Wide pH Tolerance Research Articles

Enhanced organic pollutant degradation in a two-dimensional Fe-doped crystalline carbon nitride membrane with near 100 % singlet oxygen generation through the Fe–O–N configuration

The singlet oxygen (1O2)-based nonradical AOP process, realized in carbon materials after nitrogen and metal doping, has drawn much attention in recent years. However, the exclusive generation of 1O2 in the specialized two-dimensional (2D) catalytic membranes and the associated contaminant degradation mechanisms remain unclear. Herein, a Fe-doped crystalline carbon nitride (Fe-CCN) material without additional nitrogen doping was developed to preferentially initiate 1O2-based nanoconfined oxidation of organic pollutants in the 2D Fe-CCN membrane/PMS system. Density functional theory calculation revealed that the Fe-O-N configuration formed after Fe doping altered the electronic structure of Fe centers, enhancing PMS adsorption and promoting the thermodynamically favorable generation of the –O* intermediate, leading to fast and highly selective 1O2 generation. EPR characterization and ROS quenching experiment also confirmed that the Fe-CCN activated PMS, generating nearly 100 % 1O2. The Fe-CCN membrane/PMS system exhibited excellent resistance to natural organic matter (NOM) interference and dramatically increased Bisphenol A (BPA) degradation kinetics, approximately 590 times faster than in conventional batch systems. Enhanced 1O2 exposure concentration within the Fe-CCN membrane nanochannels was supported by EPR data and 1O2 exposure simulations. Furthermore, The Fe-CCN membrane/PMS system showed wide pH tolerance, excellent pollutant degradation performance, and high stability. This work underscores the practical significance of 1O2-based oxidation reactions in membrane-confined AOPs for the rapid and efficient removal of organic contaminants from water.

Novel triphenylamine-pyrene-based AIEgens: Specific detection and imaging of H2O2 in aqueous solution and cells

H2O2 plays a key regulatory role as a bioendogenous reactive oxygen species in cells and organisms. However, excessive production or accumulation of H2O2 during mitochondrial oxidative stress may lead to oxidative damage of cellular proteins and trigger rheumatic diseases, cancers, and a variety of neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. In addition, H2O2 is a very useful chemical widely employed in the textile and chemical industries, and its excessive emission not only pollutes the environment but also jeopardizes human health. Therefore, the sensitive and specific detection and removal of H2O2 is important for early diagnosis of diseases, treatment prognosis and environmental pollution monitoring. We have designed two novel triphenylamine-based AIEgens MOTPP and MOTPP-B, which each have a high solid-state fluorescence quantum yield and excellent aggregation-induced emission properties. MOTPP-B has high selectivity and anti-interference ability toward H2O2, a wide pH tolerance range, a sensing process that is complete in under 40 min, and a low detection limit of 120.77 nM. It has been successfully applied for the detection of low concentrations of H2O2 in the environment and to dual-channel imaging of low concentrations of exogenous H2O2 in living cells.

Exploiting the Thermotolerance of Clostridium Strain M1NH for Efficient Caproic Acid Fermentation from Ethanol and Acetic Acid.

A novel thermotolerant caproic acid-producing bacterial strain, Clostridium M1NH, was successfully isolated from sewage sludge. Ethanol and acetic acid at a molar ratio of 4:1 proved to be the optimal substrates, yielding a maximum caproic acid production of 3.5g/L. Clostridium M1NH exhibited remarkable tolerance to high concentrations of ethanol (up to 5% v/v), acetic acid (up to 5% w/v), and caproic acid (up to 2% w/v). The strain also demonstrated a wide pH tolerance range (pH 5.5-7.5) and an elevated temperature optimum between 35 and 40°C. Phylogenetic analysis based on 16S rRNA gene sequences revealed that Clostridium M1NH shares a 98% similarity with Clostridium luticellarii DSM 29923T. The robustness of strain M1NH and its efficient caproic acid production from low-cost substrates highlight its potential for sustainable bio-based chemical production. The maximum caproic acid yield achieved by Clostridium M1NH was 1.6-fold higher than that reported for C. kluyveri under similar fermentation conditions. This study opens new avenues for valorizing waste streams and advancing a circular economy model in the chemical industry.

