Actual Wastewater Research Articles

Decolorization and degradation of crystal violet dye by electron beam radiation: Performance, degradation pathways, and synergetic effect with peroxymonosulfate

Ionizing radiation (mainly including gamma ray and electron beam) technology provides a more efficient and ecological option for dye-containing wastewater treatment, which is supported by its successful achievements in industrial-scale applications. However, the degradation pathway of triphenylmethane dyes by radiation technology is still unclear. In this study, crystal violet (CV) was selected as representative cationic triphenylmethane dye, the decolorization and degradation performance by electron beam radiation technology was systematically evaluated. The results showed that CV can be efficiently decolorized and mineralized by radiation, and its degradation kinetics followed the first-order kinetic model. The effect of inorganic anions and chelating agents commonly existed in dye-containing wastewater on CV decolorization and total organic carbon (TOC) removal was explored. Quenching experiments, density functional theory (DFT) calculation and high performance liquid chromatography mass spectrometry (HPLC-MS) analysis were employed to reveal CV decolorization and degradation mechanism and pathway, which mainly included N-demethylation, triphenylmethane chromophore cleavage, ring-opening of aromatic products and further oxidation to carboxylic acid, and mineralization to CO2 and H2O. Additionally, electron beam radiation/PMS process was explored to decrease the absorbed dose required for decolorization and degradation, and the synergetic effect of radiation with PMS was elucidated. More importantly, the findings of this study would provide the support for treating actual dyeing wastewater by electron beam radiation technology.

A novel bifunctional particle electrode with abundant Fe/Fe3C and Fe-N-C sites to enhance the performance of electro-Fenton in degrading organic pollutant

Electro-Fenton (EF) technology emerges as a promising approach to address the treatment of persistent organic pollutants. Nevertheless, its practical implementation often comes with certain drawbacks, like the low H2O2 activation efficiency, poor pH adaptability, and difficult recycling of the catalysts. To this end, we introduced highly active Fe-N-C sites onto the surface of nitrogen-doped graphene, improved the chemical environment of its central Fe atoms with Fe/Fe3C nanoparticles, effectively regulated the multi-electron oxygen reduction process of the catalyst in the electrochemical reaction, and realized the efficient production and activation of H2O2 in the electro-Fenton process. The synthesized Fe/Fe3C@FeNG-1000 achieved efficient removal of refractory organic pollutants in neutral conditions. The rate constant of degradation for tetracycline hydrochloride (TC) in the electro-Fenton reaction system at pH 7 was recorded as 0.1011 min−1. Additionally, a removal rate of 67.4% for total organic carbon (TOC) was achieved in just 120 min. The treatment of actual wastewater also showed excellent performance, with an average specific energy consumption of 6.16 kWh kg−1 COD−1. Fe/Fe3C@FeNG-1000 can still achieve more than 90% degradation efficiency after 5 consecutive cycles of the experiment, showing excellent stability, and the catalyst can be conveniently retrieved via magnetic methods following the reaction. The results show that the Fe/Fe3C@FeNG-1000-EF system has a wide range of pH applicability, long-term stability and good recyclability, has a good application value in practical wastewater treatment.

Enhanced fluoride removal using Mg-Zr binary metal oxide nanoparticles confined in a strong-base anion exchanger

Generally, the pH of fluorinated groundwater or many industrial wastewater is neutral, while the majority of metal-modified adsorbents can work efficiently only under acidic conditions. In this study, we synthesized a novel hybrid adsorbent, Mg–Zr-D213, by loading nano-Mg/Zr binary metal (hydrogen) oxides in a strong-base anion exchanger, D213, to enhance the adsorption of fluoride from neutral water. Mg–Zr-D213 exhibited a better fluoride-removal capacity in neutral water than monometallic modified resins. Under the interference of competing anions and coexisting organic acids, Mg–Zr-D213 exhibited superior selectivity. The Langmuir model indicated that the fitted maximum sorption capacity of Mg–Zr-D213 was 41.38 mg/g. The results of column experiments showed that the effective treatment volume of Mg–Zr-D213 was 8–16-times higher than that of D213 for both synthetic groundwater and actual industrial wastewater, and that NaOH–NaCl eluent could effectively recover more than 95% of fluoride. Adsorption experiments with Mg/Zr metal (hydrogen) oxide particles and D213 separately demonstrated a synergistic effect between –N+(CH3)3 and Mg/Zr metal (hydrogen) oxide particles. The ligand exchange or metal-ligand interaction of Mg/Zr metal (hydrogen) oxide particles on fluoride was further demonstrated via X-ray photoelectron spectroscopy. Overall, Mg–Zr-D213 has great potential for enhanced fluoride removal in neutral water.

