Organic Wastewater Treatment Research Articles

Novel sludge-sugarcane bagasse mixed biochar as an efficient activator for peroxymonosulfate to degrade bisphenol AF

The exploitation of cost-effective and environmentally friendly biochar catalysts is of major importance for the oxidative treatment of toxic organic wastewater and the resource utilization of waste biomass. In this work, sewage sludge and bagasse waste were co-pyrolyzed into a novel biochar catalyst (SB-BC-900) for efficiently activating peroxymonosulfate (PMS) to degrade bisphenol AF (BPAF) in wastewater. Compared with single sludge biochar (S-BC-900), SB-BC-900 had a larger cumulative pore volume, more oxygenated functional groups (OFGs) and higher graphitization degree, with a significantly higher catalytic capacity. SB-BC-900 enabled rapid degradation of BPAF within 10 min at a low PMS dosage (molar ratio [PMS]: [BPAF] = 2.67:1). There was mainly the non-free radical pathway dominated by singlet oxygen (1O2) in the SB-BC-900/PMS system. Graphitic carbon (sp2 C=C) and OFGs on SB-BC-900 played a crucial part in the catalytic degradation of BPAF. A green approach is provided to resource waste biomass for efficient wastewater treatment in this work.

The selective and enhanced adsorptive behaviors of supramolecular recrystallized 1,3,5-benzenetricarboxylic acid assembled nano-bacterial cellulose

The effluent discharge produced in the textile printing and dyeing, leather and other fields, will cause the irreversible environmental pollution and extremely threatening safety of living organisms. The appropriate and efficient disposal method of dyestuff originated wastewater has been widely concerned in the past decades. In this study, the recrystallization of 1,3,5-benzene tricarboxylic acid (RCTMA) was put forward via a hydrothermal method to form the supramolecular RCTMA-based hexamer and thereafter assembled into the porous nano-bacterial cellulose (NBC) to construct the RCTMA@NBC composite. The morphology and surface properties of RCTMA@NBC were examined by scanning electron microscope, X-ray diffraction, and Fourier transform infrared spectroscopy. This RCTMA@NBC was employed to adsorb methylene blue (MB) adjusting the pH, temperature, and dosage of adsorbent. The result showed the maximal absorption capacity of RCTMA@NBC appeared under pH = 7.1 and higher temperature will hinder the adsorption of dyes. Moreover, the adsorption isotherms and kinetics were evaluated which was more confirmed to Langmuir model and quasi-second-order kinetic equation, and the simulated maximum adsorption capacities of MB was 1162.12 mg/g. Moreover, cationic golden XGL and anionic brilliant crocein were selected to further verify the distinct adsorptive behavior. The excellent affinity towards cationic dyes proved the easy combination was based on the chemical force originated from mutual attraction between opposite charges, π–π interactions, and H-bonding, whereas the poor attraction for brilliant crocein was due to the electrostatic repulsion between sulfonic and carboxyl groups. The synthesized RCTMA@NBC possesses higher efficiency and selective adsorption, which exhibits the promising potential in the field of precise treatment of organic dye wastewater.

Thermal effect on sulfamethoxazole degradation in a trivalent copper involved peroxymonosulfate system

Persulfate (PS) activated by thermal or homogeneous metals can generate reactive oxygen species (ROS) and high-valence-state metals for contaminants degradation, showing great potential for applications. However, thermal effect in peroxymonosulfate (PMS) system with high-valence-state metal is still ambiguous. In this study, divalent copper (Cu(II)) catalysis was taken to explore thermal effect on PMS performance. Results showed that the Sulfamethoxazole (SMX) removal efficiency in the Cu(II)/PMS system at 60 min increased by only 5.9% with temperature increase from 30 °C to 60 °C. Moreover, SMX removal efficiency was excellent at neutral or basic pH, best with PMS concentration of 2.4 mM, and slightly affected by Cu(II) concentration. The singlet oxygen (1O2) was identified as main active species at low temperature while sulfate radicals (SO4−) was more effective at high temperature with Cu(II) co-activation. Also, trivalent copper (Cu(III)) was an important active species. The higher Cu(III) content, the better SMX removal efficiency, but the stronger intermediates toxicity. In combination with removal efficiency and intermediates toxicity at different temperatures, 30 °C was the optimal reaction temperature. Overall, this study provides new perspective on utilization of waste heat and high-valence-state metal for organic wastewater treatment in PMS systems.

