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N-doped reduced graphene oxide quantum dots (N-rGQDs) have attracted more and more attention in efficient catalytic degradation of aqueous organic pollutants. However, the synthesis of N-rGQDs is generally a complex and high energy required process for the reduction and N-doping steps. In this study, a facile and green fabrication approach of N-rGQDs is established, based on a metal-free Fenton reaction without additional energy-input. The N structures of N-rGQDs play a significant role in the promotion of their catalytic performance. The N-rGQDs with relatively high percentage of aromatic nitrogen (NAr-rGQDs) perform excellent catalytic activities, with which the degradation efficiency of pollutant is enhanced by 25 times. Density functional theory (DFT) calculation also indicates aromatic nitrogen structures with electron-rich sites are prone to transfer electron, presenting a key role in the catalytic reaction. This metal-free Fenton process provides a green and cost-effective strategy for one-step fabrication of N-rGQDs with controllable features and potential environmental catalytic applications.

Photoinduced interfacial release of volatile organic compounds (VOCs) from surfactants receives emerging concerns. Here, we investigate the photoreaction of 1-nonanol (NOL) as a model surfactant at the air-water interface, especially for the important role of 1O2 in the formation of VOCs. The production of VOCs is real-time quantitated. The results indicate that the oxygen content apparently affects the total yields of VOCs during the photoreaction of interfacial NOL. The photoactivity of NOL is about 8 times higher under air than that under nitrogen, which is mainly attributed to the generation of 1O2. Additionally, the production of VOCs increased by about 4 times with the existence of the air-water interface. Quenching experiments of 1O2 also illustrate the contribution of 1O2 to VOC formation, which could reach more than 95% during photoirradiation of NOL. Furthermore, density functional theory calculations show that 1O2 generated via energy transfer of photosensitizers can abstract two hydrogen atoms from a fatty alcohol molecule. The energy barrier of this reaction is 72.3 kJ/mol, and its reaction rate coefficient is about 2.742 s-1 M-1. 1O2 significantly promotes photoinduced oxidation of fatty alcohols and VOC formation through hydrogen abstraction, which provides a new insight into the interfacial photoreaction.

A major limitation of vanadium oxides in aqueous Zn/V2O5 ion battery applications is that they suffer from strong coulombic ion–lattice interactions with divalent Zn2+. Correspondingly, vanadium oxides show the poor utilization of their electrochemically active surface areas and unsatisfactory structural stability. The Gibbs free energy of Zn2+ adsorption in the vicinity of oxygen vacancies can be reduced to a thermoneutral value, which suggests that the Zn2+ adsorption/desorption process on the oxygen-deficient oxide lattice is more reversible as compared to a less defective vanadium oxide. In this work, it is demonstrated that these problems can be significantly ameliorated via creating oxygen vacancies in vanadium oxide host materials. Specifically, for the first time, vanadium oxides with abundant oxygen defects (labeled Vo-V2O5) are fabricated via a new water-steam activation strategy. Such water-steam activation forms abundant oxygen defects, and the as-prepared materials show a 3.5-fold increase in the carrier density, together with larger electrochemically active surface areas compared to a less defective vanadium oxide. When used as a cathode material for aqueous zinc ion batteries, Vo-V2O5 exhibits a high specific capacity (335 mA h g−1 at 0.2 A g−1) and excellent cell stability (∼87.2% capacity retention after 3500 continuous charge/discharge cycles at 5.0 A g−1). Thus, this water-steam activation approach for disordered metal oxides yields highly competitive cathode materials, which may also aid in the future development of advanced materials in related energy fields.

A series of Ni/HZSM-5 and Ni/HIM-5 bi-functional catalysts were synthesized and applied to the aqueous-phase hydrodeoxygenation (HDO) of phenol. The Ni dispersibility and particle sizes were shown to be directly related to the porosity and crystal sizes of the parent zeolites, which further influenced the catalytic performances. The large pores and small crystal sizes of the parent zeolites were beneficial for dispersing Ni and forming small Ni particles, and the corresponding Ni/zeolite catalyst exhibited a higher phenol conversion and selectivity towards hydrocarbons. Importantly, the Ni/HIM-5 bi-functional catalyst exhibited a high activity (98.3%) and high selectivity for hydrocarbons (98.8%) when heated at 220°C for 1 h and is thus a new potential catalyst for the HDO of phenolics to form hydrocarbons in the aqueous phase.

Recovering nitrogen from source-separated urine is an important part of the sustainable nitrogen management. A novel bipolar membrane electrodialysis with membrane contactor (BMED-MC) process is demonstrated here for efficient recovery of ammonia from synthetic source-separated urine (∼3772 mg N L-1). In a BMED-MC process, electrically driven water dissociation in a bipolar membrane simultaneously increases the pH of the urine stream and produces an acid stream for ammonia stripping. With the increased pH of urine, ammonia transports across the gas-permeable membrane in the membrane contactor and is recovered by the acid stream as ammonium sulfate that can be directly used as fertilizer. Our results obtained using batch experiments demonstrate that the BMED-MC process can achieve 90% recovery. The average ammonia flux and the specific energy consumption can be regulated by varying the current density. At a current density of 20 mA cm-2, the energy required to achieve a 67.5% ammonia recovery in a 7 h batch mode is 92.8 MJ kg-1 N for a bench-scale system with one membrane stack and can approach 25.8 MJ kg-1 N for large-scale systems with multiple membrane stacks, with an average ammonia flux of 2.2 mol m-2 h-1. Modeling results show that a continuous BMED-MC process can achieve a 90% ammonia recovery with a lower energy consumption (i.e., 12.5 MJ kg-1 N). BMED-MC shows significant potential for ammonia recovery from source-separated urine as it is relatively energy-efficient and requires no external acid solution.

In this work, electrochemical impedance spectroscopy (EIS) was utilized to probe interfacial structures of antifouling anion exchange membranes (AEMs) with different modifying architectures fabrica...

Non-carbon materials in capacitive deionization (CDI) can help to enhance the capacity of removed ions. Here, we report for the first time the removal of chloride ions (Cl−) with a bismuth (Bi) anode when coupled with an activated carbon (AC) cathode in CDI. The effects of carbon black in the Bi electrode, applied voltage, electrode mass loading and initial concentration on Cl− removal are investigated. Moreover, its cycle performance is also tested. Results show that addition of carbon black to a Bi electrode (Bi@CB) significantly improves Cl− removal. The declining trend of Cl− concentration and appearance of peaks assigned to products of bismuth oxychloride (BiOCl) in XRD patterns confirm Cl− storage by the Bi electrode, which is enhanced with an increase in voltage. When coupled with AC in a fixed mass, increasing the Bi mass does not contribute to more Cl− removal. Although the cycle performance is not excellent (the attenuation rate is 74% after 10 cycles), its chloride removal capacity is ∼2–3 times the value of AC (e.g. 0.95 vs. 0.32 mmol gBi−1 at 1.2 V in 500 mg L−1 NaCl solution). Besides, the Bi–AC electrode pair in CDI is more suitable to remove Cl− from a solution with a Cl− concentration of below 600 mg L−1.

