Refractory Organic Contaminants Research Articles

Bicarbonate enhanced heterogeneous activation of peroxymonosulfate by copper ferrite nanoparticles for the efficient degradation of refractory organic contaminants in water

Nowadays, the treatment of residual refractory organic contaminants (ROCs) is a huge challenge for environmental remediation. In this study, a potential process is provided by copper ferrite catalyst (CuFe2O4) activated peroxymonosulfate (PMS, HSO5−) in the bicarbonate (HCO3−) enhanced system for efficient removal of Acid Orange 7 (AO7), 2,4-dichlorophenol, phenol and methyl orange (MO) in water. The impact of key reaction parameters, water quality components, main reactive oxygen species (ROS), probable degradation mechanism, rational degradation pathways and catalyst stability were systematically investigated. A 95.0% AO7 (C0 = 100 mg L−1) removal was achieved at initial pH (pH0) of 5.9 ± 0.1 (natural pH), CuFe2O4 dosage of 0.15 g L−1, PMS concentration of 0.98 mM, HCO3− concentration of 2 mM, and reaction time of 30 min. Both sulfate radical (SO4−•) and hydroxyl radical (•OH) on the surface of catalyst were proved as the predominant radical species through radical quenching experiments and electron paramagnetic resonance (EPR) analysis. The buffer nature of HCO3− was partially contributed for the enhanced degradation of AO7 under CuFe2O4/PMS/HCO3− system. Importantly, according to 13C nuclear magnetic resonance (NMR) and EPR analysis, the positive effect of bicarbonate may be mainly attributed to the formation of peroxymonocarbonate (HCO4−), which may enhance the generation of •OH. The magnetic CuFe2O4 particles can be well recycled and the leaching concentration of Cu was acceptable (<1 mg L−1). Considering the widespread presence of bicarbonate in water environment, this work may provide a safe, efficient, and sustainable technique for the elimination of ROCs from practical complex wastewater.

Adsorption and catalysis of peroxymonosulfate on carbocatalysts for phenol degradation: The role of pyrrolic-nitrogen

Persulfate-based nonradical oxidation processes are appealing for removing refractory aromatic organic contaminants in wastewater purification. Here, ultrathin nitrogen-doped carbonaceous catalysts with different pyrrolic-N contents were developed by a facile modifiable g-C3N4-templated strategy. We observed that N-C-6 has the highest pyrrolic-N content, and the presence of N-C-6 with Peroxymonosulfate (PMS) achieved almost 98 % degradation for phenol degradation within 30 min. Moreover, the decisive role of pyrrolic-N in activating PMS was illustrated through experiments, instrument characterization and theoretical calculations: the more pyrrolic-N-doping could exhibit the higher redox potential of the metastable complex with PMS, and the stronger interaction between both materials, the greater PMS adsorption, as a result, the oxidation rate of phenol is faster by charge abstraction reactions. The results provide a new strategy for the intrinsic roles of heteroatom doped carbon materials to activate persulfates.

Visible-light-induced photocatalytic response of easily recoverable Mn2O3/SiO2 monolith in centimeter-scale towards degradation of ofloxacin: Performance evaluation and product analysis

Monolithic-photocatalysts being easily recoverable are a suitable alternative to powdered materials for pollutant treatment. This study was conducted to prepare Mn2O3/SiO2 monoliths by wet-impregnating Mn(NO3)2․4H2O in SiO2 monoliths. The crystallinity of oxide was affirmed via XRD analyses, whereas EDS and elemental-mapping, and XPS studies revealed the constituent elements and their oxidation states. FESEM images confirmed porous morphology, while BET-analysis confirmed its mesoporous nature (∼8.44 nm) and enormous surface area (∼241 m2/g). The DRS and PL studies disclosed that Mn2O3/SiO2 monoliths consisted of narrow band-gap of ∼2.14 eV and had suitable electron/hole separation. The photocatalytic effectiveness of the monolith had been checked by degrading model dye methylene blue (MB) and antibiotic ofloxacin (OF). The influence of various reaction parameters for degradation, i.e., monolith dose, solution-pH, illumination-area, scavengers, etc., was noted. At optimal reaction conditions, outstanding competence was achieved for MB (95.23%; 0.0225 min−1) and decent results were obtained for OF-degradation (73.2%; 0.0096 min−1). The recyclable nature of the catalyst (∼12.7%-reduction in effectiveness after 10 successive cycles) was vindicated by several characterization studies after reusability. The O2•−radicals participated majorly in the degradation reaction. The reaction intermediates plus products, generated after the degradation of had been identified via LC/MS study. The mineralization extent of the OF and MB was also gauged through TOC analyses. The photocatalytic treatment of raw textile wastewater manifested ∼57.8% COD and 53% TOC-removal. This study emphasizes the competence of Mn2O3/SiO2 monoliths for the photocatalytic abatement of refractory organic contaminants.

