[Effect of low doses of active chlorine on commensal populations of intestinal bacteria in rats by oral ingestion].

Chlorine-containing substances are widely used as disinfectants for treating equipment surfaces and technological aids for antimicrobial treatment of a number of foodstuff in the food industry. The toxic and bactericidal effects of the active (free) chlorine they contain are well understood for the concentrations used in practice, whereas little is known about the effect of its residual (subinhibitory) amounts on the organism and on the microbiota, including the ability to induce antimicrobial resistance. The aim of the study was to investigate the effect of different doses of active chlorine at oral administration on the commensal bacteria of intestinal microbiota, body weight gain and micromorphological features of the liver in rats. Material and methods. The study was carried out on male Wistar rats, with an initial body weight of 90-100 g, which for 4 weeks received doses of active chlorine together with drinking water ad libitum, with the given concentration: subinhibitory (10 mg/L), threshold (50 mg/L) and aggravated (100 mg/L). Chloramine was used as a chlorinecontaining agent stable in aqueous solution. Body weight gain was monitored daily. After decapitation, the caecum was taken for microbiota examination as well as the liver. The phenotypic antimicrobial resistance characteristics of Enterobacteriaceae and Enterococci were studied by the disk diffusion method. Additionally, a micromorphologic study of liver slices was performed. Results. Insignificant negative deviations in the body weight gain of rats in the experimental groups receiving subinhibitory doses of active chlorine, combined with a reduced level of Enterococci and Enterobacteriaceae representatives, were revealed. No significant effect of chlorine on the levels of resistant Escherichia coli populations was found, but a tendency to exhibit antimicrobial resistance of Enterococci isolated from rats receiving low doses of active chlorine (10 and 50 mg/l) was detected. No signs of toxic effect on the liver tissue most sensitive to chlorine were detected, but some accumulations of inflammatory cells in the liver slice were revealed. Conclusion. Low doses of chlorine-containing substances at their oral consumption are not indifferent for rats' organism, causing negative phenomena in intestinal bacteria and in liver tissues at the level of tendency. It is expedient to continue studies in this direction.

Boosting seawater denitrification in an electrochemical flow cell.

Nitrogen compounds in current seawater treatment processes typically are converted to nitrate, threatening seawater quality and marine ecology. Electrochemical denitrification is a promising technique, but its efficiency is severely limited by the presence of excess chloride ions. In this work, a flow-through cell went through an on-demand chlorine-mediated electrochemical-chemical tandem reaction process was designed for efficient seawater denitrification. Equipped with ultrathin cobalt-based nanosheets as the cathode catalyst and commercial IrO2-RuO2/Ti as the anode, the newly designed flow-through cell achieved nitrate removal efficiency that was about 50 times greater than the batch cell and nearly 100 % N2 selectivity. Moreover, nitrite and ammonia can also be removed with over 93 % efficiency in total nitrogen (TN) removal. Furthermore, the concentration of active chlorine in the effluent could be adjusted within two orders of magnitude, enabling on-demand release of active chlorine. Finally, this flow-through cell reduced the TN of actual mariculture tailwater (40.1 mg N L-1 nitrate) to only 5.7 mg N L-1, meeting the discharge standard for aquaculture tailwater of Fujian, China. This work demonstrates the paradigm of deep denitrification from ultra-concentrated chlorine ion wastewater using an on-demand active chlorine-mediated electrochemical-chemical tandem reaction process.

Hypochlorous acid electrosynthesis and service life assessment of a Ti|Ti-Ru-Ir-oxides anode assembled in a flow electrolyzer: Understanding the influence of the concurrent O2 bubbling flow.

