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In this study, a copper-based catalyst (CuCN) with CuN

Carbon-bridge-modified malonamide (MLD)/g-C

In this work, non-thermal plasma combined with zeolites was used to remove inorganic pollutant ammonia nitrogen from wastewater. Ammonia nitrogen elimination performances at various operating parameters were investigated. Roles of active species in the removal of ammonia nitrogen were also discussed. The experimental results showed that 69.97% ammonia nitrogen can be removed from the plasma/zeolites synergistic system after 30 min treatment. The removal efficiency was 16.23% and 61.55% higher than that in sole zeolites adsorption system and that in sole discharge plasma system, respectively. Higher applied voltage, lower initial ammonia nitrogen concentration and weak acidic conditions were favorable for ammonia nitrogen removal. After the addition of zeolites, part of O3 and H2O2 generated in the plasma/zeolites system were decomposed into other oxygen species (•OH and 1O2), which improved the oxidation degree of ammonia nitrogen. In addition, the reaction mechanism of ammonia nitrogen in water by plasma/zeolites process was discussed. After repeated use three times, the effect of the zeolites in the plasma/zeolites system remained stable. Characterization of the zeolites after reaction was analyzed through BET, SEM, XRD and FT-IR. The experiments have confirmed the applicability of the plasma/zeolites system for the further treatment of low-concentration ammonia nitrogen wastewater.

In this study, a copper-based catalyst (CuCN) with CuNx active sites highly dispersed in a porous carbon nitride matrix was synthesized and applied to a heterogeneous photo-assisted Photo-Fenton (PF) system to degrade tetracycline (TET). The results showed that the CuCN/PF system degraded up to 93.6% of TET within 60 min for ultrapure water matrix under the best experimental conditions, and more than 70% of TET for both river and lake water matrix. Toxicological tests suggested that the environmental risk caused by TET can be effectively inhibited by the CuCN/PF system. The good visible-light response and charge transport abilities of CuCN catalyst were identified in photoelectrochemical experiments. Free radical scavenging experiments and electron paramagnetic resonance (EPR) spectroscopy indicated that the active species in the degradation process were·OH, h+,·O2- and 1O2. Density functional theory (DFT) calculations revealed the positive effect of CuNx sites in CuCN on the formation of hydroxyl radicals by activating H2O2. This work will provide a new insight for the development of high-efficiency heterogeneous catalysts in wastewater environmental remediation.

In this study, a polymer-supported, nanosized, and hydrated Fe(III) oxide (HFOD) was developed as a Fenton-like catalyst for the efficient removal of metal complexes in water. HFOD was prepared through the irreversible impregnation of hydrated iron(III) oxide (HFO) nanoparticles into cation exchange resin and characterized through X-ray photoelectron spectroscopy (XPS) and ion chromatography. The mechanism of Cu(II) ion removal and the degradation pathway of Cu(II)-citrate were analyzed through UV–vis spectrophotometry (UV) and liquid chromatography-mass spectrometry (LC–MS). The optimal removal rate of Cu(II) and TOC by a Fenton-like reaction at pH 4 and 40 mM H2O2 reached 81.6 % and 75.6 %, respectively. The removal efficiency of Cu(II)-citrate was remarkably affected with the addition of humic acid. However, the addition of competitive ions did not significantly reduce the removal rate of Cu(II)-citrate, thereby proving that the Fenton-like reaction by HFOD had a certain salt tolerance. Simultaneously, hydroxyl radical (•OH) was verified as the main free radical for Cu(II)-citrate degradation in a Fenton-like reaction, and citrate degradation was a process decarboxylation. HFOD recycling experiments and stability experiments showed that HFOD had high stability with good acid/alkali resistance and showed remarkable potential in the practical application of fixed-bed as catalysts for Fenton-like reactions.

Nanofiltration (NF) was investigated for the removal of glyphosate in the neutralization liquor produced by the glycine-dimethylphosphit process. The Desal-5 DK membrane was chosen as the most suitable membrane for the NF process when compared to the DL and NTR7450 membranes according to retention of glyphosate and the permeate flux. The effects of applied pressure, temperature, and feed pH on the performances of the DK membrane were investigated. An applied pressure of 2 MPa was found to be optimum since a high glyphosate rejection of 95.5% was obtained with a high flux of 7.32 L/(hm(2)); temperature had a slight impact on the retention of glyphosate with an increase in flux; both the minimum glyphosate retention and maximum permeate flux were achieved when the feed pH was around the isoelectric point of the DK membrane. In batch NF, the permeate flux decreased gradually but glyphosate rejection remained higher than 90%. After 8h of NF, glyphosate recovery from the neutralization liquor reached 89.6% with an average permeate flux of around 4 L/(hm(2)). Moreover, membrane surface crystallization induced by concentration polarization probably caused the flux to decline during the process of batch NF.

Partial desalination and concentration of glyphosate liquor by nanofiltration under different operation modes were investigated experimentally in this study. These operation modes were direct nanofiltration, diafiltration, dilute-diafiltration and interval washing-nanofiltration. The four different operation modes were evaluated and compared in terms of glyphosate recovery and NaCl removal. Diafiltration and dilute-diafiltration performed better than direct nanofiltration. The glyphosate loss was between 11.5% and 18.8% when the dilution factor varied from 0.4 to 0.8. Interval washing-nanofiltration alleviated the concentration polarization and membrane fouling to a certain extent. Dilute-diafiltration may be the best operation mode in terms of glyphosate recovery, salt removal and cost.