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The dopants of sulfur, nitrogen, or both, serving as the active sites, into the graphitic framework of graphene is an efficient strategy to improve the electrochemical performance of electrochemical membrane filtration. However, the covalent bonds between the doped atoms and the substrate that form different functional groups have a significant role in the specific activity for pollutant degradation. Herein, we found that the singly doped heteroatom graphene (NG and SG) achieved superior removal efficiency of pollutants as compared with that of the double doped heteroatom graphene (SNG). Mechanism studies showed that the doped N of NG presented as graphitic N and substantially increased electron transfer, whereas the doped S of SG posed as -C-SOx-C- provided more adsorption sites to improve electrochemical performance. However, in the case of SNG, the co-doped S and N cannot form the efficient graphitic N and -C-SOx-C- for electrochemical degradation, resulting in a low degradation efficiency. Through the fundamental insights into the bonding of the doped heteroatom on graphene, this work furnishes further directives for the design of desirable heteroatom graphene for membrane filtration.

Sulfate ions (SO 4 2− ) are ubiquitous in aqueous environments and are generally considered to be inert due to their chemical stability. For the first time, we found that SO 4 2− can be activated into SO 4 2- -type radicals (e.g., SO 3 - , SO 5 - , SO 4 - ) in the presence of phenolic compounds under simulated or natural solar irradiation. In turn, the radicals promoted the transformation and mineralization of phenolic compounds compared to that in the absence of SO 4 2− with reaction rate constants ranging from 0.008 h −1 to 0.021 h −1 . In addition, the activation mechanisms of inert SO 4 2− in the photochemical transformation of phenolic compounds were elucidated. A hydrated electron (e aq − ) is first generated during the photolysis of phenolic compounds and is the most important step in the activation of SO 4 2− . Then, the e aq − reduces SO 4 2− to SO 3 2− , and SO 3 2− is further photochemical activated to become a reactive species (e.g., e aq − and SO 3 - ), which can evolve into strong oxidants (e.g., SO 5 - and SO 4 - ), via a series of radical chain reactions. These oxidants are responsible for the enhanced phenolic compound degradation. The photochemical activation of seemingly inert SO 4 2− sheds new light on studies on the transport, transformation and environmental impact of matter (e.g., phenolic compounds) in specific water environments and provides a novel strategy for the generation of SO 4 - and photochemical removal of phenolic pollutants.

The development of phosphate-selective adsorbents is essential for addressing eutrophication-associated problems and issues about lack of phosphorus resources. In this study an imine-functionalized adsorbent (N C@CMPS) was synthesized for this purpose; briefly, the commercially available precursor, chloromethylated polystyrene adsorbent (CMPS), was grafted with ethylenediamine (EDA) to yield the intermediate (EDA@CMPS), which was subsequently subjected to synchronous elimination to yield the product with imine functional group (N C@CMPS). Spectroscopic analyses and macroscopic experiments were then employed to evaluate the as-prepared adsorbent. As compared with CMPS, EDA@CMPS, and two commercial amine-based adsorbents, N C@CMPS exhibited much higher adsorption capacity and selectivity toward phosphate [P(V)]; such improvement can be primarily attributed to the imine group of N C@CMPS and their difference in the acid-base property. The imine group, acting as the recognition unit to distinguish P(V) from background anions, can solely serve as H-bond acceptors and exclusively interact with the protonated P(V) species (H2PO4- and HPO42-, H-bond donors) under neutral pH but not with the deprotonated anions such as Cl-, NO3–, and SO42-. the thermodynamic parameters confirm the spontaneous and slightly exothermic nature of P(V) adsorption on N C@CMPS, according with the domination of hydrogen bonding interactions. N C@CMPS also exhibited very broad applicability for P(V) adsorption over a wide range of pH (3 ∼ 10). Furthermore, the exhausted N C@CMPS can be efficiently regenerated with the combination of dilute NaOH solution and dilute HNO3 solution for repeated use.

Membrane distillation (MD) is a promising green technology that can harness waste or solar heat to treat water. Since such heat sources suffer from temporal variations, a complementary, efficient means is necessary. Induction heating is attractive in providing localized heating at the feed-membrane interface where the heat matters, but the typical conductive materials (e.g., metal, alloy) corrode readily in the high-salinity, high-temperature environment. In this work, a superior induction material was proposed, namely, reduced graphene oxides (rGO) coated onto a porous Nickel foam by Nafion (rGO/Nafion/Ni), which exhibited superior and sustained performance for membrane distillation. Results indicate that rGO/Nafion/Ni achieved up to 28.1% higher water flux (6.42 ± 0.36 Lm−2h−1) and 37.5% lower energy consumption (3.13 kWhL−1) compared to other carbon materials coated on Ni or the bare Ni foam. The mechanism underlying the enhanced MD performance was the higher absorption of the electromagnetic waves via multiple internal reflections and larger eddy currents generated by rGO, leading to higher temperatures at the feed-membrane interface that increased the driving force for distillation and thereby the energy efficiency of MD. Our work demonstrated that the induction heating of rGO has high potential for augmenting MD performance in water treatment. Economic Development Board (EDB) Ministry of Education (MOE) This work was supported by the Singapore GSK (GlaxoSmithKline) – EDB (Economic Development Board, Singapore) Trust Fund and the Singapore Ministry of Education Tier 1 Grant (2019-T1-002-065) .