Role of holes in microwave-induced catalyst Co3O4 for efficient high-concentration tetracycline degradation

Microwave-induced catalytic is a potential organic wastewater treatment technology. In this work, a new type of microwave-induced catalyst Co3O4 was synthesized and used to remove tetracycline (TC) under microwave (MW). The results have shown that the spherical Co3O4 exhibited impressively high catalytic activity with 100 mg·L-1 TC degradation efficiency of 100 % under MW at 800 W within 30 min. Importantly, Co3O4 catalyst displayed excellent stability with the degradation efficiency. The electron-hole pairs were generated under MW in the presence of Co3O4, which was confirmed by electron paramagnetic resonance and active species scavenging experiments. Part of the electrons (e-) was captured by oxygen vacancies produced under MW, and holes (h+) acted as the main active species for participating in the degradation process of TC. This work indicated the effect of MW for the separation of electrons and holes and provides new ideas for the mechanism of microwave-induced catalytic degradation.

Novel Ag3PO4@ZIF-8 p-n heterojunction for effective photodegradation of organic pollutants

In this study, a novel silver phosphate@zeolitic imidazolate framework-8 (Ag3PO4@ZIF-8) p-n heterojunction was fabricated at room temperature using the chemical precipitation method. The photocatalytic properties of the developed p-n heterojunction were investigated with respect to organic water pollutants. The effects of the operation parameters on the photocatalytic performance of the fabricated photocatalyst were also studied. The fabricated Ag3PO4@ZIF-8 p-n heterojunction exhibited excellent photocatalytic properties with respect to organic pollutants crystal violet (CV), Congo red (CR), and rhodamine B (Rh B). The total organic carbon (TOC) measurements revealed that the developed Ag3PO4@ZIF-8 p-n heterojunction mineralized 99.0% of Rh B, 90.7% of CV, and 94.7% of CR in 120 min. The heterojunction also exhibited excellent cyclic stability, which is crucial for practical applications. The excellent photocatalytic performance of the developed Ag3PO4@ZIF-8 p-n heterojunction could be ascribed to the suppression of the photogenerated charge recombination, enhancement of the surface area, p-n heterojunction formation, and extended light absorption. Therefore, the developed heterojunction is promising for environmental remediation in general, and for photocatalysis-based treatment of organic pollutant-containing wastewater in particular.

The synergistic catalytic mechanism between different functional sites of boron/iron on iron oxides in Fenton-like reactions

The detoxification and harmless treatment of toxic organic industrial wastewater are essential guarantees for the global water environment and human life safety. As an important treatment technology for this wastewater, the advanced oxidation process is limited by the catalytic rate due to the low reduction rate, and the modulation and acceleration of electron transfer at the catalytic sites become the focus and difficulty in this field. Herein, we synthesized boron-doped iron oxide (FeOx-B) to enhance the interfacial electron transfer during peroxymonosulfate (PMS) catalysis, resulting in efficient degradation (91.73 %) of the contaminant (TTCH, Tetracycline hydrochloride). Compared with the commercial Fe2O3 and Fe3O4, the removal rate of TTCH is improved by 47.89 % and 24.45 %, respectively. As a new active site, B-O interacts with the contaminant and accelerates the reduction of Fe (III). The reactive species also change from sulfate radical (SO4−), hydroxyl radical (OH), and singlet oxygen (1O2) to surface reactive complexes. The system is pH-adaptive (pH = 3–11) and presents excellent resistance to humic acid (HA) and anions (10 mM). Toxicity assessment reveals that the degradation products are low toxic or harmless. This work suggests a new strategy for the development of highly reactive iron-based materials and provides theoretical insights into the mechanism of the PMS activation processes.

