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Electrocatalytic reduction of nitrate to NH3(NO3RR) on Cu offers sustainable NH3production and nitrogen recycling from nitrate-contaminated water. However, Cu affords limited NO3RR activity owing to its unfavorable electronic state and the slow proton transfer on its surface, especially in neutral/alkaline media. Furthermore, although a synchronous “NO3RR and NH3collection” system has been developed for nitrogen recycling from nitrate-laden water, no system is designed for natural water that generally contains low-concentration nitrate. Herein, we demonstrate that depositing Cu nanoparticles on a TiO2support enables the formation of electron-deficient Cuδ+species (0 < δ ≤ 2), which are more active than Cu0in NO3RR. Furthermore, TiO2–Cu coupling induces local electric-field enhancement that intensifies water adsorption/dissociation at the interface, accelerating proton transfer for NO3RR on Cu. With the dual enhancements, TiO2–Cu delivers an NH3-N selectivity of 90.5%, mass activity of 41.4 mg-N h gCu–1, specific activity of 377.8 mg-N h–1m–2, and minimal Cu leaching (<25.4 μg L–1) when treating 22.5 mg L–1of NO3–-N at −0.40 V, outperforming most of the reported Cu-based catalysts. A sequential NO3RR and NH3collection system based on TiO2–Cu was then proposed, which could recycle nitrogen from nitrate-contaminated water under a wide concentration window of 22.5–112.5 mg L–1at a rate of 209–630 mgNm–2h–1. We also demonstrated this system could collect 83.9% of nitrogen from NO3–-N (19.3 mg L–1) in natural lake water.

[Display omitted] This study aimed to treat toxic and refractory organic wastewater, and to address the limitations of Fenton method in treating organic wastewater, that the active components are easy to lose and usually operate at the pH value of 2 ∼ 3. In the present study, CuCe oxide catalyst was produced through citric acid-assisted complexation. Besides, the structural stability and catalytic wet peroxide oxidation (CWPO) performance of the catalyst after 5 times of application were delved into by characterization. The effects of catalyst dosage and pH on quinoline removal were ascertained, while the reusability of the catalyst was explored. Moreover, the variations of pH, hydroxyl radical concentration and UV–Vis spectra in the reaction system were analyzed. The possible degradation pathway and the catalytic mechanism were also discussed. As suggested from the results, the catalyst exhibited high catalytic activity, structural stability and pH adaptability; it also had high CWPO performance for quinoline at the pH from 3.8 to 10.5, and the pH value need not be regulated. Under optimal conditions, 98.1% of quinoline and 86.1% of total organic carbon (TOC) were removed. In the CWPO process of quinoline, the ·OH attacked the nitrogen ring and the benzene ring in sequence. [ABSTRACT FROM AUTHOR]

This research aimed to degrade quinoline wastewater using CWPO (short for catalytic wet peroxide oxidation). Following the complexation method Cu-Ce composite oxide catalysts were prepared. The properties of catalysts were characterized by probed into by employing XRD (short for X-ray diffraction), SEM (short for scanning electron microscopy), H2-TPR (short for temperature programmed reduction) and XPS (short for X-ray photoelectron spectroscopy). Also, the degradation properties of varying Cu/Ce molar ratios, catalysts and H2O2dosages and the initial pH of solution were investigated in the degrading of simulated quinoline wastewater. As the research results suggested, CeO2and CuO for the prepared Cu-Ce composite oxide catalyst will become a Cu-Ce-O solid solution under calcination at high temperature, taking on a loose and porous structure on the surface. A little surface Cu2O will often appear as well though CeO2and CuO are the main substances on the surface. The lattice oxygen on the surface is greater than the adsorbed oxygen and hydroxyl oxygen in amount; thus, the phase structure of this oxygen is greatly impacted by the Cu/Ce molar ratio. Besides, its reducibility decreases as Cu content increases. The Cu-Ce composite oxide catalyst takes on a potent performance of catalytic wet peroxide oxidation for simulated quinoline wastewater. The catalyst degradation performance turns the optimal under initial quinoline concentration of 100 mg L–1, Cu/Ce molar ratio of 1.0, dosage of catalyst and H2O2of 0.16 g L–1and 196 mmol L–1, respectively. Under these conditions, the TOC removal can reach 91.1%. The catalyst is highly adapted to pH. The removal efficiency of quinoline can be actually high under the pH value ranging from 5.1 and 10.5, and its reaction follows the first-order reaction kinetics equation.