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The adsorption of chelating collector octyl hydroxamate onto malachite was studied at various pH to reveal the adsorption mechanism. Below pH 6, a substantial amount of octyl hydroxamate was consumed by copper ions in solution, leading to low malachite recovery. In the pH range from 6 to 9, octyl hydroxamate mainly existed in the molecular form. The collector reacted with the chemisorbed Cu(OH)+ and Cu(CO3)22− on the malachite surface. The octyl hydroxamate anion was the predominant species above pH 9. The reaction between the anion and the chemisorbed Cu(OH)+ and Cu(CO3)22− on the malachite surface, was responsible for flotation of malachite. At pH 9, the maximum collector adsorption and flotation recovery were achieved, presumably as a result of the coadsorption of octyl hydroxamate molecules and anions. Although Cu(OH)+ and Cu(CO3)22− were the predominant active species for malachite surface below and above pH 8.3, respectively, and octyl hydroxamate anion and molecule were the predominant species below and above pH 9, respectively, the same copper hydroxamate chelate was formed on the malachite surface above pH 6. [ABSTRACT FROM AUTHOR]

Extracellular polymeric substance (EPS)-mineral associations occur naturally in soil and sediments, and they might play crucial roles in heavy metals immobilization. In this study, EPS-montmorillonite composites with different weight ratios were characterized and investigated for their Cd(II) sorption behavior. The results showed that the EPS chains can intercalate into montmorillonite layers by hydrogen bonding connection and chemical reaction between C O, C–N and COO− groups with interlayer cations of montmorillonite, therefore promoting delamination of montmorillonite, especially under a lower weight ratio. An enhancement adsorption of heavy metals was obtained with the composites at lower weight ratios of 1:50 and 0.5:50, whereas composites with higher weight ratio of 5:50 presented a reduced adsorption ability, demonstrating that adsorption of Cd(II) onto the EPS-montmorillonite composites was weight ratio dependent. AFM, CLSM, FT-IR and XPS analysis illustrated that the enhancement of sorption under low weight ratio can be attributed to the release of surface active sites of EPS because of reduced aggregation, the increase of negative surface charges when EPS and montmorillonite were interacted and additional bridging of cadmium ions between EPS and montmorillonite. These findings extend the knowledge into the mobility and fate of Cd(II) in organic matter rich soils and sediments. Image 1 • Cd(II) sequestration in the composites depends on EPS to montmorillonite mass ratio. • Enhancement of Cd(II) sorption by EPS-montmorillonite composite with low mass ratio. • Promotion of surface charge, reduction of aggregation and Cd(II) bridging contribute to the larger sorption. This study firstly reports an enhanced Cd(II) sorption by EPS-montmorillonite composite at low weight ratio. The results provided basic information for studying the fractionation effect of EPS on minerals in heavy metal retention in the natural soil environment. [ABSTRACT FROM AUTHOR]

In this work atomic force microscopy (AFM) was applied to study the wettability of mica and graphite modified with surfactant dodecyltrimethylammonium bromide (DTAB) at varying DTAB concentrations (below the cmc) and adsorption time. The coverage states of DTAB on surfaces were analyzed from the AFM images, while the contact angle measurement was made for the wettability of DTAB-modified surfaces. The experimental results have shown that the adsorption aggregates formed as needle-like dots covering on the mica surface with the surfactant concentration of 10−6-10−4 mol/L. The coverage of DTAB aggregates increased with the increasing concentration, leading to a strong hydrophobicity on the surfaces. However, the large aggregates which might be caused by bilayer adsorption of surfactant occurred on mica surface at surfactant concentration of 10−3 mol/L, resulting in the reverse of the wettability as the adsorption time extended. In the case of hydrophobic graphite, DTAB aggregates mainly formed as stripe covering on the surfaces, leading to the reduction of hydrophobicity. This reduction became stronger as more DTAB aggregates covered on graphite surfaces. [ABSTRACT FROM AUTHOR]

