Boosted Electrocatalytic Degradation of Levofloxacin by Chloride Ions: Performances Evaluation and Mechanism Insight with Different Anodes.

As chloride (Cl-) is a commonly found anion in natural water, it has a significant impact on electrocatalytic oxidation processes; yet, the mechanism of radical transformation on different types of anodes remains unexplored. Therefore, this study aims to investigate the influence of chlorine-containing environments on the electrocatalytic degradation performance of levofloxacin using BDD, Ti4O7, and Ru-Ti electrodes. The comparative analysis of the electrode performance demonstrated that the presence of Cl- improved the removal and mineralization efficiency of levofloxacin on all the electrodes. The enhancement was the most pronounced on the Ti4O7 electrode and the least significant on the Ru-Ti electrode. The evaluation experiments and EPR characterization revealed that the increased generation of hydroxyl radicals and active chlorine played a major role in the degradation process, particularly on the Ti4O7 anode. The electrochemical performance tests indicated that the concentration of Cl- affected the oxygen evolution potentials of the electrode and consequently influenced the formation of hydroxyl radicals. This study elucidates the mechanism of Cl- participation in the electrocatalytic degradation of chlorine-containing organic wastewater. Therefore, the highly chlorine-resistant electrocatalytic anode materials hold great potential for the promotion of the practical application of the electrocatalytic treatment of antibiotic wastewater.

High-Temperature Chlorination of Nickel Oxide Using Calcium Chloride.

Attempts have been made to extract nickel from ores and nickel-containing wastes using the chlorination method. However, the use of gaseous chlorinating agents is limited due to their toxicity. High-temperature chlorination of nickel oxide using calcium chloride is analyzed in this study. The volatilization percentage is positively correlated to temperature and CaCl2 dosage and negatively correlated to oxygen partial pressure. The apparent activation energy is calculated to be 142.91 kJ/mol, between 1173 K and 1323 K, which suggests that the high-temperature chlorination of nickel oxide using calcium chloride is controlled by a chemical reaction.

Space-Confined Surface Layer in Superstructured Ni-N-C Catalyst for Enhanced Catalytic Degradation of m-Cresol by PMS Activation.

The broad application of peroxymonosulfate (PMS)-assisted oxidation by heterogeneous catalysts for contaminant removal suffers from the limitation of low PMS decomposition efficiency and consequent excessive electrolyte residues. In this work, we report that a micrometer-scale superstructured Ni-N-C catalyst Ni-NCNT/CB with a nanotube-array surface layer exhibits ultrahigh m-cresol removal efficiency with low PMS input and possesses ∼17-fold higher catalytic specific activity (reaction rate constant normalized to per Ni-Nx site) compared to the traditional Ni-SAC catalyst. Electron paramagnetic resonance results indicate that 1O2 is the dominant oxygen species, and Ni-NCNT/CB with a space-confined layer exhibits high 1O2 utilization for m-cresol degradation. Electrochemical impedance spectroscopy and a normalized k value of Ni-NCNT/CB confirm the spatial confinement effect on the catalyst surface, which is beneficial for regulating the mass transfer and exerting the high activity of active sites. This study gives a new application for spatial confinement, and the configuration of Ni-NCNT/CB may guide a rational catalyst design for AOP wastewater treatment.

Eco-friendly and rapid extraction of gold by in-situ catalytic oxidation with N-bromosuccinimide.

Gold is a valued, critical element whose chemical activation or extraction is challenging. Non-cyanide extraction of gold is now the focus, and N-bromosuccinimide(NBS) is attracting attention. Herein, new insights into the possible mechanism are deeply revealed through comprehensive analysis and detection of the reaction by using elementary gold and gold bearing ore. Experiments on gold foil indicate that Au can be activated in NBS solution to perform a satisfactory dissolution. Application of NBS in gold extraction from ore show a high yield of 86.24% under optimal conditions of NBS dosage 0.05 M, liquid-solid ratio 4:1, stirring speed 400 rpm, pH 8, 25 °C and leaching for 20 h, while yields of other coexisting metals are nearly negligible. The process leads to direct, efficient, one-pot conversion of gold, into simple water-soluble salts. Characterizations show that the framework of NBS are not destroyed, only bromine separates from the framework. The oxidation of neutral gold atom to trivalent Au(III) occurs in a mild, clean and room-temperature chemistry, which converts gold to [AuBr4]-, and the framework to succinimide. The active bromine and radical Br (Br•) generated from in-situ autocatalysis of NBS are responsible for this. The systematic results herald a green procedure for preparation of gold derivatives and gold extraction industry.