Efficient decolorization performance of graphene quantum dots modulated nanofiltration membranes with tunable pore size for precise molecular sieving

The discharge of wastewater containing dyes not only causes serious environmental pollution but also poses a severe threat to human health. The selective separation of dyes and reuse of inorganic salts are vital in the textile industry. In this work, nitrogen-doped graphene quantum dots (N-GQDs) was successfully synthesized via the “one-step solvothermal method”, and the N-GQDs composite membranes were innovatively fabricated by constructing a thin selective layer top the modified multi-walled carbon nanotubes (MWCNTs) matrix membrane via interfacial polymerization process. The pore size of the N-GQDs membranes could be flexibly modulated by regulating the contents of the N-GQDs. The suitable N-GQDs membrane (M4, 0.35 wt% of N-GQDs) possessed over 96 % rejection rate for diverse charged dyes, which was higher than that of the piperazine polyamide (PA3) membrane. Notably, the rejection of the smaller molecular weight of Methylene Blue by the M4 membrane reached ∼98.93 %, which was higher than that reported in most literature, mainly owing to the relatively smaller average pore size and stronger electronegativity of the membrane. Especially compared with our previous work, the prepared M3 and M4 membranes exhibited an enhancement of ∼37.79 % and 39.48 % in rejection of Methylene Blue, ∼ 78 % and 19 % in pure water permeability, respectively. On account of the size sieving and charge effect, the N-GQDs membrane (M4) could maintain high rejection for dyes and exhibited efficient separation for dye/salt with a separation factor of 115 for the Congo Red/sodium chloride mixture after continuous cross-flow filtration for 24 h in the simulated wastewater condition. Furthermore, the N-GQDs membrane also exhibited favorable acid-base resistance and satisfactory anti-fouling performance. Importantly, the N-GQDs membranes presented excellent decolorization efficiency for the practical textile wastewater. These results revealed that the as-prepared N-GQDs membrane possessed great potential for actual textile wastewater advanced treatment and purification. This study also offers a new candidate to rationally manipulate the separation properties of nanofiltration membranes adopting new aqueous monomers.

Bifunctional boron-nitrogen-containing graphite felt cathode for highly efficient treatment on dye wastewater depending on the metal-free electro-Fenton process

The heterogeneous electro-Fenton technology can settle a matter of narrow pH application range in the traditional electro-Fenton process. Direct O2 electro-reduction to •OH on the surface of metal-free catalysts can effectively solve the problem of easy leaching of metal-based catalysts under acidic conditions and improve the oxidation efficiency of H2O2. In this work, a stable bifunctional boron-nitrogen-containing catalyst was directly synthesized on the surface of graphite felt. The H2O2 yield (4.32 mg cm-2 h−1) and rhodamine B degradation rate (0.174 min−1) of boron-nitrogen-containing catalyst were significantly improved at the pH value of 7, compared with nitrogen-containing graphite felt catalyst. The catalyst had a rapid degradation ability for various dyes and actual dye wastewater, and the specific energy consumption of actual dye wastewater degradation was 4.02 kW h kg−1 COD-1 lower than that reported in literature (6.38–29.7 kW h kg−1 COD-1). DFT calculations and XPS results revealed the potential reaction mechanism. The introduction of −BCO2 group into the nitrogen-containing plane significantly enhanced the oxygen adsorption and oxygen reduction activity, and the directly formation of •OH was promoted jointly by graphite nitrogen and −BCO2 group. This work provided a new insight into the development of metal-free electro-Fenton catalyst.