Purification and characterization of limonin D-ring lactone hydrolase from sweet orange (Citrus sinensis (L.) Osbeck) seeds.

Citrus products often suffer from delayed bitterness, which is generated from the conversion of non-bitter precursors (limonoate A-ring lactone, LARL) to limonin under the catalysis of limonin D-ring lactone hydrolase (LDLH). In this study, LDLH was isolated and purified from sweet orange seeds, and a rapid and accurate high-performance liquid chromatography method to quantify LARL was developed and applied to analyze the activity and enzymatic properties of purified LDLH. Purified LDLH (25.22 U mg-1) showed bands of 245 kDa and 17.5 kDa molecular weights in native polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate PAGE analysis respectively. After a 24 h incubation under strongly acidic (pH 3) or strongly alkaline (pH 9) conditions, LDLH still retained approximately 100% activity. Moreover, LDLH activity was not impaired by thermal treatment at 50 °C for 120 min. Enzyme inhibition assays showed that LDLH was inactivated only after ethylenediaminetetraacetic acid treatment, and other enzyme inhibitors showed no significant effect on its activity. In addition, the LDLH activity of calcium ion (Ca2+) intervention was 108% of that in the blank group, and that of zinc ion (Zn2+) intervention was 71%. LDLH purified in this study was a multimer containing 17.5 kDa monomer with a wide pH tolerance range (pH 3-9) and excellent thermal stability. Moreover, LDLH might be a metallopeptidase, and its activity was stimulated by Ca2+ and significantly inhibited by Zn2+. These findings improve our understanding of LDLH and provide some important implications for reducing the bitterness in citrus products in the future. © 2024 Society of Chemical Industry.

Highly efficient bioregeneration of high temperature-pyrolyzed biochar after trichloroethylene adsorption through biodegradation of Dehalococcoides

Biochars was widely employed to immobilize chlorinated aliphatic hydrocarbons (CAHs) in groundwater. Biodegradation of adsorbed CAHs may be able to regenerate biochars, but was scarcely explored. In this study, therefore, biodegradation of trichloroethylene (TCE) adsorbed on a biochar prepared at 700 °C (WBC700) by Dehalococcoides mccartyi 195 (Dhc 195) was investigated. Aqueous TCE was completely degraded to ethene by Dhc 195 within 28 days, while 87.5 % of WBC700-adsorbed TCE was degraded to ethene within 63 days. The slower biodegradation of WBC700-adsorbed TCE could be attributed to its lower accessibility to Dhc 195 caused by the steric effects of WBC700. The adsorption capacity of WBC700 for TCE remained 80.4 % after five adsorption-bioregeneration cycles, indicating that the microbial degradation could be a highly efficient method to regenerate biochars. The microbial degradation was mainly through the electron transfer from Dhc 195 to TCE mediated by biochars as electron conductor or shuttle, but was not assisted by desorption or extracellular redox active species. Compared with biodegradation of aqueous TCE, the biodegradation of WBC700-adsorbed TCE by Dhc 195 had a wider pH tolerance and required more VB12, due to the buffer effect and adsorption of WBC700, respectively. The obtained results could provide a cost-effective method of biochar regeneration for CAHs removal in groundwater.