With two independent pore systems (intralayer sinusoidal channels and interlayer supercages) and external 12 membered-ring (MR) cups, H-MCM-49 was selected as the acidic support for upgrading palmi...

Metal-free catalysts such as N-doped nanocarbons are sustainable alternatives to metal-based catalysts for the degradation of persistent organic pollutants (POPs), but cost-efficient methods are required for their large-scale synthesis. In this study, a facile and scalable strategy was established for synthesizing layered N-doped nanocarbons via the pyrolysis of β-cyclodextrin (β-CD) and melamine in a N2 atmosphere. Compared with undoped pyrolyzed β-CD, N-doping led to a 30.3-fold enhancement in the pseudo-first-order rate constant for catalytic ozonation of oxalic acid (OA), and complete degradation of 50 mg/L OA was achieved in 45 min. Apart from the specific surface area boosting from 78.9 to 16.2 m2/g after N doping, the OA degradation results and material characterization also suggested that quaternary N was the main active site, which was further validated by density functional theory (DFT) simulations. DFT simulations also suggested that C atoms with high charge densities adjacent to N dopants exhibited considerable potential for the catalytic dissociation of ozone. Electron paramagnetic resonance (EPR), radical quenching, and in situ Raman studies indicated occurrence of surface oxidation pathway apart from the radical-based one. Ozone on the catalyst surface was decomposed into surface-adsorbed atomic oxygen (*Oad) and free peroxide (*O2 free). Both *Oad and OH, which was further evolved on the surface or in bulk solution, contributed to OA destruction. These insights into the catalytic ozonation mechanism on N-doped nanocarbons will advance their practical application to the catalytic degradation of organic pollutants.

Wet air oxidation (WAO) has an obvious advantage in treating wastewater with high concentration of organics, but harsh reaction conditions are required and the treatment efficiency has not reached a satisfactory level. Herein, we developed a low dosage of persulfate promoted WAO process (PWAO) to remove a model heterocyclic pollutant benzothiazole (BTH). The addition of persulfate remarkably enhanced the elimination of benzothiazole (BTH) and COD from water via degradation and polymerization. Under optimized operation condition (with 11.1 mM K2S2O8 addition into WAO), about 65.0% of BTH converted into microsphere polymers and more than 94.6% COD was eliminated from water after polymers separation. Electron paramagnetic resonance (EPR) analysis and quenching experiments revealed that OH was effectively generated in a wide range of reaction temperature and it played the key role in BTH degradation and polymerization, while SO4 − was detected at low temperature for its fast decomposition at high temperature. Quantum chemical calculation together with ultra-performance liquid chromatography with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS) analysis confirmed that the degradation and polymerization of BTH mainly started from the heterocyclic ring, followed by further oxidation or polymerization. Comparing with normal WAO process, the PWAO technology had an advantage in lower operating cost in removing per unit COD and carbon resource recycle, which indicates a promising prospect in treating wastewater with high concentration of heterocyclic compounds.

Polytetrafluoroethylene (PTFE) is an attractive membrane material due to its superior chemical resistance, thermal stability and strong hydrophobicity. However, PTFE hollow fiber membranes are challenging to produce by conventional technique due to the high solvent resistance and high melt viscosity of PTFE. In this study, novel PTFE hollow fiber membranes composed of pure PTFE nanofibers were firstly fabricated via a scalable and environment-friendly method based on emulsion electrospinning with a non-rotating collector and followed by a high-temperature sintering process. The effects of PTFE/PEO mass ratio and sintering temperature on the morphologies and properties of the resulting membranes were investigated. The prepared PTFE hollow fiber membrane shows the excellent characteristics combining the advantages of both electrospun nanofibers membrane and hollow fiber membrane, such as high porosity (more than 82%), self-supporting and superhydrophobicity. The membrane sintered at 380 °C present the highest mechanical strength, which shows the tensile strength, Young's modulus, strain at break of 30.5 Mpa, 53 Mpa, and 315%, respectively. The permeate flux of the prepared PTFE hollow fiber membrane is about 4.6–8.8 times as that of the commercial PTFE hollow fiber membranes, as well as is approximately 3.2–11.6 times higher than the date of the reported PTFE hollow fiber membranes. Additionally, the prepared membrane shows high and stable flux in long-term and rising salinity experiments, indicating it is very promising for membrane distillation (MD) application and even for the treatment of hyper-saline wastewater.

In this research, a methodology named whole-process pollution control (WPPC) is demonstrated that improves the effectiveness of process optimization. This methodology considers waste/emission treatment as a step of the whole production process with respect to the minimization of cost and environmental impact for the whole process. The following procedures are introduced in a WPPC process optimization: ① a material and energy flow investigation and optimization based on a systematic understanding of the distribution and physiochemical properties of potential pollutants; ② a process optimization to increase the utilization efficiency of different elements and minimize pollutant emissions; and ③ an evaluation to reveal the effectiveness of the optimization strategies. The production of ammonium paratungstate was chosen for the case study. Two factors of the different optimization schemes—namely the cost-effectiveness factor and the environmental impact indicator—were evaluated and compared. This research demonstrates that by considering the nature of potential pollutants, technological innovations, economic viability, environmental impacts, and regulation requirements, WPPC can efficiently optimize a metal production process. Keywords: Whole-process pollution control, Process optimization, Industrial pollution, Tungsten

The peroxone reaction between O3 and H2O2 has been deemed a promising technology to resolve the increasingly serious water pollution problem by virtue of the generation of superactive hydroxyl radicals (•OH), but it suffers greatly from an extremely limited reaction rate constant under acidic conditions (ca. less than 0.1 M-1 s-1 at pH 3). This article describes a heterogeneous catalyst composed of single Mn atoms anchored on graphitic carbon nitride, which effectively overcomes such a drawback by altering the reaction pathway and thus dramatically promotes •OH generation in acid solution. Combined experimental and theoretical studies demonstrate Mn-N4 as the catalytically active sites. A distinctive catalytic pathway involving HO2• formation by the activation of H2O2 is found, which gets rid of the restriction of HO2- as the essential initiator in the conventional peroxone reaction. This work offers a new pathway of using a low-cost and easily accessible single-atom catalyst (SAC) and could inspire more catalytic oxidation strategies.

