Separation Efficiency Research Articles

A novel multifunctional photocatalytic membrane based on ternary heterojunction TiO2@PDA@BiOBr for biochemical oily wastewater purification

Membrane separation technology is a promising alternative for oily wastewater purification. However, developing membrane for the purification of biochemical oily wastewater is still challengeable. To this aim, a novel multifunctional photocatalytic membrane of PTPB-8 is fabricated by sequentially loading of TiO2, polydopamine (PDA), and BiOBr onto polyacrylonitrile (PAN) nanofibers in situ. PTPB-8 is of water contact angle (WCA) ∼ 0° and underwater oil contact angle (UOCA) 154.7 ± 2.5°, allowing it with outstanding separation and anti-fouling capability, and good reusability for emulsion separation under gravity (i.e., separation efficiency >90 %, permeation flux >300 L m-2h−1, and flux recovery rate >82 % for n-hexane-in-water emulsion after 15 cycles). Under simulated solar light, the ternary heterojunction TiO2@PDA@BiOBr is catalytically active with generating active species and the charge transfer pathway follows the mechanism of Z-type heterojunction. Consequently, PTPB-8 can kill E. coli and S. aureus by ∼ 100 % and degrade tetracycline by >90 %. The application trial results have demonstrated the great potential of PTPB-8 in the purification of biochemical oily wastewater containing bacteria and antibiotics. This study will also give a new idea for enhancing the photocatalytic activity of heterojunctions by PDA decoration.

Liquid–solid two-phase flow and separation behavior in a novel cyclone separator

In response to the prevalent issue of sand presence in liquid, particularly prominent in petroleum engineering, a novel cyclone separator has been meticulously engineered for fine-particle separation. Experiments and numerical simulation methods have provided a profound understanding of the flow-field characteristics and separation efficacy of this device. The internal architecture of the swirling flow inside the separator features a distinctive central vortex core, complemented by a turbulent secondary vortex formation in the lower section of the underflow. As the axial height increases, the secondary vortex gradually dissipates. An analysis of pressure and velocity distribution within the cyclone separator confirms the establishment of a stable cyclone field in the built-in cyclone and a tendency for the flow field within the tank to exhibit uniformity with increasing height. These flow-field characteristics show that the cyclone separator has a good separation effect on fine-rust particle impurities. Furthermore, the separation efficiency of the novel cyclone separator demonstrates a positive correlation with increasing particle size. Of the parameters studied, variation of the inlet velocity is the best method for obtaining optimum separation efficiency for a cyclone desander with a fixed particle size. Specifically, when the inlet velocity reaches 3 m/s, the desander attains an impressive separation efficiency of up to 70%.

Separation of bufadienolides from Helleborus thibetanus Franch. by a combination approach involving macroporous resin column chromatography and gradient countercurrent chromatography.

In this study, a combination approach involving macroporous resin (MR) column chromatography and gradient countercurrent chromatography (CCC) was employed to enrich and purify bufadienolides from the roots and rhizomes of Helleborus thibetanus Franch. Initially, a D101 MR-packed column chromatography was utilized for fractionation and enrichment of the bufadienolides, which were effectively eluted from the column using a 60% ethanol solution. CCC was subsequently introduced to separate the enriched product using the ethyl acetate/n-butanol/water (EBuWat, 4:1:5, v/v) and EBuWat (5:0:5, v/v) solvent systems in a gradient elution mode. As results, five bufadienolides, including 6.1mg of hellebrigenin-3-O-β-D-glucoside (1), 2.2mg of tigencaoside A (2), 8.3mg of deglucohellebrin (3), 3.5mg of 14 β-hydroxy-3β-[β-D-glucopyranosyl-(1→6)-(β-D-glucopyranosyl)oxy]-5α-bufa-20,22-dienolide (4), and 3.0mg of 14β-hydroxy-3β-[(β-D-glucopyranosyl)oxy]-5α-bufa-20,22-dienolide (5), were effectively separated from 300mg of the enriched product. The respective high-performance liquid chromatography purities were as follows: 95.2%, 75.8%, 85.7%, 82.3%, and 92.8%. This study provides valuable insights for the efficient enrichment and separation of bufadienolides from Helleborus thibetanus Franch.

