Site-2 Protease Slr1821 Regulates Carbon/Nitrogen Homeostasis during Ammonium Stress Acclimation in Cyanobacterium Synechocystis sp. PCC 6803.

Excess ammonium imposes toxicity and stress response in cyanobacteria. How cyanobacteria acclimate to NH4+ stress is so far poorly understood. Here, Synechocystis sp. PCC6803 S2P homolog Slr1821 was identified as the essential regulator through physiological characterization and transcriptomic analysis of its knockout mutant. The proper expression of 60% and 67% of the NH4+ activated and repressed genes, respectively, were actually Slr1821-dependent since they were abolished or reversed in ∆slr1821. Synechocystis 6803 suppressed nitrogen uptake and assimilation, ammonium integration and mobilization of other nitrogen sources upon NH4+ stress. Opposite regulation on genes for assimilation of nitrogen and carbon, such as repression of nitrogen regulatory protein PII, PII interactive protein PirC and activation of carbon acquisition regulator RcbR, demonstrated that Synechocystis 6803 coordinated regulation to maintain carbon/nitrogen homeostasis under increasing nitrogen, while functional Slr1821 was indispensable for most of this coordinated regulation. Additionally, slr1821 knockout disrupted the proper response of regulators and transporters in the ammonium-specific stimulon, and resulted in defective photosynthesis as well as compromised translational and transcriptional machinery. These results provide new insight into the coordinated regulation of nutritional fluctuation and the functional characterization of S2Ps. They also provide new targets for bioengineering cyanobacteria in bioremediation and improving ammonium tolerance in crop plants.

Functionalizing TiO2 with graphene oxide for enhancing photocatalytic degradation of methylene blue (MB) in contaminated wastewater.

Methylene blue is a refractory pollutant commonly present in textile wastewater. This study tests the feasibility of TiO2/graphene oxide (GO) composite in enhancing photocatalytic degradation of MB in synthetic wastewater with respect to scientific and engineering aspects. To enhance its removal, we vary the composition of the composite based on the TiO2 weight. Under UV-vis irradiation, the effects of photocatalyst's dose, pH, and reaction time on MB removal by the composites are evaluated under optimum conditions, while any changes in their physico-chemical properties before and after treatment are analyzed by using TEM, SEM, XRD, FTIR and BET. The photodegradation pathways of the target pollutant by the composite and its removal mechanisms are also elaborated. It is found that the same composite with a 1:2 wt ratio of GO/TiO2 has the largest surface area of 104.51 m2/g. Under optimum reactions (0.2 g/L of dose, pH 10, and 5 mg/L of pollutant's concentration), an almost complete MB removal could be attained within 4 h. This result is higher than that of the TiO2 alone (30%) under the same conditions. Since the treated effluents could meet the strict discharge standard limit of ≤0.2 µg/L set by China's regulation, subsequent biological treatments are unnecessary for completing biodegradation of remaining oxidation by-products in the wastewater effluents.

Removal of acetaminophen from synthetic wastewater in a fixed-bed column adsorption using low-cost coconut shell waste pretreated with NaOH, HNO3, ozone, and/or chitosan.

Acetaminophen (Ace) is a trace pollutant widely found in sewage treatment plant (STP) wastewater. We test the feasibility of coconut shell waste, a low cost adsorbent from coconut industry, for removing Ace from synthetic solution in a fixed-bed column adsorption. To enhance its performance, the surface of granular activated carbon (GAC) was pre-treated with NaOH, HNO3, ozone, and/or chitosan respectively. The results show that the chemical modification of the GAC's surface with various chemicals has enhanced its Ace removal during the column operations. Among the modified adsorbents, the ozone-treated GAC stands out for the highest Ace adsorption capacity (38.2 mg/g) under the following conditions: 40 mg/L of Ace concentration, 2 mL/min of flow rate, 45 cm of bed depth. Both the Thomas and the Yoon-Nelson models are applicable to simulate the experimental results of the column operations with their adsorption capacities: ozone-treated GAC (20.88 mg/g) > chitosan-coated GAC (16.67 mg/g) > HNO3-treated GAC (11.09 mg/g) > NaOH-treated GAC (7.57 mg/g) > as-received GAC (2.84 mg/g). This suggests that the ozone-treated GAC is promising and suitable for Ace removal in a fixed-bed reactor.

