Promoting selective water decontamination via boosting activation of periodate by nanostructured Ru-supported Co3O4 catalysts

Natural pyrite and ascorbic acid co-enhance periodate activation for inactivation of antibiotic resistant bacteria and inhibition of resistance genes transmission: A green disinfection process dominated by singlet oxygen

The transmission of antibiotic resistance genes (ARGs) and the propagation of antibiotic resistant bacteria (ARB) threaten public health security and human health, and greener and more efficient disinfection technologies are expected to be discovered for wastewater treatment. In this study, natural pyrite and ascorbic acid (AA) were proposed as environmental-friendly activator and reductant for periodate (PI) activation to inactivate ARB. The disinfection treatment of PI/pyrite/AA system could inactivate 5.62 log ARB within 30 min, and the lower pH and higher PI and natural pyrite dosage could further boost the disinfection efficiency. The 1O2 and SO4•- were demonstrated to be crucial for the inactivation of ARB in PI/pyrite/AA system. The disinfection process destroyed the morphological structure of ARB, inducing oxidative stress and stimulating the antioxidant system. The PI/pyrite/AA system effectively reduced the intracellular and extracellular DNA concentration and ARGs abundance, inhibiting the propagation of ARGs. The presence of AA facilitated the activation of PI with natural pyrite and significantly increased the concentration of Fe2+ in solution. The reusability of natural pyrite, the safety of the disinfection by-products and the inhibition of ARB regeneration indicated the application potential of PI/pyrite/AA system in wastewater disinfection.

Elimination of representative antibiotic-resistant bacteria, antibiotic resistance genes and ciprofloxacin from water via photoactivation of periodate using FeS2

The propagation of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) induced by the release of antibiotics poses great threats to ecological safety and human health. In this study, periodate (PI)/FeS2/simulated sunlight (SSL) system was employed to remove representative ARB, ARGs and antibiotics in water. 1 × 107 CFU mL-1 of gentamycin-resistant Escherichia coli was effectively disinfected below limit of detection in PI/FeS2/SSL system under different water matrix and in real water samples. Sulfadiazine-resistant Pseudomonas and Gram-positive Bacillus subtilis could also be efficiently sterilized. Theoretical calculation showed that (110) facet was the most reactive facet on FeS2 to activate PI for the generation of reactive species (·OH, ·O2-, h+ and Fe(IV)=O) to damage cell membrane and intracellular enzyme defense system. Both intracellular and extracellular ARGs could be degraded and the expression levels of multidrug resistance-related genes were downregulated during the disinfection process. Thus, horizontal gene transfer (HGT) of ARB was inhibited. Moreover, PI/FeS2/SSL system could disinfect ARB in a continuous flow reactor and in an enlarged reactor under natural sunlight irradiation. PI/FeS2/SSL system could also effectively degrade the HGT-promoting antibiotic (ciprofloxacin) via hydroxylation and ring cleavage process. Overall, PI/FeS2/SSL exhibited great promise for the elimination of antibiotic resistance from water.

The synergistic effect of periodate/ferrate (VI) system on disinfection of antibiotic resistant bacteria and removal of antibiotic resistant genes: The dominance of Fe (IV)/Fe (V)

The proliferation of antibiotic resistant genes (ARGs) and antibiotic resistant bacteria (ARB) caused by antibiotic abuse has raised concerns about the global infectious-disease crisis. This study employed periodate (PI)/ferrate (VI) (Fe (VI)) system to disinfect Gram-negative ARB (Escherichia coli DH5α) and Gram-positive bacteria (Bacillus subtilis ATCC6633). The PI/Fe (VI) system could inactivate 1 × 108 CFU/mL of Gram-negative ARB and Gram-positive bacteria by 4.0 and 2.8 log in 30 min. Neutral and acidic pH, increase of PI dosage and Fe (VI) dosage had positive impacts on the inactivation efficiency of ARB, while alkaline solution and the coexistence of 10 mM Cl-, NO3-, SO42- and 20 mg/L humic acid had slightly negative impacts. The reactive species generated by PI/Fe (VI) system could disrupt the integrity of cell membrane and wall, leading to oxidative stress and lipid peroxidation. Intracellular hereditary substance, including DNA and ARGs (tetA), would leak into the external environment through damaged cells and be degraded. The electron spin resonance analysis and quenching experiments indicated that Fe (IV)/Fe (V) played a leading role in disinfection. Meanwhile, PI/Fe (VI) system also had an efficient removal effect on sulfadiazine, which was expected to inhibit the ARGs transmission from the source.