Excessive ammonia nitrogen in wastewater seriously endangers ecological environment, so high-flux and selectivity membrane is urgently needed for ammonia removal using membrane absorption (MA). In this paper, a high-performance electrospun hollow fiber membrane was fabricated and solvent vapor welding treatment was adopted to enhance mechanical strength. The post-treatment membrane showed 103.8% higher in the Young’s modulus than the pristine membrane. High mechanical strength, porosity and hydrophobicity of the membrane make it superior in mass transfer and selectivity. The effects of membrane thickness, pH and temperature of feed solution on experimental overall mass transfer coefficient (KOE) and selectivity coefficient (SNH3/H2O (g)) were intensively investigated to examine the membrane performance in MA application. The results show KOE is 1.35 * 10−5 m s−1 and SNH3/H2O (g) is 7.58 when pH is 11, which are higher than that of commercial membrane. Moreover, the selectivity can be improved greatly from 6.91 to 9.74 by increasing the thickness of the hollow fiber membrane from 55 ± 5 μm to 115 ± 5 μm. The welded electrospun hollow fiber membrane demonstrates great potential for ammonia removal in MA application.

Photocatalytic ozonation is an attractive advanced oxidation process for wastewater treatment, but highly active catalysts with strong response to visible light are urgently needed to push forward its practical application. In this study, a hierarchical biomimetic monoclinic bismuth vanadate (BiVO4) with leaves morphology was synthesized by a hydrothermal method, and employed as catalyst for oxalic acid and penicillin degradation in photocatalytic ozonation. The results show that the organics degradation was more efficient using leaves shaped BiVO4 as catalyst than the bulk shaped one in photocatalytic ozonation and the synergy index is ranged from 2.8 to 3.3, indicating a superior positive synergistic effect between photocatalysis and ozonation. The higher activity of the leaves shaped BiVO4 was probably attributed to the distinctive biomimetic morphology and preferable band structure with more negative CB potential. Mechanism studies suggested that the main reactive species were h+ and OH for the degradation of persistent oxalic acid in photocatalytic ozonation. In addition, the effect of ozone concentration and inorganic ions and reusability of the material were also intensively investigated.

La-based perovskites are catalytically active owing to the oxygen vacancies, redox metal centers of B sites and surface hydroxyl groups. Nevertheless, the insights into these active centers on environmental catalysis are still insufficient. In this study, hierarchical mixed oxides perovskite microspheres were synthesized for catalytic ozonation over oxalic acid and benzotriazole. LaMn4Ox, with LaMnO3-δ as the dominant crystal phase, demonstrated superior catalytic activity to Mn2O3 and LaMnO3 synthesized from citric acid sol-gel method. Temperature-programmed desorption of NH3 (NH3-TPD) and pyridine-Fourier transform infrared spectroscopy (pyridine-FTIR) tests proved Lewis acid as the main acid type. Temperature-programmed reduction of H2 (H2-TPR), O2-TPD and X-ray photoelectron spectroscopy (XPS) analysis indicated the presence of oxygen vacancies and mixed valences of Mn in the crystal structure facilitated the catalytic process. Moreover, the content of oxygen vacancy was calculated by iodometric titration method. With the aid of theoretical calculations, oxygen vacancies were found to exhibit a strong affinity toward ozone adsorption, where ozone molecules spontaneously dissociated into reactive oxygen species (ROS) such as O2 − and 1O2. The B site of Mn facilitated ozone decomposition by extending the O O bond of ozone due to the electron transfer from Mn3+/Mn4+ redox cycle. In-situ EPR and quenching tests confirmed the contribution of O2 − and 1O2 in benzotriazole degradation along with OH. This study stepped further to unveil the ozone adsorption/decomposition and ROS generation on nanoscale perovskite-based composites.

It is challenging to selectively upgrade phenolic compounds to aromatics because of much weaker adsorption of hydroxyl compared to that of phenyl upon Ni catalysts. With 10% Ni loading in theory, three Ni catalysts with different Ni nanoparticle sizes were prepared with the wet impregnation method on SiO2 and Silicalite-1 and with the in situ encapsulation method (Silicalite-1). On the basis of the results, we proposed a general rule concerning temperature-dependent selectivity control on phenol hydroconversion over Ni catalysts. As well as benzene saturation in consecutive mode, hydrogenation of phenyl ring was more dramatically inhibited at elevated temperature via decreased adsorption of benzene rings than that of hydroxyl to selectively favor hydrogenolysis over hydrogenation in parallel mode. Among three Ni catalysts, Ni@Silicalite-1 with 3–5 nm Ni nanoparticle sizes encapsulated imposed the restricted adsorption conformation of phenol via end-up mode within channels of Silicalite-1 zeolite to furthe...

PM2.5-bound PAHs are ubiquitous in urban atmospheres and are characterized as carcinogenic, teratogenic and mutagenic upon inhalation. A total of 218 daily PM2.5 samples were collected during one year in the urban district of Beijing, China. Analysis showed that the annual mean concentration of total PAHs (TPAHs) was 66.2 ng/m3, with benzo(a)pyrene (BaP) accounting for 12.4%. High-molecular-weight (HMW, 4–6 rings) PAHs were the dominant components. Seasonal TPAH concentrations decreased in the order of heating season (156 ng/m3) > autumn (20.4 ng/m3) > spring (16.0 ng/m3) > summer (12.5 ng/m3) and were related to meteorological conditions and source emission intensity. The source-attributed mass contribution and source regions of three sources (i.e., (1) vehicle emissions; (2) coal combustion; and (3) petroleum volatilization, natural gas and biomass combustion) were identified by integrating the positive matrix factorization (PMF), potential source contribution function (PSCF) and conditional probability function (CPF). Vehicle emissions contributed the most mass (54.6%), followed by coal combustion (29.8%), on an annual basis. Combined with actual regional emissions, vehicle emissions were mainly derived from local sources, while coal combustion mainly came from regional transport from surrounding areas. Vehicle emissions and coal combustion have much higher mass contributions in the heating season. The source-attributed cancer risk was further evaluated based on source mass contribution and inhalation unit risk. Vehicle emissions contributed the largest risk (2.8 × 10−6, accounting for 71%) as a result of 30 years of exposure for local residents, exceeding the acceptable level (10−6). The heating season showed the most risk, especially in response to vehicle emissions and coal combustion. Overall, the source-attributed cancer risk was regarded as the better index for the development of a control strategy of PM2.5-bound PAHs for protecting residents. Based on this index, priority control sources in each season were identified to supply a more effective management solution.

This study investigated a combined low-thermal and CaO2 pretreatment to enhance the volatile fatty acid (VFA) production from waste activated sludge (WAS). The fermentative product was added to a sequencing batch reactor (SBR) as an external carbon source to enhance nitrogen removal. The results showed that the combined pretreatment improved WAS solubilization, releasing more biodegradable substrates, such as proteins and polysaccharides, from TB-EPS to LB-EPS and S-EPS. The maximum VFA production of 3529 ± 188 mg COD/L was obtained in the combined pretreatment (0.2 g CaO2/g VS + 70 °C for 60 min), which was 2.1 and 1.4-fold of that obtained from the sole low-thermal pretreatment and the control test, respectively. Consequently, when the fermentative liquid was added as an external denitrification carbon source, the effluent total nitrogen decreased to Class A of the discharge standard for pollutants in rural wastewater treatment plants in most areas of China.

