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A new adsorbing material for crystal violet (CV) and methylene blue (MB) dye removal, fly ash and bentonite-supported microscale zero-valent iron (FB-mZVI), was synthesized by using iron-ore tailings (IOT) as the iron source. Palm kernel shells (PKSs) were used to reduce the iron oxide of the IOT to Feo. A statistical orthogonal method was used to evaluate the factors determining the adsorbent synthesis. It was found that the important factors were the mass ratio of the fly ash, bentonite, IOT, and PKSs as well as the synthesis time, temperature, and heating rate. Optimum mass ratio of the fly ash, bentonite, PKSs, and IOT was found to be 2:2:1:1, and optimum synthesis temperature, time, and heating rate were found to be 800°C, 10 min, and 10°C/min, respectively. An FB-mZVI adsorbent was used to remove the CV and MB from aqueous solutions. Removal efficiency for CV was much higher than that for MB. UV, XRD, and FTIR analyses revealed that the adsorption mechanisms for removal of CV were different from those for MB. Adsorption process was well described by the pseudo-second-order kinetic model, and Langmuir isotherm model better represented the adsorption isotherm data. [ABSTRACT FROM AUTHOR]

Delamination of montmorillonite (Na-MMT) is an outstanding property of the dispersed MMT particles. Na-MMT particles delaminated in water and isopropanol under shear forces have been studied in this work. The difference in the intercalation and delamination of Na-MMT by water and isopropanol was studied by molecule dynamic simulation and experiment. Molecule dynamic simulation was carried out on Material Studio (MS) 8.0. The experimental study was performed on a Na-MMT through the measurements of Stokes size, optical size, scanning electron microscope, atomic force microscope, and dynamic molecule simulation. The results demonstrated that under the effect of interlayer hydration, the Na+that resides near the siloxane surface was moved to the middle plane of interlayer space, and the interlayer spacing was opened 1.38A. Compared with the interlayer hydration, the interlayer spacing was increased only a little (0.32A) treated by isopropanol; meanwhile, the interlayer sheets were joined together by isopropanol molecule. Because of that the effect of water and isopropanol in the interlayer of Na-MMT was totally different, the Na-MMT particles were indeed delaminated into plate-like super fine particles in water instead of in isopropanol, and delamination was closely correlated with shear force only if hydration was occurred in the interlayer. [ABSTRACT FROM AUTHOR]

The adsorption of Zn(II) in aqueous solutions on graphene oxide (GO) prepared from low-purity of natural amorphous graphite has been studied in this work. The study was performed through the measurements of Zeta potential, atomic force microscope, Fourier transform infrared spectrum and X-ray photoelectron spectroscopy. The results indicated that the adsorption followed the Langmuir model with the maximum Zn(II) adsorption capacity of 73 mg/g at pH 7.0. In addition, the adsorption was well described by the pseudo-second-order kinetics model. The mechanism of the Zn(II) adsorption on GO was mainly attributed to chemical adsorption through complexation reaction between Zn(II) and hydroxyl or carboxyl groups on the GO sheets, while the electrostatic interaction also contribute to the whole interaction. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The preparation and characterization of nanoscale zero-valent iron-loaded porous sepiolite, as well as its application in the decolorization of methylene blue in aqueous solution, have been studied in this work through the measurements of field emission scanning electron microscope with energy dispersive spectrometry, x-ray photoelectron spectrometry, Fourier transform infrared spectroscopy and specific surface area. The results showed that nanoscale zero-valent iron particles were successfully loaded on the surface and interior pores of sepiolite through physical adsorption. It was revealed that the decoloration capacity of methylene blue on nanoscale zero-valent iron-loaded porous sepiolite in water was comparable to that of nanoscale zero-valent iron, and nine times higher than that of natural sepiolite. This indicates that porous sepiolite was a good supporter for the loading of nanoscale zero-valent iron and nanoscale zero-valent iron-loaded sepiolite was a good decolorant because of its high decoloration efficiency and easy separation. [ABSTRACT FROM AUTHOR]

In this work, a novel method to determine the point of zero net proton charge (PZNPC) of colloidal kaolinite in aqueous solutions was presented through the measurement of zeta potential of the particles in various concentrations of NaCl solution and the mathematic regression of the zeta potential versus pH curves. This method is based on the observation that there are two common intersection points (CIP) in the two curves of zeta potential versus pH of colloidal kaolinite with a low and a high NaCl concentration. The observation might be attributed to that NaCl would compress the electric double layer of kaolinite particles and affect the efficiency of the protonation/deprotonation of the HD-faces. The experimental result showed that the PZNPC of kaolinite is 5.37. [ABSTRACT FROM AUTHOR]