Deciphering visible light photoreductive conversion of CO2 to formic acid and methanol using waste prepared material.

As gradual increases in atmospheric CO2 and depletion of fossil fuels have raised considerable public concern in recent decades, utilizing the unlimited solar energy to convert CO2 to fuels (e.g., formic acid and methanol) apparently could simultaneously resolve these issues for sustainable development. However, due to the complicated characteristics of CO2 reduction, the mechanism has yet to be disclosed. To clarify the postulated pathway as mentioned in the literature, the technique of electron paramagnetic resonance (ESR) was implemented herein to confirm the mechanism and related pathways of CO2 reduction under visible light using graphene-TiO2 as catalyst. The findings indicated that CO(-•) radicals, as the main intermediates, were first detected herein to react with several hydrogen ions and electrons for the formation of CH3OH. For example, the generation of CO(-•) radicals is possibly the vital rate-controlling step for conversion of CO2 to methanol as hypothesized elsewhere. The kinetics behind the proposed mechanism was also determined in this study. The mechanism and kinetics could provide the in-depth understanding to the pathway of CO2 reduction and disclose system optimization of maximal conversion for further application.

Preparation of 13X from Waste Quartz and Photocatalytic Reaction of Methyl Orange on TiO2/ZSM-5, 13X and Y-Zeolite.

TiO2 photocatalytic reactions not only remove a variety of organic pollutants via complete mineralization, but also destroy the bacterial cell wall and cell membrane, thus playing an important bactericidal role. However, the post-filtration procedures to separate nanometer-levels of TiO2 and the gradual inactivity of photocatalyst during continuous use are defects that limit its application. In this case, we propose loading TiO2 on zeolite for easy separation and 13X is considered as a promising one. In our study, 13X-zeolite was prepared by a hydrothermal method and the source of Si was extracted from waste quartz sand. For comparison, commercial zeolite with different microporous and mesoporous diameters (ZSM-5 and Y-zeolites) were also used as TiO2 supports. The pore size of the three kinds of zeolites are as follows: Y-zeolite > 13X > ZSM-5. Different TiO2 loading content over ZSM-5, 13X and Y-zeolite were prepared by the sol-gel method. XRD, FTIR, BET, UV-vis, TGA and SEM were used for investigation of material characteristics. In addition, the efficiencies of mineralization and photodegradation were studied in this paper. The effects of the loading ratio of TiO2 over zeolites, initial pH, and concentration on photocatalytic performance are investigated. The relationship between best loading content of TiO2 and pore size of the zeolite was studied. The possible roles of the ZSM-5, 13X-zeolites and Y-zeolites support on the reactions and the possible mechanisms of effects were also explored. The best loading content of TiO2 over ZSM-5, 13X and Y-zeolite was found to be 50 wt%, 12.5 wt% and 7 wt%, respectively. The optimum pH condition is 3 with TiO2 over ZSM-5, 13X-zeolites and Y-zeolites. The results showed that the degradation and mineralization efficiency of 12.5 wt%GT13X (TiO2 over 13X) after 90 min irradiation reached 57.9% and 22.0%, which was better than that of 7 wt%GTYZ (TiO2 over Y-zeolites) while much lower than that of 50 wt%GTZ (TiO2 over ZSM-5). The materials were recycled four times while the degradation was remained at a higher level.

Study on the degradation of the dye wastewater with polyaniline on titanium nanotubes.

Polyaniline/titanium nanotube composite (PANI/TNT) photocatalysts were prepared by 'in situ'chemical oxidative polymerization of aniline. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform IR spectra (FTIR) and UV-Visible spectroscopy measurements were used to characterize the obtained photocatalysts, and their photocatalytic activities were investigated by degrading Reactive Green19 (RG19) under near visible light irradiation (lambda = 365 nm). The content of PANI, pH, dosage, and concentration of RG19 were also investigated. The results showed that the inner diameter of the PANI/TNT was 6 nm and that the PANI did not change the structure of the TNT. The PANI was coated on the surface of the TNT. The light response of the PANI/TNT was extended to the visible-light regions. Among the six different kinds of photocatalysts, the 1.17 wt% PANI/TNT had the best performance in treating 10 ppm RG19. The best pH is 3 for the largely protonated surface of the composite at low pH. The adsorption amount was increased as the dosage increased. The decolonization efficiency decreased with increasing initial RG19 concentration. The performance of the photocatalyst in decomposing RG19 was stable after 5 time cycles.