Engineering MXene-based photocatalyst for efficient NADH regeneration and photoenzymatic CO2 reduction without electron mediator

In this study, an MXene-based photocatalyst, ARTM to regenerate NADH without electron mediator is reported. The ARTM was able to achieve a regenerated NADH yield of 65 % within 50 min in the absence of electron mediator, with a 1,4-NADH selectivity of 90.8 %. The turnover frequency (TOF) of 1,4-NADH was as high as 0.148 h−1, which was 74 and 148 times higher than that of A-TiO2 and R-TiO2, respectively. The synergetic effect between anatase/rutile TiO2 phase junction (ART-PJ) and TiO2@Ti3C2Tx heterojunction (TM-HJ) facilitates the efficient carriers separation and NADH regeneration. Enzymatic assay and HNMR revealed that the incorporation of Ti3C2Tx promoted the highly selective generation of 1,4-NADH. DFT calculation elucidated that this could be attributed to the end-on adsorption of the nicotinamide ring of NAD+. Subsequently, an electron mediator free photoenzyme cascade catalysis system was constructed, which could effectively promote CO2 photoreduction to formate (594 μmol g−1 h−1).

Enhancing Photoelectrochemical Water Oxidation on WO3 via Electrochromic Modulation: Universal Effects and Mechanistic Insights.

Although WO3 exhibits both electrochromic and photoelectrochemical (PEC) properties, there is no research conducted to investigate the correlation between them. The study herein reports the electrochromic enhancement of PEC activity on WO3. The electrochromic WO3 (e-WO3) exhibits a significantly enhanced activity for PEC water oxidation compared to raw WO3 (r-WO3), with a limiting photocurrent density three times that of r-WO3. The electrochromic enhancement of PEC activity is universal and independent of the type of cations inserted during electrochromism. Decoloring reduces the PEC activity but a simple re-coloring restores the activity to its maximum value. Electrochromism induces large amounts of oxygen vacancies and surface states, the former improving the electron density of WO3 and the latter facilitating the hole transfer across e-WO3/electrolyte interface. It is proved that the electrochromic enhancement effect is due to the significantly improved electron-hole separation efficiency and the charge transfer efficiency across the WO3/electrolyte interface.

Magnetically separable Z-scheme ZnFe2O4/MoS2 photocatalyst for boosting photo-Fenton degradation activity by a hole-mediated mechanism

The development of high-efficiency and robust photocatalysts is imperative and challenging in advanced oxidation processes (AOPs). Herein, magnetically separable ZnFe2O4/MoS2 photocatalyst was prepared by a simple hydrothermal method. The degradation characteristics of several organic pollutants (rhodamine B (RhB), methyl orange, methylene blue, and antibiotic tetracycline) were investigated with/without the addition of H2O2 under visible light irradiation. It is found that the synergistic effect of Z-scheme ZnFe2O4/MoS2 photocatalyst and photo-fenton-like reaction promotes the decomposition of H2O2, accelerates the separation efficiency of photogenerated electrons and holes, and thus improves the photocatalytic activity. The RhB photo-degradation of the constructed Z-scheme ZnFe2O4/MoS2 (96.3%) photocatalyst in the absence of H2O2 for 100min is better than that of MoS2 (74.8%) and ZnFe2O4 (6.2%), with a rate constant of 0.0332min-1. The slight amount of H2O2 boosts the photocatalytic performance significantly. Its degradation rate is 98.6% within 8min with the rate constant of 0.396min-1, 12 times higher than that of ZnFe2O4/MoS2 photocatalyst without H2O2. The magnetic separation, recycling stability and neutral solution process are also confirmed in ZnFe2O4/MoS2 system, indicating the enormous potential of this photocatalyst in environmental remediation and waste water treatment. The hole-mediated oxidation mechanism has been proposed instead of conventional active radicals of •OH based on the free radicals capture and electron spin resonance experiments. MoS2 plays a crucial role in facilitating the H2O2 decomposition and realizing the conversion circulation from Fe3+ to Fe2+ by the redox cycling as a co-catalyst. This study provides insights into the photocatalytic mechanism of Z-scheme photo-Fenton heterojunction photocatalysts, conducive to the development of high-efficient and stable photocatalysts in AOPs.