In this work the morphology of agglomerates formed in the hydrophobic agglomeration of molybdenite fines in aqueous suspensions has been studied by measuring fractal dimension with image analysis method. The results have shown that the morphology closely correlated with the mechanical conditioning in the hydrophobic agglomeration. The higher the stirring speed and the longer the stirring, the more spherical and more compact the agglomerates. Also, kerosene addition could make the agglomerates to be more spherical and compact. [ABSTRACT FROM AUTHOR]

Hydrophobic agglomeration is originated from the hydrophobic attraction between particles, which is essentially different from electrolyte coagulation and polymer flocculation. It is applied to mineral processing in floc-flotation process to improve the recovery of mineral fines. In this paper, the applications of this phenomenon in mineral fines were summarized, including the origin of hydrophobic agglomeration, the main factors affect hydrophobic agglomeration (particle hydrophobicity, shear rate and duration, nonpolar oil and tank geometry), as well as hydrophobic agglomeration based separation processes (carrier flotation and floc-flotation). [ABSTRACT FROM AUTHOR]

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The synthesis and characterization of silver (Ag) nanorods through the Turkevich method in aqueous sodium dodecylsulfate (SDS) solutions have been studied in this work. The results have shown that the shape of Ag nanoparticles closely correlated with SDS concentration in the synthesis process. With high SDS concentrations, the majority of the synthesized Ag nanoparticles appeared in the form of nanorods; with low SDS concentrations, the Ag nanoparticles were spherical. This observation might be attributed to that the Ag nanoparticles grew up in SDS micelles and precipitated in the same shape of the micelles, because surfactant micelles were of cylinders in high concentrations and of spheres in low concentrations. [ABSTRACT FROM PUBLISHER]

[Display omitted] • Several dewatering strategies are proposed based on the properties of MMTNS. • Anisotropy of MMTNS edge contributes to crosslinking agglomeration and dewatering. • TEPA not only acts as a cross-linker, but as a switch to tuning viscosity. • Calcification modification is induced by CaCl 2 via ion exchange property of MMTNS. Two-dimensional montmorillonite nanosheet (MMTNS) is desirable building block for fabricating multifunctional materials as due to its extraordinary properties. In practical applications, however, the concentration of MMTNS prepared by exfoliation is normally too low to be used for material assembling. The general thermal-concentration method is effective, however, it can be time-consuming and require a lot of energy. In this case, the remarkable dispersion stability of MMTNS is worth noting. Herein, the extraordinary dispersion stability of MMTNS derived from electrostatic and hydration repulsion was firstly revealed by molecular dynamics (MD) simulation, which caused the poor dewatering of MMTNS. Further, based on the surface and structural chemistry of MMTNS, a series of strategies, involving charge and cross-linked structure regulation on the edge surface, as well as electrical double-layer modulation and calcification modification based on the electrolytes, were proposed to inhibit the dispersion and enhance the aggregation of MMTNS. Intriguingly, a novel chemical, Tetraethylenepentamine (TEPA) was applied in the dewatering of MMTNS. The TEPA not only act as a cross-linker to bond with MMTNS into an easy-to-dewatering 3D network structure, but also act as a switch for effortless viscosity tuning. Meanwhile, the dual function of electrolytes for electrical double layer compression and calcification modification of MMTNS was investigated by DLVO theory and structural analyses. This work offers explicit directions for improving the dewatering performance of MMTNS to meet the requirements of practical implementation. [ABSTRACT FROM AUTHOR]

The electrosorption of As(III) in aqueous solutions by using activated carbon (AC) as the electrode was studied in this work. This study was performed through the measurements of adsorption and desorption, Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and X-ray photoelectron spectra (XPS). Three parameters, applied voltage, solution pH and initial As(III) concentration, on the electrosoprtion of As(III) were investigated. The experimental results have demonstrated that the electrosorption followed three steps: migration of As(III) to the anode, oxidation of As(III) to As(V) and accumulation of As(V) in the electric double layers of the anode. The electrodorption capacity increased with increasing applied voltage and initial As(III) concentration, whereas the effect of pH was complicated for the variation of arsenite species and the competition of OH − . The oxidation of As(III) increased with the increasing voltage and pH due to the increasing redox potential acted on As(III). The electrosorption served to reduce the toxicity of arsenic and was a promising technology for As(III) removal from water. [ABSTRACT FROM AUTHOR]

In this work, the effect of the exfoliation degree of montmorillonite (MMT) platelets on their electrophoretic mobility distributions in aqueous suspensions was investigated in order to approach into the correlation of MMT exfoliation with electrokinetic property. The experimental results have shown that the negative mobility increased with the increase of exfoliation degree or with the decrease of MMT thickness. This observation might be attributed to the “exposing” of permanent layer negative charge during the exfoliation processing and the “spillover” of electrostatic potential from basal surfaces onto edges. The former would increase the permanent negative charge of the MMT platelets because of the large amounts of layer charge; the latter would decrease the positive edge charge. It is demonstrated that MMT exfoliation would change the electrokinetic property, which might be helpful of the applications of MMT in the related industries. [ABSTRACT FROM AUTHOR]