High-Tcsuperconductivity in doped molecular superconductors ofK4B8-xMxH32(M = C, N) under high pressure.

Stabilized and metallic light elements hydrides have provided a potential route to achieve the goal of room-temperature superconductors at moderate or ambient pressures. Here, we have performed systematic DFT theoretical calculations to examine the effects of different light elements C and N atoms doped in cubic K4B8H32hydrides on the superconductivity at low pressures. As a result of various atoms substituting, we have found that metallic K4B_{8-x}MxH32(M = C, N) hydrides are dynamically stable at 50 GPa, band structures and density of states (DOS) indicate that sizeableTccorrelates with a high B-H DOS at the Fermi level. With the increasing of B atoms in K4B_{8-x}MxH32hydrides, the DOS values at Fermi level have been improved due to the delocalized electrons in B-H bonds, which result in strong electron-phonon coupling (EPC) interaction and increase theTcfrom 19.04 to 77.07 K for KC2H8and KB2H8at 50 GPa. The NH4unit in stable K4B7NH32hydrides has weakened the EPC and led to lowTcvalue of 21.47 K. Our results suggest the light elements hydrides KB2H8and K4B7CH32could estimate highTcvalues at 50 GPa, and the boron hydrides would be potential candidates to design or modulate hydrides superconductors with highTcat moderate or ambient pressures.

Photocatalytic degradation of malathion by TiO2 and Pt-TiO2 nanotube photocatalyst and kinetic study.

Photocatalytic degradation of malathion, is investigated using Titanium Nanotubes (TNT) and Pt modified TNT (Pt-TNT) photocatalyst in an aqueous solution under 365 nm UV lamp irradiation. The TNT photocatalyst is prepared on pretreated strong alkaline solution via the hydrothermal method. The Pt-TNT was prepared by light deposition. The variations in morphology, formation mechanism, phase structure, and pore structure of TNT and Pt-TNT are characterized using UV-Vis, transmission electron microscopy (TEM), and N2 adsorption/desorption isotherm analyzer, respectively. The effect of the initial malathion concentration, reaction temperature, catalyst loading, solution pH value, irradiation time and Pt loading are studied and the optimized values are obtained. Moreover, the photodegradation performance and kinetics of malathion onto TNT and Pt-TNT are also examined with the aid of model analysis by kinetic data. The results show that under acid conditions, the performance of photocatalysts for treating malathion is high. The time of complete degradation increases with an increase in the initial malathion concentration. The degradation rate decreases with increasing initial malathion concentration. The degradation efficiency can reach 100% under acid conditions for any initial malathion concentration when the reaction time is 70 min. In addition, experimental decoloration kinetics data follow the pseudo-first-order reaction model.

Partial quaternization promoted metal-organic frameworks for efficient photocatalytic removal of chromium(VI).

A one-step strategy is applied to partially quaternize the ligand of UiO-66-NH2, and the resultant UiO-66-N(CH3)3+ showed greatly improved photocatalytic performance for Cr(VI) reduction, with the apparent reaction rate constant k increasing by 8.3 times. This strategy could be used to effectively promote the performance of other MOFs-NH2, demonstrating general applicability.

Competitive Analysis of Rumen and Hindgut Microbiota Composition and Fermentation Function in Diarrheic and Non-Diarrheic Postpartum Dairy Cows.

Postpartum dairy cows can develop nutritional diarrhea when their diet is abruptly changed for milk production. However, it is unclear whether nutritional diarrhea develops as a result of gut acidosis and/or dysbiosis. This study aimed to uncover changes in the gastrointestinal microbiota and its fermentation parameters in response to nutritional diarrhea in postpartum dairy cows. Rumen and fecal samples were collected from twenty-four postpartum cows fed with the same diet but with different fecal scores: the low-fecal-score (LFS: diarrheic) group and high-fecal-score (HFS: non-diarrheic) group. A microbiota difference was only observed for fecal microbiota, with the relative abundance of Defluviitaleaceae_UCG-011 and Lachnospiraceae_UCG-001 tending (p < 0.10) to be higher in HFS cows compared to LFS cows, and Frisingicoccus were only detected in HFS cows. The fecal bacterial community in LFS cows had higher robustness (p < 0.05) compared to that in HFS cows, and also had lower negative cohesion (less competitive behaviors) and higher positive cohesion (more cooperative behaviors) (p < 0.05) compared that in to HFS cows. Lower total volatile fatty acids and higher ammonia nitrogen (p < 0.05) were observed in LFS cows' feces compared to HFS cows. The observed shift in fecal bacterial composition, community networks, and metabolites suggests that hindgut dysbiosis could be related to nutritional diarrhea in postpartum cows.

