Abatement Of Contaminants Research Articles

Construction of MOFs-based nanocomposite membranes for emerging organic contaminants abatement in water

Construction of MOFs-based nanocomposite membranes for emerging organic contaminants abatement in water

N-Rich Algal Sludge Biochar for Peroxymonosulfate Activation toward Sulfadiazine Removal

The fabrication of a green, high activity and low-cost carbon-based catalyst capable of activating new oxidant (peroxymonosulfate, PMS) for contaminants abatement is needed. In this research, we prepared novel N-doped biochars via one-step pyrolysis of algal sludge without external nitrogen sources. The obtained ASBC800 possessed the largest specific surface area (SBET = 145.596 m2 g−1) and thus it displayed the best catalytic performance, as revealed by the effective elimination of sulfadiazine (SDZ, >95% within 70 min) with 0.2 g L−1 ASBC800 and 0.5 mM PMS. Both radical species (e.g., SO4•−, and •OH), and nonradical regime (1O2 and electron-transfer) contributed to SDZ oxidation, in which ASBC800 played essential roles in activating PMS, accumulating SDZ, and regulating electron shuttle from SDZ to ASBC800-PMS*. Overall, this work not only provides a novel strategy for the synthesis of N-rich and cost-effective biochar but also promotes the development and application of carbon-based functional materials in environmental remediation.

Accelerated Fe(III)/Fe(II) cycle for rapid elimination of Rhodamine B by a novel Mo2C co-catalytic Fe2+/H2O2 system

Commercial molybdenum carbide (Mo2C) and ferrous iron (Fe2+) were investigated for the first time to co-catalyze the activation of H2O2 for the treatment of organic contaminants. Compared with traditional Fenton process, the presence of Mo2C decomposed hydrogen peroxide (H2O2) more effectively and accelerated the conversion of Fe3+/Fe2+. The Rhodamine B (RhB) degradation rate constant in Mo2C/Fe2+/H2O2 reached appropriately three times that in Fe2+/H2O2, and the co-catalytic reactivity of Mo2C was significantly higher than that of MoS2. In addition, Mo2C/Fe2+/H2O2 exhibited a board effective pH range of 2.8–8.8, and four-cycle experiments confirmed the stability and reusability of Mo2C. The results of X-ray photoelectron spectroscopy (XPS) indicated that Mo(Ⅱ) and Mo(IV) played major roles in Fe3+ reduction. Electron Paramagnetic Resonance analysis and quenching experiments demonstrated that hydroxyl radical (·OH), superoxide anion radical (O2−) and singlet oxygen radical (1O2) were all involved in Mo2C/Fe2+/H2O2. Particularly, Mo2C/Fe2+/H2O2 significantly enhanced the generation of ·OH and 1O2 in comparison to Fe2+/H2O2. Moreover, toxicity assessment analysis by ECOSAR suggested that the toxicity of most degradation products of RhB decreased after treatment. Overall, this study offers a promising Mo2C co-catalyzed Fenton process for rapid and efficient abatement of organic contaminants.

A Novel Source of Radicals from UV/Dichloroisocyanurate for Surpassing Abatement of Emerging Contaminants Versus Conventional UV/Chlor(am)ine Processes.

Ultraviolet (UV)/chlor(am)ine processes are emerging advanced oxidation processes (AOPs) for water decontamination and raising continuous attention. However, limitations appear in the UV/hypochlorite and UV/monochloramine for removing specific contaminants ascribed to the differences in the sorts and yields of free radicals. Here, this study reports UV/dichloroisocyanurate (NaDCC) as a novel source of radicals. NaDCC was demonstrated to be a well-balanced compound between hypochlorite and monochloramine, and it had significant UV absorption and a medium intrinsic quantum yield. The UV/NaDCC produced more substantial hydroxyl radicals (·OH) and reactive chlorine species (RCSs, including Cl·, ClO·, and Cl2·-) than conventional UV/chlor(am)ine, thereby generating a higher oxidation efficiency. The reaction mechanisms, environmental applicability, and energy requirements of the UV/NaDCC process for emerging contaminants (ECs) abatement were further investigated. The results showed that ·OH and ·NH2 attacked ECs mostly through hydrogen atom transfer (HAT) and radical adduct formation, whereas Cl· destroyed ECs mainly through HAT and single electron transfer, with ClO· playing a certain role through HAT. Kinetic model analyses revealed that the UV/NaDCC outperformed the conventional UV/chlor(am)ine in a variety of water matrices with superior degradation efficiency, significantly saving up to 96% electrical energy per order. Overall, this study first demonstrates application prospects of a novel AOP using UV/NaDCC, which can compensate for the deficiency of the conventional UV/chlor(am)ine AOPs.