Hydrogen peroxide and peroxymonosulfate intensifying Fe−doped NiC−Al2O3−framework−based catalytic ozonation for advanced treatment of landfill leachate: Performance and mechanisms

The biotreated effluent of landfill leachate still contains numerous refractory organic contaminants, which poses potential threats to human health and ecosystems. Influenced by landfill ages and other factors, the concentration of organic matter varies. Heterogeneous catalytic ozonation (HCO) is a promising technology for advanced wastewater treatment. Aiming to achieve the up−to−standard discharge of low−concentration landfill leachate (COD ≈ 108 mg·L−1) and improve the biodegradability of high−concentration landfill leachate (COD ≈ 1720 mg·L−1), the active component Fe was incorporated into a firm Ni−induced C−Al2O3−framework (NiCAF) composite support to synthesize a Fe−NiCAF catalyst for efficient catalytic ozonation. When the Fe−NiCAF dosage was 4 g·L−1, the gas flow rate was 0.5 L·min−1, and the ozone concentration was 20.0 mg·L−1, the COD of low−concentration landfill leachate effluent decreased to 43 mg·L−1, and the COD removal rate constant of low−concentration landfill leachate was 154% higher than that of pure ozone. For high−concentration landfill leachate with the BOD5/COD of 0.058, the COD removal efficiency in Fe−NiCAF/O3 increased from 39% to 57% compared with ozonation, and the effluent BOD5/COD increased to 0.282. Furthermore, the addition of hydrogen peroxide (H2O2) and peroxymonosulfate (PMS) can further enhance the treatment performance of Fe−NiCAF/O3 process and different strengthening mechanisms were revealed. The results indicated that surface hydroxyls on the Fe−NiCAF catalyst surface were the main catalytic sites for ozone, and hydroxyl radical (•OH) and singlet oxygen (1O2) were identified as the main reactive oxygen species for the removal of organics in landfill leachate. Adding H2O2 can promote the generation of •OH for nonselective degradation of various organics, while PMS mainly enhanced the production of 1O2 to decompose macromolecular humus. This work highlighted an efficient Fe−NiCAF ozone catalyst and an innovative peroxide intensified HCO strategy for the advanced treatment of landfill leachate.

Treatment of contaminants by a cathode/FeIII/peroxydisulfate process: Formation of suspended solid organic-polymers

Treatment of highly contaminated wastewaters containing refractory or toxic organic contaminants (e.g. industrial wastewaters) is becoming a global challenge. Most technologies focus on efficient degradation of organic contaminants. Here we improve the cathode/FeIII/peroxydisulfate (PDS) technology by turning down the current density and develop an innovative mechanism for organic contaminants abatement, namely polymerization rather than degradation, which allows simultaneous contaminants removal and resource recovery from wastewater. This polymerization leads to organic-particles (suspended solid organic-polymers) formation in bulk solution, which is demonstrated by eight kinds of representative organic contaminants. Taking phenol as a representative, 83% of PDS is saved compared to degradation process, with 87.2% of DOC removal. The formed suspended solid organic-polymers occupy 59.2% of COD of the original organics in solution, and can be easily separated from aqueous solution by sedimentation or filtration. The separated organic-polymers are a series of polymers coupled by phenolic monomers, as confirmed by FTIR and ESI-MS analyzes. The energy contained in the recovered organic polymers (4.76 × 10−5 kWh for 100 mL of 1 mM phenol solution in this study) can fully compensate the consumed electrical energy (2.8 × 10−5 kWh) in the treatment process. A representative polymerization model for this process is established, in which the SO4•− and HO• generated from PDS activation initiate the polymerization and improve the polymerization degree by the production of oligomer intermediates. A practical coking wastewater treatment is carried out to verify the research results and get positive feedback, with 56.0% of DOC abatement and the suspended solid organic-polymers accounts for 42.5% of the total COD in the raw wastewater. The energy consumption (47 kWh/kg COD, including electricity and PDS cost) is lower than the values in previous reports. This study provides a novel method for industrial wastewater treatment based on polymerization mechanism, which is expected to recover resources while removing pollutants with low consumption.

