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The mineralization of tetracycline by electrochemical advanced oxidation processes (EAOPs) as well as the study of the toxicity of its intermediates and degradation products are presented. Electro-Fenton (EF), anodic oxidation (AO), and electro-Fenton coupled with anodic oxidation (EF/AO) were used to degrade tetracycline on carbon felt (cathode) and a sub-stoichiometric titanium oxide (Ti4O7) layer deposited on Ti (anode). As compared to EF and AO, the coupled EF/AO system resulted in the highest pollutant removal efficiencies: total organic carbon removal was 69 ± 1% and 68 ± 1%, at 20 ppm and 50 ppm of initial concentration of tetracycline, respectively. The effect of electrolysis current on removal efficiency, mineralization current efficiency, energy consumption, and solution toxicity of tetracycline mineralization were investigated for 20 ppm and 50 ppm tetracycline. The EF/AO process using a Ti4O7 anode and CF cathode provides low energy and high removal efficiency of tetracycline caused by the production of hydroxyl radicals both at the surface of the non-active Ti4O7 electrode and in solution by the electro-Fenton process at the cathodic carbon felt. Complete removal of tetracycline was observed from HPLC data after 30 min at optimized conditions of 120 mA and 210 mA for 20 ppm and 50 ppm tetracycline concentrations. Degradation products were elucidated, and the toxicity of the products were measured with luminescence using Microtox® bacteria toxicity test.

M-doped TiO2 and mixed oxides MxOy–TiO2 (M = V, Bi, W) were synthesized by the reactive mineralization of ash-free filter paper under anhydrous conditions. Mixtures of metal chlorides (TiCl4 with VOCl3, WCl6, or BiCl3) were reacted directly with cellulose, and three different Ti/M atomic ratios were used (99, 19, and 9). The resulting materials consist of original nanoflower assemblies of needle-shaped primary particles. Their physicochemical characteristics were investigated by various techniques (X-ray diffraction, diffuse-reflectance UV/Vis spectroscopy, electron microscopy, and elemental analysis). The incorporation of the doping metal or the formation of mixture of oxides with TiO2 (WO3, Bi2O3) depends on the metal and the proportions used. The photocatalytic activities of the materials were tested for the degradation of phenol. The vanadium-doped materials exhibit true solid-solution formation and their band gaps shift into the visible range.

International audience; Metal hollow fibre membranes offer excellent chemical and mechanical stability and are promising platforms for the removal of harsh contaminants from solutions. Stainless steel (SS) membranes are however prone to oxidation and advanced decoration routes are required to passivate the surface of such materials. Here, SS membranes were modified with nanoscale coatings of graphene to promote electrochemical reactions and prevent premature corrosion of the bare metal reinforcement upon electro-Fenton (EF) reaction. Samples decorated with graphene oxide or reduced graphene oxide were compared to bare SS membranes to assess the impact of graphitization on the electrochemical performance of the membranes. Membranes properties were characterized using both cyclic and linear scanning voltammetry. The results evidenced that electron transfer kinetics were significantly enhanced on the reduced graphene oxide, compared to raw material. In addition, the removal efficiency of a pharmaceutical pollutant, paracetamol, was evaluated in electro-Fenton batch experiments, on the three membrane electrodes. The best mineralization current efficiency at 37% was found when using reduced graphene oxide membrane cathode at optimal applied potential of -0.5 V vs. SCE (Saturated Calomel Electrode). Finally, the coupling of electro-Fenton and filtration processes was carried out on a pilot-scale unit. Various electrochemical and hydrodynamic parameters that affect mineralization efficiency were studied. By coupling filtration and electrochemical processes, the mineralization current efficiency value was increased remarkably by 165% and remained stable for three consecutive cycles. This strategy opens up opportunities to generate low cost catalytic membrane reactors with high flux and selectivity from the materials reactivity as opposed to sieving, with potential for harsh chemicals mineralization.

Metal oxides and metal oxide/carbon composites are entering the development of new technologies and should therefore to be prepared by sustainable chemistry processes. Therefore, a new aspect of the reactivity of cellulose is presented through its solid/gas reaction with vapour of titanium(IV) chloride in anhydrous conditions at low temperature (80 °C). This reaction leads to two transformations both for cellulose and titanium(IV) chloride. A reductive dehydration of cellulose is seen at the lowest temperature ever reported and results in the formation of a carbonaceous fibrous solid as the only carbon-containing product. Simultaneously, the in situ generation of water leads to the formation of titanium dioxide with an unexpected nanoplate morphology (ca. 50 nm thickness) and a high photocatalytic activity. We present the evidence showing the evolution of the cellulose and the TiO

We report on observations of the temperature dependence ( T = 5–40 °C) of the titanium oxide sols precipitation kinetics in the sol–gel process using Ti(OPr i ) 4 as a metal organic precursor. The nanometric sol particles are produced in the sol–gel reactor with rapid reagent mixing and temperature and atmosphere control. Precipitation kinetics was followed in situ by the light scattering method using an optical fibre probe. From these measurements the activation energy E a = 0.33 ± 0.02 eV has been obtained and assigned to the secondary hydrolysis–condensation reactions between surface Ti–OPr i groups. Careful analysis of experimental data allows concluding about a decrease of the fractal dimension D f of the precipitate with an increase of the temperature, which provides D f = 1 at 35 °C.

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