Enhanced treatment of landfill leachate by biochar-based aerobic denitrifying bacteria functional microbial materials: Preparation and performance.

In this work, polyvinyl alcohol (PVA) and sodium alginate (SA) were used as entrapped carriers and Artemisia argyi stem biochar (ABC) was used as an absorption carrier to immobilize aerobic denitrifying bacteria screened from landfill leachate, thus a new carbon-based functional microbial material (PVA/SA/ABC@BS) was successfully prepared. The structure and characteristics of the new material were revealed by using a scanning electron microscope and Fourier transform infrared spectroscopy, and the performance of the material for treating landfill leachate under different working conditions was studied. ABC had abundant pore structures and that the surface contained many oxygen-containing functional groups, carboxyl groups, and amide groups, etc. and it had good absorbing performance and strong acid and alkali buffering capacity, which was beneficial to the adhesion and proliferation of microorganisms. After adding ABC as a composite carrier, the damage rate of immobilized particles was decreased by 1.2%, and the acid stability, alkaline stability, and mass transfer performance were increased by 9.00, 7.00, and 56%, respectively. When the dosage of PVA/SA/ABC@BS was 0.017g/ml, the removal rates of nitrate nitrogen (NO3 --N) and ammonia nitrogen (NH4 +-N) were the highest, which were 98.7 and 59.4%, respectively. When the pH values were 11, 7, 1, and 9, the removal rates of chemical oxygen demand (COD), NO3 --N, nitrite nitrogen (NO2 --N) and NH4 +-N reached the maximum values, which were 14.39, 98.38, 75.87, and 79.31%, respectively. After PVA/SA/ABC@BS was reused in 5 batches, the removal rates of NO3 --N all reached 95.50%. PVA, SA and ABC have excellent reusability for immobilization of microorganisms and degradation of nitrate nitrogen. This study can provide some guidance for the great application potential of immobilized gel spheres in the treatment of high concentration organic wastewater.

Enhanced catalysis for degradation of rhodamine B by amino-functionalized Fe-MOFs with high adsorption capacity

Activation of peroxydisulfate (PDS) by iron-based metal organic frameworks (Fe-MOFs) presents a promising method to degrade various environmental contaminants. Herein, a series of environmentally friendly Fe-MOFs with different topological structures were synthesized and compared as catalysts for rhodamine B (RhB) removal process. The results indicated that amino-functionalized Fe-MOFs possessed large specific surface area and high affinity for RhB, which significantly improved the high adsorption capacity of RhB and PDS. It is found that NH2-MIL-101(Fe), containing Fe3-μ3-oxo clusters, showed high adsorption ability and excellent catalytic degradation of RhB. The efficient charge transfer from -NH2 to Fe-O clusters could efficiently accelerate Fe(II)/Fe(III) cycle. That is, NH2-MIL-101(Fe) was proved to be the most effective catalyst for removing RhB with a removal rate of 93%. The first-order kinetic constant (0.016 min−1) of NH2-MIL-101(Fe) was 2 times that of MIL-101(Fe). Singlet oxygen (1O2) was the main active species. Additionally, according to liquid chromatograph mass spectrometer (LC-MS) analysis, the degradation of RhB was mainly related to chromophore cleavage. This study guides for designing high-performance catalysts by introducing electron donating groups in organic dyes wastewater treatment.