Research on Sustainable Development of Competitive Sports in China Based on PSR and DEA Model.

From the 2008 Beijing Olympic Games to the 2022 Beijing Winter Olympics, the sustainable development of competitive sports has become more and more popular in China. Therefore, for the sustainable development of China's competitive sports, first, the logical relationship of "pressure-state-response" is adopted to select the index system, covering the elements of the economy, society, policy, and so on. Principal component analysis and entropy weight method are used to construct the comprehensive evaluation model of the sustainable development of competitive sports. Second, through the coupling coordination method to study the coordinated development of China's competitive sports and economic society, and then from the perspective of the obstacle factor diagnosis method to determine the obstacles to the sustainable development of China's competitive sports system. Finally, the DEA model is used to predict the development level of competitive sports in China's provinces in the next 10-20 years. The research shows that the overall development level of competitive sports in China is good, but there are certain differences among different regions. Meanwhile, from the forecast results, the development level of competitive sports in Hainan, Shanxi, Anhui, Jiangxi, Inner Mongolia, Gansu, and Ningxia may be greatly improved in the future. Based on the above research conclusions, this study puts forward some suggestions to give full play to the joint and synergistic development effect among different regions, reasonably draw lessons from the advanced experience of competitive sports development at home and abroad, and scientifically construct the comprehensive development system of competitive sports. At the same time, the research of this study provides some reference value for the sustainable development of China's competitive sports and the coordinated development of China's competitive sports and economic society.

The short-term and long-term effects of Fe(II) on the performance of anammox granules.

Fe(II) is one of the commonly used additives in wastewater treatment and proved to be beneficial for promoting microbial activity. In this study, the effects of Fe(II) on the specific anammox activity (SAA) and reactor performance were proved to be concentration-dependent. In the short-term experiment, low concentration of Fe(II) (5-80 mg/L) significantly enhanced the SAA, while high concentration of Fe(II) (120-300 mg/L) inhibited the SAA. It was confirmed that anammox can be domesticated after long-term exposure to low Fe(II) concentration, and the SAA could be further enhanced by higher Fe(II) concentration in the following phases. In addition, as an important factor for anammox granulation and maintaining the SAA, the extracellular polymeric substance (EPS) was also affected by Fe(II) addition. In spite of the effects on SAA and EPS, Fe(II) was proved to be the key factor that enhances the N2 O emission via abiotic pathway in the anammox reactor. PRACTITIONER POINTS: Low Fe(II) concentrations enhanced SAA, while high concentrations inhibited SAA. Long-term acclimatization by Fe(II) improved the tolerance of anammox to Fe(II). Fe(II) affects the amount and constituent of EPS and the performance of anammox granules. Accumulation of Fe(II) in the AAFEB reactor promoted the N2 O emission.

Applicability of TiO2(B) nanosheets@hydrochar composites for adsorption of tetracycline (TC) from contaminated water.

We test the feasibility of TiO2(B)@carbon composites as adsorbents, derived from wheat straws, for tetracycline (TC) adsorption from aqueous solutions. Hydrochar (HC), biochar (BC), and hydrochar-derived pyrolysis char (HDPC) are synthesized hydrothermally from the waste and then functionalized with TiO2(B), named as 'Composite-1', 'Composite-2', and 'Composite-3', respectively. A higher loading of TiO2(B) into the HC was also synthesized for comparison, named as 'Composite-4'. To compare their physico-chemical changes before and after surface modification, the composites are characterized using FESEM-EDS, XRD, BET, FRTEM, and FTIR. The effects of H2O2 addition on TC removal are investigated. Adsorption kinetics and isotherms of TC removal are studied, while TC adsorption mechanisms are elaborated. We found that the Composite-4 has the highest TC removal (93%) at pH 7, 1 g/L of dose, and 4 h of reaction time at 50 mg/L of TC after adding H2O2 (10 mM). The TC adsorption capacities of the Composite-1 and Composite-4 are 40.65 and 49.26 mg/g, respectively. The TC removal by the Composite-1 follows the pseudo-second order. Overall, this suggests that converting the wheat straw into HC and then functionalizing its surface with TiO2(B) as a composite has added values to the waste as an adsorbent for wastewater treatment.