Ti4O7-C3N4 anode with a low charge transfer resistance value for degradation of imidacloprid in actual wastewater

Imidacloprid (IMD) is a kind of neonicotinoid insecticide, which is widely used in the agricultural production. There are few reports on electrocatalytic degradation of IMD with the low concentration. In this study Ti4O7-C3N4 electrode was employed for the first time to electrocatalytically degrade low concentration IMD. Compared with pure Ti4O7 electrode, the oxygen evolution potential was increased from 1.84 V to 2.50 V, the charge transfer resistance (Rct) was reduced by 66.05 %, and the oxygen vacancies were increased by 2.5 times compared to the original Ti4O7. Especially, the Rct for Ti4O7 (5.45 Ω·cm2) was only 1/7 of that for boron-doped diamond (BDD) (38.89 Ω·cm2). IMD degradation ratio was up to 98 % in only 1.256 min (75.360 s) using a Ti4O7-C3N4. When SongShan Lake water, Wanjiang water, and secondary effluent were treated, the degradation radios of IMD were 70.30 %, 72.33 % and 81.12 %, respectively. In the presence of Cl− coexisting ions, no disinfection by-product of ClO4− was detected, which is an advantage for Ti4O7-C3N4 compared with BDD. The first and 48th degradation ratios were 99 % and 97 %, respectively, indicating the good stability of Ti4O7-C3N4. The development of Ti4O7-C3N4 provides a stable, low energy consumptions and no secondary pollution anode for the treatment of actual wastewater.

Effects of Salts and Other Contaminants on Ciprofloxacin Removal Efficiency of Green Synthesized Copper Nanoparticles.

Ciprofloxacin (CIP), a broad-spectrum fluoroquinolone antibiotic, is commonly used in aquaculture to prevent and treat bacterial infections in aquatic animals. For this reason, aquatic environments contain CIP and its derivatives, which lead to the development of drug-resistant bacteria. In the present study, copper nanoparticles were prepared using Garcinia mangostana extract (GME-CuNPs) as a reducing agent and evaluated for their CIP removal efficiency (CRE). The results demonstrate that within 20 min, GME-CuNPs at 25 mM possess a CRE of 92.02 ± 0.09% from CIP-containing aqueous media with pH 6-7. The CRE is influenced by both monovalent and divalent salts. A high salt concentration significantly reduces the CRE. Contaminants in fish wastewater can reduce the CRE, but phenolics, flavonoids, tannins, and ammonia do not affect the CRE. Our results reveal that the CRE is controlled by electrostatic attraction between the negatively charged GME-CuNPs and the cationic species of CIP. The CRE is reduced by wastewater with a pH higher than 8.0, in which the CIP molecules have a negative charge, resulting in a repulsive force due to the negative charge of GME-CuNPs. In fish wastewater with a pH lower than 7.0, GME-CuNPs show the potential to achieve a CRE above 80%. Therefore, pH adjustment to a range of 6-7 in fish wastewater before treatment is deemed imperative. It is concluded that the newly developed GME-CuNPs possess excellent activity in CIP elimination from actual fish wastewater samples. Our findings suggest that GME-CuNPs can be a promising tool to effectively eliminate antibiotics from the environment.

Promoting bioremediation of brewery wastewater, production of bioelectricity and microbial community shift by sludge microbial fuel cells using biochar as anode