Activation of peroxydisulfate via photothermal synergistic strategy for wastewater treatment: Efficiency and mechanism

Peroxydisulfate (PDS)-based advanced oxidation processes (AOPs) have been demonstrated to be an effective technology for the removal of refractory organic contaminants from the aquatic environment. Herein, a photothermal synergistic strategy is developed to realize the green activation of PDS under solar light irradiation. An innovative solar photothermal reaction system and its corresponding evaluation method are established. The results show that there is a synergistic effect between light and light-generated thermal effects on the activation of PDS for effectively removing fulvic acid (FA). The maximum degradation percentage of FA increases from 42.6% to 90.8% after introducing ZrC nanoparticles as photothermal materials. The maximum temperature of the whole system is up to 66.4 ℃ after 120 min irradiation at 0.007 wt% solid content of ZrC, which is higher by 26.9% compared with that in the absence of ZrC nanoparticles. Furthermore, the underlying mechanism and PDS activation efficiency are deeply investigated. This work provides a viable strategy for directly using solar radiation to activate PDS for degrading refractory organic compounds, which creates a new avenue toward the utilization of solar energy for wastewater treatment.

Efficient activation of peroxymonosulfate mediated by Co(II)-CeO2 as a novel heterogeneous catalyst for the degradation of refractory organic contaminants: Degradation pathway, mechanism and toxicity assessment

A series of Co(II)-CeO2 mixed metal oxides were synthesized by a facile hydrothermal-calcination procedure for activating peroxymonosulfate (PMS) and degrading toxic and difficult biodegradable organics. Co(II)-CeO2 showed excellent degradation performance toward rhodamine B (RhB), toluidine blue, methylene blue and diclofenac. RhB is a refractory organic contaminant, and ecotoxicological evaluation unraveled its harmfulness to the biosphere. RhB was selected as the model pollutant to investigate catalytic mechanisms. Parameters affecting degradation performance were profoundly investigated, including Co:Ce feed ratio, initial pH, PMS dosage, catalyst dosage, RhB concentration, coexisting ions and reaction temperature. Reaction mechanisms were proposed based on density functional theory calculations and identifications of reactive oxygen species. Improvements have been achieved in seven aspects compared to previous studies, including 100% degradation ratio in both real water samples and each reuse of the catalyst, ultrafast degradation rate, cost-effectiveness of the catalyst, toxicity-attenuation provided by the developed degradation method, high degree of mineralization for the model pollutant, negligible leaching of active sites, and the enhancement of catalytic performance by utilizing trace leached cobalt, endowing the technique with broad applicability and prospect.

Rapid degradation of atrazine by a novel advanced oxidation process of bisulfite/chlorine dioxide: Efficiency, mechanism, pathway

Recently, (bi)sulfite as the precursor of SOx− generation has drawn significant attention in advance oxidation process based on SO4− (SR-AOP) due to its low cost and conforming to waste utilization. The current activation on (bi)sulfite mainly employs the transition metals and their composite materials, which limited its application. In this study, chlorine dioxide (ClO2) was employed to activate bisulfite (BS). It was found that the dominant radicals in BS/ClO2 process were ClO and SO4− according to scavenger experiments and ESR detection. To investigate the performance of the established BS/ClO2 system, atrazine (ATZ) was used as target pollutant. The degradation efficiency of ATZ reached 86.8% within 3 min and nearly half of the degradation occurred at the first 10 s. The optimum ClO2 dosage for the ATZ degradation was 100 μM when the BS dosage was 200 μM. The effects of pH, temperature and coexisting substances including halide ions, bicarbonate ion and humic acid on ATZ degradation by BS/ClO2 were investigated. It is predicted that the degradation pathway of ATZ in this study involved olefination, dealkylation and the combination of dichlorination with hydroxylation according to the final products identified after degradation. The system has also shown the ability on degradation of four pharmaceuticals and personal care products (PPCPs) including ibuprofen, bisphenol A, sulfamethoxazole and carbamazepine. This study reveals that ClO2 is capable of activating BS and provides a method for effectively degrading refractory organic contaminants.

