Sulfur doping-induced morphological and electronic structure modification of polyoxometalate FeWO4 for enhanced removal of organic pollutants from water.

Wolframite (FeWO4), a typical polyoxometalate, serves as an auspicious candidate for heterogeneous catalysts, courtesy of its high chemical stability and electronic properties. However, the electron-deficient surface-active Fe species in FeWO4 are insufficient to cleave H2O2 via Fe redox-mediated Fenton-like catalytic reaction. Herein, we doped Sulfur (S) atom into FeWO4 catalysts to refine the electronic structure of FeWO4 for H2O2 activation and sulfamethoxazole (SMX) degradation. Furthermore, spin-state reconstruction on S-doped FeWO4 was found to effectively refine the electronic structure of Fe in the d orbital, thereby enhancing H2O2 activation. S doping also accelerated electron transfer during the conversion of sulfur species, promoting the cycling of Fe(III) to Fe(II). Consequently, S-doped FeWO4 bolstered the Fenton-like reaction by nearly two orders of magnitude compared to FeWO4. Significantly, the developed S-doped FeWO4 exhibited a remarkable removal efficiency of approximately 100% for SMX within 40 min in real water samples. This underscores its extensive pH adaptability, robust catalytic stability, and leaching resistance. The matrix effects of water constituents on the performance of S-doped FeWO4 were also investigated, and the results showed that a certain amount of Cl-, SO42-, NO3-, HCO3- and PO43- exhibited negligible effects on the degradation of SMX. Theoretical calculations corroborate that the distinctive spin-state reconstruction of Fe center in S-doped FeWO4 is advantageous for H2O2 decomposition. This discovery offers novel mechanistic insight into the enhanced catalytic activity of S doping in Fenton-like reactions and paves the way for expanding the application of FeWO4 in wastewater treatment.

[Distribution Characteristics and Risk Assessment of PPCPs in Surface Water and Sediments of Lakes in the Lower Reaches of the Huaihe River].

In order to understand the occurrence characteristics and ecological risks of pharmaceuticals and personal care products (PPCPs) in surface water and sediments of Hongze Lake and Gaoyou Lake in the lower reaches of the Huaihe River, 43 surface water and sediment samples from 23 sampling sites were collected, and 61 PPCPs were detected in the samples. The concentration level and spatial distribution of target PPCPs in Hongze Lake and Gaoyou Lake were analyzed, the distribution coefficient of typical PPCPs in the water/sediment system in the study area was calculated, and the ecological risk of target PPCPs was evaluated using the entropy method. The results showed that the PPCPs in surface water of Hongze Lake and Gaoyou Lake were 1.56-2534.44 ng·L-1 and 3.32-1027.47 ng·L-1, respectively, and those in sediment were 1.7-926.7 ng·g-1 and 1.02-289.37 ng·g-1, respectively. The concentrations of lincomycin (LIN) in surface water and doxycycline (DOX) in sediment were the highest, and antibiotics were the main components. The spatial distribution of PPCPs was higher in Hongze Lake and lower in Gaoyou Lake. The distribution characteristics of typical PPCPs in the study area showed that typical PPCPs tended to stay in the water phase, and there was a significant correlation between lg Koc and lg Kd, indicating that total organic carbon (TOC) played an important role in the distribution of typical PPCPs in the water/sediment system. The ecological risk assessment results showed that the ecological risk of PPCPs to algae in surface water and sediment was significantly higher than that of fleas and fish, the ecological risk value of PPCPs in surface water was higher than that in sediment, and the ecological risk of Hongze Lake was higher than that of Gaoyou Lake.

[Characteristics, Sources, and Risk Assessment of Perlyfluoroalkyl Substances in Surface Water and Sediment of Luoma Lake].

Through the investigation and detection of the surface water and sediments of Luoma Lake, the structure and occurrence characteristics of PFASs (perlyfluoroalkyl substances) in the two types of media were analyzed, and the principal component analysis method was used to analyze the characteristics of such substances in the surface water. The source was analyzed, and the potential health risks of such substances were evaluated using the risk quotient method. The results showed that a total of 13 PFASs were detected in the surface sediments of Luoma Lake, and one more species was detected in the surface water (PFTeA); ρ(ΣPFASs) in the surface water ranged from 46.09 to 120.34 ng·L-1, and ω(ΣPFASs) in sediments ranged from 2.22 to 9.55 ng·g-1. PFPeA was the major component in surface water, and the mass fraction of PFPeA was 38%. PFBA was the major component in sediment, and the mass fraction of PFPeA was 61%. The multi-media PFASs in Luoma Lake were mainly short-chain substances; the high concentration area of PFASs in the surface water of Luoma Lake was concentrated and distributed at the mouth of the northern rivers. Its concentration showed a decreasing trend from north to south, and the content of PFASs in the sediments showed a decreasing trend from southwest to northeast. The distribution of ΣPFASs, PFBA, and PFOS in the sediments of Luoma Lake and the TOC content in the sediment were related; the principal component analysis showed that the PFASs in the surface water of Luoma Lake were mainly from textile flame retardant, rubber product emulsification, food packaging processes and paper surface treatment industries, the metal electroplating industry, and leather and textile manufacturing industries. PFASs in the surface water of Luoma Lake were at a relatively low health risk level.

