Effect of household pipe materials on formation and chlorine resistance of the early-stage biofilm: various interspecific interactions exhibited by the same microbial biofilm in different pipe materials.

Microbial community biofilm exists in the household drinking water system and would pose threat to water quality. This paper explored biofilm formation and chlorination resistance of ten dual-species biofilms in three typical household pipes (stainless steel (SS), polypropylene random (PPR), and copper), and investigated the role of interspecific interaction. Biofilm biomass was lowest in copper pipes and highest in PPR pipes. A synergistic or neutralistic relationship between bacteria was evident in most biofilms formed in SS pipes, whereas four groups displayed a competitive relationship in biofilms formed in copper pipe. Chlorine resistance of biofilms was better in SS pipes and worse in copper pipes. It may be helped by interspecific relationships, but was more dependent on bacteria and resistance mechanisms such as more stable extracellular polymeric substance. The corrosion sites may also protect bacteria from chlorination. The findings provide useful insights for microbial control strategies in household drinking water systems.

Resistance of Blastocystis to chlorine and hydrogen peroxide.

Blastocystis is a ubiquitous, widely distributed protist inhabiting the gastrointestinal tract of humans and other animals. The organism is genetically diverse, and so far, at least 28 subtypes (STs) have been identified with ST1-ST9 being the most common in humans. The pathogenicity of Blastocystis is controversial. Several routes of transmission have been proposed including fecal-oral (e.g., zoonotic, anthroponotic) and waterborne. Research on the latter has gained traction in the last few years with the organism having been identified in various bodies of water, tap water, and rainwater collection containers including water that has been previously filtered and/or chlorinated. Herein, we assessed the resistance of 11 strains maintained in culture, spanning ST1-ST9 to various chlorine and hydrogen peroxide concentrations for 24 h, and performed recovery assays along with re-exposure. Following the treatment with both compounds, all subtypes showed increased resistance, and viability could be visualized at the cellular level. These results are hinting at the presence of mechanism of resistance to both chlorine and hydrogen peroxide. As such, this pilot study can be the platform for developing guidelines for water treatment processes.

Chlorine-Coordinated Pd Single Atom Enhanced the Chlorine Resistance for Volatile Organic Compound Degradation: Mechanism Study.

The development of catalysts with high chlorine resistance for volatile organic compound (VOC) degradation is of great significance to achieve air purification. Herein, Pd@ZrO2 catalysts with monodispersed Pd atoms coordinated with Cl were prepared using an in situ grown Zr-based metal-organic framework (MOF) as the sacrifice templates to enhance the chlorine resistance for VOC elimination. The residual Cl species from the Zr-MOF coordinated with Pd, forming Pd1-Cl species during the pyrolysis. Meanwhile, abundant oxygen vacancies (VO) were generated, which enhanced the adsorption and activation of gaseous oxygen molecules, accelerating the degradation of VOCs. In addition, the Pd@ZrO2 catalysts exhibited satisfactory water resistance, long-term stability, and great resistance to CO and dichloromethane (DCM) for VOC elimination. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results elucidated that the generation of Pd1-Cl species in Pd@ZrO2 suppressed the absorption of DCM, releasing more active sites for toluene and its intermediate adsorption. Simultaneously, the monodispersed Pd atoms and VO improved the reactivity of gaseous oxygen molecule adsorption and dissociation, boosting the deep decomposition of toluene and its intermediates. This work may provide a new strategy for rationally designing high-chlorine resistance catalysts for VOC elimination to improve the atmospheric environment.

Modification Mechanism of Polyamide Reverse Osmosis Membrane by Persulfate: Roles of Hydroxyl and Sulfate Radicals.