Degradative removal of Sulfamethoxazole through visible light driven peroxymonosulfate activation by direct Z-scheme MIL-53(Co/Fe)/MoS2 heterojunction composite: Role of dual redox mechanism and efficient charge separation

MIL-53(Co/Fe)/MoS2 (MIL-MS) binary photocatalyst was synthesized by a hydrothermal procedure through insitu growth of MoS2 on MIL-53(Co/Fe). In comparison to pure MIL-53(Co/Fe) and MoS2, the binary catalyst having 10 wt% MoS2 (MIL-MS(10)) (0.01 g/L) achieved 99% Sulfamethoxazole (SMX) removal (10 mg/L) through visible light driven activation of peroxymonosulfate (PMS, 0.2 g/L), at initial solution pH of 6. The formation of heterojunction enhances the charge separation efficiency, activation of adsorbed PMS moieties and harvesting of incident visible light. Surface-bound Fe2+/Fe3+|surf., Co2+/Co3+|surf. and Mo4+/Mo6+|surf.redox perform significant roles towards charge transport and production of reactive species. EPR analysis, coupled with scavenging studies indicate that radical(SO4•−,O•H,O2•−,h+)involving oxidation mechanism imparted maximum contribution towards SMX degradation. Detailed degradation pathway was designed based on substantial intermediate analysis. Excellent visible light responsiveness, charge transfer ability and reusability over multiple catalytic cycles, coupled with excellent performance in various real water matrixes established MIL-MS composite as an ideal candidate for facile removal and mineralization of refractory organic contaminants under visible light irradiation.

Advanced oxidation process: a sustainable technology for treating refractory organic compounds present in industrial wastewater.

The world faces tremendous challenges and environmental crises due to the rising strength of wastewater. The conventional technologies fail to achieve the quality water that can be reused after treatment means "zero effluent" discharge of the industrial effluent. Therefore, now the key challenge is to develop improved technologies which will have no contribution to secondary pollution and at the same time more efficient for the socio-economic growth of the environment. Sustainable technologies are needed for wastewater treatment, reducing footprint by recycling, reusing, and recovering resources. Advanced oxidation process (AOP) is one of the sustainable emerging technologies for treating refractory organic contaminants present in different industrial wastewaters like textile, paper and pulp, pharmaceuticals, petrochemicals, and refineries. This critical review emerges details of advanced oxidation processes (AOPs), mentioning all possible permutations and combinations of components like ozone, UV, the catalyst used in the process. Non-conventional AOP systems, microwave, ultrasound, and plasma pulse assisted are the future of the oxidation process. This review aims to enlighten the role of AOPs for the mineralization of refractory organic contaminants (ROC) to readily biodegradable organics that cannot be either possible by conventional treatment. The integrated AOPs can improve the biodegradability of recalcitrant organic compounds and reduce the toxicity of wastewater, making them suitable for further biological treatment.

Magnetic Co/Fe nanocomposites derived from ferric sludge as an efficient peroxymonosulfate catalyst for ciprofloxacin degradation

• Cobalt adsorbed on ferric sludge was recycled to create bimetallic catalyst via a facile solvothermal method. • Co/Fe nanocomposites derived from ferric sludge (CoFe@FS) exhibited an excellent performance toward PMS. • SO 4 •− , • OH, O 2 •− and 1 O 2 were produced from PMS activation by synergetic effect of Co and Fe on the catalyst surface. • The possible degradation mechanism of CIP is proposed based on DFT calculations and LC/MS analyses. • This is a cost-effective method to achieve “treating wastewater by waste residuals”. Ferric sludge, generated during drinking water purification process, can be considered as a promising support with potential iron resource. Herein, magnetic bimetallic Co/Fe nanocomposite derived from ferric sludge (CoFe@FS) was created via a facile solvothermal treatment and employed as an efficient peroxymonosulfate (PMS) activator for the elimination of antibiotic ciprofloxacin (CIP) in water. CoFe@FS exhibited nano-sphere structure with the composites of CoO, CoFe 2 O 4 and SiO 2 crystals and presented excellent catalytic performance with 97.3% removal efficiency of 10 mg/L CIP within 15 min. Sulfate radicals (SO 4 •− ), hydroxyl radicals ( • OH) superoxide radicals (O 2 •− ) and singlet oxygen ( 1 O 2 ) all contributed to CIP degradation, and SO 4 •− functioned as the dominant reactive species in this activation system. CoFe@FS composite exhibited great reusability due to the strong Co/Fe-Si interaction and was able to regenerate by a simple solvothermal process. The CIP degradation mechanism in the CoFe@FS/PMS system were also proposed based on density functional theory (DFT) calculations and analysis of intermediate products. Overall, the magnetic Co/Fe bimetallic catalyst derived from ferric sludge could be employed as high-efficiency and low-cost candidate for the degradation of refractory organic contaminants. This work not only provides a promising reclamation strategy of water treatment waste from ferric sludge to high-effective catalyst, but also clarifies the mechanisms of PMS activation and CIP degradation. The more stable bimetallic CoFe catalysts derived from waste sludge need to be developed in the future study to relieve the occurrence of metal leaching.