Construction of defective hydroxyl-rich metal–organic framework for effective capture of borate ion

Developing high-efficiency adsorbents for borate ion still remains up to now. Herein, a facile and green method is used to obtain serial hydroxyl functionalized UiO-66-(OH)2-AA-X (AA, acetic acid; X, AA usage) by using AA as a modulator. The addition of AA can induce the generation of defect units in the adsorbents due to its partial substitution for the organic linkers. It is found that the defect degree as well as the porosity can be neatly regulated by the AA amount. In particular, UiO-66-(OH)2-AA-20 with the most defects exhibits a high adsorption capacity (891.1 mg g−1) towards borate ion, outperforming the most previously reported adsorbents. The adsorption reaches equilibrium at 600 min. The adsorption behavior can be well described by the Langmuir isotherm model and pseudo-second-order model. Besides, UiO-66-(OH)2-AA-20 possesses a wide pH (3–10) tolerance, excellent anti-interference ability, and good reusability. A combination of experimental characterization and density functional theory calculation indicates the free hydroxyl groups serve as the main adsorption sites, and the adsorption-driven forces involve electrostatic, coordination, hydrogen bonds and π–π stacking interactions. On these basis, our work may provide a guideline for constructing high-efficiency defective adsorbents for borate ions via a modulated strategy.

Room temperature synthesis of nanocomposite thin films with embedded Cs2AgIn0.9Bi0.1Cl6 lead-free double perovskite nanocrystals with long-term water stability, wide range pH tolerance, and high quantum yield

Cs2AgIn0.9Bi0.1Cl6 nanocrystals encapsulated with polystyrene or polymethyl methacrylate are described with high quantum yields, long luminescence lifetimes and water stability.

Simultaneous chromatographic separation of the anomers of saccharides on a polymer sulfobetaine zwitterionic stationary phase.

Simultaneous chromatographic separation of the anomers of saccharides was achieved by using a polymer zwitterionic stationary phase functionalized by acrylamide-type sulfobetaine. By optimization of separation parameters including column temperature, pH, and flow rate, the column operated in hydrophilic interaction chromatography mode exhibited excellent separation selectivity toward five monosaccharides and their anomers (including ribose, xylose, galactose, glucose, and arabinose) and two disaccharides (lactose and maltose). Baseline separation could be achieved at mild operation conditions such as 20-30°C of column temperature or typical mobile phase composition (85% acetrontrile-15% 20mM ammonium formate [NH4 FA]) with wide pH tolerance range of 2-8. This offers a rapid way to determine the configuration of α or β anomer of the saccharides.

Complexes of cupric ion and tartaric acid enhanced calcium peroxide Fenton-like reaction for metronidazole degradation

To surmount the obstacles of traditional Fenton method and synchronously utilize Cu2+ and polyphenol in water, an improved Fenton-like reaction applying calcium peroxide (CaO2) as H2O2 source and regulating by the complex of Cu2+-tartaric acid (TA, a representative of polyphenol) was constructed. A typical antibiotic, metronidazole (MTZ) could be effectively eliminated by the Cu2+/TA/CaO2 system, and the optimized parameters were as follows: 0.1 mmol/L Cu2+, 2 mmol/L TA, 2 mmol/L CaO2, and initial pH 5. UV spectrum confirmed the formation of Cu2+-TA complex, which promoted the Cu2+/Cu+ circulation through decreasing the Cu2+/Cu+ couple redox potential, which further enhanced the H2O2 decomposition and the formation of reactive species. Hydroxyl radical was dominant for MTZ degradation, followed by oxygen and superoxide radical. The degradation intermediates of MTZ were detected and their evolution way was speculated. Furthermore, the ternary process showed a wide pH tolerance (3–8) for removing MTZ and broad applicability for eliminating other dyes and antibiotics. This work provided a reference for Cu-based Fenton-like strategy for organic wastewater settlement.