Electrochemical technology attracts much research interest for the treatment of metal complexes, but most electrocatalysts are incapable of effectively degrading metal complexes, which generally have highly stable cages with five or six rings coordinating with metal ions. To address this, a bridging agent linking the catalysts and metal complexes can lower the energy barrier, and thus holds much promise to facilitate the removal of such pollutants. In this study, 1-pyrenesulfonic acid (PSA) functionalization of acidic nitrogen-doped graphene (ANG) is successfully synthesized and found to effectively remove metal complexes through electrochemical membrane filtration. Results indicate that PSA, interacting with Cu-EDTA via the strong ion exchange of super acidic sulfonic (−SO3H) groups, acts as a conductive “bridge” connecting the electrocatalyst and metal complexes to overcome the challenge with penetrating the “cage” structure of metal complexes. The pyrrolic nitrogen of ANG is found to be the active sites in the electrochemical process, with the intrinsic electrochemical activity realized by the bridging agent, namely, PSA. This study highlights the importance of compounds with sulfonyl groups in circumventing the stable “cage” of the metal complexes, and thereby paves the way for effective degradation of such pollutants. Ministry of Education (MOE) This work was supported by the Singapore GSK (GlaxoSmithKline) – EDB (Economic Development Board, Singapore) Trust Fund and Singapore Ministry of Education Tier 1 Grant (2019-T1-002-065).

The employment of electrochemical technology in membrane filtration promises high separation efficiency with minimal membrane fouling. Herein, we fabricated single cobalt atom and nitrogen atom codoped graphene (NG-Co) as a conductive membrane, and showed that it achieved 99.5% rejection at a small voltage of 2.5 V and exhibited excellent reusability. The turnover frequency of the single Co site was about 13.5 times larger than that of traditional Co-based nanocatalysts, because the single Co site served as the key electrochemical active site to degrade the organic pollutants, while the nitrogen-doped groups of graphene served as efficient binding sites for the immobilization of the single Co site to improve the intrinsic catalytic activity of the Co sites. This study has important implications for the design of graphene-based conductive membranes in the electrochemical remediation of wastewater. Economic Development Board (EDB) This work was supported by the Singapore GSK (GlaxoSmithKline) – EDB (Economic Development Board) Trust Fund.

Sulfate ions (SO

Iron is one of the most abundant elements in aquatic environments, and plays important roles in the fate and transport of environmental contaminants. Previous studies on the photochemical properties of Fe(III) species have largely focused on complexes formed between Fe(III) and environmental ligands such as natural organic matter (NOM) under UV irradiation, whereas the potentially important roles of hydrolysis species of Fe(III) in Fe(III)-mediated photo-transformation of environmental contaminants under solar light are not fully understood. In this study, the solar light-driven photochemical activities of hydrolysis species of Fe(III) were further explored, using a system containing only 0.5 mM Fe2(SO4)3 and bisphenol A. The important role of colloidal [Fe(OH)3]m, formed from the hydrolysis of Fe3+, as a core photochemical species of Fe(III) was proposed and verified. Interestingly, O2− , rather than OH, was identified (via electron spin resonance) as the key active radical responsible for the degradation of bisphenol A. We propose that unlike Fe(OH)2+, which under UV irradiation can yield OH (Fe(OH)2+ + hv → Fe2+ + OH), colloidal [Fe(OH)3]m produces O2− even in sunlight ([Fe(OH)3]m + 2O2 + hv → Fe(II) + 2O2− + H2O). The fact that Fe(III) can produce strong radicals in sunlight may have important environmental implications.

Aims. To establish a logistic regression (LR) prediction model for hepatotoxicity of Chinese herbal medicines (HMs) based on traditional Chinese medicine (TCM) theory and to provide a statistical basis for predicting hepatotoxicity of HMs.Methods. The correlations of hepatotoxic and nonhepatotoxic Chinese HMs with four properties, five flavors, and channel tropism were analyzed with chi-square test for two-way unordered categorical data. LR prediction model was established and the accuracy of the prediction by this model was evaluated.Results. The hepatotoxic and nonhepatotoxic Chinese HMs were related with four properties (p<0.05), and the coefficient was 0.178 (p<0.05); also they were related with five flavors (p<0.05), and the coefficient was 0.145 (p<0.05); they were not related with channel tropism (p>0.05). There were totally 12 variables from four properties and five flavors for the LR. Four variables, warm and neutral of the four properties and pungent and salty of five flavors, were selected to establish the LR prediction model, with the cutoff value being 0.204.Conclusions. Warm and neutral of the four properties and pungent and salty of five flavors were the variables to affect the hepatotoxicity. Based on such results, the established LR prediction model had some predictive power for hepatotoxicity of Chinese HMs.