Seeking low-cost and eco-friendly electrode catalyst of microbial fuel cell (MFC) reactor has received extensive attention in recent decades. In this study, a sludge MFC was coupled with biochar-modified-anode (BC-300, BC-400, and BC-500) for actual brewery wastewater treatment. The physicochemical properties of biochar largely depended on the pyrolysis temperature, further affecting the removal efficiency of wastewater indicators. BC-400 MFC proved to be efficient for TN and NH4+-N removal, while the maximum removal efficiencies of COD and TP were achieved by BC-500 MFC, reaching respectively 97.14 % and 89.67 %. Biochar could promote the degradation of dissolved organic matter (DOM) in wastewater by increasing the electrochemical performances of MFC. The maximum output voltage of BC-400 MFC reached 410.24 mV, and the maximum electricity generation of 108.05 mW/m2 was also obtained, surpassing the pristine MFC (BCC-MFC) by 4.67 times. High-throughput sequencing results illustrated that the enrichment of electrochemically active bacteria (EAB) and functional bacteria (Longilinea, Denitratisoma, and Pseudomonas) in BC-MFCs, contributed to pollutants degradation and electron transfer. Furthermore, biochar affected directly the electrical conductivity of wastewater, simultaneously changing microbial community composition of MFC anode. Considering both enhanced removal efficiency of pollutants and increased power generation, the results of this study would offer technical reference for the application of biochar as MFC catalyst for brewery wastewater treatment.

Magnetically recyclable hydrothermal biochar functionalized with β-CD for simultaneous capturing of cationic methylene blue and auramine O in wastewater

The highly efficient and recoverable magnetic hydrothermal biochar (β-CD@MHBC) was prepared by combining red sandalwood and β-cyclodextrin, and was used for removing methylene blue (MB) and auramine O (AO) dyes in the single and binary systems. The physical and chemical properties of the β-CD@MHBC were characterized using SEM-EDS, BET, XRD, VSM, FT-IR, and XPS techniques. Batch adsorption studies revealed that the obtained maximum adsorption capacities of β-CD@MHBC for MB and AO in the single system were 303.1 and 400.0 mg g−1, while in the binary system were 151.1 and 169.1 mg g−1 under the optimal conditions of pH 6, 1.0 g L−1 dosage, 150 mg L−1 dye concentration and adsorption time of 180 min, indicating the presence of competitive adsorption with AO possessing stronger affinity in the binary system. The adsorption behaviors of MB and AO could be well described by the Langmuir isotherm model and pseudo-second-order kinetic model in both single and binary systems. The possible adsorption mechanism involved pore filling, electrostatic attraction and hydrogen bonds between β-CD@MHBC and dye molecules. Furthermore, the spent β-CD@MHBC displayed excellent reusability and stability with removal efficiencies of 94 % for MB and 83 % for AO after five cycles of adsorption-desorption. In summary, the prepared β-CD@MHBC with excellent adsorption property and regeneration performance could have great potential for continuous removal of target pollutants in actual wastewater treatment.

Lignin-modified graphitic carbon nitride nanotubes for photocatalytic H2O2 production and degradation of brilliant black BN

As a renewable aromatic compound with enormous production potential, lignin has various potential high-value utilization pathways, but the success achieved in the field of photocatalysis is limited. Herein, this work prepares a new type of photocatalyst by modifying Graphitic Carbon Nitride Nanotubes (CNT) with self-assembled lignin nanospheres for the photocatalytic production of H2O2 and the degradation of azo dyes. Under light conditions, lignin enhances the production of H2O2 through oxygen reduction and collaborates with carbon nitride tubes to generate O2− and 1O2. Furthermore, carbon nitride tubes form electron-rich regions with lignin, promoting the transfer of electrons from adsorbed aromatic pollutants to this region, thereby facilitating their degradation. The experimental results indicate that the addition of 5 % lignin significantly enhances the photocatalytic degradation efficiency of azo dyes, with a degradation rate 1.87 times higher than that of the original carbon nitride tubes. Furthermore, CNL also have excellent degradation ability to pollutants in actual wastewater. This study provides new insights and prospects for the high-value utilization of lignin, enabling it to be used as a photocatalytic co-catalyst to participate in the photocatalytic degradation of environmental pollutants.