Abatement of Aromatic Contaminants from Wastewater by a Heat/Persulfate Process Based on a Polymerization Mechanism.

A novel approach to the abatement of pollutants consisting of their conversion to separable solid polymers is explored by a heat/persulfate (PDS) process for the treatment of high-temperature wastewaters. During this process, a simultaneous decontamination and carbon recovery can be achieved with minimal use of PDS, which is significantly different from conventional degradation processes. The feasibility of this process is demonstrated by eight kinds of typical organic pollutants and by a real coking wastewater. For the treatment of the selected pollutants, 30.2-91.9% DOC abatement was achieved with 24.8-91.2% carbon recovery; meanwhile, only 5.2-47.0% of PDS was consumed compared to a conventional degradation process. For the treatment of a real coking wastewater, 71.0% DOC abatement was achieved with 66.0% carbon recovery. With phenol as a representative compound, our polymerization-based heat/PDS process is applicable in a wide pH range (3.5-9.0) with a carbon recovery of >87%. Both SO4•- and HO• can be initiators for polymerization, with different contribution ratios under various conditions. Phenol monomers are semioxidized to form phenolic radicals, which are polymerized via chain transfer or chain growth processes to form separable solid phenol polymers, benzenediol polymers, and cross-linked polymers.

Electrochemical advanced oxidation process with simultaneous persulfate and hydrogen peroxide on-site generations for high salinity wastewater

Organic contaminant abatement via an upgraded electrochemical process is considered one of the most efficient techniques. Here, an electrochemical advanced oxidation process is developed, combining persulfate in situ electro-generation on the β-PbO2 anode and hydrogen peroxide in situ electro-generation on the carbon cathode using a tank reactor. The abatement ability of organic contaminants is evaluated by real H-acid wastewater. COD and color can be entirely removed at a cell voltage of 2.5 V. The strong oxidant power and mineralization are attributed to the significant amount of the on-site produced reactive species, e.g.1O2, ·OH, and SO4·−. The β-PbO2 coated Ti anode exhibits excellent electro-activity for SO42− to S2O82−. The commercial carbon powder Vulcan XC-72R treated with H3PO4 solution exhibits good hydrogen peroxide selectivity in an acid medium. The application of the oxygen-depolarized electrode not only can produce hydrogen peroxide but also reduces cell voltage and energy consumption.

Using integrative samplers to estimate the removal of pharmaceuticals and personal care products in a WWTP and by soil aquifer treatment enhanced with a reactive barrier

The need and availability of freshwater is a major environmental issue, aggravated by climate change. It is necessary to find alternative sources of freshwater. Wastewater could represent a valid option but requires extensive treatment to remove wastewater-borne contaminants, such as contaminants of emerging concern (CECs). It is urgent to develop not only sustainable and effective wastewater treatment techniques, but also water quality assessment methods. In this study, we used polar organic chemical integrative samplers (POCIS) to investigate the presence and abatement of contaminants in an urban wastewater treatment plant (WWTP) and in soil aquifer treatment (SAT) systems (a conventional one and one enhanced with a reactive barrier). This approach allowed us to overcome inter-day and intraday variability of the wastewater composition. Passive sampler extracts were analyzed to investigate contamination from 56 pharmaceuticals and personal care products (PPCPs). Data from the POCIS were used to estimate PPCPs' removal efficiency along the WWTP and the SAT systems. A total of 31 compounds, out of the 56 investigated, were detected in the WWTP influent. Removal rates along WWTP were highly variable (16-100 %), with benzophenone-3, benzophenone-1, parabens, ciprofloxacin, ibuprofen, and acetaminophen as the most effectively removed chemicals. The two SAT systems yielded much higher elimination rates than those achieved through the primary and secondary treatments together. The SAT system that integrated a reactive barrier, based on sustainable materials to promote enhanced elimination of CECs, was significantly more efficient than the conventional one. The removal of the recalcitrant carbamazepine and its epoxy- metabolite was especially remarkable in this SAT, with removal rates between 69–81 % and 63–70 %, respectively.