Revealing the role of interlayer spacing in radioactive-ion sieving of functionalized graphene membranes

Functionalization of graphene enables precise control over interlayer spacing during film formation, thereby enhancing the separation efficiency of radioactive ions in graphene membranes. However, the systematic impact of interlayer spacing of graphene membranes on radioactive-ion separation remains unexplored. This study aims to elucidate how interlayer spacing in functionalized graphene membranes affects the separation of radioactive ions. Utilizing polyamidoxime (PAO) to modify graphene oxide, we controlled the interlayer spacing of graphene membranes. Experimental results indicate that tuning interlayer spacing enables control of the permeation flux of radioactive ions (UO22+ 1.01 × 10−5–8.32 × 10−5 mol/m2·h, and K+ remains stable at 3.60 × 10−4 mol/m2·h), and the K+/UO22+ separation factors up to 36.2 at an interlayer spacing of 8.8 Å. Using density functional theory and molecular dynamics simulations, we discovered that the effective separation is mainly determined via interlayer spacing and the quantity of introduced functional groups, explaining the anomalous high permeation flux of target ions at low interlayer spacing (4.3 Å). This study deepens our comprehension of interlayer spacing within nanoconfined spaces for ion separation and recovery via graphene membranes, offering valuable insights for the design and synthesis of high-performance nanomembrane materials.

Titanium-coated high-density Fe2O3 single crystal nanowire array for solar water splitting

Fe2O3 holds promising n-type semiconductor material in the field of solar water splitting due to its excellent photocatalytic properties. However, the photoelectrochemical performance of Fe2O3 is limited by its inherent properties such as poor conductivity, and charge separation efficiency owing to its recombination rate. Therefore, researchers are more focused on nanostructuring, doping, and surface coating to overcome these issues of Fe2O3. In this study, we have investigated a low-cost way to fabricate a Ti coating layer on a high-density Fe2O3 single-crystal nanowire array for solar water splitting. Firstly, we have prepared a high-density single-crystal Fe2O3 nanowire array at lower temperatures by a new approach stress-induced atomic diffusion method. Thereafter, the prepared nanowire array was coated by Ti film using RF sputtering. The optimal film thickness of 13 nm titanium coatings layer into Fe2O3 single crystal nanowire array exhibited a high photocurrent density of 1.36 mA/cm2 at 1.23 V versus RHE and solar to hydrogen conversion efficiency (STH) of 1.67%, which could be resulting from adjusted optoelectronic properties of the nanowires.

Enhanced water stability and catalytic activity of Fe-based metal–organic frameworks with co-ligands for 2,4-dichlorophenol degradation

Fe-based metal–organic frameworks (MOFs) have good photocatalytic performance, environmental friendliness, low cost, and abundance. However, their applications are limited by low water stability, particularly in the presence of light irradiation and oxidizing agents. In this study, we present a MIL-53(Fe)-based MOF using 1,4-naphthalene dicarboxylic (1,4-NDC) and 1,4-benzenedicarboxylic (H2BDC) acid co-ligands, denoted MIL-53(Fe)-Nx, where Nx represents the ratio of 1,4-NDC. This MOF exhibits high water stability and good photocatalytic activity because of the hydrophobicity of naphthalene. The removal and mineralization rates for 100 mg/L 2,4-dichlorophenol reached 100% and 22%, respectively, within 60 min. After three cycles of use, the Fe leached into the solution from the catalysts was significantly lower than the maximum permissible limit indicated in the European Union standard. Of note, 1,4-NDC can be used to make a rigid MOF, thereby improving the crystallinity, porosity, and hydrophobicity of the resultant materials. It also significantly reduced the bandgap energy and improved the charge separation efficiency of the catalysts. This study provides a route to enhance the water stability of Fe-based MOFs via a mixed-ligand strategy to expand their applications in pollutant control.