Green synthesis and high-performance fluoride ion removal using lanthanum-modulated MOF-808 (Zr)

In a water solution and with a low reaction temperature of 85 °C, the green preparation of lanthanum-modulated MOF-808 (Zr) was realized, the obtained La-MOF-808 have smaller grain size, larger specific surface area, higher pore volume and larger average pore diameter. When the molar ratio of La: Zr=1:1, 1L-MOF-808 had the best fluoride ion removal performance, and its maximum adsorption capacity for F- reached 101.4 mg/g, which was higher than that of the unmodulated MOF-808 and some other reported fluorine adsorbents. Meanwhile, the regeneration experiment demonstrated that even after five cycles, 1L-MOF-808 retained 73.8 % of its initial adsorption capacity, highlighting its commendable reusability. In addition, when 1L-MOF-808 was applied to actual fluorine-containing wastewater, with the fluoride ion concentration of 25.3 mg/L and an adsorbent dosage of 0.6 g/L, 1L-MOF-808 exhibited excellent resistance to anionic interference (SO42-, Cl-), the concentration of fluoride ions in effluent was lower than 10 mg/L, meeting the stipulations of fluoride ion discharge outlined in GB39371–2020. Further adsorption mechanism investigation revealed that 1L-MOF-808's affinity for F- was attributed to electrostatic interaction and ligand exchange. Overall, the as-synthesized 1L-MOF-808 not only presents an environmentally friendly approach to producing MOF materials without organic solvents but also develops a new strategy for the design of high-performance adsorbent for effectively removing fluoride ions from wastewater.

Efficient chlorination reaction of Pt/RuO2/g-C3N4 under visible light irradiation for simultaneous removal of ammonia and bacteria from mariculture wastewater

The removal of ammonia nitrogen (NH4+-N) and bacteria from aquaculture wastewater holds paramount ecological and production significance. In this study, Pt/RuO2/g-C3N4 photocatalysts were prepared by depositing Pt and RuO2 particles onto g-C3N4. The physicochemical properties of photocatalysts were explored by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV–vis diffuse reflectance spectrometer (UV–vis DRS). The photocatalysts were then applied to the removal of both NH4+-N and bacteria from simulated mariculture wastewater. The results clarified that the removals of both NH4+-N and bacteria were in the sequence of g-C3N4 < RuO2/g-C3N4 < Pt/g-C3N4 < Pt/RuO2/g-C3N4. This magnificent photocatalytic ability of Pt/RuO2/g-C3N4 can be interpreted by the transfer of holes from g-C3N4 to RuO2 to facilitate the in situ generation of HClO from Cl− in wastewater, while Pt extracts photogenerated electrons for H2 formation to enhance the reaction. The removal of NH4+-N and disinfection effect were more pronounced in simulated seawater than in pure water. The removal efficiency of NH4+-N increases with an increase in pH of wastewater, while the bactericidal effect was more significant under a lower pH in a pH range of 6–9. In actual seawater aquaculture wastewater, Pt/RuO2/g-C3N4 still exhibits effective removal efficiency of NH4+-N and bactericidal performance under sunlight. This study provides an alternative avenue for removement of NH4+-N and bacteria from saline waters under sunlight.

Improved piezo-photocatalysis for aquatic multi-pollutant removal via BiOBr/BaTiO3 heterojunction construction

Piezo-catalysis is a green and effective method for degrading rich and obstinate molecules in wastewater. Yet, the piezo-catalytic performance of frequently-used barium titanate (BTO) is still limited for practical applications, thus it is crucial to construct high-efficiency BTO-based catalysts. Herein, BiOBr/BTO heterojunction-based piezo-photocatalysts were successfully prepared using the chemical precipitation method, and an internal electric field was established via ultrasound to promote the separation of photogenerated electron-hole pairs through the synergistic effect of piezocatalysis and photocatalysis. Transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy were utilized to characterize the heterojunction. The degradation performance of Rhodamine B (RhB) by BiOBr/BTO is the best among various pollutants, giving a reaction rate constant up to 20.839 × 10−2 min−1, exceeding numerous previously reported catalysts. In addition, the piezo-photocatalytic reaction rate of BiOBr/BTO for Methyl Orange was 9.298 × 10−2 min−1, ≈ 3.3 times than those of pure BTO (2.806 × 10−2 min−1), and also ≈ 15.9 times and 3.3 times than those of single photocatalysis (0.585 × 10−2 min−1) or piezocatalysis (2.848 × 10−2 min−1). Importantly, the BiOBr/BTO heterojunction demonstrates excellent catalytic degradation performance for a broad range of pollutants (e.g., dyes and antibiotics) and their mixtures, as well as favorable cycling stability and repeatability with changed environmental conditions, displaying applicability in actual wastewater treatment. The possible degradation pathways of RhB were analyzed by liquid chromatography-mass spectrometry. The present work supplies a feasible strategy for the preparation of high-efficiency piezo-photocatalytic BTO-based heterojunctions, which can guide other composites for environmental remediation.