Facile pyrolysis of fishbone charcoal towards Pb (II) adsorption was investigated in this study. The parameters of carbonization synthesis of fishbone charcoal have been examined, including heating atmosphere, heating temperature, heating rate. Furthermore, the effect of initial Pb (II) concentration, contact time, pH and temperature on the adsorption of Pb (II) onto the fishbone charcoal was also investigated in a batch system. The fishbone charcoal was characterized using scanning electron microscopy with EDX, Fourier transform infrared spectrometry, X-ray diffraction analysis, thermogravimetry, and Brunauer-Emmett-Teller method. The equilibrium adsorption results showed that the fishbone charcoal prepared in this study exhibited a very high adsorption capacity which could reach up to 688.523 mg/g, 761.471 mg/g, 961.130 mg/g at 25 °C, 35 °C and 45 °C aqueous temperature, respectively. The adsorption isotherms data showed that the adsorption fitted Langmuir model. The kinetic data followed pseudo-first-order. Furthermore, the thermodynamic parameters (ΔG 0 , ΔH 0 and ΔS 0 ) data also indicated that it was a feasible, non-spontaneous, and endothermic adsorption process. This study suggests that the fishbone charcoal can be prepared as a high-efficient, low-cost and environmentally adsorbent towards to Pb(II) adsorption. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of inorganic cations (Na+, Ca2+, and Al3+) with different valences and concentrations on the stability of Na-montmorillonite (Na-MMT) suspension. The stability was studied by turbidity and zeta potential measurements and adsorption thermodynamics. The results showed that the Na-MMT particles coagulated at pH 3-4.8, the stability of which was much inhibited by cations with higher concentration and higher valence. This was caused by the adsorption of cations and the reduction of electrostatic repulsion. Adsorption of Ca2+ on Na-MMT surface fits the Freundlich curve model well. Furthermore, the adsorption reduced the zeta potential of Na-MMT and then the energy barrier between the particles which well obeyed the classic DLVO theory. [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]

Adsorption is widely applied to remove arsenic from water. This paper reviewed and compared the recent progresses on the arsenic removal by adsorption using two-dimensional and three-dimensional graphene-based materials as adsorbents. Functional graphene sheet achieved the largest As(III) adsorption capacity of 138.79mg/g, while Mg-Al LDH/GO2 showed the largest As(V) adsorption capacity of 183.11mg/g. Parameters including pH, temperature, co-existing ions and loaded metal or metal oxide affected the adsorption process. The adsorption mechanisms of graphene-based materials for As(III) and As(V) could be explained by surface complexation and the electrostatic attraction, respectively. Future works are suggested to focus on regenerating of two-dimensional graphene-based adsorbents and developing the three-dimensional with large specific surface area and better adsorption performance. [ABSTRACT FROM AUTHOR]

Effects of co-existing ions on the adsorption of As(V) in aqueous solutions by porous hematite have been investigated in this work. The porous hematite was prepared by the goethite concentrate which was concentrated from the iron oxide tailings. The co-existing ions include Cl − , NO 3 − , HCO 3 − , SO 4 2− , PO 4 3− anions and Na + , K + , Mg 2+ , Ca 2+ . The arsenic aqueous solutions with these co-existing ions were simulated using chemical reagents and deionized water. The adsorption isotherm and kinetics were all examined. The experimental results showed that HCO 3 − and PO 4 3− anions inhibited the As(V) adsorption, whereas Mg 2+ and Ca 2+ ions have promoting effects on the As(V) adsorption. Furthermore, the ionic strength has no significant effect on the arsenate adsorption to the porous hematite. These results may be attributed to competitive adsorption of As(V) on porous hematite in aqueous solutions. [ABSTRACT FROM AUTHOR]

This review highlights the adsorption process by using iron oxide minerals as the adsorbent for arsenic removal from water. It includes the characteristics of arsenic in water and its toxicities, the adsorption process for arsenic removal from contaminated water, iron oxide minerals as the adsorbent, arsenic adsorption capacity on iron oxide minerals, main factors of the adsorption, and arsenic removal from water by the adsorption process, as well as the mechanisms by which arsenic species adsorb on iron oxide minerals. [ABSTRACT FROM PUBLISHER]