Assessment of the bioaccessibility of polycyclic aromatic hydrocarbons in topsoils from different urban functional areas using an in vitro gastrointestinal test.

Profiles of the bioaccessibility of soil polycyclic aromatic hydrocarbons (PAHs) in different urban functional areas of Xiamen City, Fujian, China were investigated. A physiologically based in vitro test was used to evaluate the bioaccessibility of total and individual PAHs. There was no obvious correlation between total concentrations of PAHs and bioaccessibility during the gastrointestinal phase for the soils from different functional areas. Results showed that the bioaccessibility variation in the gastrointestinal phase (ranging from 14.6% to 63.2%) was significantly higher than that in the gastric phase (ranging from 4.9% to 21.8%). The bioaccessibility in the gastrointestinal phase was not only determined by soil organic materials but also directly related to physical and chemical properties of individual PAHs, except for two-ring PAHs. Increasing soil organic material content or decreasing ring numbers of PAHs could result in the decrease of PAH bioaccessibility. The total PAH bioaccessibility was largely contributed by individual PAHs with relatively high molecular weight.

Photocatalytic Degradation of Oxytetracycline by Photosensitive Materials and Toxicological Analysis by Caenorhabditis elegans.

This study explored a facile one-step hydrothermal method of preparing a high-performance photocatalyst, namely, graphene-TiO2, for oxytetracycline (OTC) removal. The nanocomposites were characterized by Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy, UV-Vis diffuse reflectance spectroscopy and X-ray diffraction (XRD). The photocatalytic properties of different graphene loading types and various OTC initial concentrations, temperatures, and initial pH values were investigated. Results showed that the material with 10% graphene content exhibited the best performance and removal efficiency (beyond 99%) of OTC within 180 min at 35 °C and pH 5.5. The effects of different reactive oxygen species scavengers on photodegradation and the contributions were evaluated, and a possible reaction mechanism was proposed. Caenorhabditis elegans was used for toxicity testing during the entire degradation process and achieved a favorable result.

Preparation of Graphene Oxide Modified Rice Husk for Cr(VI) Removal.

The objective of this paper is to study the removal of Cr(VI) in aqueous solution by using a new graphene oxide-coated rice husk biochar composite (GO-RHB). GO-RHB is a synthetic material having a porous structure with lots of oxygen-containing functional groups and a large surface area that provide effective adsorption sites. Experiments showed that GO-RHB had higher adsorption capacity under acidic than under alkaline conditions. At pH of 2, GO-RHB has the maximum adsorption capacity(48.8 mg g-1). Equilibrium data obtained by fitting with the Langmuir and Freundlich models indicate that the reaction process was monolayer adsorption. The adsorption of Cr(VI) followed the pseudo-second-order kinetic model that illustrates chemical adsorption. Intraparticlediffusion studies further revealed that film diffusion was taking place. Moreover, the results of thermodynamics showed that the adsorption process was endothermic and spontaneous in nature. The removal mechanism of Cr(VI) was also explained in detail. The prepared adsorbent is highly efficient and might be useful than many other conventional adsorbent used for the removal of Cr(VI) from wastewater.

Process optimization of anammox-driven hydroxyapatite crystallization for simultaneous nitrogen removal and phosphorus recovery.

Based on the requirements for advanced treatment and resource recovery of nitrogen and phosphorus pollutants in wastewater, the coupled anammox and hydroxyapatite crystallization (anammox-HAP) process was studied with an aim of achieving high efficiency and low energy consumption during simultaneous nitrogen and phosphorus removal. In the long-term experiments and batch tests, the effects of substrate conditions (nitrogen and phosphorus load, calcium concentration, etc.) on the nitrogen removal and phosphorus recovery efficiencies were investigated. The granular structure and crystal properties were analyzed together with microscopic characterization methods, and the formation mechanism of coupled anammox-HAP granules was verified. Based on these experiments, a theoretical model and technical method for realizing the coupled process were established, and a reference for practical engineering application was provided.

Applicability of BaTiO3/graphene oxide (GO) composite for enhanced photodegradation of methylene blue (MB) in synthetic wastewater under UV-vis irradiation.