Beneficial effect of cerium excess on in situ grown Sr0.86Ce0.14FeO3-CeO2 thermocatalysts for the degradation of bisphenol A.

Ce-doped SrFeO3 perovskite-type compounds are known as good thermocatalysts for the abatement of wastewater contaminants of emerging concern. In this work, Sr0.86Ce0.14FeO3-CeO2 perovskite-oxide systems with increasing amounts of cerium excess (0, 5, 10 and 15 mol% Ce), with respect to its maximum solubility in the perovskite, were prepared in one-pot by solution combustion synthesis and the effects of cerium excess on the chemical physical properties and thermocatalytic activity in the bisphenol A degradation were evaluated. The powders were characterized by powder X-ray diffraction combined with Rietveld refinement, X-ray photoelectron spectroscopy, thermal gravimetry, temperature programmed reduction, nitrogen adsorption, scanning electron microscopy and energy dispersive X-ray spectroscopy techniques. Results highlight that the perovskite structural, redox, surface, and morphological properties are affected by the in situ co-growth of the main perovskite phase and ceria and that a larger cerium excess has a beneficial effect on the thermocatalytic performance of the perovskite oxide-ceria biphasic system, although ceria is not active as a thermocatalyst itself. Perovskite properties and performance are enhanced by the tetragonal distortion induced by the introduction of cerium excess in the synthesis. It is supposed that a larger oxygen mobility and an easier reducibility are among the most relevant features that contribute to superior thermocatalytic properties of these perovskite oxide-based systems. These results also suggest new perspectives in the nanocomposite preparation and their catalytic applications.

Organics abatement and recovery from wastewater by a polymerization-based electrochemically assisted persulfate process: Promotion effect of chloride ion and its mechanism

Ubiquitous chloride ion (Cl-) in wastewaters usually inhibits the degradation of organic contaminants and generates numerous toxic chlorinated products in conventional degradation-based advanced oxidation processes (AOPs). Herein, a more Cl- tolerant polymerization-based electrochemical AOP for organic contaminants abatement and simultaneous organic resource recovery was demonstrated with eight typical organic contaminants and two real industrial wastewaters for the first time. This process can significantly promote dissolved organic carbon (DOC) abatement in the presence of Cl-, differing greatly from conventional degradation-based processes. Compared to sulfate radical (SO4•-) (or hydroxyl radical (HO•)), dichloride radical (Cl2•-) derived from Cl- has moderate reactivity towards most contaminants, which facilitates the organics polymerization as it ensures the formation of polymerizable organic radicals while inhibiting their excessive degradation. Thus, high DOC abatement (over 75 %) and high organic resource recovery ratio (48–79 % separable organic-polymer yield) can be achieved for most contaminants. Both soluble chlorinated compounds and solid chlorinated polymers are formed in the presence of Cl-. The chlorinated products (e.g. chlorophenols) can be polymerized as new monomers, thus the concentration of dissolved organic chlorinated products is much lower than that in conventional degradation-based process. The tolerance of the present process to Cl- is tested in real coking wastewaters, and exceeding 60 % of the abated chemical oxygen demand (COD) is obtained in the form of recoverable organic-polymers.