[Distribution of Typical Pollutants from Rainwater Sewer Sediments in Suzhou City].

In this study, we separately collected rainwater sewer sediments from typical samples in Suzhou city, such as the urban commercial district, historical and cultural protection area, cultural and educational area, and living area, and analyzed the particle size distribution of the sediments and the characteristics of carbon, nitrogen, phosphorus content, and pollution load distribution under each graded particle size. The median particle size D50 of each sample point was 16.55-327.50 µm, and the particle size trend was as follows:commercial area > living area > historical and cultural protection area > cultural and educational area. D50 was related to the total organic carbon (TOC). The total nitrogen (TN), total phosphorus (TP), and ammonia nitrogen (NH4+-N) were significantly positively correlated, as were the pollutants. The spatial difference of ω(TOC), ω(TN), ω(TP), and ω(NH4+-N) in rainwater sewer sediments from different regions was as follows:commercial area > historical and cultural protection area > living area > cultural and educational area, in which ω(TOC) was 0.84%-6.76%, and ω(TN), ω(TP), and ω(NH4+-N) were 917.5-12707.1, 196.1-2524.8, and 9.3-156.8 mg·kg-1, respectively. TOC, TP, and NH4+-N pollution loads were mainly concentrated on particles ≤ 75 µm and 250-1000 µm. Street dust pollutants highly differed spatially, with a high content of attached pollutants on street dust particles with a particle size of ≤ 75 µm. Various pollutants migrated into the street dust-pipes, and TP and TN showed certain enrichment characteristics in the sewer. Controlling the transportation of street dust and the accumulation of sediments in the sewer can reduce the pollution of sediment into the rivers during the rainy season.

Anaerobic self-assembly of a regenerable bacteria-quantum dot hybrid for solar hydrogen production.

Inorganic-biological hybrid systems (bio-hybrids), comprising fermentative bacteria and inorganic semiconductor photosensitizers for synergistic utilization of solar energy and organic wastes, offer opportunities for sustainable fuel biosynthesis, but the low quantum efficiency, photosensitizer biotoxicity and inability for self-regeneration are remaining hurdles to practical application. Here, we unveil a previously neglected role of oxygen in suppressing the biosynthesis of cadmium selenide quantum dots (CdSe QDs) and the metabolic activities of Escherichia coli, and accordingly propose a simple oxygen-regulation strategy to enable the self-assembly of bacterial-QD hybrids for efficient solar hydrogen production. Shifting from aerobic to anaerobic biosynthesis significantly lowered the intracellular reactive oxygen species level and increased NADPH and thiol-protein production, enabling a two-order-of-magnitude higher bio-QD synthesis rate and resulting in CdSe-rich products. Bacteria with abundant biocompatible intracellular bio-QDs naturally formed a highly active and self-regenerable bio-hybrid and achieved a quantum efficiency of 28.7% for hydrogen production under visible light, outperforming all the existing bio-hybrids. It also exhibited high stability during cyclic operation and robust performance for treating real wastewater under simulated sunlight. Our work provides valuable new insights into the metallic nanomaterial biosynthesis process to guide the design of self-assembled bio-hybrids towards sustainable energy and environmental applications.

[Degradation of AO7 with Magnetic Fe3O4-CuO Heterogeneous Catalyzed Sodium Percarbonate System].