In this work, the heterocoagulation of fine montmorillonite (MMT) and fluorite particles in aqueous suspensions was investigated through the measurement of electrophoretic mobility distributions. The experimental results have shown that the heterocoagulation closely correlated to the electrophoretic mobility distribution of the mixed mineral dispersion. If a strong heterocoagulation happened, a single-modal electrophoretic mobility distribution with only one peak could be determined, and the peak located between the peaks of the two individual minerals. Without heterocoagulation, a bimodal electrophoretic mobility distribution with two peaks could be observed, which was consistent with the peaks of the two individual minerals. It is demonstrated that the heterocoagulation of two mineral fines in aqueous suspensions could be predicted by the electrophoretic mobility distribution of the mixed mineral dispersion. [ABSTRACT FROM AUTHOR]

To deal with water scarcity, solar steam generation has been widely regarded as one of the promising methods for freshwater production. In this work, for the first time, a novel recyclable MoS 2 -based nanocomposite (magnetic MoS 2 nanosheets) was fabricated via the in-situ growth of nano Fe 3 O 4 on the polydopamine (PDA)-functionalized MoS 2 nanosheets, and subsequently applied as the solar absorber in the volumetric evaporation systems to generate solar steam. The magnetic MoS 2 nanosheets showed a superhigh solar absorption of over 96% within the whole wavelength range of 200–2500 nm. As a result, a high evaporation efficiency of 79.2% under the low illumination of 2.5 kW m−2 was achieved. In addition, the magnetic MoS 2 nanosheets not only showed the long-term well dispersion in aqueous solution due to the introduction of hydrophilic PDA, but also exhibited a fast and effective separation from aqueous solution with the help of the decorating nano Fe 3 O 4 , which much benefited to the continuously efficient solar steam generation and its good recyclability, respectively. Therefore, the MoS 2 -based nanomaterials in this work showed good prospects for solar energy harvesting. Image 1 • A magnetic MoS 2 -based solar absorber was successfully prepared in this work. • This was the first time for MoS 2 -based nanocomposites to be used in volumetric solar steam generation. • A high evaporation efficiency up to 79.2% under a low illumination of 2.5 kW m−2 was achieved. • The magnetic MoS 2 nanosheets exhibited well recyclability and reusability. [ABSTRACT FROM AUTHOR]

Manganese dioxides (MnO 2) and biochar materials are both desirable candidates for environmental remediation of toxic organic pollutants (TOPs) in water due to wide availability and environmental-friendly. In practical application, however, MnO 2 suffers from low redox activity owing to deprotonation, while biochar is subject to limited removal capacity. Herein, a difunctional engineering sulfuric acid-pretreated biochar supporting MnO 2 composite (MBC-A) was firstly synthesized and optimized to remove various TOPs from aqueous solution. Specifically, sulfuric acid not only served as an active agent to improve the specific surface area of biochar for improvement of adsorption capacity and more MnO 2 loading, but also facilitated the introduction of sulfonic acid groups (-SO 3 H) as an internal proton reservoir to inhibit inactivation of MnO 2 due to deprotonation in alkaline. Thanks to adsorption and oxidation, MBC-A showed excellent removal capacity (214.9 mg/g) and fast reaction kinetics (360 min) for tetracycline (TC), exceeding precursor and other materials reported in literature. Importantly, the effective operation pH range of MBC-A was broadened to 1–13 with the help of buffering capacity of –SO 3 H groups. The dominant driving force of adsorption were π-π interaction and hydrogen bond; while reactive oxidative species were mainly ascribed to singlet oxygen (1O 2), hydroxyl radical (·OH) and reactive Mn3+. The possible reactive sites and pathway were investigated by combining experimental results with density functional theory (DFT) calculation. Further, the results of multiple cyclic runs, removal in real river water and toxicity assessment demonstrated well reusability, high environmental security, and excellent practical applicability of MBC-A. [Display omitted] • A novel –SO 3 H modified biochar-supported MnO 2 composite (MBC-A) was prepared. • MBC-A exhibited observably enhanced removal of toxic organic pollutants (TOPs). • With the introduction of –SO 3 H, the working pH range of MBC-A was broadened to 1–13. • 1O 2 , ·OH, and Mn3+ served as main reactive species for oxidation of TOPs by MBC-A. • MBC-A showed well reusability, nontoxicity, and excellent applicability in real water. [ABSTRACT FROM AUTHOR]