Coordination-driven boron and copper on carbon nitride for peroxymonosulfate activation to efficiently degrade organic contaminants

Effective treatment of toxic organic pollutants is crucial to the safety of water environment. Herein, we ingeniously constructed coordination-driven boron (B) and copper (Cu) on carbon nitride to solve the trouble that kinetically sluggish reduction reaction of sites on catalysts in heterogeneous Fenton-like systems for efficient toxic organic wastewater treatment. The electrons of the contaminants are transferred from B to Cu in catalytic processes, which facilitates the cycling of the Cu(I)/Cu(II) redox pairs, and the degradation rate of Bisphenol A (BPA) increases by 16 times. Singlet oxygen (1O2) and surface-active complexes play essential roles in the reaction. The system could effectively reduce the toxicity of BPA and has excellent stability and adaptability under different environmental conditions (pH, humic acid, and anions). This work provides insight into exploiting coordination-driven effect between sites in Fenton-like systems for efficient wastewater treatment.

Activation of chloride by oxygen vacancies-enriched TiO2 photoanode for efficient photoelectrochemical treatment of persistent organic pollutants and simultaneous H2 generation.

Photoelectrochemical (PEC) activation of chloride ions (Cl-) to degrade persistent organic pollutants (POPs) is a promising strategy for the treatment of industrial saline organic wastewater. However, the wide application of this technology is greatly restricted due to the general photoanode activation of Cl- with poor capability, the propensity to produce toxic by-products chlorates, and the narrow pH range. Herein, oxygen vacancies-enriched titanium dioxide (Ov-TiO2) photoanode is explored to strongly activate Cl- to drive the deep mineralization of POPs wastewater in a wide pH range (2-12) with simultaneous production of H2. More importantly, nearly no toxic by-product of chlorates was produced during such PEC-Cl system. The degradation efficiency of 4-CP and H2 generation rate by Ov-TiO2 were 99.9% within 60min and 198.2 μmol h-1 cm-2, respectively, which are far superior to that on the TiO2 (33.1% within 60min, 27.5 μmol h-1 cm-2) working electrode. DFT calculation and capture experiments revealed that Ov-TiO2 with abundant oxygen vacancies is conducive to the activation of Cl- to produce more reactive chlorine species, evidenced by its high production of free chlorine (48.7mgL-1 vs 7.5mgL-1 of TiO2). The as-designed PEC-Cl system in this work is expected to realize the purification of industrial saline organic wastewater coupling with green energy H2 evolution.

BSA-Cu3(PO4)2 hybrid nanoflower-an efficient and low-cost nanoenzyme for decolorization of organic pollutants.

The Fenton reaction is one of the most effective methods for treating organic wastewater, which is extremely harmful to humans but difficult to treat. However, finding simple, low-cost, and efficient catalysts for the Fenton reaction remains a challenge. In this study, a BSA-Cu3(PO4)2 hybrid nanoflower (NF) was synthesized to investigate its peroxidase-like activity for the treatment of organic wastewater. Its morphology, composition, and crystallization had been fully studied and the results confirmed that the NFs were successfully prepared. Subsequently, the origin of the peroxidase-like activity of the NFs was further analyzed, with the results suggesting two reasons: (i) the transformation between Cu(I) and Cu(II) and (ii) nano-effects. Additionally, Congo red was selected as the organic pollutant to simulate the decolorization of wastewater. After 3h, the decolorization efficiency reached 96%. Furthermore, the NFs exhibited good storage performance, maintaining approximately 90% relative activity after storage for 30days. In summary, the NFs have great application prospects in the treatment of organic wastewater.

Effective removal of hazardous organic contaminant using integrated photocatalytic adsorbents: Ternary zinc oxide/zeolite-coal fly ash/reduced graphene oxide nanocomposites