Five negatively charged organic compounds with different structures, sodium methane sulfonate (MS), sodium benzene sulfonate (BS), sodium 6-hydroxynaphthalene-2-sulfonate (NSS), sodium dodecyl sulfate (SDS), and sodium dodecyl benzene sulfonate (SDBS), were used to examine the fouling of an anion exchange membrane (AEM) in electrodialysis (ED), to explore the effect of molecular characteristics on the fouling behavior on the AEM and changes in the surface and electrochemical properties of the AEM. Results indicated that the fouling degree of the AEM by the different organics followed the order: SDBS > SDS > NSS > BS > MS. SDBS and SDS formed a dense fouling layer on the surface of the AEM, which was the main factor in the much more severe membrane fouling, and completely restricted the transmembrane ion migration. The other three organics caused fouling of the AEM by adsorption on the surface and /or accumulation in the interlayer of the AEM, and exhibited almost no influence on the transmembrane ion migration. It was also concluded that the organics with benzene rings caused more severe fouling of the AEM due to the stronger affinity interaction and steric effect between the organics and the AEM compared with organics with aliphatic chains.

As an important raw material and intermediate of widely used antibiotics cefazolin and cefazedone, 2-mecapto-5-methyl-1,3,4-thiadizaole (MMTD) in antibiotic wastewater is hardly decyclized during wastewater treatment, posing great risk to the environment. This work proposed a green “coupling-oxidation” process to enhance ring-opening of MMTD during antibiotic wastewater treatment. In particular, the significant role of humic substances (HS) as pre-coupling reagent was emphasized. Real HS and different model HS, especially quinones, not only efficiently pre-coupled MMTD (>95%) but also promoted the MMTD removal by MnO2 (from 72.4% to 92.4%). Mass spectrometric analysis indicated that MMTD pre-coupled to HS would be oxidized with ring opening to environmental-friendly sulfonated HS, while direct oxidation of MMTD produced MMTD dimers or sulfonated MMTD that would not undergo ring opening. Theoretical calculations indicated that pre-coupling to HS enabled the ring-opening oxidation by increasing the nucleophilicity and decreasing ring-opening barrier of thiadiazole. Based on the density function theory (DFT), the global nucleophilicity index (Nu) followed the trend of HS-MMTD > MMTD dimer > sulfonated MMTD, while the ring-opening barrier followed the trend of HS-MMTD (274 kJ/mol)

Single-atom electrocatalysts have attracted board interest in the recent years as they combine the advantages of heterogeneous and homogeneous electrocatalysts. Nevertheless, single-atom electrocatalysts with single metal component cannot further satisfy the demand of catalytic properties. This work developed atomic Co/Ni dual sites in N-doped porous carbon Janus-like frameworks through epitaxial growth of cobalt based MOFs on nickel complexes. Structural characterization and atomic-scale transmission electron microscopy revealed the homogeneously dispersed active sites of Co-Ni alloy and single Co/Ni atoms. Electrochemical data strongly demonstrated the advantages of integrating Co-MOF and Ni complex with different topological structures to form a Janus-like structure. The resultant catalysts afforded onset potential of 0.93 V and half-wave potential of 0.84 V for oxygen reduction reaction in alkaline media, and 0.86 V and 0.73 V in acid media, which is better than single noble-metal-free catalysts, even close to commercial Pt/C. Besides, the catalysts also exhibited good oxygen evolution reaction performance (a current density of 10 mA cm−2 at a potential of 1.59 V) and overvoltage between ORR and OER is 0.78 V. Density functional theory calculations indicated the high electrocatalytic activities are originated from the synergetic effect of atomic Co/Ni-N-C bonds and microstructure of the prepared materials. This work paves a new avenue for the development of multiatomic electrocatalysts for energy conversion.

N-doped graphene has demonstrated exceptional activities in versatile metal-free catalytic processes. In this study, reduced graphene oxide (rGO) and N-doped rGO were synthesized by a facile approach via microwave reduction with a low energy input and short reaction time. The activities of the derived carbocatalysts were evaluated by catalytic ozonation of 4-nitrophenol (4-NP). Compared with thermally annealed rGOs in argon atmosphere, microwave treated rGO demonstrated a better performance in catalytic oxidation, and N-doping would further improve the catalytic activity. It is discovered that microwave irradiation not only gave rise to more edging sites and dangling bonds in rGO, making higher catalytic potentials for ozone decomposition than that from thermal annealing, but also resulted in a higher concentration of N dopants. XPS studies revealed that more graphitic N species were incorporated into the carbon basal plane during the microwave reduction processes. The reactive oxygen species (ROS) in 4-NP oxidation were evaluated and identified by liquid-phase electron spin resonance (ESR) and radical scavenging tests, which indicated the generation of O2 −, OH and 1O2 for 4-NP degradation. This study provides a facile protocol for fabricating advanced nanocarbon materials for green oxidation and enables new insights in catalytic ozonation with state-of-the-art carbocatalysis.

Recycling of spent lithium-ion batteries (LIBs) has attracted intensive attention owing to their potential environmental risk and the importance of the supply of critical metals. Sulfation roasting as a traditional technology is not considered environmentally friendly due to serious SOx emission. The usage of over-stoichiometric amounts of sodium salt results in high sodium content in the leaching solutions bringing about difficulties for the preparation of qualified lithium products. It is usually not easy to achieve high recovery selectivity of metals. Herein, we find it is possible to eliminate secondary emission and no sodium is included in the process of spent LIB (LiCoO2 as a case study) recycling if the transfer pathway of sulfur among different phases is well controlled. At the same time, high lithium recovery selectivity is achieved. The principles of green chemistry for substitution of chemicals with a low environmental impact and improving the atomic efficiency of sulfur are introduced during traditional sulfation roasting. A pretreatment step of aging with sulfuric acid at 393 K is introduced to form cobalt sulfate which in the following heat treatment step will further preferentially react with the remaining LiCoO2 until it is completely consumed. By controlling the amount of sulfuric acid, sulfur can be recirculated and recycled thoroughly in the form of SO42−, instead of SOx emission and the atomic efficiency of sulfur can be highly improved. After leaching with water, the concentration of Li+ in the leachate reaches 19.82 g L−1; 99.3% lithium and 98.7% cobalt were recuperated as Li2CO3 and Co3O4 with a purity of 99.89% and 99.95%, respectively. Our findings propose an environmentally benign and easily implemented strategy for selective recycling of spent LIBs. The fundamentals provide inspiration for separation and extraction fields such as mining and recycling of complex systems composed of multiple metals.