Efficient peroxymonosulfate activation by nanoscale zerovalent iron for removal of sulfadiazine and sulfadiazine resistance bacteria: Sulfidated modification or not

Whether it's necessary to extra chemical synthesis steps to modify nZVI in peroxymonosulfate (PMS) activation process are worth to further investigation. The 56 mg/L nZVI/153.65 mg/L PMS and 56 mg/L sulfidated nZVI (S-nZVI) (S/Fe molar ratio = 1:5)/153.65 mg/L PMS) processes could effectively attain 97.7% (with kobs of 3.7817 min-1) and 97.0% (with kobs of 3.4966 min-1) of the degradation of 20 mg/L sulfadiazine (SDZ) in 1 min, respectively. The nZVI/PMS system could quickly achieve 85.5% degradation of 20 mg/L SDZ in 1 min and effectively inactivate 99.99% of coexisting Pseudomonas. HLS-6 (5.81-log) in 30 min. Electron paramagnetic resonance tests and radical quenching experiments determined SO4•-, HO•, 1O2 and O2•- were responsible for SDZ degradation. The nZVI/PMS system could still achieve the satisfactory degradation efficiency of SDZ under the influence of humic acid (exceeded 96.1%), common anions (exceeded 67.3%), synthetic wastewater effluent (exceeded 90.7%) and real wastewater effluent (exceeded 78.7%). The high degradation efficiency of tetracycline (exceeded 98.9%) and five common disinfectants (exceeded 96.3%) confirmed the applicability of the two systems for pollutants removal. It's no necessary to extra chemical synthesis steps to modify nZVI for PMS activation to remove both chemical and biological pollutants.

Myriophyllum Biochar-Supported Mn/Mg Nano-Composites as Efficient Periodate Activators to Enhance Triphenyl Phosphate Removal from Wastewater

Transition metals and their oxide compounds exhibit excellent chemical reactivity; however, their easy agglomeration and high cost limit their catalysis applications. In this study, an interpolation structure of a Myriophyllum verticillatum L. biochar-supported Mn/Mg composite (Mn/Mg@MV) was prepared to degrade triphenyl phosphate (TPhP) from wastewater through the activating periodate (PI) process. Interestingly, the Mn/Mg@MV composite showed strong radical self-producing capacities. The Mn/Mg@MV system degraded 93.34% TPhP (pH 5, 10 μM) within 150 min. The experimental results confirmed that the predominant role of IO3· and the auxiliary ·OH jointly contributed to the TPhP degradation. In addition, the TPhP pollutants were degraded to various intermediates and subsequent Mg mineral phase mineralization via mechanisms like interfacial processes and radical oxidation. DFT theoretical calculations further indicated that the synergy between Mn and Mg induced the charge transfer of the carbon-based surface, leading to the formation of an ·OH radical-enriched surface and enhancing the multivariate interface process of ·OH, IO3, and Mn(VII) to TPhP degradation, resulting in the further formation of Mg PO4 mineralization.