In order to develop a more effective method for removal of heavy metals with low concentration and explore the feasibility of using MoS 2 as a super electrode material, removal of Pb(II) at low concentration was studied with combined electrosorption and chemisorption (CEC) by using molybdenum disulfide electrode. The experimental results indicated that Pb(II) could be highly removed by using CEC method when the initial concentration of Pb(II) was less than 6 mg/L. MoS 2 electrode achieved 86.26 mg/m 2 uptake capacity of Pb(II) with CEC, which was almost five times of that with pure chemisorption. The great improvement was attributed to the cooperation of electrosorption and chemisorption. The electric field helped to attract positively charged Pb(II) to the surface of the cathode and thus concentrated Pb(II) in the electric double layer (EDL) of MoS 2 electrode, while the intrinsic S atoms on the surface of MoS 2 immobilized Pb(II) on the electrode through the formation of Pb-S complex. It is suggested that CEC might be a promising process to immobilize heavy metals with low concentration from aqueous solutions. [ABSTRACT FROM AUTHOR]

In this work, the exfoliation of montmorillonite related with electric charges on the layers in aqueous solutions were investigated through the measurements of zeta potential, turbidity and atomic force microscopy, as well as molecular dynamics simulation. The charge amount on montmorillonite layers was adjusted by blocking or neutralizing the layer charges with tetraethylenepentaminecopper (II) ([Cu(tetren)] 2+ ) through cation exchange reaction. The experimental results have shown that the exfoliation closely correlated to the amount of the layer charges. The larger are the charge amount on montmorillonite layers, the more easily the montmorillonite is exfoliated. This observation might be attributed to the repulsive energy (electrostatic and hydration repulsion) was stronger between the high charged montmorillonite layers than low charged ones. [ABSTRACT FROM AUTHOR]

Magnetic reduced graphene oxide hydrogel as an adsorbent could be easily separated from water or solid suspensions. In this work, reduced graphene oxide/magnetite/ascorbic acid hydrogel (rGO/Fe 3 O 4 /AAH) was fabricated through one-step hydrothermal method as the adsorbent for gold-cyanide complex ions (Au(CN) 2 − ) in aqueous solution. The study was performed through the measurement of adsorption capacity and characterization via XRD, FT-IR, Raman, SEM, TEM and XPS. The results indicated that nano-scale magnetite particles were successfully anchored on rGO sheets and three-dimensional rGO/Fe 3 O 4 /AAH was generated during the hydrothermal process. The adsorption results suggested that rGO/Fe 3 O 4 /AAH was an effective adsorbent for recovering Au(CN) 2 − from aqueous solution with the maximum adsorption capacity of 309 mg/g, while the spent rGO/Fe 3 O 4 /AAH could be easily collected using a magnetic separator. The adsorption of Au(CN) 2 − on rGO/Fe 3 O 4 /AAH was found to be spontaneous, endothermic process. These results could be of great significant guidance for efficiently recovering Au(CN) 2 − from ore slurry in the future. [ABSTRACT FROM AUTHOR]

In this work, hydrophobic agglomeration of fine talc particles in aqueous solutions under mechanical conditioning and without any addition of surfactants has been experimentally studied. A method of in-situ measurement of turbidity of flocs suspension in the settlement process has been applied, and the turbidity as a function of settling time has been attempted to fit a certain function so as to assess the hydrophobic agglomeration behaviors. Effects of kerosene dosages, stirring rate, and wettability of talc particles on the hydrophobic agglomeration behaviors have been investigated. The results show that the addition of kerosene can greatly enhance the aggregation of colloidal talc in aqueous suspensions. Besides, the stirring strength and duration make an enormous influence on the aggregation through providing the kinetic energy for overcoming the energy barrier between the approaching particles. It is also found that the wettability of talc is closely related to the aggregation degree. More hydrophobic talc particles show a much stronger aggregation behaviors. [ABSTRACT FROM AUTHOR]

A novel granular adsorbent material containing zero-valent iron (ZVI-GAM) was prepared with fly ash as skeletal material, bentonite as binder and Enteromorpha prolifera as pore former. ZVI was synthesized by direct reduction of iron ore tailings powder with the coke as reductant in high temperature reducing atmosphere and embedded in the fly ash-based porous adsorbent, which could reduce the agglomeration and oxidation of ZVI. The structure of ZVI-GAM was characterized by SEM, EDX, XRD, FTIR and BET. The removal amount of crystal violet (CV) and methylene blue (MB) was evaluated at different contact time, initial dye concentration, pH values and temperature. The adsorption isotherms of CV and MB fitted well to the Langmuir model. The maximum removal capacity of ZVI-GAM for CV and MB was found to be 172.41 mg/g and 151.52 mg/g, respectively. The adsorption processes of CV and MB could be described by a pseudo-second-order kinetic model. The reduction kinetics of CV by ZVI-GAM fitted to pseudo-first-order kinetics model. The results indicated that chemisorption and reduction controlled the removal process of CV while chemisorption only controlled the removal process of MB. The thermodynamic study indicated that the adsorption processes of CV and MB were found to be endothermic and spontaneous. Therefore, ZVI-GAM was an effective, low-cost and recyclable material for dye removal. [ABSTRACT FROM AUTHOR]