A state of the art review on electrochemical technique for the remediation of pharmaceuticals containing wastewater

Pharmaceutical wastewater is a frequent kind of wastewater with high quantities of organic pollutants, although little research has been done in the area. Pharmaceutical wastewaters containing antibiotics and high salinity may impair traditional biological treatment, resulting in the propagation of antibiotic resistance genes. The potential for advanced oxidation processes (AOPs) to break down hazardous substances instead of present techniques that essentially transfer contaminants from wastewater to sludge, a membrane filter, or an adsorbent has attracted interest. Among a variety of AOPs, electrochemical systems are a feasible choice for treating pharmaceutical wastewater. Many electrochemical approaches exist now to remediate rivers polluted by refractory organic contaminants, like pharmaceutical micro-pollutants, which have become a severe environmental problem. The first part of this investigation provides the bibliometric analysis of the title search from 1970 to 2021 for keywords such as wastewater and electrochemical. We have provided information on relations between keywords, countries, and journals based on three fields plot, inter-country co-authorship network analysis, and co-occurrence network visualization. The second part introduces electrochemical water treatment approaches customized to these very distinct discarded flows, containing how processes, electrode materials, and operating conditions influence the results (with selective highlighting cathode reduction and anodic oxidation). This section looks at how electrochemistry may be utilized with typical treatment approaches to improve the integrated system's overall efficiency. We discuss how electrochemical cells might be beneficial and what compromises to consider when putting them into practice. We wrap up our analysis with a discussion of known technical obstacles and suggestions for further research.

Magnetic sludge-based biochar derived from Fenton sludge as an efficient heterogeneous Fenton catalyst for degrading Methylene blue

Fenton sludge was converted into magnetic sludge-based biochar (SMBC) using a one-step pyrolysis process and employed as a novel heterogeneous catalyst to activate hydrogen peroxide (H2O2) for the oxidative removal of methylene blue (MB). The crystal structure and catalytic activity of SMBC are strongly affected by the pyrolysis temperature. X-ray powder diffraction, Mössbauer, and scanning electron microscope-energy dispersive spectrometer analyses were conducted to determine the crystal phase transfer of iron (Fe) oxides at different pyrolytic temperatures and retention times. The results revealed that the catalytic efficiency of SMBC was strongly related to the crystal phase of Fe oxides. The catalyst obtained at 800 °C for 1 h exhibited superior catalytic properties and degraded 98.56% of the MB (100 mg·L−1) in 3 min via the synergistic effect of Fe3O4, Fe0, and biochar. Free radical quenching experiments and electron paramagnetic resonance studies demonstrated that ·OH, O2·− and 1O2 participated in the H2O2 system, and·OH radicals were promptly generated owing to the catalysis of the SMBC. Aging tests were repeated for four cycles in three conditions to examine the stability of the material. The results showed that SMBC was relatively stable in non-aerated and aqueous conditions, but its activation performance was severely inhibited in an oxygen environment. Furthermore, the catalytic ability of SMBC was maintained at 88.13% after the 4th run. This study presents a cost-effective method of converting ferric sludge to an environmentally friendly catalyst that enables H2O2 activation for degrading refractory organic contaminants.