Activation of periodate by ABTS as an electron shuttle for degradation of aqueous organic pollutants and enhancement effect of phosphate

Periodate (PI) based advanced oxidation processes (AOPs) have recently attracted much attention due to their high application potential in water purification through production of reactive species. In the study, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) was used as a representative electron shuttle, and its reaction with PI was investigated in detail. It was found that PI can be activated by ABTS via one-electron transfer to produce ABTS•+ and IO3•, cooperatively promoting oxidation of organic contaminants such as bisphenol A (BPA). Their contribution in BPA oxidation at pH 7 was estimated as 81.9% and 18.1%, respectively. With phosphate, BPA oxidation rate in the PI/ABTS process increased linearly with raised phosphate concentrations from 0 to 10 mM. The enhancement effect of phosphate is attributed to formation of PI-phosphate complexes, which facilitate PI activation by ABTS, and production of more ABTS•+ and IO3•, and additional phosphate radicals. Accordingly, the contribution of IO3• and phosphate radicals in BPA oxidation raised to 57.7% in the process with 4 mM phosphate, while that of ABTS•+ decreased to 42.3%. The reaction stoichiometry ratio of ABTS to PI was measured as 1.1 at pH 7, suggesting the little involvement of IO3• and phosphate radicals in production of ABTS•+ due to their high self-quenching. The PI/ABTS process exhibited excellent anti-interference capacity towards water matrix components (e.g. Cl-, HCO3- and natural organic matters). Moreover, an immobilized ABTS (ABTS/ZnAl-LDH) was successfully developed as a heterogeneous electron shuttle for PI oxidation, which resultantly exhibited the good catalytic activity and stability in degradation of BPA, further improving feasibility of the process in treatment of actual water. This work advances understanding on reaction of PI with ABTS from stoichiometric and kinetic aspects, and provides a high performance AOP for selective oxidation of trace organic contaminants.

Target-prepared sludge biochar-derived synergistic Mn and N/O induces high-performance periodate activation for reactive iodine radicals generation towards ofloxacin degradation

Converting waste activated sludge into catalysts for the removal of antibiotics in water fulfils the dual purpose of waste-to-resource and hazardous pollution elimination. In this study, sludge-derived biochar (SDB) for efficient periodate (PI) activation was first prepared via one-step pyrolysis of potassium permanganate-polyhexamethylenebiguanide conditioned sludge without additional modification. The SDB (750 °C)-PI system degraded 100% ofloxacin (OFL, 41.5 μM) within 6 min and was almost undisturbed by inorganic ions or humic acids. The experimental results confirmed that the predominant role of reactive iodine species (RIS) and the auxiliary involvement of singlet oxygen (1O2) jointly contributed to the OFL degradation. Theoretical calculations further indicated that the synergy between Mn and N/O induced local charge redistribution and improved electron transfer capability of SDB, leading to the formation of electron-rich Mn sites and enhanced Mn(II)↔Mn(III)↔Mn(IV) redox to promote PI activation. More importantly, the enhanced adsorption and charge transfer of PI on the Mn site of the Mn-N/O-C structures induced the I-O bond stretching and the rapid generation of RIS. This study offered a cost-effective strategy for developing SDB-based catalysts, further advancing the comprehension of sludge management and the intricate mechanisms underlying RIS formation in PI-advanced oxidation processes.

Selective abatement of electron-rich organic contaminants by trace complexed Mn(II)-catalyzed periodate via high-valent manganese-oxo species

Mn(II) is among the most efficient catalysts for the periodate (PI)-based oxidation process. In-situ formed colloidal MnO2 simultaneously serves as the catalyst and oxidant during the degradation of organic contaminants by PI. Here, it is revealed that the complexation of Mn(II) by ethylene diamine tetraacetic acid (EDTA) further enhances the performance of PI-based oxidation in the selective degradation of organic contaminants. As evidenced by methyl phenyl sulfoxide probing, 18O-isotope labeling, and mass spectroscopy, EDTA complexation modulates the reaction pathway between Mn(II) and PI, triggering the generation of high-valent manganese-oxo (MnV-oxo) as the dominant reactive species. PI mediates the single-electron oxidation of Mn(II) to Mn(III), which is stabilized by EDTA complexation and then further oxidized by PI via the oxygen-atom transfer step, ultimately producing the MnV-oxo species. Ligands analogous to EDTA, namely, [S,S]-ethylenediaminedisuccinic acid and L-glutamic acid N,N-diacetic acid, also enhances the Mn(II)/PI process and favors MnV-oxo as the dominant species. This study demonstrates that functional ligands can tune the efficiency and reaction pathways of Mn(II)-catalyzed peroxide and peroxyacid-based oxidation processes.