In this study, a granular adsorbent material containing zero valent iron (ZVI-GAM) was made with fly ash as skeletal material, bentonite as binder and Enteromorpha prolifera as pore former. Zero-valent iron was synthesized by direct reduction of iron ore tailings with the coke as reductant at 900 °C in the anoxic atmosphere. SEM/EDX, XRD, FTIR and BET analysis were used to characterize ZVI-GAM. SEM image showed that there were many different size pores in ZVI-GAM. XRD analysis indicated the presence of iron in zero-valent state. FTIR analysis revealed that the surface of ZVI-GAM owned the groups responsible for the heavy metals adsorption. The specific surface area of ZVI-GAM was 8.19 m 2 /g. ZVI-GAM was used as reaction and adsorbent material for the removal of Pb(II) and Cr(VI) from aqueous solutions. The factors affecting Pb(II) and Cr(VI) ions removal by ZVI-GAM in a batch model were studied including initial heavy metal concentrations, contact time, adsorbent dosage, pH values and temperature. Maximum removal capacity for Pb(II) and Cr(VI) by ZVI-GAM was found to be 78.13 mg/g and 15.70 mg/g. ZVI-GAM had the best adsorption and reduction capacity for Cr(VI) and Pb(II) and could reduce Cr(VI) to Cr(III) and Pb(II) to Pb 0 . Therefore, ZVI-GAM was an effective, low-cost and recyclable material and had great potential to be a promising technique for heavy metal remediation. [ABSTRACT FROM AUTHOR]

The hydration of two-dimensional (2D) particles in aqueous solutions plays an important role in many scientific and technological fields. In this work, a novel method for the determination of the thickness of hydration shell on nanosheets in water has been presented, which was realized through the measurements of the viscosity of aqueous nanosheet dispersion as the function of solid volume concentration and the thickness and size of the nanosheets with atomic force microscope. The principle of the method was based on the viscosity theory of the dispersions of solid nanosheets. This method was applied to montmorillonite nanosheets, showing that the thickness of the hydration shell on the nanosheets was of 1.63 nm. This value of the thickness was verified by molecular dynamics simulation. [ABSTRACT FROM AUTHOR]

• Graphene oxide was modified by polyaluminium chloride; • HAO@GO exhibited an excellent adsorption capacity towards fluoride; • Chemical adsorption and ligand exchange are responsible for the adsorption of fluoride onto HAO@GO. Adsorption methods have garnered significant attention for fluoride removal from water bodies owing to their superior selectivity, simple operations, and wider applicability. However, the development of adsorbents with higher adsorption performances requires significant attention. Here, graphene oxide is endowed with excellent affinity towards fluoride by doping polyhydroxy complexes onto its surface structure and regulating the potential charge. Multiple detection measurements involving scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS), Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), and transmission electron microscopy (TEM) were employed to demonstrate the textural properties of graphene oxide (GO) modified by polyaluminium chloride (HAO@GO). Conversely, the effects of parameters including the preparation conditions, co-existing competitive ions, recyclability, contact time, and initial concentration on the adsorption behaviors were systematically determined. The adsorption experimental data were fitted well by the Langmuir isotherm model and pseudo-first-order model. The calculated maximum adsorption capacity was 129.23 mg/g at room temperature (25 °C) and a pH of 7.00, which is greater than that of most reported adsorbents. The existence of competitive anions, such as NO 3 - , SO 4 2 - , and PO 4 3 - , unavoidably interferes with fluoride adsorption. TEM, zero point of charge test, adsorption isotherm, and X-ray photoelectron spectroscopy (XPS) tests indicated that chemical adsorption and ligand exchange are responsible for the adsorption of fluoride onto HAO@GO. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDH) have been extensively studied because of their unique characteristics. The available reviews have dealt with the applications of LDH normally prepared with aqueous solution approaches. Recently mechanochemical ways to synthesize LDH and intercalated LDH have received more and more attention from researchers and several mechanochemical processes have been reported. This article reviews the recent advances in the preparation and intercalation of layered double hydroxides by mechanochemical approaches. Although conventional solution methods for the syntheses of LDH were widely studied, several problems remain to be resolved; such as treatment of aqueous waste, high energy consumption, complex operation etc. It is believed that mechanochemical methods may have potentials to effectively overcome the difficulties and also to synthesize various new types of LDH with further development of this new technique. [ABSTRACT FROM AUTHOR]