Interfacial permeation preparation of ZIF-8 in reactive deep eutectic for efficient adsorption and selective removal of Congo red

Metal-based deep eutectic solvents (MDES) were used as reactive DESs and structure directing agents to control the morphology and oriented growth of ZIF-8. A series of ZIF-8-DESs were prepared in three MDESs (ZnCl2-urea, ZnCl2-1,3-dimethylurea and ZnCl2-tetramethyl urea) by the interfacial synthesis and two-phase permeation. The results showed that MDES acts as multi roles to affect the morphology and adsorption performance of ZIF-8-DES. The growth mechanism of ZIF-8-DES was also proposed. ZIF-8-DES could effectively adsorb anionic Congo red with 99.98 % removal efficiency, 2454 mg·g−1 adsorption capacity and a wide pH tolerance. ZIF-8-DES possesses excellent selectivity for Congo red in the presence of methyl orange and outstanding reusability as compared with pristine ZIF-8 and most reported adsorbents. The thermodynamics and adsorption kinetics was well described by a Langmuir model and pseudo-second-order model, respectively. The adsorption mechanism including π-π interaction and hydrogen bonding interactions was proposed. This work provided a facile synthesis route for MOFs with different morphologies and surface properties as well as novel insights into the design of selective absorbent for organic dyes.

A novel Bacillus subtilis BPM12 with high bis(2 hydroxyethyl)terephthalate hydrolytic activity efficiently interacts with virgin and mechanically recycled polyethylene terephthalate

Biotechnological treatment of plastic waste has gathered substantial attention as an efficient and generally greener approach for polyethylene terephthalate (PET) depolymerization and upcycling in comparison to mechanical and chemical processes. Nevertheless, a suitable combination of mechanical and microbial degradation may be the key to bringing forward PET upcycling. In this study, a new strain with an excellent bis(2 hydroxyethyl)terephthalate (BHET) degradation potential (1000 mg/mL in 120 h at 30 °C) and wide temperature (20-47 °C) and pH (5-10) tolerance was isolated from a pristine soil sample. It was identified as Bacillus subtilis BPM12 via phenotypical and genome analysis. A number of enzymes with potential polymer degrading activities were identified, including carboxylesterase BPM12CE that was efficiently expressed both, homologously in B. subtilis BPM12 and heterologously in B. subtilis 168 strain. Overexpression of this enzyme enabled B. subtilis 168 to degrade BHET, while the activity of BPM12 increased up to 1.8-fold, confirming its BHET-ase activity. Interaction of B. subtilis BPM12 with virgin PET films and films that were re-extruded up to 5 times mimicking mechanical recycling, revealed the ability of the strain to attach and form biofilm on each surface. Mechanical recycling resulted in PET materials that are more susceptible to chemical hydrolysis, however only slight differences were detected in biological degradation when BPM12 whole-cells or cell-free enzyme preparations were used. Mixed mechano/bio-degradation with whole-cells and crude enzyme mixes from this strain can serve to further increase the percentage of PET- based plastics that can enter circularity.

Expression and Characterization of Two α-l-Arabinofuranosidases from Talaromyces amestolkiae: Role of These Enzymes in Biomass Valorization.

α-l-arabinofuranosidases are glycosyl hydrolases that catalyze the break between α-l-arabinofuranosyl substituents or between α-l-arabinofuranosides and xylose from xylan or xylooligosaccharide backbones. While they belong to several glycosyl hydrolase (GH) families, there are only 24 characterized GH62 arabinofuranosidases, making them a small and underrepresented group, with many of their features remaining unknown. Aside from their applications in the food industry, arabinofuranosidases can also aid in the processing of complex lignocellulosic materials, where cellulose, hemicelluloses, and lignin are closely linked. These materials can be fully converted into sugar monomers to produce secondary products like second-generation bioethanol. Alternatively, they can be partially hydrolyzed to release xylooligosaccharides, which have prebiotic properties. While endoxylanases and β-xylosidases are also necessary to fully break down the xylose backbone from xylan, these enzymes are limited when it comes to branched polysaccharides. In this article, two new GH62 α-l-arabinofuranosidases from Talaromyces amestolkiae (named ARA1 and ARA-2) have been heterologously expressed and characterized. ARA-1 is more sensitive to changes in pH and temperature, whereas ARA-2 is a robust enzyme with wide pH and temperature tolerance. Both enzymes preferentially act on arabinoxylan over arabinan, although ARA-1 has twice the catalytic efficiency of ARA-2 on this substrate. The production of xylooligosaccharides from arabinoxylan catalyzed by a T. amestolkiae endoxylanase was significantly increased upon pretreatment of the polysaccharide with ARA-1 or ARA-2, with the highest synergism values reported to date. Finally, both enzymes (ARA-1 or ARA-2 and endoxylanase) were successfully applied to enhance saccharification by combining them with a β-xylosidase already characterized from the same fungus.