Lanthanum(III) − 2,5 − Pyrazinedicarboxylate framework as an antibacterial adsorbent for highly efficient and selective capture of Pb(II) and Cd(II) from wastewater

Removing heavy metal ions and microorganisms from wastewater remains a persistent challenge in wastewater treatment. The development of a novel metal–organic framework (MOF), synthesized from 2,5-pyrazine-dicarboxylic acid and lanthanide (La(III), Ce(III), Pr(III)), targeting the concurrent remediation of heavy metal and bacterial pollutants in wastewater. La-PzDC demonstrated remarkable efficacy in removing Pb(II) and Cd(II), achieving maximum adsorption capacities of 697.72 mg g−1 and 398.26 mg g−1, respectively. La-PzDC achieved rapid adsorption equilibria—within 10 min for Pb(II) and 20 min for Cd(II), and conformed to the pseudo-second-order kinetics and Langmuir isotherm models. La-PzDC captured Pb(II) and Cd(II) from actual wastewater, and its residual levels met the relevant wastewater discharge standards. La-PzDC also exhibited excellent reusability and selectivity for Pb(II) and Cd(II). The adsorption mechanism through spectroscopic analysis and density functional theory (DFT) calculations, pinpointing coordination with oxygen and nitrogen-containing groups as a key factor. Significantly, La-PzDC achieves nearly 99 % bacterial elimination against E. coli and S. aureus. The above results indicated that La-PzDC has high selectivity, rapid removal capacity and excellent antibacterial activity, offering a new strategy for the dual challenge of heavy metal and bacterial contamination in wastewater treatment.

In-silico and in-vitro targeting of organic dye pollutants from synthetic and real wastewater by the hierarchically self-assembled laccase@bismuth phosphate hybrid nanorods

The increasing presence of dyes in wastewater and even surface or groundwater has progressively become an emerging global concern. This study evaluated the potential use of facile, straightforward, and hierarchical laccase@BiPO4•hybrid nanostructures (HNSs) in the elimination of anthraquinone, monoazo, diazo, and triarylmethane dyes from municipal wastewater through in-silico and in-vitro analyses. The prepared HNSs possessed rod-like morphological features with more than 8 cycles of reusability and about 10 U mg–1 catalytic activity. The nitrogen sorption analysis revealed that the prepared HNRs presented a Brunauer-Emmett-Teller (BET) surface area of 15.3 ± 1.6 m2 g−1 and an average pore size of 9.7 ± 0.5 nm. The total pore volume of HNRs was also measured at 4.0 ± 0.1 (× 10−2 cm3 g−1). Molecular docking predicted the preferred orientation of dye molecules with the enzyme's active site, facilitating the formation of stable complexes. The constructed hybrid nanorods (HNRs) showed proper in-vitro oxidation activity on the pollutant dyes with a more than 95% bioremoval for Direct Blue-15, Direct Blue-71, Crystal Violet, and Acid Blue-92. The maximum adsorption capacity of the prepared HNRs was 401 ± 11 mg per g of the carrier after 240 min of contact time with initial dyes' concentrations. Freundlich isotherm well fitted on the removal data compared with the Langmuir model due to the formation of a uniform monolayer of the dyes onto the prepared HNRs. For Direct Blue-15, Direct Blue-71, Crystal Violet, Acid Blue-92, and Acid Red-18, R2 values of pseudo-second-order kinetic were closer to 1 than that of first-order. The thermodynamic evaluations indicated that the removal of the dyes by the immobilized enzyme proceeded spontaneously and favorably (0 > ΔG°), albeit with endothermic characteristics (0 < ΔH°). Bioremoval efficiencies of 32%, 51%, 64%, and 72% were recorded when actual wastewater samples underwent treatment with 0.3 U mL−1, 0.6 U mL−1, 0.9 U mL−1and 1.2 ≤ U mL−1 of HNPs, respectively. Furthermore, the enzymatic removal process led to less toxic metabolites as confirmed using the bacterial growth inhibition test. Therefore, laccase@BiPO4•HNRs can be a worthy approach in dye removal from wastewater due to their distinct physicochemical and catalytic properties.