Oxidative modification is a facile method to improve the desalination performance of thin-film composite membranes. In this study, we comparatively investigated the modification mechanisms induced by sulfate radical (SO4• -) and hydroxyl radical (HO•) for polyamide reverse osmosis (RO) membrane. The SO4• -- and HO•-based membrane modifications were manipulated by simply adjusting the pH of the thermal-activated persulfate solution. Although both of them improved the water permeability of the RO membrane under certain conditions, the SO4• --modified membrane notably prevailed over the HO•-modified one due to higher permeability, more consistent salt rejection rates over wide pH and salinity ranges, and better stability when exposed to high doses of chlorine. The differences of the membranes modified by the two radical species probably can be related to their distinct surface properties in terms of morphology, hydrophilicity, surface charge, and chemical composition. Further identification of the transformation products of a model polyamide monomer using high-resolution mass spectrometry demonstrated that SO4• - initiated polymerization reactions and produced hydroquinone/benzoquinone and polyaromatic structures; whereas the amide group of the monomer was degraded by HO•, generating hydroxyl, carboxyl, and nitro groups. The results will enlighten effective ways for practical modification of polyamide RO membranes to improve desalination performances and the development of sustainable oxidation-combined membrane processes.

Engineering Platinum Catalysts via a Site-Isolation Strategy with Enhanced Chlorine Resistance for the Elimination of Multicomponent VOCs.

Pt-based catalysts can be poisoned by the chlorine formed during the oxidation of multicomponent volatile organic compounds (VOCs) containing chlorinated VOCs. Improving the low-temperature chlorine resistance of catalysts is important for industrial applications, although it is yet challenging. We hereby demonstrate the essential catalytic roles of a bifunctional catalyst with an atomic-scale metal/oxide interface constructed by an intermetallic compound nanocrystal. Introducing trichloroethylene (TCE) exhibits a less negative effect on the catalytic activity of the bimetallic catalyst for o-xylene oxidation, and the partial deactivation caused by TCE addition is reversible, suggesting that the bimetallic, HCl-etched Pt3Sn(E)/CeO2 catalyst possesses much stronger chlorine resistance than the conventional Pt/CeO2 catalyst. On the site-isolated Pt-Sn catalyst, the presence of aromatic hydrocarbon significantly inhibits the adsorption strength of TCE, resulting in excellent catalytic stability in the oxidation of the VOC mixture. Furthermore, the large amount of surface-adsorbed oxygen species generated on the electronegative Pt is highly effective for low-temperature C-Cl bond dissociation. The adjacent promoter (Sn-O) possesses the functionality of acid sites to provide sufficient protons for HCl formation over the bifunctional catalyst, which is considered critical to maintaining the reactivity of Pt by removing Cl and decreasing the polychlorinated byproducts.

Global bibliometric meta-analytic assessment of research trends on microbial chlorine resistance in drinking water/water treatment systems.

Chlorine is the commonest and cheapest disinfectant used in drinking water and wastewater treatment at household, municipal and industrial levels. However, the uprising of microbial chlorine resistance (MCR) pose critical public health hazard concerns; because, its potentiate exposure to difficult-to-treat resistant pathogens. Therefore, this study aimed at evaluating the burden of MCR in drinking water/wastewater treatment and distribution systems (DWWTDS) via science mapping of research productivity (authors, countries, institutions), thematic conceptual framework, disciplines, research networks and associated intellectual landscape. MCR data were mined from Scopus and Web of Science based on optimized algorithms with the root key term "chlorine* resistant*'' and analysed for pre-set indicator variables. Results revealed 1127 documents from 442 journals and 1430% average growth rate (AGR) of research articles from 2017 to 2019 on MCR. Country-wise, the USA (n = 299), China (n = 119), and Japan (n = 43) ranked in the 1st, 2nd, and 3rd positions respectively, among the top participating countries in MCR research. MCR research had considerable performance in public health and sustainable concern subjects namely, Environmental Sciences & Ecology, Engineering, Microbiology, Water Resources, Biotechnology & Applied Microbiology, Food Science & Technology, Public, Environ & Occupational Health, Chemistry, Infectious Diseases, and Marine & Freshwater Biology; and with noticeable AGR in Environmental Sciences & Ecology (330%) and Infectious Diseases (130%). The study found biofilm-related thrusts (n = 90, 270% AGR) as main research hotspots on MCR. Overall, the study identified and discussed four important thematic areas of public health challenges in MCR that could promote increasing waterborne diseases due to (re)emerging pathogens, enteric viruses and dissemination in DWWTDS. In conclusion, this study provides comprehensive overview of the growing burden of MCR in DWWTDS and standout as a primer of information for researchers on MCR. It recommends direct, intentional and integrated research priorities on MCR to overcome accompanying public health and environmental threats. In addition, chlorine resistance in waterborne fungi have not received research attention. Research activities related to fungal chlorine resistance will be an invaluable future direction in DWWTDS and guide against exposure to waterborne pathogenic fungi and mycotoxins. It is unknown whether chlorine resistance can be acquired by horizontal gene transfer in microorganisms and future research should elucidate this important thrust.