Isolation and identification of protease-producing Bacillus amyloliquefaciens LX-6 and its application in the solid fermentation of soybean meal.

Soybean meal (SM) is considered an ideal substitute for fish meal; however, its application is mainly limited because of its antigen proteins, glycinin and β-conglycinin. To improve the value of SM in the aquaculture industry, we employed an aerobic bacterial strain (LX-6) with protease activity of 1,390.6 ± 12.5 U/mL. This strain was isolated from soil samples and identified as Bacillus amyloliquefaciens based on morphological and physiological biochemical characteristics and 16S rDNA gene sequence analyses. Subsequently, we quantified the extent of glycinin and β-conglycinin degradation and the total protein and water-soluble protein content after SM fermentation with B. amyloliquefaciens LX-6. At 24h of fermentation, the macromolecular antigen proteins of SM were almost completely degraded; the maximum degradation rates of glycinin and β-conglycinin reached 77.9% and 57.1%, respectively. Accordingly, not only did the concentration of water-soluble proteins increase from 5.74% to 44.45% after 48h of fermentation but so did the concentrations of total protein and amino acids compared to those of unfermented SM. Field emission scanning electron microscopy revealed that the LX-6 strain gradually disrupted the surface structure of SM during the fermentation process. In addition, B. amyloliquefaciens LX-6 exhibited broad-spectrum antagonistic activity and a wide pH tolerance, suggesting its application in SM fermentation for fish meal replacement.

Biological Characterization of Pseudomonas fluorescens Phage Pf17397_F_PD1 and Its Application in Food Preservation

In order to explore the application prospects of phages for controlling bacterial contamination, a lytic phage Pf17397_F_PD1 (Later abbreviated as PD1) was isolated from fish guts using Pseudomonas fluorescens ATCC 17397 as the host bacterium. The phage displayed short latency (18 min), long lysis period (212 min), and high lysis volume (1.47 × 102 PFU/each cell). It displayed wide temperature (30–70°C) and pH (4–11) tolerance. Genomic comparison revealed a maximum sequence identity of 48.65% between phage PD1 and other identified phages, indicating that PD1 was a new phage. The phage PD1 significantly inhibited the growth of P. fluorescens in milk and grass carp at 4°C and 25°C. Compared to the negative control, bacterial levels in milk stored at 25°C for 48 h were reduced by 2.71 log CFU/mL and 2.84 log CFU/mL at the multiplicity of infection (MOI) of 100 and 1,000, respectively. In contrast, when grass carp were stored at 25°C for 24 h, the bacterial load was reduced by 1.28 log CFU/g and 2.64 log CFU/g compared to the control (MOI of 100 and 1,000). When the phage was applied for preservation of grass carp blocks, total volatile salt nitrogen (TVB-N) values of phage-treated samples increased by 6.8 mg/100 g and 7.5 mg/100 g at MOI of 100 and 1,000, respectively, after 7 days of storage, which was significantly lower than that of the control group (15.83 mg/100 g). This study showed that phage PD1 was a good natural biological antimicrobial agent against P. fluorescens ATCC 17397.