Ultrafast photosensitized degradation of xanthates by using methylene blue as photosensitizer under simulated and natural solar light irradiation: Operational parameters, mechanism and toxicity evolution

Xanthates have attracted considerable attention due to their broad applications in mineral flotation process and unique natures including environmental persistence and toxicity. This study proposed an innovative approach for the efficient xanthates treatment from mineral processing wastewater. Methylene blue (MB) with good water solubility and strong light absorption in visible range was used as the photosensitizer to degrade potassium ethyl xanthate (PEX) under homogeneous conditions. MB, even at a very low concentration (0.5 mg/L), was found to rapidly remove PEX in only 10 min whether under simulated or natural solar light irradiation. Besides, the influences of various operational parameters, including photosensitizer dosage, PEX concentration, pH, light intensity, common ions, and water source on the photosensitized oxidation process was evaluated and analyzed. The possible degradation path of PEX was investigated depending on the intermediates detected by Liquid chromatography-mass spectrometry (LC-MS), and the photosensitized degradation mechanism was further speculated and validated by the radicals quenching experiments and electron paramagnetic resonance (EPR) spectroscopy. Furthermore, the toxicity of PEX was assessed against Bullfrog tadpole and Lemna minor, and it was found to be greatly reduced after treating with MB photosensitization. Overall, it is the first time that MB is proved to be an outstanding candidate for actual flotation wastewater treatment, providing a more efficient, economical and greener alternative to conventional methods.

Fine-Tune the Electronic Structure of Copper Nanowire Networks by Heteroatom Doping Toward Enhanced Fenton-like Reaction

To fine-tune the configuration of electrons around metal centers is critical to enhancing the activation of peroxymonosulfate (PMS) for organic decontamination in a manner similar to the Fenton-like reaction. Herein, we systematically explored the inclusion of different heteroatoms to manipulate the electronic configuration of copper nanowire (CuNW) networks toward PMS activation. Both experimental results and theoretical simulations unveiled that doping the CuNW with boron (B) to generate CuNW-B adjusted the d orbital of CuNW, optimized the electronic density of Cu active sites and endowed a proper adsorption energy of PMS, which provided the most active oxidation capacity of the materials studied. Conversely, doping with phosphorus (P) to generate CuNW-P caused evident performance decay in terms of the activation of PMS, as strong adsorption energy hindered the effective desorption of key intermediates. Accordingly, the CuNW-B boosts the Fenton-like reaction and is nearly triple and twice as effectively at degrading bisphenol A (92.5%) as CuNW-P (36.0%) and CuNW (50.5%). Thus, it was reasonably hypothesized that electronic reconstruction played an important role in improving the Fenton-like reaction. During this process, an applied potential (AP) facilitated the catalytic process by reducing Cu2+ to Cu+, which was followed by the formation of primary active species (Cu3+). Additionally, the use of a recirculating fluid flow in the reactor provided convective mass transfer, which led to more charge transfer to the structure of electrode relative to a conventional diffusion-limited batch reactor. Moreover, tests in a variety of challenging conditions demonstrated the robustness and stability of the combined CuNW-B/PMS/AP approach. This study provides an approach to finely control the electronic structure of Cu sites and is expected to guide the design of advanced Fenton-like catalysts, which could further provide a promising technology for the treatment of actual organic wastewater in a sustainable manner.