The Locus of Heat Resistance Confers Resistance to Chlorine and Other Oxidizing Chemicals in Escherichia coli.

Some chlorine-resistant Escherichia coli isolates harbor the locus of heat resistance (LHR), a genomic island conferring heat resistance. In this study, the protective effect of the LHR for cells challenged by chlorine and oxidative stress was quantified. Cloning of the LHR protected against NaClO (32 mM; 5 min), H2O2 (120 mM; 5 min), and peroxyacetic acid (105 mg/liter; 5 min) but not against 5.8 mM KIO4, 10 mM acrolein, or 75 mg/liter allyl isothiocyanate. The lethality of oxidizing treatments for LHR-negative strains of E. coli was about 2 log10 CFU/ml higher than that for LHR-positive strains of E. coli The oxidation of cytoplasmic proteins and membrane lipids was quantified with the fusion probe roGFP2-Orp1 and the fluorescent probe BODIPY581/591, respectively. The fragment of the LHR coding for heat shock proteins protected cytoplasmic proteins but not membrane lipids against oxidation. The middle fragment of the LHR protected against the oxidation of membrane lipids but not of cytoplasmic proteins. The addition of H2O2, NaClO, and peroxyacetic acid also induced green fluorescent protein (GFP) expression in the oxidation-sensitive reporter strain E. coli O104:H4 Δstx2::gfp::amp Cloning of pLHR reduced phage induction in E. coli O104:H4 Δstx2::gfp::amp after treatment with oxidizing chemicals. Screening of 160 strains of Shiga toxin-producing E. coli (STEC) revealed that none of them harbors the LHR, additionally suggesting that the LHR and Stx prophages are mutually exclusive. Taking our findings together, the contribution of the LHR to resistance to chlorine and oxidative stress is based on the protection of multiple cellular targets by different proteins encoded by the genetic island.IMPORTANCE Chlorine treatments are used in water and wastewater sanitation; the resistance of Escherichia coli to chlorine is thus of concern to public health. We show that a genetic island termed the locus of heat resistance (LHR) protects E. coli not only against heat but also against chlorine and other oxidizing chemicals, adding to our knowledge of the tools used by E. coli to resist stress. Specific detection of the oxidation of different cellular targets in combination with the cloning of fragments of the LHR provided insight into mechanisms of protection and demonstrated that different fragments of the LHR protect different cellular targets. In E. coli, the presence of the LHR virtually always excluded other virulence factors. It is tempting to speculate that the LHR is maintained by strains of E. coli with an environmental lifestyle but is excluded by pathogenic strains that adapted to interact with vertebrate hosts.

Machine Learning Method to Explore the Correlation between Fly Ash Content and Chloride Resistance.