Biphase Co@C core-shell catalysts for efficient Fenton-like catalysis

Despite the vital roles of Co nanoparticles catalytic oxidation in the Fenton-like system for eliminating pollutants, contributions of Co phases are typically overlooked. Herein, a biphase Co@C core-shell catalyst was synthesized by the electrochemical co-reduction of CaCO3 and Co3O4 in molten carbonate. Unlike the traditional pyrolysis method that is performed over 700 °C, the electrolysis was deployed at 450 °C, at which biphase structures, i.e., face-centered cubic (FCC) and hexagonal close-packed (HCP) structures, can be obtained. The biphase Co@C shows excellent catalytic oxidation performance of diethyl phthalate (DEP) with a high turnover frequency value (TOF, 28.14 min–1) and low catalyst dosage (4 mg L–1). Furthermore, density functional theory (DFT) calculations confirm that the synergistic catalytic effect of biphase Co@C is the enhancement for the breaking of the peroxide O–O bond and the charge transfer from catalysts to PMS molecule for the activation. Moreover, the results of radicals quenching experiments and electron paramagnetic resonance (EPR) tests confirm that SO4•–, •OH, O2•–, and 1O2 co-degrade DEP. Remarkably, 100% removals of three model contaminants, including DEP, sulfamethoxazole (SMX) and 2,4-dichlorophen (2,4-DCP), were achieved, either in pure water or actual river water. This paper provides an electrochemical pathway to leverage the phase of catalysts and thereby mediate their catalytic capability for remediating refractory organic contaminants.

Hydroxylamine enhanced Cu(II)/peroxydisulfate system for diclofenac degradation: Efficiency, influence factors and mechanism

In this work, diclofenac (DCF), a nonsteroidal anti-inflammatory drug, was effectively removed in Cu(Ⅱ)/hydroxylamine (HAm)/peroxydisulfate (PDS) system in neutral condition. It was proved that the introduction of HAm significantly enhanced DCF degradation in Cu(Ⅱ)/PDS system by accelerating Cu(Ι)/Cu(Ⅱ) cycle. According to the results of electron paramagnetic resonance (EPR) and scavenging experiments, the contribution of SO4•- and •OH to DCF degradation in Cu(Ⅱ)/HAm/PDS system was comparable at pH 7. The effects of operational parameters including initial pH, Cu(Ⅱ) dose, HAm concentration, PDS concentration and initial DCF concentration on the removal of DCF were systematically investigated, and the influence of water matrix components (i.e., SO42-, NO3-, Cl-, HCO3- and natural organic matter) on DCF degradation were also studied. Five degradation products were detected using UPLC-Q-TOF-MS, and four degradation pathways were thereby proposed including hydroxylation, dehydrogenation, dehydration and decarboxylation. The mineralization of DCF in Cu(Ⅱ)/HAm/PDS system was limited according to the result of total organic carbon (TOC) test. Various emerging contaminants were also effectively degraded in Cu(Ⅱ)/HAm/PDS system, suggesting the applicability of this system in degradation of other refractory organic contaminants. This study provides a method to enhance the treatment efficiency of Cu(Ⅱ)/PDS system and an effective way to degrade emerging contaminants at mild condition.

Removal of refractory organics and heavy metals in landfill leachate concentrate by peroxi-coagulation process

Landfill leachate is a complex effluent and it is difficult to deal with. Electrochemical methods have been considered as a promising alternative technology for treatment of landfill leachate with refractory organic contaminants and heavy metals. Peroxi-coagulation (PC) process with iron anode and modified graphite felt cathode was developed for efficient landfill leachate concentrate treatment. Compared to electro-Fenton (EF) and electrocoagulation (EC) processes, the PC process was more cost-effective due to the combined action of •OH oxidation and iron hydroxides coagulation. A maximal TOC removal of 77.2% ± 1.4% was obtained after 360 min at initial pH = 5.0 and current density of 10 mA/cm2. After the PC process, concentrations of all seven heavy metals in the final effluents were below the allowable emission limits given by the present regulatory standards. The method preference for heavy metal removal was PC > EC > EF. Based on the three-dimensional fluorescence spectroscopy coupled with regional integration analysis during the PC treatment, the florescence peaks of both humic acids and fulvic acids disappeared after treatment for 360 min. Decreasing trends were observed in the fluorescent regional standard volumes for aromatic protein I (31.4%), aromatic protein II (63.7%), fulvic acid-like (69.5%), soluble microbial by-product-like (75%) and humic acid-like regions (76.3%). The results indicate that comparing to the EF and EC process, the PC process provide a promising and more cost-effective alternative for the treatment of landfill leachate concentrate.