Synergistic degradation performance of UV/TiO2 photocatalysis and biotrickling filtration inoculated with Aspergillus sp. S1 for gaseous m‐xylene

AbstractBackgroundBiotricking filtration (BTF) based on absorption and biodegradation of waste gas by microorganisms in a biofilm can be used to degrade with difficulty hydrophobic volatile pollutants. Photocatalysis is a promising technology for the abatement of gaseous contaminants because of its nonselective oxidation of volatile organic compounds; however, photocatalysis technology has the limitations of high energy consumption and low mineralization efficiency. This study, therefore, aimed to investigate the synergistic effects of UV/TiO2 photocatalysis (PCO) pretreatment and BTF in treating gaseous m‐xylene.ResultsBTF incubated with a mold, Aspergillus sp. S1, was acclimated with m‐xylene as the sole carbon source. A combined system of PCO with BTF was developed to remove gaseous m‐xylene. The results showed that the startup period was shortened by 3 days in the PCO‐BTF combined system compared to that with BTF alone. The removal efficiency reached 73% and 91% for the BTF and PCO‐BTF systems respectively when the empty bed residence time was extended to 90 s. In addition, PCO‐BTF could withstand transient shock loading of m‐xylene of 5000 mg m−3 and gradually restore its decontamination performance.ConclusionsPCO pretreatment was effective in the enhancement of the removal capacity of BTF for m‐xylene. The PCO‐BTF system proposed in this study provides an attractive alternative to abate hydrophobic volatile pollutants. The integration of PCO essentially prompted the capability of Aspergillus sp. S1 in the BTF unit, which paves the way for the treatment of gaseous waste at an industrial scale. © 2022 Society of Chemical Industry (SCI).

The key role of crystal boron in enhanced degradation of refractory contaminants using heterogeneous Fe3+/SPC system

An origin Fenton-like system was discussed for the abatement of refractory contaminants. Sodium percarbonate (SPC) was utilized as the source of H2O2 and crystal boron (C-boron) was applied to enhance the activation of H2O2. Under the conditions of 0.50 mM Fe3+, 0.34 mM SPC, and heterogeneous catalysis using 100 mg L−1 C-boron, four target pollutants, at the initial concentrations of 20 μM, could be efficiently degraded by the Fenton-like system, with a degradation rate within 20 min up to 81.1% (aspirin, ASA), 92.8% (nitrobenzene, NB), 94.7% (flunixin meglumine, FMME), and 94.3% (benzoic acid, BA) respectively and total organic carbon removal up to 25.0%. The increase of Fe2+ concentration indicated that the conversion of Fe2+/Fe3+ was remarkably promoted by C-boron. Degradation reactions at acidic pH were comparatively fast, with pH-dependent kobs of 9.9 × 10−2 min−1 (ASA), 1.5 × 10−1 min−1 (NB), 1.7 × 10−1 min−1 (FMME), and 1.9 × 10−1 min−1 (BA), whereas those at neutral and alkaline pH were slower. Furthermore, reactive oxygen species including ·OH, 1O2, and O2·− were identified by in-situ electron paramagnetic resonance tests. The contribution ratios of ·OH turned out to be about 71.3–86.7% for the decomposition of four contaminants. The elimination of natural organic matter and the performance of material recycling highlighted the potential for its application in water treatment. The inhibition rate of Chlorella pyrenoidosa reached 211.9% in the C-boron/Fe3+/SPC system. The relatively high algae toxicity limited its application scope, which requires additional research to resolve.

Enhanced activation of sulfite by the Co(II)-bicarbonate complexes for iohexol abatement: Role of free radicals versus high valent cobalt species