This paper addresses the influence of bubbling flow and service life of the Ti|Ti-Ru-Ir-oxides anode during the electrosynthesis of HClO in a laboratory-scale filter-press-type electrolyzer. The electrolyzer was assembled in a flow plant in recirculation mode. Polarization curves in rotating disk electrode (RDE) revealed the coexistence of the oxygen evolution reaction (OER) during HClO electrosynthesis in diluted chloride solutions (containing 35 mM NaCl at pH 3). CFD simulations of the two-phase (O2-H2O) flow were obtained by solving simultaneously the Navier-Stokes and charge conservation equations using a finite element method code. The O2-H2O simulations show the efficient gas release in the electrolyzer provoked by the continuous phase (H2O) inertia and the well-engineered cell design. The moderated O2 dispersion caused a quasi-homogeneous current distribution along the anode. However, the current efficiency during HClO electrosynthesis gave values of ∼32% provoked by the OER on the anode. The HClO accumulations (from 3.02 to 6.64 mM) showed excellent agreement with CFD simulations. The accelerated life tests revealed that the Ti | Ti-Ru-Ir-oxides anode has a lifetime of at least 26 years during the HClO electrosynthesis in diluted chloride solutions.

N-Chlorotaurine Solutions as Agents for Infusion Detoxification Therapy: Preclinical Studies.

N-chlorotaurine (NCT) is a broad-spectrum antimicrobial agent with outstanding tolerability, effective for topical and inhalation use. This paper presents the results of studies of single and repeated intravenous infusions of NCT to laboratory animals. The studies were conducted on female Wistar Han rats. The effect of NCT infusions on the general condition, behavioral reactions, main biochemical and hematological parameters, hemocoagulation system, cardiovascular system, and on the condition of the internal organs was studied. It was found that NCT infusions do not reveal deviations in the studied parameters that could indicate a toxic effect. The estimated LD50 is more than 80 mg/kg. In a subchronic experiment, a statistically significant decrease in cholesterol (by up to 11%), glucose (by up to 15%) and excess bases (up to four times) in the blood, and an increase in heart rate (by up to 31%) and frequency of defecations (by up to 35%), as well as pronounced antiplatelet effect, were found. In animals with simulated endotoxicosis, a decrease in the cytolysis and oxidative stress markers was observed. Such effects are caused by both chlorine-active compounds and taurine.The results obtained indicate broad prospects for the use of NCT solutions as an infusion detoxifying agent.

Electro-oxidation of ammonia nitrogen using W, Ti-doped IrO2 DSA as a treatment method for mariculture and livestock wastewater.

Animal farming wastewater is one of the most important sources of ammonia nitrogen (NH4+-N) emissions. Electro-oxidation can be a viable solution for removing NH4+-N in wastewater. Compared with other treatment methods, electro-oxidation has the advantages of i) high removal efficiency, ii) smaller size of treatment facilities, and iii) complete removal of contaminant. In this study, a previously prepared DSA (W, Ti-doped IrO2) was used for electro-oxidation of synthetic mariculture and livestock wastewater. The DSA was tested for chlorine evolution reaction (CER) activity, and the reaction kinetics was investigated. CER current efficiency reaches 60-80% in mariculture wastewater and less than 20% in livestock wastewater. In the absence of NH4+-N, the generation of active chlorine follows zero-order kinetics and its consumption follows first-order kinetics, with cathodic reduction being its main consumption pathway, rather than escape or conversion to ClO3-. Cyclic voltammetry experiments show that NH4+-N in the form of NH3 can be oxidized directly on the anode surface. In addition, the generated active chlorine combines with NH4+-N at a fast rate near the anode, rather than in the bulk solution. In electrolysis experiments, the NH4+-N removal rate in synthetic mariculture wastewater (30-40 mg/L NH4+-N) and livestock wastewater (~ 450 mg/L NH4+-N) is 112.9 g NH4+-N/(m2·d) and 186.5 g NH4+-N/(m2·d), respectively, which is much more efficient than biological treatment. The specific energy consumption (SEC) in synthetic mariculture wastewater is 31.5 kWh/kg NH4+-N, comparable to other modified electro-catalysts reported in the literature. However, in synthetic livestock wastewater, the SEC is as high as 260 kWh/kg NH4+-N, mainly due to the suppression of active chlorine generation by HCO3- and the generation of NO3- as a by-product. Therefore, we conclude that electro-oxidation is suitable for mariculture wastewater treatment, but is not recommended for livestock wastewater. Electrolysis prior to urea hydrolysis may enhance the treatment efficiency in livestock wastewater.

Electrochemical chlorine evolution reaction to improve the desalination of sea sand.