A novel surface modified anion exchange membrane (AEM) was prepared by electrodeposition of graphene oxide (GO) and polydopamine (PDA) coating, aiming at improving antifouling performance and stability. The AEM was firstly modified by electrodeposition of GO and then immersed into the dopamine solution to form a thin PDA layer. The effects of GO and PDA composite modification were investigated by various analytical techniques and electrodialysis application. The GO@PDA-modified AEM (GO@PDA-M) exhibited highly hydrophilic and negatively charged. In addition, the introduction of PDA coating helped to construct a smoother and denser composite modifying layer composed of GO and PDA, and reduced the roughness of membrane surface. Depending on these properties, the GO@PDA-modified AEM showed significant antifouling ability without compromising the desalination performance. After being fouled by 150 mg/L sodium dodecyl benzene sulfonate (SDBS) for 4 h, the desalination rate of GO@PDA-M increased by 39.3% compared to pristine membrane, while for PDA-modified membrane (PDA-M) and GO-modified membrane (GO-M) were 5.7% and 18.2% respectively. Moreover, it still maintained antifouling ability after 20 h of continuous operation. The stability of GO@PDA-M was immensely improved compared with the GO-M due to the introduction of PDA layer.

Photocatalytic ozonation has great potential in wastewater treatment. However, the role of ozone and the contribution of photogenerated hole in this process have not been fully understood. Here three WO3 materials are synthesized and used as model catalysts in visible-light photocatalytic ozonation for the mineralization of pharmaceutical pollutants. A dual role of ozone in this process has been confirmed: (i) direct oxidation of the pollutant till formation of refractory intermediates, (ii) efficient trapping of photoelectron that cannot be captured by O2. The latter is crucial because it not only induces the O3--mediated pathway for hydroxyl radical (OH) formation but also separates the hole which has proven to be capable of oxidizing water into OH. Evidenced by photoluminescence results, the intrinsic charge separation ability of WO3 in photocatalytic ozonation is no more as important as that in photocatalysis with O2. Finally, this process is more applicable under acidic condition. This work contributes to a better understanding of the significance of ozone in WO3 photocatalytic ozonation and provides us an insight into the mechanism of photocatalytic ozonation.

Arsenic (As) is a well-known carcinogenic substance whose biological toxicity in soils and plants depends on its concentration and chemical forms. Silicon (Si) generally can alleviate biotic and abiotic stresses, including As stress. However, its effects vary depending on As chemical form, plant species and other factors. A pot experiment was performed to investigate the effects of Si addition on the content and forms of As in red soil and its uptake, transport and speciation in Panax notoginseng. The results showed that additions of 25 and 75 mg kg-1 of Si both significantly decreased the concentrations of water-soluble As and exchangeable As in soil and therefore decreased the bioavailability of soil As. However, the As uptake by Panax notoginseng (PN) was increased, which resulted in increases in As concentration by 18.5% and 2.3% in roots and by 56.7% and 58.3% in shoots, respectively, when compared with the control. Arsenate (As(V)) was the dominant As species in all the treatment soils (99.8-100%), whereas arsenite (As(III)) was prevalent in plant roots (75.2-92.4%), shoots (74.1-87.9%) and leaves (73.9-84.3%). Si addition (25 and 75 mg kg-1) significantly increased As(III) concentration in roots by 167.5% and 83.3%, respectively. Monomethylarsonic acid (MMA) was the only detected methylated As but at low concentrations (0.01-0.29 mg kg-1) and only in PN leaves. Si addition (25 and 75 mg kg-1) significantly increased the copy number of the arsenite methyltransferase (arsM) gene by 31.0% and 47.2% but did not increase the methylated As species content in PN leaves. The detected copy number of the arsM gene did not represent the capacity of soil to methylate As, and the sources of MMA in leaves need to be explored in further research.

SiC is a newly developed photocatalyst, but it is often used together with a co-catalyst rather than solely for its relatively low activity. Here we reported the high activity of a commercial SiC in a photocatalysis and ozone combined process (photocatalytic ozonation). The commercial SiC showed very weak activity in photocatalysis of oxalic acid (OA) and para-hydroxybenzoic acid (PHBA) degradation, and its performance in catalytic ozonation was also not satisfied. However, the organics degradation and mineralization rates dramatically increased in the SiC photocatalytic ozonation. The different operation parameters were optimized, and the main reactive radicals in this process and its generation pathways were studied. It was found that photo-generated electron reduction of ozone and oxygen are the main pathways to produce hydroxyl radical, which was responsible to the high oxidizing ability of this process.

In this paper, a sustainable process to recover valuable metals from spent lithium ion batteries (LIBs) in sulfuric acid using ammonium chloride as reductant was proposed and studied. Being easily reused, ammonium chloride is found to be efficient and posing minor environmental impacts during the overall process. By investigating the effects of a wide range of parameters, e.g., H2SO4 concentration, NH4Cl concentration, temperature, leaching time, and solid-to-liquid mass ratio, the leaching behaviour of Li, Ni, Co, and Mn was systematically investigated. And the leaching mechanism and kinetics were determined by mineralogically characterization of residues at various reaction times and by fitting using different kinetic models. With this research, it is possible to provide a win-win solution to improve the recycling effectiveness of spent LIBs by using waste salt that is easily reused as the reductant.

Anode graphite was recovered from a spent lithium ion battery (LIB) and reutilized as a carbon precursor to obtain graphene-based materials. Characterization results revealed that impurities were removed from the obtained graphite powder by cleansing processes. The as-synthesized reduced graphene oxide (rGO) from the purified graphite (LIB-rGO) demonstrated excellent catalytic ozonation activity against organic pollutants removal. To probe potential catalytic active sites, LIB-rGOs with different defective levels but similar oxygen contents were synthesized. Catalytic ozonation tests revealed that a higher defective level resulted in a greater catalytic activity. Density functional theory (DFT) calculation further demonstrated that ozone molecules could spontaneously decompose into active oxygen species on graphene structural vacancies and edges, which consolidated the role of defective structure in catalytic ozonation activity. Meanwhile, we discovered the pollutant-structure-dependent behavior of dominant reactive oxygen species (ROS) with the aid of radical scavenging tests and electron paramagnetic resonance (EPR) spectra. For phenolic pollutants vulnerable to direct ozone attacking, superoxide radicals (O2 −) and singlet oxygen (1O2) were found to be responsible ROS, whereas hydroxyl radicals ( OH) were identified as the principle ROS for aliphatic organic pollutants destruction. This study not only put forward a possible way for reutilization of waste LIB anode, but also stepped further for investigating the catalytic ozonation mechanism towards the graphene-based materials including the active sites and the generation of ROS.

In this work, phenol and oxalic acid (OA) degradation in an ozone and photocatalysis integrated process was intensively conducted with Fe3 +/TiO2 catalyst. The ferrioxalate complex formed between Fe3 + and oxalate accelerated the removal of OA in the ozonation, photolysis and photocatalytic ozonation process, for its high reactivity with ozone and UV. Phenol was degraded in ozonation and photolysis with limited TOC removal rates, but much higher TOC removal was achieved in photocatalytic ozonation due to the generation of OH. The sequence of UV light and ozone in the sequential process also influences the TOC removal, and ozone is very powerful to oxidize intermediates catechol and hydroquinone to maleic acid. Fenton or photo-Fenton reactions only played a small part in Fe3 +/TiO2 catalyzed processes, because Fe3 + was greatly reduced but not regenerated in many cases. The synergetic effect was found to be highly related with the property of the target pollutants. Fe3 +/TiO2 catalyzed system showed the highest ability to destroy organics, but the TiO2 catalyzed system showed little higher synergy.