Sulfite activation with Co(II) (simplified as Co(II)/sulfite process) has been widely studied for the abatement of organic contaminants, yet the efficiency in the Co(II)/sulfite process is compromised by the slow redox cycling of Co(II)/Co(III). Regarding that the complexation effect between Co(II) and bicarbonate (HCO3−) can enhance the conversion between Co(II) and Co(III) in the advanced oxidation processes, a novel Co(II)/HCO3−/sulfite process is constructed in this study. The iohexol abatement efficiency in the Co(II)/HCO3−/sulfite process is >92 % within 10 min of reaction at trace Co(II) dosage, which is significantly higher that of Co(II)/sulfite process. Apart from the conventional radical generation in the Co(II)/sulfite process, it is unexpectedly found that high valence cobalt species (Co(IV)) are generated. HCO3− can enhance the generation of Co(IV), sulfate radical (SO4•−) and hydroxyl radical (HO•), which play the important role in iohexol abatement. The identification of Co(IV) and its contribution to iohexol abatement is elucidated in the Co(II)/HCO3−/sulfite process. The enhancement can be attributed to the complexation effect between Co(II) and HCO3−, in which the CoHCO3+ and CoCO3 species exhibit excellent ability on sulfite activation. According to electrochemical characterization and theoretical calculation, the presence of HCO3− can reduce the energy barrier in the reaction process, accelerating the Co(II)/Co(III) redox cycling. The Co(II)/HCO3−/sulfite process exhibits excellent practical application potential in the abatement of various pollutants in the water and wastewater treatment.

Peroxymonosulfate-based photocatalytic oxidation of tetracycline by Fe2(MoO4)3/Cd0.5Ni0.5S heterostructure; DFT simulation

The current research is meant to develop novel semiconductor photocatalysts, for the decomposition of tetracycline (TC) as a model organic contaminant in the aquatic environment. The fabrication of Fe2(MoO4)3/Cd0.5Ni0.5S (FMO/CNS) composite has proven to be an effective method for improving the sustainability and photocatalytic activity of Cd0.5Ni0.5S (CNS). Under visible light irradiation, FMO/CNS nanocomposite demonstrated significant PMS activation which led to 1.36 and 1.81 times TC removal efficiency as compared to immaculate Fe2(MoO4)3(FMO) and CNS. FMO/CNS composite potentially promotes the segregation of electron-hole pairs (e−-h+) and exemplifies amazing photocatalytic performance for TC degradation. Its significant photocatalytic activity is due to its unique structure, which includes tiny pores on the surface that confine the PMS molecule to the interface. The FMO/CNS composite has significantly greater piezocatalytic activity than pure FMO and CNS, demonstrating the synergistic effect of FMO and CNS. In the degradation of TC, holes and key reactive radicals (•O2−/•OH/SO4−•) played a major role. Computational studies (DFT) estimates, including the determination of intermediates, confirmed that the hydroxyl addition and C–N cleavage pathways were responsible for TC degradation. As a result, this work delivers a new approach to developing novel photocatalysts with high photocatalytic activity for the abatement of organic contaminants in water.

Defects controlling, elements doping, and crystallinity improving triple-strategy modified carbon nitride for efficient photocatalytic diclofenac degradation and H2O2 production

The development of an effective dual-function photocatalyst for refractory contaminant abatement and sacrificial-free in-situ H2O2 generation is a major challenge. Herein, defects controlling, elements doping, and crystallinity improving triple-strategy is established to synthesize modified g-C3N4 (SCBCN0.4). The triple-strategy of modification reconciles crystallinity improvement and the decoration of moderate cyano-group defects and B and O co-dopants. Characterization experiments and theoretical calculations reveal microstructure and electronic structure optimization, improved light-harvesting capability, and enhanced carrier separation efficiency. SCBCN0.4 performs admirably in the degradation of diclofenac and a variety of other pharmaceuticals. Through synchronous oxygen reduction and water oxidation processes, SCBCN0.4 has an excellent in-situ photocatalytic H2O2 generation rate of 620 μmol/g/h (309 μmol/g/h without sacrificial agents). SCBCN0.4's detoxification, reusability, and stability were validated in several experiments. Hence, this research offers a ground-breaking approach to manufacturing triple-strategy modified g-C3N4 for environmental remediation and (sacrificial-free) in-situ H2O2 production.

Nanostructured photocatalysts for the abatement of contaminants by photocatalysis and photocatalytic ozonation: An overview.