Electrocatalytic Degradation of Levofloxacin, a Typical Antibiotic in Hospital Wastewater.

Presently, in the context of the novel coronavirus pneumonia epidemic, several antibiotics are overused in hospitals, causing heavy pressure on the hospital's wastewater treatment process. Therefore, developing stable, safe, and efficient hospital wastewater treatment equipment is crucial. Herein, a bench-scale electrooxidation equipment for hospital wastewater was used to evaluate the removal effect of the main antibiotic levofloxacin (LVX) in hospital wastewater using response surface methodology (RSM). During the degradation process, the influence of the following five factors on total organic carbon (TOC) removal was discussed and the best reaction condition was obtained: current density, initial pH, flow rate, chloride ion concentration, and reaction time of 39.6 A/m2, 6.5, 50 mL/min, 4‱, and 120 min, respectively. The TOC removal could reach 41% after a reaction time of 120 min, which was consistent with the result predicted by the response surface (40.48%). Moreover, the morphology and properties of the electrode were analyzed. The degradation pathway of LVX was analyzed using high-performance liquid chromatography-mass spectrometry (LC-MS). Subsequently, the bench-scale electrooxidation equipment was changed into onboard-scale electrooxidation equipment, and the onboard-scale equipment was promoted to several hospitals in Dalian.

Oxygen-vacancy-mediated LaFe1-xMnxO3-δ perovskite nanocatalysts for degradation of organic pollutants through enhanced surface ozone adsorption and metal doping effects.

Here, a series of LaFe1-xMnxO3-δ perovskite nanocatalysts were synthesized and tested for the catalytic ozonation of m-cresol for the first time. The B-site cation is regulated by metal doping, and the resulting LaFe0.26Mn0.74O3-δ with a rhombohedral structure showed excellent catalytic performance and structural stability owing to the abundant oxygen vacancies and the higher Fe2+/Fe3+ and Mn3+/Mn4+ ratios. Theoretical calculations have revealed that the oxygen vacancy has a strong affinity for ozone adsorption, and thus facilitated ozone decomposition by extending the O-O bond. Combined with low-valence Fe2+ and Mn3+ cations, the electron transfer in the catalytic ozonation reaction has been enhanced, which has promoted the production of reactive oxygen species (ROS). Taken together, the degradation pathway of m-cresol was proposed. Additionally, the LaFe0.26Mn0.74O3-δ catalyst remained stable during a 60 h reaction. This study has not only revealed the adsorption/decomposition pathways of ozone using LaFe0.26Mn0.74O3-δ perovskite nanocatalysts but also provided indepth insight into the electron transfer pathway on the surface of nanocatalysts during the process of catalytic ozonation.

Fabrication of boron-doped diamond films electrode for efficient electrocatalytic degradation of cresols.

The choice of anode materials has a significant influence on the electrocatalytic degradation of organics. Accordingly, the electrocatalytic activity of several active anodes (Ti/Ru-Ir, Ti/Ir-Ta, Ti/Pt) and non-active anodes (Ti/PbO2, Ti/SnO2, Si/BDD (boron-doped diamond)) was compared by electrocatalytic degradation of m-cresol. The results indicated Si/BDD electrode had the strongest mineralization ability and the lowest energy consumption. And the order of the activity of m-cresol degradation was as follows: Si/BDD > Ti/SnO2>Ti/PbO2>Ti/Pt > Ti/Ir-Ta > Ti/Ru-Ir. Also their intermediate products were compared. The effects of experimental parameters on electrocatalytic degradation of m-cresol with Si/BDD electrode showed m-cresol conversion was affected slightly by the electrode spacing and electrolyte concentration, but affected greatly by the temperature and current density. And smaller electrode spacing and current density, higher electrolyte concentration and temperature were beneficial to reduce energy consumption. Their degradation processes were all accord with the pseudo-first-order reaction kinetics completely. In addition, the results of electrocatalytic degradation of m, o, p-cresol indicated there was almost no significant difference on conversion rate between cresols isomers with the current density of 30 mA cm-2. However, the influence of group position was shown when the current density was reduced to 10 mA cm-2 and cresols conversion followed the sequence of m-cresol ≈ o-cresol > p-cresol.

The effect of different inorganic anions on mineralization of acrylic acid in wet air oxidation.