Sm-doped ZnO with enhanced photocatalytic performance toward destruction of RhB

In this work, Sm-doped ZnO was prepared by a Sol-Gel method. The structure, morphology, composition and optical properties of the prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), surface photovoltage spectrum (SPS) and X-ray photoelectron spectros­copy (XPS). Sm-doping results in high specific surface area and boosted photogenerated carriers separation efficiency, and produces more active free radicals to participate in the photocatalytic reaction. Photocatalytic activities of the samples toward removal of rhodamine B(RhB) were evaluated under UV light irradiation, the results display that Sm-doped ZnO shows higher photocatalytic activity than the reference ZnO.

Photocatalytic Synthesis of Ammonia from Hollow Coral-Like Graphitic Carbon Nitride/FeOCl Loaded with Fe-1T MoS2 Nanosheets as Cocatalysts.

Photocatalytic ammonia synthesis (PAS) represents an emerging environmentally friendly approach to ammonia production. In this work, we employed Fe doping to modify the cocatalyst 1T MoS2, enhancing the active N2 sites on Fe-1T MoS2 by inducing defects on the surface of 1T MoS2. Afterward, Fe-1T MoS2 was loaded onto a hollow coral-like graphitic carbon nitride (CCN)/FeOCl composite. Under simulated sunlight, the efficiency of 5% Fe-1T MoS2@CCN/FeOCl (Fe-MCN/FeOCl) reached 367.62 μmol g-1 h-1, surpassing 1T MoS2@CCN(MCN) by 3.2 times, CCN by 16.9 times, and g-C3N4 by 32.5 times, where 5% means the doping amount of Fe in 1T MoS2. The good performance of Fe MCN/FeOCl should be attributed to the Fe doping in Fe-MCN/FeOCl which not only increases the separation efficiency of active sites and charge carriers, but also reduces the sample impedance significantly through the heterojunction formed between CCN and FeOCl. This work also presents a method for creating more efficient and stable photocatalysts for ammonia synthesis.

Engineered exosome-based drug delivery system for synergistic cancer therapy via autophagy inhibition and chemotherapy

Exosomes (EXOs) are a class of natural nanovesicles secreted endogenously by mammalian cells. Recent decades have witnessed the broad applications of exosomes in cancer diagnosis and treatment. In the present study, an exosome-based drug delivery system employing synergistic miRNA-based autophagy inhibition and 7-coumarin-based chemotherapy was established for ovarian cancer therapy. Taking advantage of the outstanding biocompatibility and immune evasion, exosomes are used as carriers for targeted drug delivery. Magnetic nanoparticles (MNPs) were coupled to exosomes to improve the separation efficiency of exosomes. Two drugs, miRNA-FAM and 7-coumarin, were loaded into EXOs-MNPs by electroporation to achieve the miRNA-FAM/7-coumarin@EXOs-MNPs drug delivery system. The engineered exosome-based drug delivery system improved the cell entry ability of drugs and the targeting of cancer cells. Simultaneous application of the two drugs significantly improved the efficacy of cancer cell therapy, indicating that the two drugs have synergistic effects. Therefore, this work provided a new drug delivery system and synergistic therapy idea, which showed great potential for future clinical applications.