Highlights: [•] Found out that DDA induced a much stronger aggregation in aqueous kaolinite suspensions. [•] Presented a good correlation of kaolinite aggregation with DDA adsorption and surface hydrophobicity. [•] DDA induced hydrophobic agglomeration of colloidal kaolinite was negatively affected by NaCl addition. [Copyright &y& Elsevier]

Magnetic MoS 2 could be easily separated from water or solid suspensions. In this work, shell-core structured MoS 2 @Fe 3 O 4 composite was fabricated through hydrothermal method and used as catalyst for recovering gold-thiosulfate complex ions (Au(S 2 O 3) 2 3−) in aqueous solution. The results suggested that MoS 2 @Fe 3 O 4 composite could effectively in-situ reduce Au(S 2 O 3) 2 3− to gold particles (Au0) with an extremely high reduction capacity of 1541.1 mg/g; moreover, the gold loaded MoS 2 @Fe 3 O 4 could be easily collected using a magnetic separator. The mechanism of reducing Au(S 2 O 3) 2 3− to Au0 was ascribed to the photoexcited electrons from MoS 2 @Fe 3 O 4 composite. More importantly, the incorporation of Fe 3 O 4 could effectively enhance the transferred efficiency of photoexcited electrons and accelerate separation of electrons-holes pairs. With great gold reduction capacity and magnetic recyclability, the MoS 2 @Fe 3 O 4 composite could be a promising material for recovering gold from leaching solutions. Unlabelled Image • Magnetic shell-core structured MoS 2 @Fe 3 O 4 composite was prepared and first used to recover Au(S 2 O 3) 2 3− complex ions. • Au(S 2 O 3) 2 3− was in-situ reduced into Au0 by MoS 2 @Fe 3 O 4 composite. • The incorporation of Fe 3 O 4 improving the photocatalytic property. • The spent MoS 2 @Fe 3 O 4 composite can be easily collected. [ABSTRACT FROM AUTHOR]

A novel Fe/La oxide magnetic microspheres for enhanced As(V) removal from diluted wastewater was synthesized and characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectrometer, and vibrating sample magnetometer. The prepared Fe/La oxide magnetic microspheres possessed satisfactory pore size distribution with stable spheres structure. Adsorption of arsenate onto Fe/La OMMs was first investigated using batch experiments for the determination of pH edge, adsorption kinetics, and isotherm. The removal of As(V) by Fe/La oxide magnetic microspheres could reach almost 100% under As(V) solution of 1 mg/L at the optimum adsorbent dosage of 0.1 g/L. The adsorption kinetics followed an intraparticle diffusion model, and the adsorption isotherm was well described by the Langmuir model with the maximum adsorption capacity of 62.32 mg/g for As(V) at pH 4. Besides, the Fe/La oxide magnetic microspheres performed well in selectivity and magnetic separation. PHREEQC programming suggested the adsorption process could be better described by the surface complexation model and reinforced the understanding of the Fe/La oxide magnetic microspheres in true wastewater treatment applications. The adsorption mechanism is attributed to surface complexation and intraparticle diffusion, including electrostatic interaction, ligand exchange, and complex formation. The developed Fe/La oxide magnetic microspheres showed great potential in the advanced As(V) processing for the dilute natural arsenic-contaminated water. Image 1 • A novel porous Fe–La oxide magnetic microspheres was synthesized. • Efficient removal of As(V) was achieved at diluted concentrations. • PHREEQC geochemical modelling was used to describe the adsorption behaviour. • Outer- and inner-sphere complexation were main mechanisms for excellent As(V) removal. [ABSTRACT FROM AUTHOR]

Thermal modification was simply performed on molybdenite to enhance the adsorption of Pb(II) in aqueous solutions, and the root of this phenomenon was well studied in this work. Various thermal modification temperatures at 300 °C, 400 °C and 500 °C were applied to modify the surface property of molybdenite, producing different degrees of edge defect and surface wettability in molybdenite samples. Contact angle tests, atomic force microscopy (AFM) observations and adsorption tests illustrated that molybdenite thermally modified at 400 °C contained most edge defects and achieved a 147.846 mg/g Pb(II) adsorption, which was almost 10 times of that obtained by natural molybdenite. The adsorption experiment also indicated that the increase of surface hydrophilia of molybdenite would slightly benefit the Pb(II) adsorption. The X-ray photoelectron spectroscope (XPS) exhibited that a strong chemical adsorption existed between Pb(II) and S elements. AFM study further demonstrated that the interaction between Pb(II) and S atoms exposed at the triangular edges of molybdenite were the intrinsic reason for the great enhancement of Pb(II) adsorption. This work provides a new insight to absorb Pb(II) in aqueous solutions using natural molybdenite. Image 1098194 • M-400 achieved 147.8 mg/g Pb (II) adsorption in aqueous solutions. • Thermal modification enabled molybdenite with a 10 times enhancement on Pb (II) adsorption compared with natural molybdenite. • Sulfur vacancies on edges had strong affinity to Pb ions. [ABSTRACT FROM AUTHOR]