This study developed a novel Hg(II) immobilization strategy by firstly incubating algal cells in high-phosphate cultures for surface modification, followed by obtaining the P-rich biomass as adsorbents for enhanced Hg(II) removal and then charring the Hg-loaded biomass to prevent leaching of phosphate and to immobilize Hg(II). For algal surface modification, Scenedesmus obtusus XJ-15 were cultivated under different P concentrations and obtained the highest sites concentration of surface phosphoryl functional groups in 80 mg L−1 P cultures. For Hg(II) adsorption, biomass from 80 mg L−1 P cultures (B-80) achieved the highest saturated sorption capacity of 95 mg g−1 fitting to Langmuir isotherm model under the optimum pH of 5.0. For charring stabilization, the Hg-loaded B-80 was calcinated under different temperatures, and the product obtained from 300 °C charring showed the lowest Hg(II) leaching rate without P release. Moreover, FT-IR and XPS analysis indicate that the surge of surface phosphoryl functional groups dominated the enhancement of Hg(II) sorption and also Hg(II) charring immobilization. The above results suggested that the developed strategy is promising for both phosphate and mercury removal from water and for co-immobilization of P and Hg(II) to prevent leaching. Image 1 • Microalgal surface properties were successfully modified by changing cultivation conditions. • Phosphate-cultivated modification increased the surface phosphoryl functional groups. • Larger adsorption of Hg was achieved by using modified algal biomass. • Hg and phosphorus were both removed from water and stabilized by charring. • Real effluent of desulfurization wastewater was treated by the developed biosorbent. [ABSTRACT FROM AUTHOR]

The adsorption performance of manganese oxide in treating arsenic wastewater that contained different As(III)/As(V) molar ratios was investigated, and the samples before and after their reactions were characterized by XRD, TEM, N 2 adsorption/desorption, SEM-EDS, FTIR, and XPS. The batch experimental results show that the coexisting molar ratio of As(III) and As(V) has a remarkable effect on arsenic removal by manganese oxide. Upon increasing the As(III)/As(V) molar ratio from 10 μM/90 μM to 50 μM/50 μM and 90 μM/10 μM, respectively, the total arsenic removal by manganese oxide significantly increased from 39.5% to 55.6% and 71.2%, respectively. The origin of the molar ratio effect was studied by combining both the experimental and theoretical results of the Mn 2+ release detection, effect of Na 2 SO 3 -pretreatment on arsenic removal, and density functional theory (DFT) calculations. The results reveal that the highest arsenic removal by manganese oxide in an arsenic solution with the highest As(III)/As(V) molar ratio is attributed to the Mn 2+ release caused by As(III) oxidation, forming more Mn vacancy defects, which makes the adsorption site more active, thus significantly promoting the adsorption performance of manganese oxide in arsenic removal. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mixed collectors improve the collecting ability and selectivity of bastnaesite comprehensively. • The BHA and SHA are chemically adsorbed by Ce site on the bastnaesite surfaces. • The two mixed collectors have a stronger adsorption ability on bastnaesite surface than single collectors. • The chelate formed of BHA and SHA on banaesite is most likely to exist in the form of the five-membered ring. Bastnaesite, as one of the most important sources of rare earth elements, are typically separated through flotation. However, the complex association and fine particle size of bastnaesite make it challenging to achieve high flotation recovery and grade. In this study, mixed collectors composed of benzohydroxamic acid (BHA) and salicyhydroxamic acid (SHA) has been developed for the flotation of bastnaesite. Results show that BHA has better collection performance while SHA show better selectivity in the flotation separation of calcite and dolomite. The combination of BHA and SHA in the flotation turn out that the recovery and grade of bastnaesite are simultaneous promoted compared to single collector. Adsorption experiments indicate that bastnaesite has larger adsorption capacity to BHA, while SHA are more selective adsorbed on bastnaesite rather than calcite and dolomite. Zeta potential measurements confirm the stronger adsorption of mixed collector onto the bastnaesite surface compare to single collectors, which agree well with the flotation results. The FTIR analyses show that the mixed collector undergoes a chemical reaction on the bastnaesite surface, facilitating chelation between the collector and bastnaesite. The XPS analyses verified that the newly formed bonds are Ce-O bonds between the collectors and bastnaesite. Overall, this study developed a kind of mixed collector for bastnaesite flotation, the synergistic effect and co-adsorption of BHA and SHA on bastnaesite surface have been demonstrated, which provide new approach to improve the flotation recovery and grade of bastnaesite. [ABSTRACT FROM AUTHOR]