Methylene blue (MB) is a dye pollutant commonly present in textile wastewater. We investigate and critically evaluate the applicability of BaTiO3/GO composite for photodegradation of MB in synthetic wastewater under UV-vis irradiation. To enhance its performance, the BaTiO3/GO composite is varied based on the BaTiO3 weight. To compare and evaluate any changes in their morphologies and crystalline structures before and after treatment, BET (Brunauer-Emmett-Teller), XRD (X-ray diffraction), FTIR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy) and TEM (transmission electron microscopy) tests are conducted, while the effects of reaction time, pH, dose of photocatalyst and initial MB concentration on its photodegradation by the composite are also investigated under identical conditions. The degradation pathways and removal mechanisms of MB by the BaTiO3/GO are elaborated. It is evident from this study that the BaTiO3/GO composite is promising for MB photodegradation through ·OH. Under optimized conditions (0.5 g/L of dose, pH 9.0, and 5 mg/L of MB concentration), the composite with 1:2 dose ratio of BaTiO3/GO has the highest MB degradation rate (95%) after 3 h of UV vis irradiation. However, its treated effluents still could not comply with the discharge standard limit of less than 0.2 mg/L imposed by national environmental legislation. This suggests that additional biological treatments are still required to deal with the remaining oxidation by-products of MB, still present in the wastewater samples such as 3,7-bis (dimethyl-amino)-10H-phenothiazine 5-oxide.

Heavy metal contamination in western Xiamen Bay sediments and its vicinity, China.

Concentrations of selected heavy metals (Cu, Pb, Zn, Cd, Cr, Ni and Fe) in surface sediments from nine sites in western Xiamen Bay and its vicinity were studied in order to understand current metal contamination due to urbanization and economic development in Xiamen, China. The sediment samples were collected in December 2004 and July 2005 respectively in order to examine temporal variations. In this study, we found that heavy metal concentrations in surface sediments sampled in the western Xiamen Bay and adjacent Maluan Bay and Yuandang Lagoon varied from 19 to 97mg kg(-1) for Cu, 45 to 60mg kg(-1) for Pb, 65 to 223mg kg(-1) for Zn, 0.11 to 1.01mg kg(-1) for Cd, 37 to 134mg kg(-1) for Cr, 25 to 65mg kg(-1) for Ni and 3.08 to 4.81% for Fe. Although all metal concentrations in sediments meets Chinese National Standard Criteria for Marine Sediment Quality, both metal enrichment factors (EF) and geoaccumulation index (I(geo)) show that Pb contamination exists in the entire study area and contamination of other metals are also present in some locations depending on the sources, of which sewage outlets and commercial ports are the main sources of contaminants to the area. This study shows that using the sediment quality standard criteria only to assess sediments cannot properly reflect sediment contamination. A multiple approaches should be applied for the sediment quality assessment.

Chemical reactive features of novel amino acids intercalated layered double hydroxides in As(III) and As(V) adsorption.

Layered double hydroxides (LDHs) intercalated with amino acids such as methionine (Met) were synthesized as new adsorbents to remediate arsenic-polluted water. This Zn2Al-Met-LDHs, identified with the formula of Zn0.7Al0.3(OH)2(Met)0.3·0.32H2O, has good thermal stability. Adsorption experiments with Zn2Al-Met-LDHs showed that the residual arsenic in solution could be reduced below the regulation limit, and this adsorption process fitted Langmuir isotherm and the pseudo-second-order kinetics well. A remarkably high removal efficiency and the maximum adsorption capacity for As(III) were achieved, 96.7% and 94.1 mg/g, respectively, at 298 K. The desorption efficiency of As(III) from the arsenic-saturated Zn2Al-Met-LDHs (<8.7%), far less than that of As(V), promises a specific and reliable uptake of As(III) in sorts of solutions. More importantly, a complete and in-depth spectra analysis through FTIR, XPS and NMR was conducted to explain the excellent performance of Zn2Al-Met-LDHs in arsenic removal. Herein, two special chemical reactions were proposed as the dominant mechanisms, i.e., hydrogen bonding between the carboxyl group of the host Met and the hydroxyl group of As(III) or As(V), and the formation of a chelate ring between the guest As(III) and the S, N bidentate ligands of the intercalated Met in the LDHs.