The water scarcity, the presence of different contaminants in the worldwide waters and wastewaters and their impacts should motivate their good elimination and water management. With this, photocatalysis and photocatalytic ozonation are strong solutions to obtain good quality reclaimed water, for different applications. Nanostructured supported photo-active catalysts, such as the TiO2, WO3 or ZnO can positively affect the performance of such technologies. Therefore, different semiconductors materials have been aroused the interest of the scientific community, mainly due to its functional properties as well as characteristics imposed by the different nanostructures. With this, this work overviews different works and perspective on the TiO2 nanotubes and other semiconductors nanostructures, with the analysis of different works from 2001 to 2022. Aspects as the substrate effect, electrolyte nature, aspect ratio, electrolyte aging, and annealing treatment but also the effect of morphology, anodization time, applied voltage, temperature and viscosity are discussed. Modification of TiO2 nanotubes is also presented in this paper. The main objective of this work is to present and discuss the key parameters and their effects on the anodization of different semiconductors, as well as the results obtained until today on the degradation of different contaminants by photocatalysis and photocatalytic ozonation, as well as their use on the treatment of real wastewater. TiO2 nanotubes present unique properties and highly ordered configuration, which motivate their use on photo-driven technologies for the pollutant's abatement, even when compared to other nanostructures. However, photocatalysts with activity on the visible range and solar radiation, such as the WO3, can present higher performance and can decrease operational costs, and must be an important source and a key to find efficient and cost-friendly solutions.

Abatement of Organic Contaminants by Mn(VII)/TEMPOs: Effects of TEMPOs Structure, Organic Contaminant Speciation, and Active Oxidizing Species.

In this study, a representative redox mediator, 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), and its para-substituted derivatives (TEMPOs: 4-hydroxyl-TEMPO, 4-acetylamino-TEMPO, and 4-amino-TEMPO) significantly accelerated the abatement of trace organic contaminants (TrOCs, i.e., bisphenol-A (BPA), phenol, amines, and phenylbutazone) by Mn(VII) over a wide pH range of 4.0-9.0. The addition of substituents at para to the > N-O• moiety significantly influenced the degradation kinetics of TrOCs by changing the reduction potentials of TEMPOs and the corresponding oxoammonium cations (TEMPOs+); a linear relationship was observed between the substituents' para Hammett sigma constants and the reduction potentials of TEMPOs and TEMPOs+. Pseudo-first-order reaction rate constants (kobs, min-1) of TrOC degradation by Mn(VII)/TEMPOs were also affected by the pKa of the TrOCs. Generally, the highest kobs values for individual TrOCs were observed at pH near the pKa even for TEMPOs+ with relatively pH-invariant reduction potentials. Overall, TrOC abatement kinetics were related to a combination of reactive species (Mn(VII), in situ formed MnO2, and TEMPOs+). For BPA, the relative contributions (R) of reactive species ranked as R(TEMPOs+) > R(Mn(VII)) > R(in situ formed MnO2) at pH 4.0-8.0, whereas R(Mn(VII)) > R(TEMPOs+) at pH 9.0 mainly owing to a change in BPA speciation as the pH approached the pKa1 value for BPA. The results of this study are useful for the development of heterogeneous TEMPO-based redox mediators and future applications of TEMPO-mediated oxidation systems for accelerated abatement of TrOCs in water.

Effective sulfite activation with atomically dispersed cobalt loaded SBA-15 for iohexol abatement