Sea sand, a vital sand and gravel resource, is rich in chloride, which causes corrosion of steel reinforcements. This study investigates the effect of the electrochemical chlorine evolution reaction (CER) on the desalination of sea sand. The results indicate that the chlorine removal efficiency (RE) of sea sand increased from 48.76 to 56.40 % under optimal conditions: a current density of 15 mA/cm2, an electrolysis time of 1 min, and a sodium sulphate-supported electrolyte concentration of 0.05 mol/L. After 30 days of resting, the dissolved chlorine content in sea sand was 0.154 %, which was 21.03 % lower than that of the control group. The electrically active chlorine-mediated desalination process demonstrated excellent dechlorination ability, facilitated the transformation of metal and organic chlorine into liquid and gaseous forms, and reduced the slow release of chloride from sea sand. Therefore, CER is expected to be an efficient method for sea sand desalination.

Modified activated carbon material-assisted electrochemical disinfection effectively inactivate antibiotic-resistant bacteria.

ABSTRACTThe production and widespread transmission of antibiotic-resistant bacteria (ARB) pose an emerging threat to global public health. Electrochemical disinfection (ED) is an environmentally friendly disinfection technology widely utilized to inactivate ARB. This study explored the effect of modified activated carbon material (MACM) assisted ED on multi-ARB inactivation and the regeneration ability. The established ED technique was proven to be effective in inactivating multi-resistant ARB. Specifically, a 5-log ARB removal was achieved within 30 min treatment of MACM-assisted ED at 2.5 V. Additionally, no ARB regrowth was observed, indicating a permanent inactivation of ARB. The high level of reactive chlorine induced by MACM electrolysis was stressful to the ARB. Reactive chlorine led to overproduction of reactive oxygen species and damage of cell membranes in cells, accelerating the inactivation of ARB. Conclusively, the MACM-assisted ED method demonstrated efficient performance for ARB inactivation, implying this method is a promising alternative to traditional disinfection methods in countering ARB transmission.

Oxidation of organics in water by active chlorine performed in microfluidic electrochemical reactors: a new way to improve the performances of the process.

Wastewater polluted by organics can be treated by using electro-generated active chlorine, even if this promising route presents some important drawbacks such as the production of chlorinated by-products. Here, for the first time, this process was studied in a microfluidic electrochemical reactor with a very small inter-electrode distance (145 µm) using a water solution of NaCl and phenol and a BDD anode. The potential production of chloroacetic acids, chlorophenols, carboxylic acids, chlorate and perchlorate was carefully evaluated. It was shown, for the first time, up to our knowledge, that the use of the microfluidic device allows to perform the treatment under a continuous mode and to achieve higher current efficiencies and a lower generation of some important by-products such as chlorate and perchlorate. As an example, the use of the microfluidic apparatus equipped with an Ag cathode allowed to achieve a high removal of total organic carbon (about 76%) coupled with a current efficiency of 17% and the production of a small amount of chlorate (about 30 ppm) and no perchlorate. The effect of many parameters (namely, flow rate, current density and nature of cathode) was also investigated.

Complete abatement of the antibiotic ciprofloxacin from water using a visible-light-active nanostructured photoanode.

The wide use of the fluoroquinolone antibiotic ciprofloxacin (CIP), combined with its limited removal in wastewater treatment plants, results in a dangerous accumulation in natural water. Here, the complete degradation of CIP by photoelectrocatalysis (PEC), using an FTO/ZnO/TiO2/Ag2Se photoanode that is responsive to blue light, has been investigated. A slow antibiotic concentration decay was found in 0.050 M Na2SO4 under the oxidizing action of holes and OH photogenerated at the anode surface. The degradation was strongly enhanced in 0.070 M NaCl due to mediated oxidation by electrogenerated active chlorine. The latter process became faster at pH 7.0, with total abatement of CIP at concentrations below 2.5 mg L-1 operating at a bias potential of +0.8 V. The performance was enhanced when increasing the anodic potential and decreasing the initial drug content. The use of solar radiation from a simulator was also beneficial, owing to the greater lamp power. In contrast, the electrochemical oxidation in the dark yielded a poor removal, thus confirming the critical role of oxidants formed under light irradiation. The generation of holes and OH was confirmed from tests with specific scavengers like ammonium oxalate and tert-butanol, respectively. The prolonged usage of the photoanode affected its performance due to poisoning of its active centers by degradation by-products, although a good PEC reproducibility was obtained upon surface cleaning.