Magnetically recyclable Fe3O4-CuO was synthesized by a one-step hydrothermal method and characterized by scanning electron microscopy coupled with energy dispersive spectrometer (SEM-EDS) and X-ray diffraction (XRD). The degradation of azo dye acid orange 7 (AO7) by percarbonate (SPC) activated with Fe3O4-CuO was studied. The effects of Fe3O4-CuO catalyst loading, SPC concentration, pH value, and common chloride ions on AO7 degradation in the Fe3O4-CuO/SPC system were evaluated. The main reaction mechanism of AO7 degradation was analyzed. The results show that Fe3O4-CuO could effectively activate SPC to degrade AO7 and the reaction was accelerated with the increase of Fe3O4-CuO dosage. The increase of SPC dosage was favorable for the degradation of AO7, but excessive SPC dosage inhibited the degradation of AO7. Common ions (e.g., Cl-) in dye wastewater could promote the degradation of AO7, and the degradation rate increased with increasing concentration of Cl-. The reaction mainly occurred on the surface of the catalyst, and·OH was identified as the main active species for the degradation of AO7. The catalyst Fe3O4-CuO showed excellent stability owing to the high catalytic activity remaining after 4 cycles of repeated use. The Fe3O4-CuO/SPC system achieved a high mineralization rate in the process of decolorization of AO7.

Degradation of non-oxidizing biocide benzalkonium chloride and bulk dissolved organic matter in reverse osmosis concentrate by UV/chlorine oxidation.

Non-oxidizing biocide that is used to inhibit the microorganism growth on RO membrane, are observed to be high concentration and toxic in RO concentrate. The synergistic oxidation process (SOP) of UV/chlorine was investigated to simultaneously reduced the content (60.2 %) and toxicity (57.0 %) of a representative biocide dodecylbenzyldimethylammonium chloride (DDBAC) in real RO concentrate, with a UV fluence 1080 mJ/cm2 and chlorine dose 20 mg/L. Besides eliminating the DDBAC, UV/chlorine reduced the UVA254 and fluorescence of the dissolved organic matters (DOM). The oxidation mechanism was verified to be the radical electrophilic addition rather than the chlorine-electrophilic substitution through the decay of electron-donation moiety and UVA254. As results, high molecular weight fractions of DOM (>2k Da, 79.2 %) was cleaved into low molecular weight fractions (<0.4k Da, 18.4 %) and organic halide was formed. Parallel-factor analysis of the fluorescence components suggested that decomposition of the protein-like fluorophore is most likely to surrogate the biocide removal and organic halide formation compared to other fluorophore components and UVA254. Accordingly, a portable fluorescence probe with 400 nm excitation and 410-600 nm emission wavelengths was developed as an online surrogate for the DDBAC removal and organic halide formation.

[Degradation of OG with Peroxymonosulfate Activated by a MnFe2O4-graphene Hybrid].

The rG-MnFe2O4 was synthesized by hydrothermal method and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and Raman spectra. The rG-MnFe2O4 was used to activate peroxymonosulfate (PMS) to decolorize azo dyes, e.g., Orange G, and the effect of PMS dosage, rG-MnFe2O4 loadings, initial pH, and the concentration of Cl- were investigated. The results indicated that the degradation rate of OG was 100% within 27 min with 0.3 g ·L-1 of rG-MnFe2O4 and at a 40:1 of PMS:OG molar ratio. The decolorization efficiency of OG increased with increasing PMS concentration and increasing rG-MnFe2O4 dosage. The initial pH had a significant effect on OG degradation, and pH 5.00 was most favorable for its decolorization. In addition, the addition of Cl- accelerated the decolorization of OG, and the decolorization rate increased with increasing concentration of Cl-. The rG-MnFe2O4 also exhibited an excellent reusability, and its activation of PMS was still observed after five rounds of tests. From the analysis of UV-vis spectra and gas chromatography-mass spectrometry (GC/MS), the naphthalene ring and azo band were found to be destroyed, with p-nitrophenol and phthalic acid as the main degradation products. Finally, a TOC analysis indicated that a certain degree of OG mineralization was obtained in the rG-MnFe2O4/PMS system.

[Impact of Anthraquinone-2-sulfonic Acid on the MO Decolorization, Hydrogen Production and Energy Creation During Anaerobic Fermentation of Klebsiella oxytocaGS-4-08 with Sucrose].

The effect of 0-0.5 mmol·L-1 anthraquinone-2-sulfonic acid on anaerobic fermentation of Klebsiella oxytocaGS-4-08 was analyzed. By comparing bio-hydrogen production, carbon source degradation, and degradation products, the optimal concentration of 0.1 mmol·L-1 was acquired. Under this concentration, Klebsiella oxytocaGS-4-08 could decolorize 100% methyl orange within 10 h, degrade 92% sucrose within 25 h, meanwhile produce 0.117 mol·mol-1 ethanol, 0.116 mol·mol-1 acetic acid, 2.25 mol·mol-1 hydrogen. Besides, the promoting mechanism of AQS on MO decolorization and hydrogen production by Klebsiella oxytocaGS-4-08 was analyzed by comparing the experimental results and the literatures. The electron transfer and energy conversion are analyzed during the bacterial degradation process by converting the substances into COD; the optimal electron yield was 87.98% and the optimal energy generation rate was 802 kJ·mol-1, and both were achieved under 0.1 mmol·L-1 of AQS. Using Klebsiella oxytoca GS-4-08, at least two types of biofuels could be produced via fermentation process, which showed prospects in future applications.