Enhanced photocatalytic CO2 reduction activity on the novel Z-scheme Co-MOF/Bi2MoO6 to form CO and CH4

Herein, a novel Z-scheme Co-MOF/Bi2MoO6 was synthesized by in-situ growth method. The photocatalytic CO2 reduction effect of Co-MOF/Bi2MoO6 was significantly improved, and the formation rates of CO and CH4 reached 19.76 and 8.24 μmol·g−1·h−1, which corresponded to 1.61 and 2.38 times of Co-MOF (CO: 12.31 μmol·g−1·h−1) and Bi2MoO6 (CH4: 3.46 μmol·g−1·h−1), respectively. The increased photocatalytic activity of Co-MOF/Bi2MoO6 resulted from the enhanced visible light capture capability and the Z-scheme heterojunction formed among Co-MOF and Bi2MoO6, which promoted the efficient separation of photogenerated carriers while retaining the highest redox capacity. The Z-scheme charge transfer direction of Co-MOF/Bi2MoO6 was confirmed by DRS, XPS, ESR, UPS, and the photocatalytic reaction mechanism was explained. In addition, the active substances and intermediates of Co-MOF/Bi2MoO6 in the photocatalytic CO2 reduction process were investigated using ESR and in-situ FT-IR. The work offers a idea for building MOFs-based heterojunctions to improve the effect of photocatalytic CO2 reduction.

Design and fabrication of magnetically recoverable SnO2/CoFe2O4 nanocomposite for enhanced visible light-driven wastewater treatment

This study emphasizes the critical importance of ensuring the availability of clean and secure water resources amid global concerns about water contamination, highlighting the necessity for effective and enduring methods to eliminate hazardous pollutants. The research introduces a sustainable approach to environmental protection through the creation of a high-performance photocatalyst, employing a co-precipitation route to incorporate CoFe2O4 onto SnO2 for efficient wastewater treatment under solar light irradiation. Comprehensive composition and morphological studies of the SnO2/CoFe2O4 composites are conducted using techniques such as XRD, SEM, TEM, Raman, UV–Vis, PL spectra, and FT-IR spectra. The synergistic behavior of the SnO2/CoFe2O4 composite results in efficient separation of electron/hole pairs, reducing the recombination rate and leading to improved photocatalytic performance under solar-light illumination. Notably, the rate constant for Chromium (VI) removal reaches 87 % and the degradation of Rhodamine 6G attains 92 % within 105 mins intervals. The catalyst demonstrates stability and ease of regeneration through a five-cycle recycle study, further supporting its potential for practical application in wastewater treatment.

Solvent-responsive switching wettability of superoleophobic/superhydrophilic quartz sand filter medium facilitates rapidly oil/water separation and demulsification

Oil-spill accidents occur frequently, and the oil pollution caused by oil spills is attracting extensive attention from all circles of society. To resolve this problem, solvent-responsive superoleophobic/superhydrophilic quartz sand (SSQS) was manufactured by introducing ZnO nanoparticles, short-chain fluorinated compounds, and hydrophilic-induced units into the surface of quartz sand. Experimental results showed that SSQS can reversibly convert the superoleophobic/superhydrophilic surfaces into superoleophilic/underoil superhydrophobic surfaces within 10 s. The solvent-responsive surface of SSQS demonstrated selective separation performance for mixtures of oil/water and various surfactant-stabilized oil-in-water emulsions and water-in-oil emulsions before and after wettability conversion. Oil/water solutions were separated synchronously and continuously using the "┴" type of oil/water separating system, with a separation efficiencies of 99.33 % at high flux. After ten runs of the wettability transition, the oil/water mixture's separation efficiency remained over 99 %. More importantly, SSQS can accomplish the on-demand, gravity-driven demulsification and separation of oil/water emulsions with excellent separation efficiency and flux. The directional migration of oil droplets on the SSQS surface could possibly be described by the wetting performance of oil phase on the special wettability surface, and the solvent-responsive wettability transition of the SSQS surface. SSQS also exhibited brilliant mechanical durability, anticorrosion ability, and wetting stability under severe conditions. Therefore, this work provided a new research direction for the reversible wettability transition of granular filter media.