This study demonstrates the feasibility of layer-by-layer (LbL) assembly of poly(sodium 4-styrene sulfonate) (PSS)/poly(diallyldimethylammonium chloride) (PDADMAC) polyelectrolyte multilayers on an anion exchange membrane (AEM). The electrodeposition of (PSS/PDADMAC)n multilayers on the AEM with a PSS layer as the top surface endows the surface with negative charges and increases the surface hydrophilicity, leading to a significantly improved antifouling performance in electrodialysis (ED) to an organic foulant, i.e., sodium dodecyl sulfate (SDS). The desalination rate during 180 min increased from 24.0% for the pristine AEM to 30.5% for a 5.5 PSS/PDADMAC bilayers modified AEM with 75 mg/L SDS in the initial solution. A SDS fouling layer was formed at the dilute side of the pristine AEM, causing a sharp increase of electrical resistance and restricting the ion transport through the AEM completely. Electrodeposition of 5.5 PSS/PDADMAC bilayers prevented the formation of the SDS fouling layer at the surface of AEM, which reduced the sharp increase of electrical resistance and kept the ion transport through the AEM unaffected. With 100 or 150 mg/L SDS in the initial solution, the desalination rate during 180 min increased from 24.1% or 15.4% for the pristine AEM to 28.4% or 26.8% for the 5.5 PSS/PDADMAC bilayers modified AEM.

This study introduces a doughnut-like, highly porous g-C3N4 photocatalyst fabricated using a double bubble templating method which employs two synergistic gas-generating agents (H2O2 and NH4Cl). The concurrent thermolysis of H2O2 and NH4Cl synergistically enhances g-C3N4 exfoliation and nanopore production, as the released O2 and NH3 undergo violent exothermic reactions during g-C3N4 growth. The resultant g-C3N4 (H2O2-NH4Cl-g-C3N4) exhibited 8.9 times higher specific surface area compared to bulk g-C3N4, and 3.2–6.4 times as large as those synthesized using individual NH4Cl or H2O2. The photocatalytic activities of these g-C3N4 samples were found to linearly correlate with their valance band (VB) maximum potentials; for example, H2O2-NH4Cl-g-C3N4 possessed a VB maximum down-shifted by 0.34 eV, and consequently exhibited 7.1 times larger photocatalytic hydroquinone degradation rate than the bulk g-C3N4. Electrochemical analysis and trapping experiments collectively suggested that the VB downshift caused more efficient separation of charge carriers, and subsequent enhancement in positive hole-dominated photocatalytic oxidation of hydroquinone.

The heterogeneous anion exchange membranes (AEMs) were modified by electrodeposition of graphene oxide (GO) under different conditions. The physicochemical properties of GO-modified membranes were characterized systemically to obtain the optimized conditions for the electrodeposition of GO on the surface of AEMs. The results indicated that the contact angle and zeta potential of the modified AEMs decreased when increasing the concentration of GO from 0.05 g/L to 0.1 g/L. The higher concentration of NaCl, as the supporting electrolyte, could hinder the electrodeposition of GO on the AEMs for the competitive migration between the GO and Cl− ions. The increase of current density had a positive effect on properties of GO-modified membranes in the range of 1–5 mA/cm2. Compared with the pristine AEM, all the GO-modified AEMs exhibited smoother surface, higher hydrophilicity and negative zeta potential. It was also found that the GO modifying layer did not increase electrical resistance and had only a negligible effect on the desalination performance of AEMs. In the fouling experiments with sodium dodecyl benzene sulfonate (SDBS) as the model foulant, the GO-modified AEMs exhibited improved fouling resistance to SDBS.

Three kinds of graphitic carbon nitride materials (bulk, porous and nanosheet g-C3N4) were composited with a multiwall carbon nanotube (MWCNT) by a hydrothermal method, and the obtained b-C3N4/CNT, p-C3N4/CNT and n-C3N4/CNT materials were used in the electrodes for electro-peroxone process. It was found that the n-C3N4/CNT composite exhibited the highest efficiency in oxalate degradation, though it performed the worst in the oxygen-reduction reaction for H2O2 production. The n-C3N4/CNT composite exhibited higher activity than CNT and other composites in catalytic ozonation experiments, due to the higher pyrrolic-N content modified on the CNT surface and higher surface area. It also has higher electron transfer ability, which benefited to the electro-reduction of both O2 and O3. The result confirmed that catalytic ozonation process was an important means to enhance the degradation efficiency in the electro-peroxone process, besides peroxone process and O3-electrolysis.

Ion exchange process is an alternative technique for removal of heavy metal ions from industrial wastewater. The main aim of this paper is to evaluate the performance of different ion exchange resins in removing Cr(VI) from wastewater. The effects of resin types and dosage, initial pH were examined systemically. The results showed that the performance of different resins had obvious difference for the removal of the Cr(VI) ions, in which the type of functional groups of the resin was the main factor. The SEM images indicated that the micro-morphology of resins before and after adsorption of the Cr(VI) presented a little difference. The EDS analysis showed that the adsorbed Cr(VI) was uniformly distributed at the surface of the resins with formation of oxygen-containing groups. The adsorption isotherms and kinetics of Cr(VI) by the different resins are also discussed.

An appropriate co-catalyst can significantly promote the photocatalytic efficacy, but this has been seldom studied in the visible-light photocatalysis combined with ozone, namely photocatalytic ozonation. In this work, a dendritic bismuth vanadium tetraoxide (BiVO4) material composited with highly dispersed MnOx nanoparticles was synthesized, and its catalytic activity is 86.6% higher than bare BiVO4 in a visible light and ozone combined process. Catalytic ozonation experiments, ultraviolet- visible (UV-Vis) diffuse reflectance spectra and photoluminescence spectra jointly indicate that MnOx plays a triple role in this process. MnOx strengthens the light adsorption and promotes the charge separation on the composite material, and it also shows good activity in catalytic ozonation. The key reactive species in this process is $OH, and various pathways for its generation in this process is proposed. This work provides a new direction of catalyst preparation and pushes forward the application of photocatalytic ozonation in water treatment.