Abstract Because of the easy-separation, high specific surface areas and rich binding sites, magnetic MoS 2 with nanoscale architectures showed great potential in working as adsorbents for heavy metal ions. However, the general composites of nanoscale MoS 2 and Fe 3 O 4 suffered from the poor stability in acidic solution due to their entire exposures of Fe 3 O 4 to H+, which made it difficult to regenerate the used adsorbents by the general acid treatment. This work reported a facile approach to prepare Fe 3 O 4 @Polydopamine (PDA)-MoS 2 nanospheres via in-situ growth of MoS 2 on the PDA modified Fe 3 O 4 nanospheres. Fe 3 O 4 @PDA-MoS 2 nanospheres possessed a fast adsorption of 2.4076 g/mg·min (Initial concentration of Pb2+: 200 mg/L) and high adsorption capacity of 508.9 mg/g at 298 K to Pb2+. This was because the specific surface area of MoS 2 grown in-situ on Fe 3 O 4 @PDA was 7.6 times that of the pure MoS 2 , which significantly increased the binding sites of MoS 2 for heavy metal ions. In addition, the as-prepared nanocomposites exhibited not only easy-separation within 120 s by an external magnet, but also long-term stability in strong acid solutions as well as facile regeneration by general acid treatment. The tight PDA layers outside the Fe 3 O 4 nanospheres could work as not only a template for the formation of MoS 2 nanoflowers but also an efficient protective coating for the improvement of the stability of nanocomposites. The findings might open up the possibility of expanding the practical application of nanoadsorbent in environmental remediation. Graphic abstract Unlabelled Image Highlights • Fe 3 O 4 @Polydopamine-MoS 2 nanocomposites were successfully prepared. • Polydopamine coating turned to be a necessary and efficient protective layer. • The nanocomposites exhibited easy separation and long-term stability. • The nanocomposites exhibited an outstanding adsorption performance for Pb2+. [ABSTRACT FROM AUTHOR]

Highlights • The N-MG and P-MG is possibly not reactive enough, while B-MG and Al-MG are able to chemically bind CH 4. This supports the notion that the CH 4 /Al-MG possesses a much stronger CH 4 adsorption ability. • The MG, B-MG, P-MG and N-MG acquire charges from CH 4 gas molecule, while PG and Al-MG donate charges to the CH 4 gas molecule. • It's find that the Al-doped mono-vacancy graphene show the largest adsorption energies upon CH 4 with the most appreciable effects on the electronic structures. Abstract The interaction of CH 4 gas molecule on pure graphene and Al, B, N, P doped mono-vacancy graphene by using the density functional theory (DFT) to explore their potential applications as gas sensors. The results demonstrate that the system of Al doped mono-vacancy graphene is the most stable, and Al-doped mono-vacancy graphene performs the largest adsorption energies upon CH 4 with the most appreciable effects on the electronic structures. In addition, the adsorption of CH 4 can largely enhance the conductivity of these graphene. In summary, we believe that the Al-doped mono-vacancy graphene could be a promising candidate material for the CH 4 gas sensors. [ABSTRACT FROM AUTHOR]

In this work, self-assembled hydrogels were prepared with exfoliated montmorillonite nanosheets (MMTNS) and chitosan (CS) as the adsorbent for removing methylene blue (MB) from water. Adsorption properties were determined by studying the kinetics and thermodynamic of MB adsorption onto the hydrogels from aqueous solutions, and AFM, FTIR, SEM, and XPS were used for the characterization of the MMTNS and hydrogels. The experimental results have shown that the montmorillonite nanosheets/chitosan hydrogels were superb adsorbents for removing MB from water, reaching the maximum adsorption capacity of 530 mg/g. The adsorption well followed the pseudo-second-order kinetics and Langmuir isotherm, and was spontaneous endothermic. The adsorption of MB on the hydrogels could be easily realized through cation exchange and hydrogen binding. It was also found that the hydrogels prepared with lower solid concentration of MMTNS had a looser stratified structure and thus a greater adsorption capacity for MB in aqueous solutions. [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 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]

Graphene oxide (GO) and its composites have attracted widespread attentions as novel adsorbents for the adsorption of various heavy metal contaminants. Because of the unique physicochemical characteristics, they might become an excellent and most potential adsorbent. This review summarizes the application of GO and its composites as a superior adsorbent for the removal of heavy metal ions from water. The adsorption affinity and mechanisms, affecting factors and regeneration are highlighted. Moreover, the challenges for the commercial uses are discussed. [ABSTRACT FROM AUTHOR]