Elucidating sulfate radical-induced oxidizing mechanisms of solid-phase pharmaceuticals: Comparison with liquid-phase reactions

As a class of organic micropollutants of global concern, pharmaceuticals have prevalent distributions in the aqueous environment (e.g., groundwater and surface water) and solid matrices (e.g., soil, sediments, and dried sludge). Their contamination levels have been further aggravated by the annually increased production of expired drugs as emerging harmful wastes worldwide. Sulfate radicals (SO4•-)-based oxidation has attracted increasing attention for abating pharmaceuticals in the environment, whereas the transformation mechanisms of solid-phase pharmaceuticals remain unknown thus far. This investigation presented for the first time that SO4•-, individually produced by mechanical force-activated and heat-activated persulfate treatments, could effectively oxidize three model pharmaceuticals (i.e., methotrexate, sitagliptin, and salbutamol) in both solid and liquid phases. The high-resolution mass spectrometric analysis suggested their distinct transformation products formed by different phases of SO4•- oxidation. Accordingly, the SO4•--mediated mechanistic differences between the solid-phase and liquid-phase pharmaceuticals were proposed. It is noteworthy that the products from both systems were predicted with the remaining persistence, bioaccumulation, and multi-endpoint toxicity. Therefore, some post-treatment strategies need to be considered during practical applications of SO4•--based technologies in remediating different phases of micropollutants. This work has environmental implications for understanding the comparative transformation mechanisms of pharmaceuticals by SO4•- oxidation in remediating the contaminated solid and aqueous matrices.

Fe(VI) activation system mediated by a solar-driven TiO2 nanotubes electrode for CLQ degradation: Performances, mechanisms and pathways

Ferrate (Fe(VI), FeO₄^2-) has been widely used in the degradation of micropollutants with the advantages of high redox potential, no secondary pollution and inhibition of disinfection byproducts. However, the low transformation of Fe(V) and/or Fe(IV) by Fe(VI) and incomplete mineralization of pollutants limit their application. In this work, we designed a photo electric cell with TiO₂ nanotubes (TNTs) and Pt serving as the anode and cathode to enhance the utilization of Fe(VI) (Fe(VI)-TNTs system). TNTs accelerated the generation of •OH via h_VB⁺ oxidation of OH^- and photogenerated electrons at Pt boosted the transformation of Fe(VI) to Fe(V) and/or Fe(IV), resulting in a 22.2 % enhancement of chloroquine (CLQ) removal compared to Fe(VI) alone. The results from EPR and quenching tests showed that Fe(VI), Fe(V), Fe(IV), •OH, O₂^•- and h_VB⁺ coexisted in the Fe(VI)-TNTs system, among which Fe(V) and Fe(IV) were testified as the primary reactive substances accounting for 59 % of CLQ removal. The performance tests and recycling tests demonstrated that the Fe(VI)-TNTs system maintained excellent performance in an authentic water environment. The plausible degradation pathway of CLQ oxidized in the Fe(VI)-TNTs system was proposed with nine identified oxidation products via N-C cleavage, electrophilic addition and carboxylation processes. Based on the ECOSAR calculation, the constructed reaction system allowed a decrease in acute and chronic toxicity. Our findings provide a highly efficient and cost-effective strategy to enhance Fe(VI) application for micropollutant degradation in the future.