Comparison of treatment performance and microbial community evolution of typical dye wastewater by different combined processes

The degradation of typical dye wastewater is a focus of research in the printing and dyeing industry. In this study, a combined micro-electrolysis and microbial treatment method was established to treat refractory dye wastewater, and the pivotal factors in the microbial treatment were optimized. In the series and coupled modes, the removal rates of chroma reached 98.75% and 92.50%, and the removal rates of chemical oxygen demand (COD) reached 96.17% and 82.29%, respectively. The high-throughput sequencing results showed that the microbial communities in the microbial system varied at different treatment stages. From the culture stage to the domestication stage, the dominant phylum was Proteobacteria; however, the community abundance of microorganisms decreased. A combination of micro-electrolysis and biological methods can alter the characteristics of the microbial community, increase the number of dominant phyla, and increase the abundance of microorganisms. The degradation effect of the series mode and the overall strengthening effect of micro-electrolysis on the microorganisms were better than those of the coupled mode. In actual wastewater, the maximum removal rates of chroma, COD, total nitrogen (TN), ammonia nitrogen (NH3-N), and total phosphorus (TP) are 97.50%, 98.90%, 94.35%, 93.95%, and 91.17%, respectively. Three-dimensional fluorescence spectrum analysis showed that microbial processes could significantly degrade fluorescent components in wastewater, and methanogenic active enzymes in anaerobic processes could continue to react. The combined process can realize the efficient treatment of toxic dye wastewater by reducing the toxicity of wastewater and efficiently degrading organic matter, which has important guiding significance for the treatment of refractory dye wastewater.

Resourceful application and mechanism of oyster shell-microalgae synergistic system：Sustainable treatment of harsh low carbon nitrogen ratio actual wastewater

Microalgal technology holds great promise for both low C/N wastewater treatment and resource recovery simultaneously. Nevertheless, the advancement of microalgal technology is hindered by its reduced nitrogen removal efficiency in low C/N ratio wastewater. In this work, microalgae and waste oyster shells were combined to achieve a total inorganic nitrogen removal efficiency of 93.85% at a rate of 2.05 mg L−1 h−1 in low C/N wastewater. Notably, over four cycles of oyster shell reuse, the reactor achieved an average 85% ammonia nitrogen removal extent, with a wastewater treatment cost of only $0.092/ton. Moreover, microbial community analysis during the reuse of oyster shells revealed the critical importance of timely replacement in inhibiting the growth of non-functional bacteria (Poterioochromonas_malhamensi). The work demonstrated that the oyster shell - microalgae system provides a time- and cost-saving, environmental approach for the resourceful treatment of harsh low C/N wastewater.

Active and stable Co[sbnd]Ox sites promote peroxymonosulfate activation for sulfamethoxazole degradation through nonradical pathways

Cobalt (Co) single-atom sites are considered as the most efficient active sites in peroxymonosulfate (PMS) based advanced oxidation processes. However, CoO configurations instead of Co-N configurations were scarcely explored. Herein, isolated Co single atoms were successfully implanted onto hydroxyl decorated UiO-66 (Co/UiO-66-220) to generate [Zr6O4(OH)4(BDC)5.35(OH)1.30(OH2)1.30] structure to form {ZrOCoOZr} single-site through coordination strategy. Owing to the strong electron transfer ability of CoOx sites, the Co/UiO-66-220/PMS system displayed outstanding degradation performance and 100 % sulfamethoxazole (SMX) degradation efficiency was achieved within 10 min. Remarkably, the system also displayed excellent degradation performance in the presence of anions and complex actual wastewater. The membrane system was particularly effective, achieving a 90.32 % removal efficiency within 240 min. The nonradical species, singlet oxygen (52.8 %), electron transfer (4.9 %) and high-valent cobalt-oxo species (Co (IV) = O) (23.9 %), were dominated in the degradation process. The generated intermediates are low-toxicity. The results demonstrate the excellent activity of CoOx sites for PMS activation and its practical application potential for remediation of organic contaminants.