[Particle Size Distribution and Pollutant Speciation Analyses of Stormwater Runoff in the Ancient Town of Suzhou].

The particle size distribution (PSD) and its transformation processes in the stormwater runoffs in the ancient town of Suzhou were studied based on the particles size analyses, the water-quality monitoring data and the parameters of the rainfall-runoff models. The commercial districts, the modern residential area, the old residential area, the traffic area and the landscape tourist area were selected as the five functional example areas in the ancient town of Suzhou. The effects of antecedent dry period, the rainfall intensity and the amount of runoffs on the particle size distributions were studied, and the existing forms of the main pollutants in different functional areas and their possible relations were analyzed as well. The results showed that the particle size distribution, the migration processes and the output characteristics in the stormwater runoffs were greatly different in these five functional areas, which indicated different control measures for the pollution of the runoffs should be taken in the design process. The antecedent dry period, the rainfall intensity and the amount of runoffs showed significant correlations with the particle size distribution, showing these were the important factors. The output of the particles was greatly influenced by the flow scouring in the early period of the rainfall, and the correlations between the amount of runoffs and the particle migration ability presented significant difference in 30% (early period) and 70% (later period) of the runoff volume. The major existence form of the output pollutants was particle, and the correlation analyses of different diameter particles showed that the particles smaller than 150 microm were the dominant carrier of the pollutants via adsorption and accumulation processes.

[Adsorption Characteristics of Phosphorus Wastewater on the Synthetic Ferrihydrite].

The synthetic ferrihydrite, FerrorMox (FM), was used as adsorbent for removing phosphorus from wastewater. SEM, EDS, XRD, FTIR and Raman were used to characterize FM, and the results indicated that FM was amorphous 2 L ferrihydrite and was composed of Fe, O, Ca and Si, etc. Afterwards, FM was applied to adsorb phosphorus from wastewater, and the adsorption performance, influence factors and adsorption mechanism were investigated. The phosphorus removal rate reached 99.14% under the condition of adsorption time of 60 min, initial pH phosphate solution of 2, relative dosing quantity of 7 g·L-1, reaction temperature of 25℃, initial concentration of 10 mg·L-1, and solution volume of 50 mL. Adsorption isotherms were well fitted with the Langmuir isothermal adsorption model at different temperature with the correlation coefficient reaching above 0.95. The thermodynamic parameters showed that the phosphorus adsorption by FM was a spontaneous endothermic reaction. The phosphate removal kinetics well followed both pseudo-first-order model and pseudo-second-order model. About 99% of phosphate adsorbed on FM could be desorbed in 0.1 mol·L-1 NaOH solution. Therefore, FM was a promising absorbent material for the removal of phosphate from waste water.

[Kinetics for Degradation of Orange G with Peroxymonosulfate Activated by Carbon Nanotubes].

Carbon nanotube (CNT) was used as an activator to activate peroxymonosulfate (PMS) to degrade azo dye orange G (OG) in aqueous solution. The results indicated that CNT exhibited a much better performance in activating PMS to decolorize OG than activated carbon (GAC), with 99% decolorization of OG achieved within 45 min. Afterwards, the degradation mechanism of OG in CNT activated PMS system was explored, and SO4-·was found to be dominantly responsible for OG degradation, which mainly took place on the surface of CNT. Effects of various factors, including temperatures, initial concentration of OG, CNT loadings, PMS dosage, and initial pH, on degradation of OG were then investigated, and OG degradation in these cases well conformed to first-order kinetics. From the analysis of UV-vis spectra of OG during the reaction, the peaks at 479 nm and 330 nm were found to be significantly decreased, suggesting that the azo band and naphthaline ring were destructed, respectively. Finally, TOC analysis indicated that a certain degree of OG mineralization was obtained in CNT activated PMS system.

[Activated Carbon Supported Co3O4 Catalysts to Activate Peroxymonosulfate for Orange G Degradation].