Electrochemical activation of periodate with graphite electrodes for water decontamination: Excellent applicability and selective oxidation mechanism

Advanced oxidation technologies based on periodate (PI, IO₄^-) have garnered significant attention in water decontamination. In this work, we found that electrochemical activation using graphite electrodes (E-GP) can significantly accelerate the degradation of micropollutants by PI. The E-GP/PI system achieved almost complete removal of bisphenol A (BPA) within 15 min, exhibited unprecedented pH tolerance ranging from pH 3.0 to 9.0, and showed more than 90% BPA depletion after 20 h of continuous operation. Additionally, the E-GP/PI system can realize the stoichiometric transformation of PI into iodate, dramatically decreasing the formation of iodinated disinfection by-products. Mechanistic studies confirmed that singlet oxygen (¹O₂) is the primary reactive oxygen species in the E-GP/PI system. A comprehensive evaluation of the oxidation kinetics of ¹O₂ with 15 phenolic compounds revealed a dual descriptor model based on quantitative structure-activity relationship (QSAR) analysis. The model corroborates that pollutants exhibiting strong electron-donating capabilities and high pK_a values are more susceptible to attack by ¹O₂ through a proton transfer mechanism. The unique selectivity induced by ¹O₂ in the E-GP/PI system allows it to exhibit strong resistance to aqueous matrices. Thus, this study demonstrates a green system for the sustainable and effective elimination of pollutants, while providing mechanistic insights into the selective oxidation behaviour of ¹O₂.

α-Fe2O3 mediated periodate activation for selective degradation of phenolic compounds via electron transfer pathway under visible irradiation

Periodate (PI)-photoactivated advanced oxidation process (AOP) has recently received increasing attention for the removal of micropollutants from water. However, periodate is mainly driven by high-energy ultraviolet light (UV) in most cases, and few studies have extended it to the visible range. Herein, we proposed a new PI visible light activation system employing α-Fe₂O₃ as catalyst. It is completely different from traditional PI-AOP based on hydroxyl radicals (•OH) and iodine radical (•IO₃). The vis-α-Fe₂O₃/PI system can selectively degrade the phenolic compounds via non-radical pathway under the visible range. Notably, the designed system not only shows a well pH tolerance and environmental stability, but also exhibits a strong substrate-dependent reactivity. Both quenching experiments and electron paramagnetic resonance (EPR) experiments demonstrate that photogenerated holes are the main active species in this system. Moreover, a series of photoelectrochemical experiments reveal that PI can effectively inhibit the carrier recombination on the α-Fe₂O₃ surface, thereby improving the utilization of photogenerated charges and increasing the number of photogenerated holes, which effectively reacts with 4-CP through electron transfer way. In a word, this work proposes a cost-effective, green and mild mean to activate PI, and provides a facile way to solve the fatal shortcomings (i.e., inappropriate band edge position, rapid charge recombination and short hole diffusion length) of traditional iron oxide semiconductor photocatalysts.

Cobalt and nitrogen co-doped monolithic carbon foam for ultrafast degradation of emerging organic pollutants via peroxymonosulfate activation

Cobalt-based catalysts are expected as one of the most promising peroxymonosulfate (PMS) activators for the removal of organic pollutants from industrial wastewater. However, the easy agglomeration, difficult separation, and secondary pollution of cobalt ions limit their practical application. In this study, a novel, highly efficient, reusable cobalt and nitrogen co-doped monolithic carbon foam (Co-N-CMF) was utilized to activate PMS for ultrafast pollutant degradation. Co-N-CMF (0.2 g/L) showed ultrafast catalytic kinetics and higher total organic carbon (TOC) removal efficiency. Bisphenol A, ciprofloxacin, 2,4-dichlorophenoxyacetic acid, and 2,4-dichlorophenol could be completely degraded after 2, 4, 5, and 5 min, and the TOC removal efficiencies were 77.4 %, 68.9 %, 72.8 %, and 79.8 %, respectively, corresponding to the above pollution. The sulfate radical (SO4•-) was the main reactive oxygen species in Co-N-CMF/PMS based on electron paramagnetic resonance. The ecological structure-activity relationship program analysis via the quantitative structure activity relationship analysis and phytotoxicity assessment revealed that the Co-N-CMF/PMS system demonstrates good ecological safety and ecological compatibility. The Co-N-CMF catalyst has good catalytic activity and facile recycling, which provides a fine method with excellent PMS activation capacity for 2,4-dichlorophenol elimination from simulated industrial wastewater. This study provides new insights into the development of monolithic catalysts for ultrafast wastewater treatment via PMS activation.