using TiO2 photocatalysts immobilized on glass spheres. The durability of the photocatalysts has been evaluated by measuring its performance during 4 consecutive cycles. TiO2 was prepared by the sol–gel method using titanium isopropoxide as precursor, combined with commercial TiO2 Degussa P25 and polyethylene glycol (PEG) as the pore generating agent. The following microcontaminants in a concentration of 100 μg L−1 have been studied: acetaminophen, antipyrine, atrazine, carbamazepine, diclofenac, flumequine, hydroxybiphenyl, ibuprofen, isoproturon, ketorolac, ofloxacin, progesterone, sulfamethoxazole and triclosan. The fluorine containing ECs, this is, flumequine and ofloxacin, are totally degraded under the studied reaction conditions. By contrary, a progressive decay of the photocatalytic activity is observed for the other contaminants. The contaminants with amine or amide groups but without halogen heteroatoms in the structure record the lowest degradation rates. In order to recover the photoactivity, different strategies using aqueous solutions containing H2O2 under UV irradiation, NaOH, NH4OH and direct heat treatment in air at 400 °C, were adopted. For the sake of simplicity, these experiments have been performed in a solar simulator at 765 W m−2. In order to determinate the nature of the species adsorbed on the titania active sites, the used and the regenerated photocatalysts were analyzed by XPS. Chemical treatment with NaOH results in the removal of the TiO2 layer. The ECs containing sulphate, fluoride or chloride groups are easily adsorbed on the photocatalyst active sites as compared to the ECs containing amide or amine groups and are easily desorbed by the regeneration treatments. Amongst the different pretreatment studied, calcination and H2O2/UV irradiation are the most efficient methods to recover the photocatalytic activity.

This article reports on degradation using TiO2 immobilized on glass spheres of 15 emerging contaminants (ECs) at low concentrations in simulated and real Municipal Wastewater Treatment Plant (MWTP) effluents. A sol containing titanium isopropoxide, commercial P25 and polyethylene glycol (PEG) was prepared, and a layer of the photoactive precursor was immobilized on glass spheres by dip-coating. The raw materials and the xerogels were characterized by N2 adsorption/desorption, XRD and TGA-DTA. The xerogel showed the TiO2 anatase, rutile and brookite crystal phases characteristic of the reference materials. The diffraction pattern showed no modification of the crystal size from incorporation of the PEG. Two different TiO2 anatase crystal sizes were identified, which was attributed to the different TiO2 precursors used in the synthesis route. Degradation of the emerging contaminants (acetaminophen, antipyrine, atrazine, carbamazepine, diclofenac, flumequine, hydroxybiphenyl, ibuprofen, isoproturon, ketorolac, ofloxacin, progesterone, sulfamethoxazole and triclosan), at an initial concentration of 100 μg L−1 each was determined by ultra-performance liquid chromatography (UPLC-UV) and mineralization was monitored by measuring the dissolved organic carbon (DOC). The experiments were performed in a pilot compound parabolic collector (CPC) solar plant at the Plataforma Solar of Almeria (Spain). 85% of the compounds were degraded within 120 min of illumination time depending on the water. The results show the potential application of this technology as a good alternative to suspension systems for the treatment of polluted water.

The efficiencies of different solar oxidation processes on the degradation of bisphenol A in water were studied. The work focuses on the removal and mineralization of bisphenol A and the formation of phenolic intermediates. The processes tested were Fe(III) photolysis, ferricarboxylate photolysis, TiO2 photocatalysis, H2O2 photolysis and combinations thereof. The influence of pH and the presence of hematite (α-Fe2O3) on their efficiency, as well as the nature of intermediates formed and development of toxicity were evaluated.

The purpose of this study was to develop a municipal wastewater treatment method based on a solar advanced oxidation process (AOP) permitting reuse of the treated wastewater. The photoactive layer of TiO 2 was deposited on glass spheres using the sol–gel dip-coating technique. The film was characterized by X-ray diffraction and scanning electron microscopy (SEM). Degradation of 15 emerging contaminants (ECs), each with an initial concentration of 100 μg L −1 was determined by ultra-performance liquid chromatography (UPLC–UV) and mineralization was monitored by measuring the dissolved organic carbon (DOC). The experiments were performed in a pilot compound parabolic collector (CPC) solar plant at the Plataforma Solar of Almeria. Five cycles of photocatalysis were studied for photocatalyst durability and activity. It was demonstrated that after five cycles, although photoactivity of the catalyst slowly decreases, it continues degrading contaminants.

The aim of this work is to evaluate the degradation of the emerging pharmaceutical contaminant ibuprofen (IBP) in water by heterogeneous photocatalysis in three different solar pilot plants. IBP and TOC removal increase directly proportional to concentration of catalyst (TiO2). The addition of H2O2 increases the removal efficiency. The complete IBP removal and decrease of TOC to sufficient extent was stated in optimal experimental conditions and biodegradability and average oxidation state (AOS) results conducted suggest a post-biological treatment of solution. Surface responses obtained from the experimental results, for different initial IBP and TiO2 concentrations used, can allow to predict time needed for a sufficient TOC removal to reach sufficient biodegradability.