A novel colorimetric fluorescence probe for the sensitive and selective detection of hypochlorite and its bioimaging in living cells

Hypochlorite (ClO−) is a well-known redox regulator among reactive oxygen species and plays a crucial role in bacterial disinfection and body immunity. Therefore, there is a high demand for an analytical technique to monitor ClO− under physiological conditions. Herein, a novel fluorescence probe, RES-DPPT, was developed for detecting ClO−. This probe employs diphenylphosphinothioyl unit as the recognition group and resorufin as the fluorescent platform. RES-DPPT has high sensitivity and specificity, rapid response, and wide pH tolerance for monitoring ClO−. Additionally, RES-DPPT undergoes colorimetric and fluorescence color changes in the solution, which can be observed by the “naked eye.” Furthermore, RES-DPPT is successfully able to detect exogenous and endogenous ClO− in living cells.

Activation of peroxymonosulfate by an Enteromorpha prolifera derived biochar supported CoFe2O4 catalyst for highly efficient lomefloxacin hydrochloride degradation under a wide pH range

Heterogeneous catalysts with high-activity and wide pH tolerance are urgently needed for water pollutant degradation. In this work, CoFe2O4-loaded biochar prepared from the marine biomass Enteromorpha prolifera (CFO@EPBC) was successfully developed as an efficient heterogeneous catalyst for the degradation of lomefloxacin hydrochloride (LMH) by activating peroxymonosulfate (PMS). The crystalline structure, porous structure and surface chemistry of CFO@EPBC were characterized. The catalytic performance of CFO@EPBC activated PMS for the decomposition of LMH was estimated, and the reusability, stability and applicability of CFO@EPBC were also evaluated. The results showed that CFO@EPBC displayed 35.2-, 3.7- and 6.6-times degradation rates (kobs) towards LMH than that of EPBC, CoFe2O4 and EPBC + CoFe2O4, respectively, demonstrating remarkable synergistic interaction between EPBC and CoFe2O4. More importantly, excellent catalytic ability of the CFO@EPBC/PMS system for LMH degradation under a wide initial pH range (3–11) was observed due to a suitable pHzpc of catalysts. Also, CFO@EPBC showed a good application prospect for treating LMH in different types of water matrixes (river water and seawater). Reactive oxygen species (SO4·−, ·OH, ·O−2 and 1O2) produced marked effects during the degradation process, while the radical process played a dominant role. This study also demonstrates a typical case for turning trash into treasure using Enteromorpha prolifera, providing a new idea for the value-added transformation of other similar bio-wastes.

Application of a novel lytic Jerseyvirus phage LPSent1 for the biological control of the multidrug-resistant Salmonella Enteritidis in foods.

Non-typhoidal Salmonella is the tremendously predominant source of acquired foodborne infection in humans, causing salmonellosis which is a global threat to the healthcare system. This threat is even worse when it is combined with the incidence of multidrug-resistant Salmonella strains. Bacteriophage therapy has been proposed as a promising potential candidate to control a diversity of foodborne infective bacteria. The objective of this study designed to isolate and characterize lytic phages infecting zoonotic multi-drug resistant and strong biofilm producer Salmonella enterica serovar Enteritidis EG.SmE1 and then apply the isolated phage/s as a biocontrol agent against infections in ready-to-eat food articles including milk, water, apple juice, and chicken breasts. One lytic phage (LPSent1) was selected based on its robust and stable lytic activity. Phage LPSent1 belonged to the genus Jerseyvirus within the Jerseyvirinae subfamily. The lysis time of phage LPSent1 was 60 min with a latent period of 30 min and each infected cell burst about 112 plaque-forming units. Phage LPSent1 showed a narrow host range. Furthermore, the LPSent1 genome did not encode any virulence or lysogenic genes. In addition, phage LPSent1 had wide pH tolerance, prolonged thermal stability, and was stable in food articles lacking its susceptible host for 48 h. In vitro applications of phage LPSent1 inhibited free planktonic cells and biofilms of Salmonella Enteritidis EG.SmE1 with a lower occurrence to form phage-resistant bacterial mutants which suggests promising applications on food articles. Application of phage LPSent1 at multiplicities of infections of 100 or 1000 showed significant inhibition in the bacterial count of Salmonella Enteritidis EG.SmE1 by 5 log10/sample in milk, water, apple juice, and chicken breasts at either 4°C or 25°C. Accordingly, taken together these findings establish phage LPSent1 as an effective, promising candidate for the biocontrol of MDR Salmonella Enteritidis in ready-to-eat food.