• The AuCl 4 − reduction by MoS 2 @PDA composite was studied. • MoS 2 @PDA composite exhibited excellent stability. • The coating of PDA on MoS 2 enhanced its AuCl 4 − reduction capacity. MoS 2 has attracted tremendous attention in reducing AuCl 4 −, however, it suffers from poor stability in solutions. In this work, MoS 2 nanosheet wrapped with polydopamine (MoS 2 @PDA composite) was successfully prepared by simple hydro-thermal synthesis. Compared to pure MoS 2 , the as-synthesized MoS 2 @PDA composite exhibited not only excellent stability, but also superb AuCl 4 − reduction capacity. With the warp of PDA, the thermal stability of the composite was improved obviously, and dissolution of the composite in aqueous solution hardly occurs. Moreover, the reduction of AuCl 4 − by MoS 2 @PDA composite could reach equilibrium in 90 min, and the maximum reduction was about 3800 mg/g, and the reaction was intensely pH-dependent. In addition, gold nanoparticles were widely distributed on the surface of MoS 2 @PDA composite, which could effectively prevent the agglomeration of gold nanoparticles. This finding might point out the possibility of applying MoS 2 @PDA composite as stable anti-agglomeration substrate for gold nanoparticles. [ABSTRACT FROM AUTHOR]

• Incorporation of oxygen dramatically improves the adsorption of Hg2+ on MoS 2. • Oxygen atom greatly facilitates the hydrated Hg2+ ions to approach to MoS 2 surfaces. • Oxygen greatly enhance complexation between sulfur atoms and Hg2+ on MoS 2 surfaces. • Increase of adsorption capacity with increasing oxygen atoms will reach a plateau. Molybdenum disulfide (MoS 2) was incorporated controllably by oxygen in order to modify the hydrophobic surfaces and thus to improve the adsorption of Hg2+ on MoS 2 in aqueous solutions in this work. The experimental results indicated that the incorporation of oxygen could dramatically improve the adsorption of Hg2+ on MoS 2. With 11% oxygen atom incorporation, the adsorption rate and capacity increased over 17 times and 21 folds, respectively, compared with that without oxygen incorporation. This vast improvement was found to be contributed to that the incorporation of oxygen would greatly enhance the complexation between S atoms and Hg2+ on MoS 2 surfaces, resulting in the great increase of the Hg2+ adsorption. The increase of the adsorption capacity with increasing incorporated oxygen reached a plateau, which might be due to the saturation of covalent bond. In addition, the incorporation of oxygen atom greatly enhanced the hydrophilicity of MoS 2 surfaces, facilitating the hydrated Hg2+ ions to approach to MoS 2 surfaces. This finding might provide a highly potential adsorbent for efficiently removing Hg2+ from water. [ABSTRACT FROM AUTHOR]

In this work, the rejection performance of methyl orange (MO) through molybdenum disulfide membranes in water combining electroosmosis has been studied in order to develop the 2D nanofiltration materials for waste water treatment. The laminar and homogeneous membranes could be prepared through mechanical exfoliation and vacuum filtration from MoS 2 nanosheets. The results indicated that MoS 2 membranes showed almost 100% retention of methyl orange within one hour, and up to 97% within four hours. Moreover, the flux showed 0.207 L/m2.h for a 5.8 μm-thick membrane, which was 3–5 times higher than GO membranes. The result of XPS test and SEM-EDS have demonstrated that there is no chemisorption between MoS 2 and MO, and the separation mechanism can basically owe to Donnan effect and sieve effect. This work suggests that molybdenum disulfide is an emerging filtration membrane material to increase the removal capacity of water contamination. [ABSTRACT FROM AUTHOR]

• Hydrophobic agglomeration behaviors of montmorillonite are firstly studied. • DTAB is used for masking the hydrophilic sites of montmorillonite. • Adsorbed DTAB tails together with siloxane site greatly increase hydrophobic agglomeration of montmorillonite. Dodecyl trimethyl ammonium bromides (DTAB) was used to adsorb on the isomorphous substitutions of montmorillonite (MMT) for masking hydrophilic sites. The adsorbed DTAB tails together with siloxane sites of MMT surfaces would greatly increase hydrophobicity of MMT, leading to stronger hydrophobic agglomeration of MMT fines in water. The experimental results showed that DTAB was adsorbed on the isomorphous substitution sites of MMT due to electrostatic interaction, and thus rendered MMT surfaces more hydrophobic. The aggregation of MMT fines in water was greatly enhanced by the addition of DTAB because of the formation of hydrophobic agglomeration at an appropriate shear field. [ABSTRACT FROM AUTHOR]