The physicochemical and structural properties of the AMX (homogeneous AEM), AMA (semi-homogeneous AEM) and HAEM (heterogeneous AEM) were characterized systematically to examine their effects on membrane fouling from sodium dodecyl sulfate (SDS) in electrodialysis. Results demonstrated that the fouling of three AEMs was closely related to their membrane structure, and the denser membrane structure caused more SDS accumulated on the membrane surface to make the severer membrane fouling. The existence of SDS in the dilute solution caused the desalination rate of AMX, AMA and HAEM decreased by 42.3%, 15.3% and 9.2%, respectively. Different fouling layer was formed on the surface of AMX and AMA except HAEM, which was demonstrated firstly by element mapping of membrane cross-section. Electrochemical impedance spectroscopy (EIS) suggested the ionic migration through the fouled AMX was restricted completely, different from the transmembrane migration of partial ions through the fouled AMA and HAEM. Compared with the fouled AMA and HAEM, the performance of the fouled AMX caused by SDS was more difficult to be recovered due to its denser membrane structure.

The electro-peroxone (E-P) process normally exhibits low efficiency in organic degradation in acid solution due to the limited rate constant of the reaction between O3 and H2O2 (peroxone reaction). In this paper, a C3N4–Mn/CNT composite material was synthetized and characterized with XRD, FTIR, SEM and XPS. With the function of the C3N4–Mn/CNT catalyst, the substrate oxalic acid (OA) was completely degraded in the E-P process within 30 min at pH 3, while only 15% degradation could be achieved after 60 min without the catalyst. The comparison of different reaction systems using the C3N4–Mn/CNT catalyst confirmed that the catalyst promoted the peroxone reaction, rather than the catalytic ozonation or electro-Fenton like reaction. Correlating the XRD and XPS analysis with the degradation data using the C3N4–Mn/CNT catalyst, we deduced that Mn coordinated with nitrogen was the active site for the peroxone reaction. Furthermore, the catalyst showed good chemical and catalytic stability in five cycles of the E-P process for OA degradation.

We developed a kind of macropore- and micropore-dominated carbon (HPAC) derived from poly(vinyl alcohol) and polyvinylpyrrolidone for electric double-layer capacitive (EDLC) applications, e.g., supercapacitors and capacitive deionization (CDI). By comparing the EDLC performance of HPAC with those of ordered mesoporous carbon (OMC) and commercial activated carbon (AC), we evaluated the pore size effects. Cyclic voltammetry (CV) was employed for static and flowing CDI processes to identify the disparities between supercapacitors and CDI. HPAC exhibits a specific capacitance of 309 F g–1 at a specific current of 0.5 A g–1 (6 M KOH) in a three-electrode half-cell and has a salt removal capacity of 16.3 mg g–1 (1.2 V, 500 mg L–1 NaCl), which is better than those of AC and OMC. Cycling tests of HPAC in supercapacitors and CDI show excellent stability. The properties of HPAC, fine, hydrophilic, macroporous, and microporous, endow HPAC with the promising possibility of use in supercapacitors and capacitive deioni...

Reactive oxygen species (ROS) are key oxidants for the degradation of organic pollutants in sunlight-driven photocatalytic water treatment, but their interaction with the photocatalyst is easily ignored and, hence, is comparatively poorly understood. Here we show that graphitic carbon nitride (C3N4, a famous visible-light-responsive photocatalyst) is chemically stable toward ozone and superoxide radical; in contrast, hydroxyl radical (•OH) can tear the heptazine unit directly from C3N4 to form cyameluric acid and further release nitrates into the aqueous environment. The ratios of released nitrogen from nanosheet-structured C3N4 and bulk C3N4 that finally exists in the form of NO3– reach 9.5 and 6.8 mol % in initially ultrapure water, respectively, after 10 h treatment by solar photocatalytic ozonation, which can rapidly generate abundant •OH to attack C3N4. On a positive note, in the presence of organic pollutants which compete against C3N4 for •OH, the C3N4 decomposition has been completely or partially...

The recent thrust in utilizing microbial electrolysis cell (MEC) has led to accelerated attention in environmental decontamination. One key factor that governs this process is electron transfer efficiency. In this study, neutral red (NR) is involved as electron transfer mediator to investigate whether it could contribute to MEC performance. Afterwards, influence of electrode material selection on NR addition system was also studied. The results indicate MEC with NR shows better electrochemistry activity, which means sulfate-reducing bacteria (SRB) can response to electron transfer mediator NR. Further study reveals graphite felt triggers a better synergy with NR to facilitate electron utilization efficiency of the system subsequently maintains bacteria metabolic activity for a longer time. Sulfate removal in this reactor reaches 79.0% with electron utilization efficiency of 54.2%. To explore the mechanism, electrode bioelectrochemical property, microorganism activity and community were investigated. Electrode morphology analysis confirms graphite felt affords abundant space for the growth of electroactive microorganisms especially SRB and promotes electron exchange through cooperating with NR, which fits in with electrochemical impedance spectroscopy (EIS) analysis. High-throughput sequencing analysis confirms improved reactor can fortify the population dominant of SRB in the community which greatly raises electron utilization efficiency of SRB.

With the increasing consumption of lithium ion batteries (LIBs) in electric and electronic products, the recycling of spent LIBs has drawn significant attention due to their high potential of environmental impacts and waste of valuable resources. Among different types of spent LIBs, the difficulties for recycling spent LiFePO4 batteries rest on their relatively low extraction efficiency and recycling selectivity in which secondary waste is frequently generated. In this research, mechanochemical activation was developed to selectively recycle Fe and Li from cathode scrap of spent LiFePO4 batteries. By mechanochemical activation pretreatment and the diluted H3PO4 leaching solution, the leaching efficiency of Fe and Li can be significantly improved to be 97.67% and 94.29%, respectively. To understand the Fe and Li extraction process and the mechanochemical activation mechanisms, the effects of various parameters during Fe and Li recovery were comprehensively investigated, including activation time, cathode p...

Microbial electrolysis cells (MEC), coupled with sulfate-reducing bacteria (SRB), was used to degrade sulfate-rich wastewater that is deficient in electron donors. However, because of the impact of electric double layers (EDLs), salt crystals formed on the electrode, thereby potentially retarding the continuity of sulfate removal during the whole operation. Here, an improved MEC reactor using intermittent electric field was established. It works better in sulfate removal for a longer period, which was higher than the conventional MEC reactor by 2.18-fold after 10 days. Observation on the activity of lactic dehydrogenase (LDH) and ATP revealed that the formation of salt crystals on the electrode led to plasmatorrhexis. Conversely, improved reactor contributed to extracellular substances production and prevented the salt crystal formation, which was conducive to biofilm formation as further verified by detection through SEM. Electrochemical impedance spectroscopy tests showed that the cathodic microorganisms accelerated electron transfer whereas the salt crystals increased the charge transfer resistance. High-throughput sequencing analysis illustrated that improved reactor could maintain the competitiveness of SRB in the microbial community for a longer period. Moreover, the improved reactor resulted in high species diversity, thereby showing the significant resistance of the microorganisms to arduous environments.