Cellulose acetate, a source from discarded cigarette butts for the development of mixed matrix loose nanofiltration membranes for selective separation

This study presents an environmentally friendly method for extracting cellulose acetate (CA) from discarded cigarette filters, which is then utilized in the fabrication of cellulose-based membranes designed for high flux and rejection rates. CA membranes are likeable to separate dyes and ions, but their separation efficiency is exposed when the contaminant concentration is very low. So, we have integrated graphene oxide (GO) and carboxylated titanium dioxide (COOH-TiO2) in CA to develop mixed matrix membranes (MMMs) and studied them against dyes and most used salts. The CA has been extracted from these butts and added GO and COOH-TiO2 nanoparticles to develop MMMs. The present work administers the effective separation of five dyes (methyl orange, methyl violet, methylene blue, cresol red, and malachite green) and salts (NaCl and Na2SO4) along with the high efficiency of water flux by prepared CA membranes. The prepared membranes rejected up to 94.94 % methyl violet, 91.28 % methyl orange, 88.28 % methylene blue, 89.91 % cresol red, and 91.70 % malachite green dye. Along with the dyes, the membranes showed ∼40.40 % and ∼ 42.97 % rejection of NaCl and Na2SO4 salts, respectively. Additionally, these membranes have tensile strength up to 1.54 MPa. Various characterization techniques were performed on all prepared CA membranes to comprehend their behaviour. The antibacterial activity of MMMs was investigated using the Muller-Hinton-Disk diffusion method against the gram-positive bacterium Staphylococcus aureus (S. aureus) and the gram-negative bacterium Escherichia coli (E. coli). We believe the present work is an approach to utilizing waste materials into valuable products for environmental care.

Nanostructural modulation of chitosan matrix for facilitating transport of organic molecules across the membrane by pervaporation

Chitosan, as the second most abundant biopolymer on earth, is constantly increasing attention from different fileds such as biomedicals, food, energy, and the environment. However, its application in membrane technology such as pervaporation is lacking of an effective membrane manufacture strategy to improve its separation efficiency. Herein, we use a chitosan-based membrane subjected to neutralization and crosslinking procedures in contrasting solvents—specifically, water and ethanol—to explore the impact of polymer-solvent interactions on the effective nanogaps between polymer nanofibers. Under identical conditions, the procedures conducted in water yield hydrated membranes, while those in ethanol resulted in anhydrous membranes. In hydrated membranes, strong hydrogen bonds formed between water and amine groups block nanogaps amongst polymer nanofibers, significantly impeding molecular transport. Conversely, the absence of such strong hydrogen bonds in anhydrous membrane avoided this effect. This study highlights the potential of controlling the transport of organic molecules by tuning the nanogaps within the membrane matrix. This was achieved through a novel strategy involving washing the chitosan-based membranes with pure ethanol to remove free acids, followed by direct crosslinking in a glutaraldehyde ethanol solution. This strategy was able to double the membrane selectivity despite a 25 % reduction in methanol permeance.

Multi-Objective optimisation of oil demisters geometry for Ultra-Low charge ammonia chillers