MoS 2 and montmorillonite (MMT) nanosheets were hybridized through a simple in-situ hydrothermal synthesis in order to develop an efficient adsorbent, MoS 2 /MMT composite, for the removal of mercury from water. Raman, XRD, and FTIR results displayed the good hybridization of MMT and MoS 2. HRTEM images indicated that the active edges of MoS 2 were clearly exposed in the hybrid, demonstrating the vital role of MMT as eco-friendly, cheap and stable substrate for the growth of MoS 2. The overall adsorption process of Hg2+ on MoS 2 /MMT proved that the composite is highly efficient for the removal of Hg2+ from water, adsorbing up to 1836 mg/g of Hg2+, which outperformed most literature reported adsorbents. The adsorption kinetic and isotherm models could be well described by pseudo-first-order and Langmuir models, respectively. Furthermore, the Langmuir dimensionless constant, R L show that Hg2+ adsorption on the composite was found favorable to occur at the temperature of 25 °C and 35 °C. The XPS analysis revealed that the S sites and slight O sites were main contributors for the remarkable adsorption performance of MoS 2 /MMT composite on Hg2+ removal. This work suggests that MoS 2 supported on MMT substrate might be a promising adsorbent with high capacity and super efficiency for the removal of heavy metals from aqueous solution. Unlabelled Image • Preparation of MoS 2 /MMT composite through a simple in-situ hydrothermal method. • Efficient adsorptive removal of Hg2+ from water. • Investigation of kinetics and isotherm model. • Montmorillonite as supporting material to improve the dispersibility of MoS 2 in water. • Elucidating the underlaying adsorption mechanism. [ABSTRACT FROM AUTHOR]

In this work, multifunctional MoS 2 prepared by hydrothermal method was studied as an adsorbent for the simultaneous removal of Hg2+, Pb2+ and Cd2+ in aqueous solutions. This study was performed through the adsorption experiments in single- and multi-metal systems. It was shown that MoS 2 exhibited a highest adsorption capacity for Hg2+, and lowest for Cd2+, which was mainly attributed to the different affinities between the S sites and the heavy metals. Based on the results of XPS and Zeta potential, the adsorption mechanisms were investigated in depth, which involved oxidation-reduction between Hg2+ and MoS 2 , electrostatic attraction between positively charged heavy metals and negatively charged MoS 2 , complexation of Hg–S, Pb–S, Cd–S, Hg–O and Pb–MoO 4 and ion-exchange reaction occurred on –SH and –OH. In the coexistence of Hg2+, Pb2+ and Cd2+, the excess MoO 3 generated during the oxidation-reduction between MoS 2 and Hg2+ resulted in a higher adsorption capacity for Pb2+ compared with the condition in single-metal system. However, the adsorption sites of S on MoS 2 would be occupied competitively by the three heavy metals so that it caused lower adsorption capacities for Hg2+ and Cd2+. These findings would make a great significance in the field of water treatment by MoS 2. Image 1 • The co-adsorption on MoS 2 for Hg2+, Pb2+ and Cd2+ has been studied first. • An original adsorption mechanism is come up with in multi-metal system. • The analysis of characteristic and mechanism is productive. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS 2)-based nanomaterials stand out from two-dimensional (2D) materials as a promising adsorbent for the removal of heavy metals from aqueous solution due to their extremely marvelous adsorption performances. The superb uptake capacity is primarily ascribed to the intrinsically rich S atoms exposed on the surface of MoS 2 , which distinguishes MoS 2 -based nanomaterials from other 2D materials. This work presents the latest advances of MoS 2 nanomaterials as adsorbent for the removal of heavy metal ions in water. Various preparation methods, as well as the structure, property and modification of MoS 2 , is summarized. The adsorption capacity and mechanisms, affecting factors and regeneration are highlighted. The practical application of MoS 2 as potential adsorbent for the removal of heavy metals from water is emphasized, and research needed for future application is simultaneously identified. • We summarize the preparation and modified methods of MoS 2 -based nanomaterials. • We describe the adsorption capacities of MoS 2 to remove heavy metals. • We summarize the mechanisms and affecting factors of MoS 2 as an adsorbent. • We propose the research of MoS 2 -based adsorbents needed for future application. [ABSTRACT FROM AUTHOR]