Energy-Efficient Electrosynthesis of High Value-Added Active Chlorine Coupled with H2 Generation from Direct Seawater Electrolysis through Decoupling Electrolytes.

Direct saline (seawater) electrolysis is a well-recognized system to generate active chlorine species for the chloride-mediated electrosynthesis, environmental remediation and sterilization over the past few decades. However, the large energy consumption originated from the high cell voltage of traditional direct saline electrolysis system, greatly restricts its practical application. Here, we report an acid-saline hybrid electrolysis system for energy-saving co-electrosynthesis of active chlorine and H2. We demonstrate that this system just requires a low cell voltage of 1.59 V to attain 10 mA cm-2 with a large energy consumption decrease of 27.7 % compared to direct saline electrolysis system (2.20 V). We further demonstrate that such acid-saline hybrid electrolysis system could be extended to realize energy-saving and sustainable seawater electrolysis. The acidified seawater in this system can absolutely avoid the formation of Ca/Mg-based sediments that always form in the seawater electrolysis system. We also prove that this system in the half-flow mode can realize real-time preparation of active chlorine used for sterilization and pea sprout production.

Effects of intensive chlorine disinfection on nitrogen and phosphorus removal in WWTPs.

The increased use of disinfection since the pandemic has led to increased effective chlorine concentration in municipal wastewater. Whereas, the specific impacts of active chlorine on nitrogen and phosphorus removal, the mediating communities, and the related metabolic activities in wastewater treatment plants (WWTPs) lack systematic investigation. We systematically analyzed the influences of chlorine disinfection on nitrogen and phosphorus removal activities using activated sludge from five full-scale WWTPs. Results showed that at an active chlorine concentration of 1.0 mg/g-SS, the nitrogen and phosphorus removal systems were not significantly affected. Major effects were observed at 5.0 mg/g-SS, where the nitrogen and phosphorus removal efficiency decreased by 38.9 % and 44.1 %, respectively. At an active chlorine concentration of 10.0 mg/g-SS, the nitrification, denitrification, phosphorus release and uptake activities decreased by 15.1 %, 69.5-95.9 %, 49.6 % and 100 %, respectively. The proportion of dead cells increased by 6.1 folds. Reverse transcriptional quantitative polymerase chain reaction (RT-qPCR) analysis showed remarkable inhibitions on transcriptions of the nitrite oxidoreductase gene (nxrB), the nitrite reductase genes (nirS and nirK), and the nitrite reductase genes (narG). The nitrogen and phosphorus removal activities completely disappeared with an active chlorine concentration of 25.0 mg/g-SS. Results also showed distinct sensitivities of different functional bacteria in the activated sludge. Even different species within the same functional group differ in their susceptibility. This study provides a reference for the understanding of the threshold active chlorine concentration values which may potentially affect biological nitrogen and phosphorus removal in full-scale WWTPs, which are expected to be beneficial for decision-making in WWTPs to counteract the potential impacts of increased active chlorine concentrations in the influent wastewater.

Approaching easy water disinfection for all: Can in situ electrochlorination outperform conventional chlorination under realistic conditions?