Wet Air Oxidation (WAO) process is being developed as a very promising technique for efficient removal of high-concentration organic pollutants. However, because of the technical constraints, many chemical wastewater contain inorganic anions (e.g., Cl-, SO42-, PO43- and NO3-). These inorganic salts can cause equipment corrosion and also affect WAO reactivity. But very limited studies of the effect of inorganic anions on WAO in chemical wastewater have been performed. Here we for the first time intensively investigate the effect of different inorganic anions on kinetics and pathways of WAO reaction, acrylic acid was selected as substrate. We used a nonlinear least-squares curve fitting method using Matlab 2014® to obtain the kinetic model. Importantly, it was demonstrated that this proposed kinetic model represented the experimental data well, and acetic acid was the only residual short-chain carboxylic acid. Moreover, the higher concentration anions the higher selectivity of WAO of CO2 by acrylic acid. And the selectivity order of WAO to acetic acid is PO43- > NO3- > Cl- > SO42- at low concentration (100 mmol L-1). Finally, the theory calculation disclosed the feasibility of the reactions between these anions and acrylic acid, calculation results revealed that atoms 1#, 7# and 8# have the strongest chargeability and are more vulnerable to oxidant attack because of their high charge density. And the Total Organic Carbon (TOC) removal was positively correlated with the electronegativity of the central atom of oxidizing acid.

Removal of cyanide adsorbed on pyrite by H2O2 oxidation under alkaline conditions.

Large amounts of cyanide tailings are produced during the cyanidation process in gold extraction, which are hazardous solid wastes due to the toxic cyanide. Pyrite is one of the main minerals in cyanide tailings. The removal of cyanide adsorbed on pyrite by H2O2 oxidation under alkaline conditions was investigated in this study. It was found that the removal efficiency was positively correlated with pH from 5 to 12, but remained almost constant when pH was higher than 12. The highest cyanide removal efficiency of 91.10% was achieved by adding no less than 0.6 wt.% of H2O2. Cyanide removal was positively correlated with the CN- adsorption amount between 1.06 and 8.5 mg/g, and temperature between 25 and 85°C. The removal of cyanide adsorbed on pyrite by H2O2 oxidation under alkaline conditions was due to the oxidation of pyrite. Hexacyanoferrate, thiocyanate and sulfate were generated with mole ratios of about 2.03:1.12:3.17 during the cyanide removal.

ESNOQ, proteomic quantification of endogenous S-nitrosation.

S-nitrosation is a post-translational protein modification and is one of the most important mechanisms of NO signaling. Endogenous S-nitrosothiol (SNO) quantification is a challenge for detailed functional studies. Here we developed an ESNOQ (Endogenous SNO Quantification) method which combines the stable isotope labeling by amino acids in cell culture (SILAC) technique with the detergent-free biotin-switch assay and LC-MS/MS. After confirming the accuracy of quantification in this method, we obtained an endogenous S-nitrosation proteome for LPS/IFN-gamma induced RAW264.7 cells. 27 S-nitrosated protein targets were confirmed and using our method we were able to obtain quantitative information on the level of S-nitrosation on each modified Cys. With this quantitative information, over 15 more S-nitrosated targets were identified than in previous studies. Based on the quantification results, we found that the S-nitrosation levels of different cysteines varied within one protein, providing direct evidence for differences in the sensitivity of cysteine residues to reactive nitrosative stress and that S-nitrosation is a site-specific modification. Gene ontology clustering shows that S-nitrosation targets in the LPS/IFN-gamma induced RAW264.7 cell model were functionally enriched in protein translation and glycolysis, suggesting that S-nitrosation may function by regulating multiple pathways. The ESNOQ method described here thus provides a solution for quantification of multiple endogenous S-nitrosation events, and makes it possible to elucidate the network of relationships between endogenous S-nitrosation targets involved in different cellular processes.

Nonlinear cooperation of p53-ING1-induced bax expression and protein S-nitrosylation in GSNO-induced thymocyte apoptosis: a quantitative approach with cross-platform validation.

Increasing evidence has been gathered for p53-dependent apoptosis, but it is still unclear how p53 initiates apoptosis by employing its transcriptional program. Pair-wise interactions of p53 with expression of other genes fail to predict p53 levels or rate of apoptosis. A more sophisticated approach, using neural networks, permits prediction of interaction among three or more genes (p53, bax, and ING1). These interactions are decidedly nonlinear. Careful measurements and advanced mathematical treatments will permit us not only to understand how expression of pro- and anti-apoptotic genes is regulated, but also to integrate cross-platform and cross-experimental data for the validation of predicted interactions.