Chloride ion corrosion has been considered to be one of the main reasons for durability deterioration of reinforced concrete structures in marine or chlorine-containing deicing salt environments. This paper studies the relationship between the amount of fly ash and the durability of concrete, especially the resistance to chloride ion erosion. The heat trend map of total chloride ion factor correlation displayed that the ranking of factor correlations was as follows: sampling depth > cement dosage > fly ash dosage. In order to verify the effect of fly ash dosage on chloride ion resistance, three different machine learning algorithms (RF, GBR, DT) are employed to predict the total chloride content of fly ash proportioned concrete with varying admixture ratios, which are evaluated based on R2, MSE, RMSE, and MAE. The results predicted by the RF model show that the threshold of fly ash admixture in chlorinated salt environments is 30-40%. Replacing part of cement with fly ash in the mixture of concrete below this threshold of fly ash, it could change the phase structure and pore structure, which could improve the permeability of fly ash concrete and reduce the content of free chloride ions in the system. Machine learning modeling using sample data can accurately predict concrete properties, which effectively reduce engineering tests. The development of machine learning models is essential for the decarbonization and intelligence of engineering.

Preparation of chlorine-resistant and regenerable antifouling nanofiltration membrane through interfacial polymerization using beta cyclodextrin monomers.

Constructing membrane with good chlorine resistance and antifouling properties is considered to be important challenges confronting membrane applications. In this study, a composite nanofiltration (NF) membrane (ß-CDx/y/PES) was prepared by interfacial polymerization using beta cyclodextrin (ß-CD) monomers. Subsequently, the ß-CD-based (AZ-ß-CDx/y/PES) membrane was prepared by assembling azobenzene labeled zwitterions into the hydrophobic internal cavity of ß-CD via host-guest interaction. The optimized membrane exhibited slight change in water flux and rejection under chlorine environment. The AZ-ß-CDx/y/PES membrane also displayed an evidently lower loss in water flux in the antifouling test in comparison with the ß-CDx/y/PES membrane. More interestingly, the trans azo groups in azobenzene labeled zwitterions can turn into the cis isomers as the visible light irradiation converted to the UV light irradiation, breaking the interaction between azobenzene labeled zwitterions and ß-CD. Hence, the contaminants upon the membrane surface can be simply eliminated by water washing under UV light irradiation. The antifouling membrane can be regenerated via immersing the reacquired ß-CD2/10/PES membrane into fresh azobenzene labeled zwitterions solution again.

A review on polyester and polyester-amide thin film composite nanofiltration membranes: Synthesis, characteristics and applications.

Nanofiltration (NF) membranes have been widely used in various fields including water treatment and other separation processes, while conventional thin film composite (TFC) membranes with polyamide (PA) selective layers suffer the problems of fouling and chlorine intolerance. Due to the abundant hydrophilic hydroxyl groups and ester bonds free from chlorine attack, the TFC membranes composed of polyester (PE) or polyester-amide (PEA) selective layers have been proven to possess enhanced anti-fouling properties and superior chlorine resistance. In this review, the research progress of PE and PEA nanofiltration membranes is systematically summarized according to the variety of hydroxyl-containing monomers for membrane fabrication by the interfacial polymerization (IP) reaction. The synthesis strategies as well as the mechanisms for tailoring properties and performance of PE and PEA membranes are analyzed, and the membrane application advantages are demonstrated. Moreover, current challenges and future perspectives of the development of PE and PEA nanofiltration membranes are proposed. This review can offer guidance for designing high-performance PE and PEA membranes, thereby further promoting the efficacy of nanofiltration.

Insights into the Electronic Structure Effect of SnMnOx Nanorod Catalysts for Low-Temperature Catalytic Combustion of o-Dichlorobenzene.