Driven by global climate objectives, the pursuit for eco-friendly refrigeration solutions has catalysed impressive advancements in the sector. Ammonia, a historically utilized refrigerant, is now widely adopted in light industrial applications, largely due to the growth of Ultra-Low Charge package chillers. Opportunities, however, persist for refining system components to further diminish refrigerant charge, fostering safer and more efficient solutions. This paper focuses on optimizing the oil separator geometry of an experimentally tested Ultra-Low Charge ammonia chiller. The principal aim and novelty is to lower the specific refrigerant charge while enhancing the separation efficiency and the pressure drop performance. Assessing the separation efficiency involves an analytical model grounded in the “orbit-equilibrium” concept, while the pressure drop is evaluated with consideration of liquid particles presence. Utilizing the validated model, a Multi-Objective Optimization process driven by the eaMuPlusLambda algorithm produces geometries able to reduce the cut-size diameter by 1.4 % up to 15.4 %, pressure drop by 66.7 % up to 89.1 %, and internal volume by 51.3 % up to 68.9 %, compared to the baseline setup. This accomplishment stems from meaningful parameter adjustments, encompassing a 12.1 – 30.0 % decrease in the main diameter, 35.8 % reduction in the main height, 25.4 – 41.2 % contraction in the outlet diameter, 10.9 – 47.1 % augmentation in the inlet diameter, and the vortex finder elimination. Consequently, this translates to a 5% to 14% decrease in the chiller’s specific charge. This study intends an initial step in optimizing oil separators for Ultra-Low Charge ammonia chillers, presenting prospects for specific charge reduction and inciting further exploration through experimental testing or Computational Fluid Dynamics.

Photocatalytic and fouling resistant MXene/3D-S-COF for efficient oil-water emulsion separation

Three-dimensional sphere covalent organic framework (3D-S-COF) membranes have received increasing attention in the field of oily wastewater and industrial organic matter due to their rich pore structure as well as having many exposed functional group sites. However, the synthesis of conventional imine COF through the Schiff base method, which suffers from the easy hydrolysis under organic solvent conditions. Herein, a novel super-wettable MXene/3D-S-COF composite membrane for oil–water emulsion separation was prepared by depositing MXene nanosheets on oxidized amide COF from the imine COF. The hydroxyl groups of the COF membrane not only improved the water permeability but also formed hydrogen bonds with the MXene layer, which enhanced the interaction and formed the high stability composite membrane. The porous 3D-S-COF and the zigzag MXene layer work synergistically to enable emulsion fluxes up to 240 L·m−2h−1 bar−1 and the separation efficiency is more than 98 %. In addition, the residual mass of the composite membrane remained above 95 % after 10 days of immersion in various solvents, and it also has photocatalytic properties and good resistance to fouling. This study provides a brand new idea for the use of MXene/3D-S-COF based composite membrane for oil–water emulsion separation.

In situ activation of peroxymonosulfate with bioelectricity for sulfamethoxazole sustainable removal

Conventional electrochemical activation of peroxymonosulfate (PMS) is not very cost-effective and practical by the excessive input of energy. The electricity generated by photosynthetic microalgae fuel cells (MFCs) is utilized to activate PMS, which would achieve the combination of green bioelectricity and advanced oxidation processes for sustainable pollutants degradation. In this study, a novel dual-chamber of MFCs was constructed by using microalgae as anode electron donor and PMS as cathode electron acceptor, which was operating under both close-circuit and open-circuit conditions. Under close-circuit condition, 1–12 mM PMS in cathode was successfully in situ activated, where 32.00%–99.83% of SMX was removed within 24 h, which was about 1.21–1.78 times of that in the open-circuit of MFCs. Meanwhile, a significant increase in bioelectricity generation in MFCs was observed after the accumulation of microalgae biomass (4.65–5.37 mg/L), which was attributed to the efficient electron separation and transfer. Furthermore, the electrochemical analysis demonstrated that SMX or its products were functioned as electronic shuttles, facilitating the electrochemical reaction and altering the electrical capacitance. The quenching experiments and voltage output results reflected that complex active radical (SO4⋅-, ⋅OH, and 1O2) were involved in SMX removal. Seven degradation products of SMX were detected and S–N bond cleavage was the main degradation pathway. Predicted toxicity values calculated by ECOSAR program showed that all the products were less toxic or nontoxic. Finally, the density functional theory (DFT) calculations revealed that the O and N atoms on SMX were more susceptible to electrophilic reactions, which were more vulnerable to be attacked by reactive species. This study provided new insights into the activation of PMS by bioelectricity for SMX degradation, proposing the mechanisms for PMS activation and degradation sites of SMX.