In this study, the simple upcycling of coal fly ash (FA) waste to produce low-cost integrated photocatalytic adsorbents (IPCAs) for the removal of hazardous organic contaminant was proposed. The IPCAs were fabricated by combining zinc oxide (ZnO) and reduced graphene oxide (rGO) on FA derived zeolite. The ternary ZnO/FA-zeolite/rGO (ZnO/Z/rGO) nanocomposites were prepared using pyrolysis-hydrothermal techniques. These nanocomposites were found to possess negative surface charges and large surface areas. Consequently, they achieved high methylene blue (MB) adsorption efficiency, owing to the increase in the number of active sites and the strong electrostatic interaction between ZnO/Z/rGO and MB molecules. ZnO and rGO improved the photocatalytic MB degradation and mineralization via reactive oxygen species generation (superoxide and hydroxyl radicals as the major reactive species), hindered the charge recombination and enhanced the reusability. These results can be used to guide the development of upcycling and utilization of FA for cost-effective, accessible, and reusable IPCAs with excellent degradation and stability in organic dye wastewater treatment.

Study on the ozonation degradation of methylene blue enhanced by microchannel and ultrasound.

Azo dye-containing wastewater poses serious risks of environmental pollution because it is generally biologically toxic and resistant to conventional wastewater treatment methods. A novel degradation system integrating ozone, microchannel, and ultrasound was designed to effectively degrade azo dye-contaminated wastewater. The effects of discharge voltage of dielectric barrier discharge (DBD) reactor, liquid flow rate, microchannel width, ultrasonic power, initial pH, and reaction temperature on methylene blue (MB) decolorization were studied. A maximum MB decolorization efficiency of 92.7% was obtained in the ozone/microchannel/ultrasound (O3/MC/US) system with 14 min of treatment. In addition, the 14-min decolorization efficiency and TOC removal efficiency obtained in O3/MC/US system were increased by 12.6 and 6.5%, respectively, compared to those obtained in the pure O3 system. Based on the results of scavenging experiments, the combined effects of microchannel and ultrasound were proved to improve the contribution rate of hydroxyl radicals, thus improving the decolorization efficiency. The present work clearly illustrates that ozonation degradation can be effectively enhanced by microchannel and ultrasound, and also provides a feasible method for the treatment of organic wastewater.

Resource recovery from textile wastewater: Dye, salt, and water regeneration using solar-driven interfacial evaporation

The solar-driven interfacial evaporation has created a new pathway in energy desalination. However, its application in the treatment of organic wastewater with high-salinity, such as textile wastewater, has not been studied. In this study, we have employed the activated carbon fiber cloth (ACFC) to treat textile wastewater. The ACFC exhibited excellent light-to-thermal conversion capacity, and the evaporation rate reached >1.188 kg m−2 h−1 for textile wastewater under 1 sun irradiation. Furthermore, salt and organic dye with high purity are well-separated by the evaporator, enabling ease of recovery. Up to 89.6% of salt can be recovered. The highest recovery rate of 69.2% was observed for Alizarin yellow R, which is an anionic dye and is repelled from the negatively charged ACFC surface. In addition, by modifying ACFC with cationic surfactant, the recovery rate for cationic dye increased significantly from 46.5% to 54.7% for rhodamine B. However, we found organic dyes can be partially degraded on the ACFC surface under solar irradiation due to carbon-mediated self-photosensitization, although its effect on the purity of recovered salt and organic dye is negligible. Overall, our study may open up new exploration of zero-liquid discharge technologies for the treatment of textile wastewater.

Electrostimulation triggers an increase in cross-niche microbial associations toward enhancing organic nitrogen wastewater treatment

As an efficient wastewater pretreatment biotechnology, electrostimulated hydrolysis acidification (eHA) has been used to accelerate the removal of refractory pollutants, which is closely related to the effects of electrostimulation on microbial interspecies associations. However, the ecological processes underpinning such linkages remain unresolved, especially for the microbial communities derived from different niches, such as the electrode surface and plankton. Herein, the principles of cross-niche microbial associations and community assembly were investigated using molecular ecological network and phylogenetic bin-based null model analysis (iCAMP) based on 16S rRNA gene sequences. The electrostimulated planktonic sludge and electrode biofilm displayed significantly (P < 0.05) 1.67 and 1.53 times higher organic nitrogen pollutant (azo dye Alizarin Yellow R) degradation efficiency than non-electrostimulation group, and the corresponding microbial community composition and structure were significantly (P < 0.05) changed. Electroactive bacteria and functional degraders were enriched in the electrode biofilm and planktonic sludge, respectively. Notably, electrostimulation strengthened the synergistic microbial associations (1.8 times more links) between sludge and biofilm members. Additionally, both electrostimulation and cross-niche microbial associations induced greater importance of deterministic assembly. Overall, this study highlights the specificity of cross-electrode surface microbial associations and ecological processes with electrostimulation and advances our understanding of the manipulation of sludge microbiomes in engineered wastewater treatment systems.