For the catalytic combustion reaction of chlorinated volatile organic compounds (CVOCs), the redox properties and acid sites of the catalyst surface are key factors in determining the activity, selectivity, and chlorine-resistance stability. Herein, a series of SnMnOx catalysts for the catalytic combustion of CVOCs were prepared by the changing of Sn-doping way to regulate the electron valance state of Mn element, including reflux (R-SnMnOx ), co-precipitation (C-SnMnOx ) and impregnation (I-SnMnOx ). It was discovered that the R-SnMnOx catalyst had better activity and chlorine resistance than the R-MnOx , C-SnMnOx and I-SnMnOx catalyst, and we discovered that the doping ways of Sn in MnOx catalyst could regulate greatly the surface acidity, active oxygen species, the chemical state of Mnn+ species, and redox ability. Especially, the R-SnMnOx catalysts exhibit excellent water resistance, and the reasons were related to the strong interaction of Snn+ and Mnn+ , which could promote obviously the dispersion of active Mn species, form a large number of acid sites, provide the abundant lattice oxygen species, and own the excellent redox ability, which accelerate the rate of charge transfer between Snn+ and Mnn+ (Sn4+ +Mn2+ →Sn2+ +Mn4+ ) to produce the abundant active species and accelerate the rapid conversion of benzene and intermediates conversion.

Incidence of co-resistance to antibiotics and chlorine in bacterial biofilm of hospital water systems: Insights into the risk of nosocomial infections.

The presence of biofilms in drinking water distribution systems (DWDS) in healthcare settings poses a considerable risk to the biological security of water, particularly when the biofilm bacteria demonstrate antimicrobial resistance characteristics. This study aimed to investigate the occurrence of antibiotic-resistant bacteria (ARB) in biofilms within DWDS of hospitals. The chlorine resistance of the isolated ARB was analyzed, and then chlorine-resistant bacteria (CRB) were identified using molecular methods. Additionally, the presence of several antibiotic resistance genes (ARGs) was monitored in the isolated ARB. Out of the 41 biofilm samples collected from hospitals, ARB were detected in 32 (78%) of the samples. A total of 109 colonies of ARB were isolated from DWDS of hospitals, with ß-lactam resistant bacteria, including ceftazidime-resistant and ampicillin-resistant bacteria, being the most frequently isolated ARB. Analyzing of ARGs revealed the highest detection of aac6, followed by sul1 gene. However, the ß-lactamase genes blaCTX-M and blaTEM were not identified in the ARB, suggesting the presence of other ß-lactamase genes not included in the tested panel. Exposure of ARB to free chlorine at a concentration of 0.5 mg/l showed that 64% of the isolates were CRB. However, increasing the chlorine concentration to 4 mg/l decreased the high fraction of ARB (91%). The domi||nant CRB identified were Sphingomonas, Brevundimonas, Stenotrophomonas, Bacillus and Staphylococcus with Bacillus exhibiting the highest frequency. The results highlight the potential risk of biofilm formation in the DWDS of hospitals, leading to the dissemination of ARB in hospital environments, which is a great concern for the health of hospitalized patients, especially vulnerable individuals. Surveillance of antimicrobial resistance in DWDS of hospitals can provide valuable insights for shaping antimicrobial use policies and practices that ensure their efficacy.

Surface Treatment by Physical Irradiation for Antifouling, Chlorine-Resistant RO Membranes.