Electrochlorination has gained research interest for its potential application as decentralized water treatment. A number of studies have displayed promising efficiency for water disinfection. However, a comprehensive comparison of in situ electrodisinfection to existing disinfection techniques, particularly under realistic water composition and flow rates, still needs additional research efforts. The aim of this study is to evaluate in situ electrochlorination while comparing the treatment with conventional chemical chlorination for point-of-entry decentralized disinfection at the household level. An electrochemical flow cell reactor was operated in a single pass mode considering water flow and water consumption for a household of four family members. Disinfection efficiency assessment of both electrochemical and chemical chlorination was conducted using bacterial and viral surrogates, E. coli and MS2 bacteriophage. Furthermore, a techno-economic analysis was conducted, using the levelized cost of water, to compare two electrochemical chlorination scenarios (i.e., electrical grid energy use, and solar panel powered system) and benchmarked against the baseline treatment of chemical chlorination. The findings revealed increased inactivation efficiency of in situ electrochlorination over conventional chlorination (p-value < 0.05). The synergetic impact of radicals and chlorine, and/or contribution of high chlorine concentration at acidic pH near anode surface were identified as key factors that could enhance disinfection performance of in situ electrochlorination. The techno-economic analysis demonstrated that electrochemical treatment, when operated using renewable energy sources, is not only a more environmentally sustainable approach, but also emerges as a more economically feasible solution for decentralized water treatment application. The results highlight that in situ electrochlorination is a more advanced alternative to decentralized water chlorination. However, further fundamental research on products and by-products formation under various water matrices is required.

Performance and applications of ZnO/pyrolusite composite particle electrode.

In this research, we employed a synergistic three-dimensional (3D)-electrode technology in combination with a photocatalytic method to effectively treat wastewater containing chlorine derived from sulfonated phenolic resin (SMP). To modulate the band gap of single ZnO through semiconductor compounding, we successfully synthesized a ZnO/pyrolusite composite particle electrode on the surface of a pyrolusite particle electrode via a hydrothermal method. By incorporating MnO2 into pyrolusite, the ZnO band gap was modified, leading to a reduction in bandwidth of approximately 1.21 eV compared to pristine ZnO. Consequently, the light absorption range of the material was significantly broadened. Through the synergistic effect of photocatalysis, we achieved an impressive 96.45% removal rate of chemical oxygen demand (COD) in SMP wastewater, which effectively enhanced the photocatalytic performance of the material. Furthermore, our quenching experimental study confirmed the involvement of active chlorine species (ACl: Cl2, HClO, and ClO-), OH, h+, and O2- in the degradation process of SMP within the photocatalytic system constructed by the ZnO/pyrolusite composite particle electrode. The relative contributions were ranked as follows: ACl > h+ > ·OH > ·O2-.

Degradation of the antibiotic ciprofloxacin in urine by electrochemical oxidation with a DSA anode.

Ciprofloxacin (CIP) is a commonly prescribed fluoroquinolone antibiotic that, even after uptake, remains unmetabolized to a significant extent-over 70%. Unmetabolized CIP is excreted through both urine and feces. This persistent compound manages to evade removal in municipal wastewater facilities, leading to its substantial accumulation in aquatic environments. This accumulation raises concerns about potential risks to the health of various living organisms. Herein, we present a study on the remediation of CIP in synthetic urine by electrochemical oxidation in an undivided cell with a DSA (Ti/IrO2) anode and a stainless-steel cathode. Physisorbed hydroxyl radical formed at the anode surface from water discharge and free chlorine generated from Cl- oxidation were the main oxidizing agents. The effect of pH and current density (j) on CIP degradation was examined, and its total removal was easily achieved at pH ≥ 7.0 and j ≥ 60 mA cm-2 due to the action of free chlorine. The CIP decay always followed a pseudo-first-order kinetics. The components of the synthetic urine were also oxidized. The main nitrogenated species released was NH3. A very small concentration of free chlorine was quantified at the end of the treatment, thus demonstrating the good performance of electrochemical oxidation and its effectiveness to destroy all the organic pollutants. The present study demonstrates the simultaneous oxidation of the organic components of urine during CIP degradation, thus showing a unique perspective for its electrochemical oxidation that enhances the environmental remediation strategies.

Modulating Cu valence state in Cu and graphene oxide composites for electrocatalytic tetracycline hydrochloride degradation.

Cu and graphene oxide composites (Cu-GO) were designed by anchoring Cu+ via oxygen groups in GO based on the heavy co-relationships of copper (Cu) anode electrocatalytic activity with Cu valence state. With the consumption of oxygen groups under various pyrolysis temperatures, the Cu valence state changed from Cu ions (as CuCl2 and CuCl) to Cu oxide (CuO and Cu2O) and the final metallic Cu. In which the Cu+ in CuCl was more favorable for electrocatalytic oxidation than other Cu valence states. Due to the dramatic contribution of 1O2 and active chlorine, 100% degradation efficiency was achieved using tetracycline hydrochloride (TCH) as the target pollutant. Cu+ showed a selective preference for 1O2 and active chlorine triggering, rather than metallic Cu. Under the attack of 1O2 and active chlorine, the degradation intermediates of TCH were then provided by LC-MS results. The final results not only prove the feasibility of the Cu-GO/electrocatalysis system for pollution control but also shed light on the anode design via Cu valence state modulation.