Fe3+-cysteine enhanced persulfate fenton-like process for quinclorac degradation: A wide pH tolerance and reaction mechanism

A green, high-efficiency, and wide pH tolerance water remediation process has been urgently acquired for the increasingly exacerbating contaminated water. In this study, a Fe3+/persulfate (Fe3+/PS) system was employed and enhanced with a green natural ligand cysteine (Cys) for the degradation of quinclorac (QNC). The introduction of Cys into the Fe3+/PS system widened the effective pH range to 9 with a superior removal rate for QNC. The mechanism revealed that the Fe3+/Cys/PS system can enhance the ability of degrading QNC by accelerating the Fe3+/Fe2+ redox cycle, maintaining Fe2+ concentration and thereby generating more HO• and SO4•–. The impact factors (i.e., pH, concentrations of PS, Fe3+ and Cys) were optimized as well. This work provides a promising strategy with high catalytic activity and wide pH tolerance for organic contaminated water remediation.

Template-directed growth of sustainable carboxymethyl cellulose-based aerogels decorated with ZIF-67 for activation peroxymonosulfate degradation of organic dyes

A novel 3D advanced oxidation catalyst ZIF-67@C-CMC/rGO based on carboxymethyl cellulose (CMC) and reduced graphene oxide (rGO) was successfully synthesized by facile in-situ growth of Zeolitic imidazolate framework-67 (ZIF-67). C-CMC/rGO aerogel crosslinked by poly (methyl vinyl ether-alt-maleic acid)/polyethylene glycol system (PMVEMA/PEG) as the host material was prepared through a template-directed growth model and exhibited outstanding mechanical properties. The sustainable composite was successfully used as an efficient catalyst for activating peroxymonosulfate (PMS) to generate SO4−· and ·OH, then leads to the removal of organic contaminants. As a result, almost 100 % of 10 ppm MB/RhB solution can be degraded within 5 min due to the combination of catalyst aerogel and PMS. What's more, the aerogel showed a wide pH tolerance range from 4 to 9 and maintained up to 93 % of the contaminant removal rate compared to the initial value after four cycles. The ZIF-67@C-CMC/rGO aerogel with high load rate and excellent catalytic degradation performance not only solved the problem of dispersion and recovery of ZIF-67 particles, but also provided a new idea for the compound wastewater purification in sulfate radical-based advanced oxidation processes (SR-AOPs).

Single atom Co-anchored nitrogen‑doped graphene for peroxymonosulfate activation with high selectivity of singlet oxygen generation

Singlet oxygen (1O2) is an excellent active species generated in advanced oxidation processes (AOPs) that exhibits high selectivity, long life and wide pH tolerance. Therefore, catalysts for highly efficient and selective generation of 1O2 in AOPs would be highly desirable. This study developed a single atom Co-anchored nitrogen‑doped graphene (CoSAC-NG), which showed excellent catalytic performance for peroxymonosulfate (PMS) activation and bisphenol A degradation, with the pseudofirst-order reaction rate constant improved from 8.13 × 10−4 min−1 without catalyst to 4.42 × 10−2 min−1 with 5 mg L−1 CoSAC-NG. Mechanism studies indicated that CoSAC-NG selectively enhanced 1O2 generation, which was the dominant active specie for pollutant degradation. Moreover, the CoSAC-NG/PMS system effectively reduced the acute toxicity of pollutant, and CoSAC-NG exhibited remarkable cycling stability and negligible leaching. This study develops a new catalyst with high selectivity for 1O2 generation and provides a reference for application of single atom catalyst in PMS-based AOPs.