Reverse osmosis (RO) membranes represent a strategic tool for the development of desalination and water treatment processes. Today's global needs for clean water supplies show stressing circumstances to secure this supply, relying upon desalination and wastewater treatment and reuse, especially in Egypt and the Middle East. However, chlorine attack and fouling of polyamide layers, the active (selective) layers of RO membranes, are representing a great obstacle to seriously spreading the use of this technology. One promising way of fouling control and chlorine resistance is surface modification using grafting by plasma or vacuum ultraviolet (VUV) irradiation as a layer-by-layer assembly on polyamide membranes. Several studies have shown the effect of grafting by plasma using methacrylic acid (atmospheric pressure plasma) and showed that grafted coatings can improve PA membranes toward permeation compared with commercial ones with fouling behavior but not chlorine resistance. In this work, the techniques of layer-by-layer (LBL) assembly for previously prepared PA RO membranes (3T) using a mixed-base polymer of polysulfone and polyacrylonitrile in the presence of nanographene oxide (GO) without chemical grafting and with chemically grafted poly-methacrylic acid (3TG) were used. Membranes 3T, 3TG, a blank one (a base polymer membrane only was surface modified using VUV activation (AKT), and one with a grafted layer with polyethylene glycol (VUV-PEG) were prepared. These were then compared with polydimethylsiloxane (VUV-PDMS) and another surface modification with low-pressure plasma using acrylic acid (acryl) and hexadimethyl siloxane (GrowPLAS). The tested membranes were evaluated by short-term permeation and salt rejection experiments together with fouling behavior and chlorine resistance. A clear improvement of chlorine resistance and antifouling was observed for 3T membranes under plasma treatment, especially with the grafting with polyacrylic acid. Better antifouling and antichlorine behaviors were achieved with the vacuum UV treatment.

Construction and Chlorine Resistance of Thiophene-Poly(ethyleneimine)-Based Dual-Functional Nanofiltration Membranes.

The demand to improve the chlorine resistance of polyamide (PA) membranes is escalated with greater amounts of chlorine-containing disinfectant being used in global water treatment during the COVID-19 pandemic. In this work, we designed thiophene-functionalized poly(ethyleneimine) (TPEI) materials first and grafted them onto a conventional PA membrane to develop novel nanofiltration membranes (PEI-M, TPEI-1-M, TPEI-2-M). These membranes have dual-functionalized selective surfaces covered by hydrophilic amino groups and electron-rich thiophene moieties, which endow these membranes with superior chlorine resistance and improved separation performance. The modified membranes increase the rejection of MgCl2 from 86.5% of the nascent PA membrane (PA-M) to higher than 93.0% without sacrificing the membrane water permeability. More stable separation performance is achieved with all of the as-prepared membranes than PA-M after exposure to a 2000 ppm sodium hypochlorite solution. TPEI-2-M outperforms other membranes after being treated in a chlorination intensity of 16,000 ppm·h with the smallest flux loss and the highest MgCl2 rejection. This is mainly ascribed to the highest amount of amino and thiophene moieties on the TPEI-2-M surface. This study provides an effective protocol for developing novel PA-based nanofiltration membranes while demonstrating its superiority over current technologies with exceptional separation performance and antichlorine ability.

Characterization of a chlorine resistant and hydrophilic TiO2/calcium alginate hydrogel filtration membrane used for protein purification maintaining protein structure.

The development of membranes for protein purification has stringent requirement of disinfection resistance, low protein adsorption and anti-fouling, without changing protein structure. In this study, hydrophilic titanium dioxide (TiO2)/calcium alginate (TiO2/CaAlg) hydrogel membranes were prepared by a simple ionic cross-linking method. The effects of the porogenic agent polyethylene glycol (PEG) concentration, the molecular weight of PEG, and the concentration of TiO2 on the filtration properties were systematically investigated. The TiO2/CaAlg membrane exhibited excellent bovine serum albumin (BSA) rejection and anti-fouling properties. The mechanical properties and surface energy of the TiO2/CaAlg membrane were significantly improved. The chemical bonding mechanism of TiO2 and NaAlg was investigated by molecular dynamic simulation. The TiO2/CaAlg membrane had good chlorine resistance and could be disinfected or cleaned with sodium hypochlorite. The TiO2/CaAlg hydrogel membrane loaded with polyhydroxybutyrate (PHB) nanofibers maintained high flux (136.7 L/m2h) and high BSA rejection (98.0 %) at 0.1 MPa. The results of circular dichroism and synchronous fluorescence indicated that the secondary structure of BSA was maintained after membrane separation. This study provides one method for the preparation of green and environmentally friendly membrane for protein purification.

High-Flux Nanofibrous Composite Reverse Osmosis Membrane Containing Interfacial Water Channels for Desalination.