Chlorine-mediated electrochemical advanced oxidation process for ammonia removal: Mechanisms, characteristics and expectation.

Chlorine-Mediated Electrochemical Advanced Oxidation (Cl-EAO) technology is a promising approach for ammonia removal from wastewater due to its numerous advantages, including small infrastructure, short processing time, easy operation, high security, and high nitrogen selectivity. This paper provides a review of the ammonia oxidation mechanisms, characteristics, and anticipated applications of Cl-EAO technology. The mechanisms of ammonia oxidation encompass breakpoint chlorination and chlorine radical oxidation, although the contributions of active chlorine, Cl, and ClO remain uncertain. This study critically examines the limitations of existing research and suggests that a combination of determining free radical concentration and simulating a kinetic model would help elucidate the contributions of active chlorine, Cl, and ClO to ammonia oxidation. Furthermore, this review comprehensively summarizes the characteristics of ammonia oxidation, including kinetic properties, influencing factors, products, and electrodes. The amalgamation of Cl-EAO technology with photocatalytic and concentration technologies has the potential to enhance ammonia oxidation efficiency. Future research should concentrate on clarifying the contributions of active chlorine, Cl, and ClO to ammonia oxidation, the production of chloramines and other byproducts, and the development of more efficient anodes for the Cl-EAO process. The main objective of this review is to enhance the understanding of the Cl-EAO process. The findings presented herein contribute to the advancement of Cl-EAO technology and provide a foundation for future studies in this field.

Role of the active chlorine generated in situ on the photoelectrocatalytic inactivation of bacteria and fungi with TiO2 nanotubes.

Immobilised TiO2 nanotube (TiO2-NT) electrodes were grown via electrochemical anodisation in an aqueous solution containing fluoride ions at 10, 20 and 30 V. The photocatalytic (PC) and photoelectrocatalytic (PEC) activity of TiO2-NTs electrodes in the oxidation of methanol and the inactivation of bacteria and fungi was studied in different chloride salts electrolytes. Low concentrations of electrochemically generated oxidising species, such as free chlorine, were measured in experiments at pH 8.5 and +1 V of applied potential. Increasing the anodising potential results in longer nanotubes with higher photoactivity. The TiO2-NT electrode anodised at 30 V (TiO2-NT30V) generates free chlorine with an average concentration of 0.03 mg·L-1 upon illumination with UV-A at +1 V of potential bias. This concentration was enough to achieve 99.99 % of inactivation of a 106 CFU·mL-1 Gram-negative bacteria (Escherichia coli) in <3 min and Gram-positive bacteria (Enterococcus faecalis) after 7 min, whereas fungi (Candida albicans) required 15 min. The low production of chlorine was found to have a big impact on the bacteria and fungi inactivation even in not favourable chlorine generation conditions. An in situ investigation of the most influential parameters in the inactivation of some microorganisms with PEC and NT30V electrode has been done. It was found that free chlorine production increases with the length of TiO2-NT, with Cl- concentration up to 15 mmol·L-1 and with the application of potential bias. TiO2-NT30V photoanode has been demonstrated to produce active chlorine at levels compatible with the water disinfection process, suggesting that the present method could be considered a promising alternative for in situ chlorine-based disinfection.

New insights into the mechanism of Fered-Fenton treatment of industrial wastewater with high chloride content: Role of multiple reactive species.