Crystallization regulation of Fe0@Fe3O4 using a g-C3N4/diatomite composite for enhancing photocatalytic peroxymonosulfate activation

Photocatalysis and persulfate synergistic catalysis have recently become promising technologies for degrading refractory organic contaminants in effluents. In this work, Fe0@Fe3O4 is successfully immobilized on a N-deficient g-C3N4/diatomite composite (NGD) via a simple self-assembly process. The structural characteristics and peroxymonosulfate activation ability of the composite under visible-light irradiation are explored in detail. Notably, the introduction of NGD affects the crystallinity and morphology of Fe0@Fe3O4, forming homogenously distributed nanoparticles rather than irregular and agglomerated crystals with rod-like structures. The synthesized Fe0@Fe3O4/N-deficient g-C3N4/diatomite composite (FNGD) exhibits a superior removal percentage of bisphenol A (&gt; 95% within 15 min). Furthermore, its degradation rate constant (k) is ~59 and ~27 times higher than those of NGD and bare Fe0@Fe3O4, respectively. Moreover, holes (hvb+), singlet oxygen (1O2) and superoxide free radicals (•O2-) play a major role in the FNGD/peroxymonosulfate/visible system based on radial quenching experiments and electron paramagnetic resonance spectra. Overall, this study provides novel insights into visible light-assisted peroxymonosulfate activation by the g-C3N4/mineral-based composite for wastewater treatment.

Enhanced electro-peroxymonosulfate activation using a carbon nanotube filter with a functionalized polyelectrolyte

An innovative electroactive membrane was designed with polyelectrolyte modification for electro-PMS activation and degradation of refractory organic contaminants in a flow-through filtration model.

Recent advances in persulfate-based advanced oxidation processes for organic wastewater treatment

In recent years, with the emergence of new pollutants, the effective treatment of wastewater has become very important. Persulfate-based advanced oxidation processes have been successfully applied to the treatment of wastewater, such as wastewater containing antibiotics, pharmaceuticals and personal care products, dyes, endocrine-disrupting chemicals, chlorinated organic pollutants, and phenolics, for the degradation of refractory organic contaminants. This paper summarizes the production of sulfate radicals, which can be generated by the activation of persulfate via conventional and emerging approaches. The existing problems of persulfate-based advanced oxidation processes were analyzed in detail, including residual sulfates, coexisting factors (coexisting inorganic anions and natural organic matter), and energy consumption. This paper proposes corresponding possible solutions to the problems mentioned above, and this paper could provide a reference for the application of persulfate-based advanced oxidation processes in actual wastewater treatment.

Improved electrocatalytic performance of Fe/CeO2 bifunctional electrocatalyst by simultaneous H2O2in-situ generation and activation

Heterogeneous Electron-Fenton (HEF) has been recognized as a prospective solution in tackling refractory organic contaminants. Nevertheless, the low production efficiency of H2O2 and external addition of H2O2 or Fe2+ limit its wide application. In this work, the bi-functional Fe/CeO2 composites were designed to achieve the simultaneous generation of H2O2 and •OH. The electro-catalysis experiments indicate Fe/CeO2 composites present 97% degradation efficiency for 17 mg/L phenol within 0.5 h and it still presented good degradation performance in high salinity condition. The H2O2 yield produced by Fe, CeO2, and Fe/CeO2 revealed that CeO2 and Fe/CeO2 have similar H2O2 productivity about 24 mg/L h−1, suggesting that H2O2 is mainly produced by CeO2. O2-TPD profiles, XPS and Raman spectra indicate that the relative amount of oxygen deficient region (Ov) and chemisorbed oxygen in Fe/CeO2 composites is higher than that in CeO2, which promote the adsorption of O2. Then the effective O2 adsorption can ensure the subsequent electrocatalysis of O2 to H2O2. The impedance measurement shows that Fe/CeO2 composite exhibits excellent conductivity, enabling the transporting of electron. EPR experiments and radical scavenging experiments disclosed that the primary reactive species was •OH, proving the in-situ activation of H2O2 to •OH by Fe/CeO2 composites. This work should offer new insights about the rational design of bi-functional catalyst towards simultaneous generation and activation H2O2 to •OH, thus improving electrocatalytic performance.