Activated carbon supported cobalt catalysts (Co/AC) were prepared through wet impregnation and high temperature calcination methods. The X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) characterization results showed that Co3O4 was the major form of Co species distributed on AC. The performance of Co/AC was evaluated as catalyst to activate peroxymonosulfate (PMS) to produce sulfate radicals (SO4-·) for Orange G (OG) degradation in solution. The activation mechanism and several influential factors were also investigated. The results demonstrated that SO4-·played a dominant role in OG degradation. And the degradation efficiency of OG increased with increasing Co/AC dosage, higher PMS concentration or elevating reaction temperature. Initial pH had a significant effect on OG degradation, with pH range of 4 to 8 as the optimal pH for degradation. In addition, the strong acidic or alkaline conditions were unfavorable for OG degradation. A dual effect of chloride ions (Cl-) was observed. The high Cl- concentration promoted degradation, while low concentration led to inhibition. The Co/AC also exhibited excellent reusability and its activating performance toward PMS was still observed after 6 rounds of tests. Finally, the degradation process and intermediate products of OG were analyzed with UV-visible spectroscopy and gas chromatography-mass spectrometry (GC/MS).

[Pollution Characteristics and Evaluation of Nitrogen, Phosphorus and Organic Matter in Sediments of Shanmei Reservoir in Fujian, China].

In order to illuminate pollutants distribution characteristics in sediment of Shanmei Reservoir, sediment samples at 47 sampling stations were collected (include 8 column samples), and concentrations of total nitrogen, total phosphorus and organic matter in the sediment of each station were measured. C/N and the correlation of TN, TP and OM were also analyzed. Finally, pollution assessment for contaminated layer sediments was conducted. The results showed that the average contents of TN, TP and OM (mass fraction) were 1,180 mg · kg⁻¹, 642 mg · kg⁻¹ and 3.30% in the contaminated layer of sediments. Concentrations of total nitrogen and total phosphorus were low and stable at the depth of the normal layer. C/N of the contaminated layer of sediments was much higher than those in normal lakes, which showed that large part of OM came from natural land-based sources. Besides, a small part of OM came from phytoplankton, zooplankton and algae. Any two of TN,TP and OM were significantly correlated. This result showed that most of the nitrogen and phosphorus were in the organic form, and they came from similar sources. Evaluation results showed that both organic index and organic nitrogen belonged to the clean category. TP was at a moderate pollution level but not far from the category of heavy pollution.

Biogenic FeS accelerates reductive dechlorination of carbon tetrachloride by Shewanella putrefaciens CN32.

Dissimilatory metal reducing bacteria (DMRB) widely exist in the subsurface environment and are involved in various contaminant degradation and element geochemical cycling processes. Recent studies suggest that DMRB can biosynthesize metal nanoparticles during metal reduction, but it is unclear yet how such biogenic nanomaterials would affect their decontamination behaviors. In this study, we found that the dechlorination rates of carbon tetrachloride (CT) by Shewanella putrefaciens CN32 was significantly increased by 8 times with the formation of biogenic ferrous sulfide (FeS) nanoparticles. The pasteurized biogenic FeS enabled 5 times faster dechlorination than abiotic FeS that had larger sizes and irregular structure, confirming a significant contribution of the biogenic FeS to CT bioreduction resulting from its good dispersion and relatively high dechlorination activity. This study highlights a potentially important role of biosynthesized nanoparticles in environmental bioremediation.

[Degradation of Acid Orange 7 with Persulfate Activated by Silver Loaded Granular Activated Carbon].

Granular activated carbon with silver loaded as activator (Ag/GAC) was prepared using impregnation method. N2 adsorption, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) were adopted to characterize the Ag/GAC, showing that silver was successfully loaded on granular activated carbon. The oxidation degradation of acid orange 7 (AO7) by the Ag/GAC activated by persulfate (PS) was investigated at ambient temperature. The influences of factors such as Ag loading, PS or Ag/GAC dosages and initial pH on the degradation of AO7 were evaluated. The results demonstrated that the degradation rate of AO7 could reach more than 95.0% after 180 min when the Ag loading content, PS/AO7 molar ratio, the Ag/GAC dosage were 12.7 mg x g(-1), 120: 1, 1.0 g x L(-1), respectively. The initial pH had significant effect on the AO7 degradation, with pH 5.0 as the optimal pH for the degradation of AO7. The possible degradation pathway was proposed for the AO7 degradation by using UV-visible spectroscopy and gas chromatography-mass spectrometry (GG/MS). The azo bond and naphthalene ring in the AO7 were destroyed during the degradation, with phthalic acid and acetophenone as the main degradation products.