Ultra-high oxygen evolution potential of CuO5-Zn1 active sites on SnO2(1 1 0) surface and its origin: DFT theoretical study

SnO2 is an anode material with the potential to form a high oxygen evolution potential for organic wastewater treatment. Previous experiments found that CuZn, co-doped with SnO2 surfaces were suspected to form Cu-O-Zn sites with high catalytic activity. By utilising DFT calculations combined with previous experimental results, it was found that CuO5-Zn1 active sites were formed on the (110) surface of CuZn co-doped SnO2 with an oxygen evolution potential of 2.80 V (vs CHE). The electronic density of states, charge density distribution, Bader charge and charge density difference analysis indicated that the formation of ultra-high oxygen evolution potential was caused by the enhanced covalency of Cu-O-Zn. The indirect covalent enhancement between transition metal atoms found on the SnO2 surface means that atomically regulated and controlled catalytic activity can be achieved on the SnO2 surface.

Treatment of saline organic wastewater by heterogeneous catalytic ozonation with Al2O3-PEC-CaxOy as catalysts

Al2O3-Pectin-CaxOy (Al2O3-PEC-CaxOy) was prepared as catalysts to improve the treatment of saline organic wastewater with heterogeneous catalytic ozonation. Compared with ozonation alone (33%), the removal rate of COD (62%) was significantly increased for Al2O3-PEC-CaxOy catalysts prepared under the optimized conditions. The introduction of pectin made Ca2+ firmly loaded on the support, and avoided the loss of active sites in the process of catalytic oxidation. In addition, the formation of porous carbon layer on the surface of the Al2O3 support after pectin calcination was conducive to improving the catalytic activity of the catalyst. Electron paramagnetic resonance (EPR) and radical quenching experiments showed that hydroxyl radical (•OH), superoxide radical (•O2−) and singlet oxygen (1O2) were the reactive oxygen species (ROS) that attributed to the organic matter removal. Both free radical and non-free radical pathways were involved in the degradation of organic pollutants during the catalytic ozonation process. The removal rate of COD was only decreased slightly after twenty times of continuous operation for Al2O3-PEC-CaxOy catalysts, indicating that Al2O3-PEC-CaxOy catalysts with the good catalytic stability and reusability. It showed a great significance for long-term practical application with the economical and effective performances.

Aerobic granular sludge treating hypersaline wastewater: Impact of pH on granulation and long-term operation at different organic loading rates

pH is one of the major parameters that influence the granulation and long-term operation of aerobic granular sludge (AGS). In hypersaline wastewater, the impact of pH on granulation and the extent of organic loading rate (OLR) that AGS can withstand under different pH are still not clear. In this study, AGS was cultivated at 3% salinity in three sequencing batch reactors with influent pH values of 5.0, 7.0, and 9.0, respectively, and the OLR was stepwise increased from 2.4 to 16.8 kg COD/m3·d after the granules maturation. The results showed the satisfactory granulation and organic removal under different influent pH conditions, in which the granulation was completed on day 43, 23, and 23, respectively. Neutral influent was the most appropriate for development of salt-tolerant aerobic granular sludge (SAGS), while acidic environment induced the formation of fluffy filamentous granules, and alkaline environment weakened the granule stability. Metagenomic analysis revealed the similar microbial community of neutral and alkaline conditions, with the predominance of genus Paracoccus_f__Rhodobacteraceae. While in acidic environment, fungus Fusarium formed the skeleton of filamentous granules and functioned as the carrier of bacteria including Azoarcus and Pararhodobacter. With the elevation of OLR, SAGSs were found to maintain the compact structure under OLRs of 2.4, 7.2, and 2.4 kg COD/m3·d, and obtain high TOC removal (>95.0%) under OLRs of 7.2, 14.4, and 14.4 kg COD/m3·d, respectively. For hypersaline high-strength organic wastewater, satisfactory TOC removal could also be obtained at broad pH ranges (5.0–9.0), in which neutral environment was the most suitable and acidic environment was the worst. This study contributed to a better understanding of SAGS granulation and treatment of hypersaline high-strength organic wastewater with different pH values.