The effective V(V) and Cr(VI) separation is very difficult due to their similarity in physiochemical properties. In this research, almost completely separation of V(V) and Cr(VI) with primary amine N1923 was firstly demonstrated by employing multistage countercurrent extraction (MCE) with annular centrifugal contactors (ACCs). The optimum operation conditions of single-stage extraction with ACC were determined by systematic experiments, and best conditions of the rotor speed, the flow rate and the flow ratio of organic phase to aqueous phase were obtained. The loaded-organic phase can be reused for extraction process after stripping with ammonia/sodium hydroxide. Vanadium, in the leaching/aqueous solution with the initial pH of 6.1, was reached to extraction equilibrium by three-stage countercurrent extraction with ACCs. V(V) and Cr(VI) were separated through 21 stages of countercurrent extraction with ACCs. 95.1% of vanadium and almost none of chromium were extracted, with the separation factor approaching infinity. Through the mechanism of hydrogen bond association and different species of two metals in the leaching/aqueous solution, an in-depth analysis to correlate the results obtained and the chemical reactions with ACCs has been made in order to establish a firm conclusion with aim of the guidance in industrial application.

In this study, the fouling of anion exchange membrane (AEM) in electrodialysis was investigated using sodium dodecyl sulfate (SDS) as a model foulant, and the effect of membrane cleaning on the properties of the fouled AEMs was examined further. Results showed that the severer fouling of AEM was caused by the higher concentration of SDS in the feed solution, and a dense SDS fouling layer was formed on the AEM surface, causing the obvious increase of electrical resistance and the deterioration of desalination performance. Electrochemical impedance spectroscopy (EIS) indicated the SDS fouling layer on the AEM could hinder, even restrict completely the transmembrane migration of the ions, especially at high concentration of SDS. The cleaning experiment showed the cleaning effect of ultra-pure water was similar to that of HCl solution, but was better than that of NaOH solution, in which most SDS on the fouled AEM could be removed effectively by cleaned in ultra-pure water. EIS of the fouled AEMs before and after cleaned indicated that the remaining SDS on the cleaned AEM had almost no influence on the transmembrane migration of the ions through AEM.

Coking wastewater (CWW) has long been a serious challenge for anaerobic treatment due to its high concentrations of phenolics and nitrogen-containing heterocyclic compounds (NHCs). Herein, we proposed and validated a new strategy of using zero-valent iron (ZVI) to strengthen the anaerobic treatment of CWW. Results showed that COD removal efficiencies was increased by 9.5–13.7% with the assistance of ZVI. GC-MS analysis indicated that the removal of phenolics and NHCs was improved, and the intermediate 2(1H)-Quinolinone of quinoline degradation was further removed by ZVI addition. High-throughput sequencing showed that phenolics and NHCs degraders, such as Levilinea and Sedimentibacter were significantly enriched, and the predicted gene abundance of xenobiotic degradation and its downstream metabolic pathways was also increased by ZVI. Network and redundancy analysis indicated that the decreased oxidation-reduction potential (ORP) by ZVI was the main driver for microbial community succession. This study provided an alternative strategy for strengthening CWW anaerobic treatment.

Metal-free mesoporous graphitic frameworks with built-in nanotubes (CPGs) were synthesized via facile co-pyrolysis of cyclodextrin and a cobalt salt with subsequent acid pickling to remove the embedded metal species. Due to the high graphitic degree and built-in few-layer nanotubes, the as-synthesized carbonaceous materials possess a higher catalytic ozonation activity than that of the state-of-the-art carbon nanotubes (CNTs) and LaMnO3 perovskite catalysts for the destruction of different aqueous contaminants. For recalcitrant oxalic acid removal, 50 mg L−1 oxalic acid was completely degraded in 20 min. Compared with other nanocarbons, the as-synthesized materials also demonstrated robust structural stability and reusability. The electron paramagnetic resonance (EPR) and selective radical quenching tests revealed that the destruction of the aqueous organics predominantly relied on surface-adsorbed complexes (O*ad and O2*) from activated ozone molecules. Owing to the occurrence of this surface oxidation pathway, the compatibility of the CPGs/O3 system was significantly enhanced for treatment of real wastewater, where the inorganic anions and organic natural organic matter would inhibit radical oxidation as radical scavengers. Furthermore, by employing organics with different ionization potentials (IPs) as the target pollutants, the CPGs/O3 system was discovered to obtain a high oxidation potential.

Lithium carbonate (Li2CO3), one of the most important lithium compounds, is usually prepared from lithium-containing solution. The lithium recovery rate and the purity of Li2CO3 are highly dependent on the lithium concentration. In order to get a high lithium recovery rate, high concentrated lithium-containing solution is required, while the purity of Li2CO3 can be low remaining a significant amount of impurities. Usually, it is not possible to obtain high purity Li2CO3 by single-step precipitation with a relatively high lithium recovery rate especially from a low concentrated lithium-containing solution. In this research, ultrasound is introduced to increase lithium recovery rate and prepare industrial grade Li2CO3. The research found that ultrasound can significantly reduce the polymerization of Li2CO3 crystal particles and promote dissociation of impurity ions. At the same time, ultrasound accelerates the nucleation process of Li2CO3 and boosts lithium recovery rate because of cavitation. The different parameters during the Li2CO3 precipitation process were systematically discussed. Under the optimized conditions, the lithium recovery rate can be increased by 12% with a global lithium recovery rate of 97.4%. Li2CO3 with a purity higher than industrial grade can be obtained by one-step precipitation. It demonstrates a potential pathway for effective lithium recovery from low concentrated lithium-containing solution and preparation of industrial grade Li2CO3. ispartof: ULTRASONICS SONOCHEMISTRY vol:52 pages:484-492 ispartof: location:Netherlands status: published

Three polyphenol-polyamine co-deposition systems containing different polyphenols (catechol (CA), gallic acid (GA) and tannic acid (TA)) and Polyethyleneimine (PEI) were established and used to construct adhesive layer on the surface of anion exchange membranes (AEMs). And graphene oxide (GO) was introduced into co-depositions to construct an antifouling modifying layer. The modified AEMs were characterized and applied in electrodialysis for antifouling experiments. The results showed that the TA-PEI-M with a large depositing amount exhibited more hydrophilic surface than those of CA-PEI-M and GA-PEI-M, but still low value in the negative charge density. The introduction of GO increased the negative charge density of membrane surface and endowed AEMs with enhanced antifouling ability significantly. Furthermore, GO-TA-PEI-M could maintain surface properties and antifouling performance after immersing in NaOH solutions, indicating good alkaline-stability. It was attributed to that the abundant phenolic groups in TA played a vital role in the formation of co-deposition layer. The abundant phenolic groups in TA could provide stronger adhesion and multiple reactive sites to generate more stable covalent structures with PEI. In addition, the hydrogel products produced by the electrostatic interaction of TA and PEI helped increase the depositing amount. This work proposed a novel approach to fabricate surface-modified antifouling AEMs with alkaline stability by polyphenol-polyamine co-deposition.