Cobalt-based heterogeneous catalysts receive research interests in the sulfite activation to generate reactive radicals for abatement of organic contaminants in the aquatic environments, yet the sulfite activation efficacy is compromised by the limited utilization of available active cobalt sites. To address this problem, the atomically dispersed cobalt loaded on mesoporous silica SBA-15 (simplified as Co/SBA-15) is constructed for sulfite activation process regarding the incorporation of cobalt species into the confined space abundant with silicon hydroxyl groups in SBA-15. Co/SBA-15 exhibits excellent sulfite activation efficacy, in which iohexol can be completely degraded within 30 min. Sulfate radical (SO4•−) and hydroxyl radical (HO•) are the dominant reactive radicals responsible for iohexol abatement, in which 7.15 μM of SO4•− and 2.23 μM of HO• are produced. The excellent electron transfer efficiency of Co/SBA-15 is demonstrated by electrochemical impedance spectroscopy (EIS). Structural characterization and valence analysis suggest that the formation of atomically dispersed cobalt species facilitates the sulfite activation and Lewis acid sites on Co/SBA-15 can adsorb organic molecular fragments to realize the rapid conversion from >Co(III) to >Co(II) by electron transfer. The iohexol degradation pathways are also proposed based on UPLC-QTOF-MS analysis. In addition, the effects of various influencing factors including the reactant dosage, coexisting anions, humic acid and the different real water backgrounds on iohexol abatement are systematically investigated. This study is expected to provide an efficient heterogeneous catalyst for sulfite activation to achieve the rapid abatement of organic contaminants.

Synergistic oxidation of organic micropollutants by Mn(VII)/periodate system: Performance and mechanism

The increased release of various emerging organic contaminants into natural waters has posed great threats to ecological safety and public health. The ensuing global water contamination has necessitated the development of highly efficient treatment strategies for water purification. Herein, we presented for the first time that the combined utilization of permanganate (Mn(VII)) and periodate (PI) could synergistically and rapidly accomplish complete destruction of different organic micropollutants (e.g., bisphenol F, methotrexate, and tetracycline) within 2–5 min. Comparatively, the single treatment only eliminated very small amounts of micropollutants. Mechanistic investigations were performed using the trapper-based electron spin resonance, scavenging and probe experiments, UV–vis spectra analysis, determination of iodine species, and multiple validation tests. These data collectively suggested that the highly reactive Mn(V)/Mn(VI) intermediates played the leading role in accelerating contaminant abatement within the Mn(VII)/PI oxidation system. Reactive oxygen/or iodine species (1O2, OH, O2-, IO3, and IO4) and low valence Mn species (Mn(II), Mn(III), and in-situ formed MnO2 colloids) did not participate in decontamination in this process. Subsequently, the oxidized products of three micropollutants were determined, and the transformation pathways were clarified. Ring-opening, C-C bond cleavage, demethylation, carbonylation, and hydroxylation reactions mainly occurred in the degradation process. Notably, the combined system did not yield any toxic iodinated end products. Finally, the environmental risks of the degradation products were also evaluated based on in silico QSAR-based prediction tools. Overall, this study provides a novel, highly efficient, and green treatment technology, i.e., Mn(VII)/PI system, which could be employed for rapid and sustainable water decontamination.

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.

Graphene-based nanocomposites and nanohybrids for the abatement of agro-industrial pollutants in aqueous environments

Incessant release of a large spectrum of agro-industrial pollutants into environmental matrices remains a serious concern due to their potential health risks to humans and aquatic animals. Existing remediation techniques are unable to remove these pollutants, necessitating the development of novel treatment approaches. Due to its unique structure, physicochemical properties, and broad application potential, graphene has attracted a lot of attention as a new type of two-dimensional nanostructure. Given its chemical stability, large surface area, electron mobility, superior thermal conductivity, and two-dimensional structure, tremendous research has been conducted on graphene and its derived composites for environmental remediation and pollution mitigation. Various methods for graphene functionalization have facilitated the development of different graphene derivatives such as graphene oxide (GO), functional reduced graphene oxide (frGO), and reduced graphene oxide (rGO) with novel attributes for multiple applications. This review provides a comprehensive read on the recent progress of multifunctional graphene-based nanocomposites and nanohybrids as a promising way of removing emerging contaminants from aqueous environments. First, a succinct overview of the fundamental structure, fabrication techniques, and features of graphene-based composites is presented. Following that, graphene and GO functionalization, i.e., covalent bonding, non-covalent, and elemental doping, are discussed. Finally, the environmental potentials of a plethora of graphene-based hybrid nanocomposites for the abatement of organic and inorganic contaminants are thoroughly covered.