Fabrication of S-PBI cation exchange membrane with excellent anti-fouling property for enhanced performance in electrodialysis

A novel anti-fouling cation exchange membrane (CEM) of sulfonated polybenzimidazole (S-PBI) was fabricated by the polymer bulk grafting modification of poly (4,4′-diphenyl ether-5,5′-bibenzimidazole) with sodium styrene sulfonate. FTIR, TGA, XPS, SEM and AFM were used to characterize membrane properties and the results showed that the ion exchange capacity and hydrophilicity of S-PBI increased with increased degrees of grafting and the electric resistance decreased accordingly. When the mass ratio of O-PBI/SSS was 1:4, the electric resistance of S-PBI-4.0 was 4.5 Ω·cm2, while the ion exchange capacity was 2.3 meq/g. The ED experiment with the S-PBI-4.0 membrane exhibited good desalination rate (>96 %), high current efficiency (80.73 %) and low energy consumption (1.13 kW·h/kg), which were very close to the results of a commercial CEM (Neosepta CMX). What's more, because of its good hydrophilicity, the S-PBI-4.0 membrane had better anti-fouling ability than Neosepta CMX, which was manifested as less resistance increase after membrane fouled by bovine serum albumin and smaller resistance after membrane cleaned by deionized water. These results demonstrate that the S-PBI-4.0 membrane is an appropriate candidate CEM and helpful to expand the application of ED in high-salinity organic industrial wastewater treatment.

Enhanced norfloxacin degradation by three-dimensional (3D) electrochemical activation of peroxymonosulfate using Mn/Cu co-doped activated carbon particle electrode

In this study, Mn/Cu co-doped activated carbon (MCAC) particle electrodes were applied in the three-dimensional (3D) electrical activation of peroxymonosulfate process (E-PMS-MCAC) for norfloxacin (NOF) degradation. Several comparative experiments demonstrated a significant synergy between catalytic and electric activation of PMS in the E-PMS-MCAC process, which could obtain 90.81 % of NOF removal within 60 min. Quenching experiments and EPR analyses revealed thatSO4·-, •OH, 1O2, and reactive Mn(III) were all involved in the E-PMS-MCAC process, while •OH was dominant reactive species for NOF degradation. The different generation ways of reactive species were also explored. Besides, multiple degradation pathways of NOF were proposed, and the toxicity of intermediates was assessed as well. The characterizations of SEM, XRD, and XPS indicated that the cathodic reduction reaction could facilitate electron transfer to Mn(IV), Mn(III), and Cu(c), triggering the sustainable Mn(I)/Mn(III)/Mn(IV) or Cu(I)/Cu(II) redox cycle. It was noted that the addition of Cl- enhanced the NOF removal, while the presence of HCO3-, NO3-, and H2PO4- inhabited it. Finally, the removal efficiencies of other contaminations including p-nitrophenol (PNP), carbamazepine (CBZ), sulfamethoxazole (SMX), and tetracycline hydrochloride (TCH) were also investigated in the E-PMS-MCAC process. All above results suggested that the E-PMS-MCAC process was a high-efficiency and sustainable technology for organic wastewater treatment.