On-gel fluorescent visualization and the site identification of S-nitrosylated proteins.

Mounting evidence indicates that S-nitrosylation of critical cysteine residues in a protein represents a common feature of protein function regulation and cell signaling. However, the progress in studying the exact role of S-nitrosylation has been hampered by a lack of rapid and accurate methods for the detection of these S-nitrosylated proteins and the exact modification sites. In this article, we report a fluorescence-based method in which the S-nitrosylated cysteines are converted into 7-amino-4-methylcoumarin-3-acetic acid (AMCA) fluorophore-labeled cysteines-termed the AMCA switch method. The labeled proteins are then analyzed by nonreducing SDS-PAGE, and the S-nitrosylated proteins can be readily detected as brilliant blue bands after the activation of ultraviolet light. Furthermore, the sites of modification can be determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) after in-gel tryptic digestion of the fluorescent band, and the recognizable AMCA tag in the MS spectra ensures the accurate site identification of the nitrosocysteines. Therefore, our method offers some apparent advantages by direct visualization of on-gel image of S-nitrosylated proteins, shorter experiment time by skipping the anti-biotin immunoblotting step, and elimination of the potential interference of endogenous biotinylated proteins. Based on this method, we detected the S-nitrosylation and the modified site in bovine serum albumin and gankyrin after in vitro S-nitrosylation. Overall, our results indicate that the AMCA switch method is a fast and accurate method to identify the S-nitrosylated protein and the modification sites.

Detergent-free biotin switch combined with liquid chromatography/tandem mass spectrometry in the analysis of S-nitrosylated proteins.

High-throughput proteomic analysis based on a biotin switch combined with liquid chromatography/tandem mass spectrometry (LC/MS/MS) enables simultaneous identification of S-nitrosylated sites and their cognate proteins in complex biological mixtures, which is a great help in elucidating the functions and mechanisms of this redox-based post-translational modification. However, detergents such as sodium dodecyl sulfate (SDS) and Triton X-100 adopted in these systems, which are hard to fully remove in the subsequent MS-based analyses, can suppress the peptide signals and influence the SNO-Cys site identification and the reproducibility of the experiments. Here we developed a detergent-free biotin-switch method, which applied urea to replace detergents, and successfully combined it with LC/MS/MS in the analysis of S-nitrosylated proteins. With this approach, 44 SNO-Cys sites were specified on 35 distinct proteins in S-nitrosoglutathione (GSNO)-treated HeLa cell extracts of proteins with good reproducibility. The LC/MS performance was greatly improved as analyzed with Pep3D and the amount of samples for analysis reduced from 40 mg used in the literature to 3-5 mg. For S-nitrosylated targets detected both in the control sample and in the GSNO-treated sample, extracted ion chromatography (XIC) was employed to estimate the quantitative change of S-nitrosylation (S-nitrosation), which facilitates the judgment on 'accept or reject' of the identified targets.

Nitric oxide destabilizes Pias3 and regulates sumoylation.

Small ubiquitin-related protein modifiers (SUMO) modification is an important mechanism for posttranslational regulation of protein function. However, it is largely unknown how the sumoylation pathway is regulated. Here, we report that nitric oxide (NO) causes global hyposumoylation in mammalian cells. Both SUMO E2 conjugating enzyme Ubc9 and E3 ligase protein inhibitor of activated STAT3 (Pias3) were targets for S-nitrosation. S-nitrosation did not interfere with the SUMO conjugating activity of Ubc9, but promoted Pias3 degradation by facilitating its interaction with tripartite motif-containing 32 (Trim32), a ubiquitin E3 ligase. On the one hand, NO promoted Trim32-mediated Pias3 ubiquitination. On the other hand, NO enhanced the stimulatory effect of Pias3 on Trim32 autoubiquitination. The residue Cys459 of Pias3 was identified as a target site for S-nitrosation. Mutation of Cys459 abolished the stimulatory effect of NO on the Pias3-Trim32 interaction, indicating a requirement of S-nitrosation at Cys459 for positive regulation of the Pias3-Trim32 interplay. This study reveals a novel crosstalk between S-nitrosation, ubiquitination, and sumoylation, which may be crucial for NO-related physiological and pathological processes.