A nanofibrous composite reverse osmosis (RO) membrane with a polyamide barrier layer containing interfacial water channels was fabricated on an electrospun nanofibrous substrate via an interfacial polymerization process. The RO membrane was employed for desalination of brackish water and exhibited enhanced permeation flux as well as rejection ratio. Nanocellulose was prepared by sequential oxidations of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and sodium periodate systems and surface grafting with different alkyl groups including octyl, decanyl, dodecanyl, tetradecanyl, cetyl, and octadecanyl groups. The chemical structure of the modified nanocellulose was verified subsequently by Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), and solid NMR measurements. Two monomers, trimesoyl chloride (TMC) and m-phenylenediamine (MPD), were employed to prepare a cross-linked polyamide matrix, i.e., the barrier layer of the RO membrane, which integrated with the alkyl groups-grafted nanocellulose to build up interfacial water channels via interfacial polymerization. The top and cross-sectional morphologies of the composite barrier layer were observed by means of scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM) to verify the integration structure of the nanofibrous composite containing water channels. The aggregation and distribution of water molecules in the nanofibrous composite RO membrane verified the existence of water channels, demonstrated by molecular dynamics (MD) simulations. The desalination performance of the nanofibrous composite RO membrane was conducted and compared with that of commercially available RO membranes in the processing of brackish water, where 3 times higher permeation flux and 99.1% rejection ratio against NaCl were accomplished. This indicated that the engineering of interfacial water channels in the barrier layer could substantially increase the permeation flux of the nanofibrous composite membrane while retaining the high rejection ratio as well, i.e., to break through the trade-off between permeation flux and rejection ratio. Antifouling properties, chlorine resistance, and long-term desalination performance were also demonstrated to evaluate the potential applications of the nanofibrous composite RO membrane; remarkable durability and robustness were achieved in addition to 3 times higher permeation flux and a higher rejection ratio against commercial RO membranes in brackish water desalination.

Interfacial Polymerization of Highly Active Thiolated Cyclodextrin for the Fabrication of a Loose Nanofiltration Membrane with a Chlorine-Resistant Poly(thioester) Linkage.

Cyclodextrins have been frequently used to fabricate membranes via interfacial polymerization (IP). However, the relatively low reactivity of pristine cyclodextrins often induces a lower cross-linking density and unsatisfactory separation performance. In this work, to introduce a highly active thiolated ß-cyclodextrin (CD-SH) monomer into IP progress, we constructed a dense and porous poly(thioester) linkage on a commercial membrane surface with loose nanofiltration by IP of CD-SH and trimesoyl trichloride (TMC) as the monomer in an aqueous phase and organic phase separately for the first time. Furthermore, the reactivity of CD-SH has been fully demonstrated by the two-phase IP aiming at unmodified ß-CD, a CD-SH/TMC freestanding membrane with a thicker interfacial layer and a smoother surface, and a PAN/CD-SH membrane with a narrow porous distribution. The composite membrane possessed superior separation performance for a high rejection (83.1-99.6%) of different anionic dyes and a low rejection (<20%) of salts, as well as a high-efficiency sieving ability of dye/dye and dye/salt mixtures. The membrane with a poly(thioester) selective layer could steadily operate in a long-term filtration test and exhibit great stability, chloride-resistance performance, and recyclability.

Effect of chlorine disinfectant influx on biological sewage treatment process under the COVID-19 pandemic: Performance, mechanisms and implications.