Hydroxyl radical (OH) is considered the dominant reactive species in the electro-Fenton (EF) and Fered-Fenton (EF-Fere) processes for wastewater treatment. However, in chloride-rich media, this is arguable due to the obscure mechanisms for the oxidant speciation and pollutant degradation. Herein, the role of active chlorine and Fe(IV)-oxo species (FeIVO2+) as primary oxidizing agents in HClO-mediated Fered-Fenton (EF-Fere-HClO) process is discussed, along with the dependence of their contribution on the pollutant structure. HClO generated from anodic oxidation of Cl- can be consumed by added H2O2 to form singlet oxygen (1O2), which is detrimental because this species is quickly deactivated by water. The reaction between HClO and Fe2+ was proved to generate FeIVO2+, rather than OH or Cl suggested in the literature. The yield of FeIVO2+ species was proportional to the Cl- concentration and barely affected by solution pH. The long-lived HClO and FeIVO2+ can selectively react with electron-rich compounds, which occurs simultaneously to the non-selective attack of OH formed from Fenton's reaction. The FeIVO2+ and OH concentration profiles were successfully modelled. Although the accumulation of toxic chlorinated by-products from HClO-mediated oxidation might cause new environmental concerns, the toxicity of pesticide wastewater with 508 mM Cl- was halved upon EF-Fere-HClO treatment.

Visible Light-Driven Conversion of Carbon-Sequestrated Seawater into Stoichiometric CO and HClO with Nitrogen-Doped BiOCl Atomic Layers.

Seawater is one of the most important CO2 sequestration media for delivering value-added chemicals/fuels and active chlorine; however, this scenario is plagued by sluggish reaction rates and poor product selectivity. Herein, we first report the synthesis of nitrogen-doped BiOCl atomic layers to directly split carbon-sequestrated natural seawater (Yellow Sea, China) into stoichiometric CO (92.8 µmol h-1 ) and HClO (83.2 µmol h-1 ) under visible light with selectivities greater than 90 %. Photoelectrons enriched on the exposed BiOCl{001} facet kinetically facilitate CO2 -to-CO reduction via surface-doped nitrogen bearing Lewis basicity. Photoholes, mainly located on the lateral facets of van der Waals gaps, promote the selective oxidation of Cl- into HClO. Sequestrated CO2 also maintains the pH of seawater at around 4.2 to prevent the alkaline earth cations from precipitating. The produced HClO can effectively kill typical bacteria in the ballast water of ocean-going cargo ships, offering a green and safe way for onsite sterilization.

Insight into micropollutant abatement during ultraviolet light-emitting diode combined electrochemical process: Reaction mechanism, contributions of reactive species and degradation routes.

Electrochemical process coupling with ultraviolet light-emitting diode for micropollutant abatement was evaluated in the treatment of wastewater containing Cl-. Four representative micropollutants, atrazine, primidone, ibuprofen and carbamazepine, were selected as target compounds. The impacts of operating conditions and water matrix on micropollutant degradation were investigated. Fluorescence excitation-emission matrix spectroscopy spectra and high performance size exclusion chromatography were employed to characterize the transformation of effluent organic matter in treatment. The degradation efficiencies of atrazine, primidone, ibuprofen and carbamazepine are 83.6 %, 80.6 %, 68.7 % and 99.8 % after 15 min treatment, respectively. The increment of current, Cl- concentration and ultraviolet irradiance promote the micropollutant degradation. However, the presence of bicarbonate and humic acid inhibit micropollutant degradation. The mechanism of micropollutant abatement was elaborated based on reactive species contributions, density functional theory calculation and degradation routes. Free radicals (HO•, Cl•, ClO• and Cl2•-) could be generated by chlorine photolysis and subsequent propagation reactions. The concentrations of HO• and Cl• are 1.14 × 10-13 M and 2.0 × 10-14 M in optimal condition, respectively, and the total contributions of HO• and Cl• for the degradation of atrazine, primidone, ibuprofen and carbamazepine are 24 %, 48 %, 70 % and 43 %, respectively. The degradation routes of four micropollutants are elucidated based on intermediate identification, Fukui function and frontier orbital theory. Micropollutants can be effectively degraded in actual wastewater effluent, and the small molecule compound proportion increases during effluent organic matter evolution. Compared with photolysis and electrolysis, the coupling of the two processes has potential for energy saving in micropollutant degradation, which shed light on the prospects of ultraviolet light-emitting diode coupling with electrochemical process for effluent treatment.