Since the onset of the COVID-19 Pandemic, large amounts of chlorine-containing disinfectants have been used to interrupt the spread of SARS-CoV-2 and residual chlorine eventually entered the hospital or municipal sewage treatment facilities. However, little is known about the effect of chlorine influx on the biological sewage treatment process. Here we investigated the effect of chlorine on the microbiome and the mechanism of microbial chlorine resistance in the activated sludge of the aerobic treatment process, using metagenomic and metatranscriptomic sequencing. We found that chlorine could negatively impact the aerobic treatment performance regarding nitrogen/COD removal with a dose-dependent effect, and the dual effects of chlorine dose and interaction time differentiated the microbial community in activated sludge. The decline of nitrogen/COD removal was attributed to the compressed activity of functional microorganisms, such as the ammonia oxidation bacteria, under chlorinated conditions, and the damage cannot be recovered in a short term. In addition, some microorganisms could survive in chlorinated conditions by up-regulating the chlorine resistance genes (CRGs) expression (approximately 1.5 times) and stimulating new CRGs expression. In particular, species Acinetobacter johnsonii could resist high concentrations of chlorine through various mechanisms, especially the overexpression of efflux pump function encoded by qac genes play a key role. Based on these results, considering the persistence of the epidemic and extensive use of chlorine disinfectants, it cannot be ignored that large amounts of residual chlorine are entering the biological treatment facility, and strictly de-chlorination measures or microbial chlorine resistance regulations before entering should be implemented.

Three-dimensional porous CuO-modified CeO2-Al2O3 catalysts with chlorine resistance for simultaneous catalytic oxidation of chlorobenzene and mercury: Cu-Ce interaction and structure.

Chlorine poisoning effects are still challenging to develop efficient catalysts for applications in chlorobenzene (CB) and mercury (Hg0) oxidation. Herein, three-dimensional porous CuO-modified CeO2-Al2O3 catalysts with macroporous framework and mesoporous walls prepared via a dual template method were employed to study simultaneous oxidation of CB and Hg0. CuO-modified CeO2-Al2O3 catalysts with three-dimensional porous structure exhibited outstanding activity and stability for simultaneous catalytic oxidation of CB and Hg0. The results demonstrated that the addition of CuO into CeO2-Al2O3 can simultaneously enhance the acid sites and redox properties through the electronic inductive effect between CuO and CeO2 (Cu2++Ce3+↔Cu++Ce4+). Importantly, the synergistic effect between Cu and Ce species can induce abundant oxygen vacancies formation, produce more reactive oxygen species and facilitate oxygen migration, which is beneficial for the deep oxidation of chlorinated intermediates. Moreover, macroporous framework and mesoporous nanostructure dramatically improved the specific surface area for enhancing the contact efficiency between reactants and active sites, leading to a remarkable decrease of byproducts deposition. CB and Hg0 had function of mutual promotion in this reaction system. In tune with the experimental results, the possible mechanistic pathways for simultaneous catalytic oxidation of CB and Hg0 were proposed.

Review of Thin Film Nanocomposite Membranes and Their Applications in Desalination.

All over the world, almost one billion people live in regions where water is scarce. It is also estimated that by 2035, almost 3.5 billion people will be experiencing water scarcity. Hence, there is a need for water based technologies. In separation processes, membrane based technologies have been a popular choice due to its advantages over other techniques. In recent decades, sustained research in the field of membrane technology has seen a remarkable surge in the development of membrane technology, particularly because of reduction of energy footprints and cost. One such development is the inclusion of nanoparticles in thin film composite membranes, commonly referred to as Thin Film Nanocomposite Membranes (TFN). This review covers the development, characteristics, advantages, and applications of TFN technology since its introduction in 2007 by Hoek. After a brief overview on the existing membrane technology, this review discusses TFN membranes. This discussion includes TFN membrane synthesis, characterization, and enhanced properties due to the incorporation of nanoparticles. An attempt is made to summarize the various nanoparticles used for preparing TFNs and the effects they have on membrane performance towards desalination. The improvement in membrane performance is generally observed in properties such as permeability, selectivity, chlorine stability, and antifouling. Subsequently, the application of TFNs in Reverse Osmosis (RO) alongside other desalination alternatives like Multiple Effect Flash evaporator and Multi-Stage Flash distillation is covered.