The adsorption of Pb 2+ at the rutile/water interface has been studied for the activation of rutile flotation with salicyl hydroxamic acid (SHA) as a collector in this work. This study was performed through measurement of the zeta potential, adsorption capacity, calorimetry and X-ray photoelectron spectroscopy. The experimental results showed that the adsorption of SHA on rutile and the flotability of rutile were significantly improved by the addition of Pb 2+ . This improvement was attributed to the specific adsorption of Pb 2+ in the form of PbOH + , which interacted with the Ti-OH at the rutile surface and formed a surface Ti-O-Pb + complex. This adsorption followed the Langmuir model. It reversed the zeta potential sign of rutile at pH 5.5–6.8 and had a heat of adsorption of −46.71 kJ/mol, suggesting the occurrence of a chemiosorptive process. [ABSTRACT FROM AUTHOR]

• 2D Mts can significantly increase the hydrophilicity of MoS 2 @ 2D Mts composites. • 2D Mts provide active sites to interact with polymers to form hydrogel for easy separation of MoS 2 from water. • MoS 2 @2D Mts-PVA composite hydrogel shows an enhanced Pb2+ removal performance. To improve the hydrophilicity and achieve easy separation of MoS 2 adsorbent fines from water, composite hydrogel of MoS 2 supported by two-dimensional montmorillonite nanosheets in poly vinyl alcohol (MoS 2 @2D Mts-PVA Gel) has been designed and synthesized. 2D Mts act as carriers to load MoS 2 and interact with polymers. The MoS 2 @2D Mts shows high hydrophilicity, and the MoS 2 @2D Mts-PVA Gel has porous three-dimensional structure for the adsorption and separation of metal ions in water. Therefore, 2D Mts are ideal carriers to load MoS 2 for well dispersion in water and interact with polymers. Adsorption tests demonstrate that the Pb2+ adsorption capacity of MoS 2 @2D Mts-PVA Gel increases significantly with the increase of MoS 2 @2D Mts content and solution pH, and a high Pb2+ adsorption capacity of 257 mg g−1 can be reached. The adsorption of Pb2+ onto MoS 2 can be attributed to the complexation of Pb2+ with S and O atoms on the surface, and electrostatic adsorption. [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]

The porous La(III)- montmorillonite hydrogel beads (La-MMT_hb) with stable structure were fabricated via hydrogen-bond and electrostatic interactions for arsenic removal from water. The structural characteristics of La-MMT_hb and its sorption performances for As(V) were evaluated. The results showed that porous La-MMT_hb were clearly observed by scanning electron microscopy, and the addition of lanthanum significantly increased the specific surface area. The maximum adsorption capacity of La-MMT_hb for As(V) was 58.75 mg/g, reached within 4 h, at the optimum pH of 4 with optimum La dosage of 1%. The mechanism of adsorption can be attributed to the electrostatic forces between La(III) and H 2 AsO 4 − at pH 4, ion exchange of O H groups on the surface of adsorbent with H 2 AsO 4 − and complex chelate formation as.-NH 3 -H 2 AsO 4 and -La-O-As. • Enhancement of As(V) adsorption capacity by montmorillonite hydrogel beads with addition of lanthanum • Increase in specific surface area of hydrogel beads result from changes of microstructure owing to lanthanum loaded • Electrostatic forces, ion exchange and complex chelate formation with lanthanum and arsenic contribute to the larger sorption [ABSTRACT FROM AUTHOR]

• Gel of Fe-chitosan/montmorillonite nanosheets efficiently degraded methylene blue. • Synergistic effect of adsorption and photo-Fenton reaction led to dye degradation. • Gel had effective reusability due to continuous reactivation of adsorption sites. • Gel was stable and worked efficiently under a wide range of pH conditions. • Methylene blue was decomposed by demethylation and oxidation reactions. Self-assembled gel of Fe-chitosan/montmorillonite nanosheets (Fe-CS/MMTNS) was prepared for elimination of methylene blue (MB) under visible light in the presence of H 2 O 2. The Fe-CS/MMTNS gel was characterized by FTIR, SEM-EDS, XPS and TG. The Fe-CS/MMTNS gel performed well in the removal of MB through the synergistic effect of adsorption and photo-Fenton reaction. Moreover, this gel worked efficiently under a wide range of pH conditions. This composite gel also showed effective reusability because the adsorption sites of the Fe-CS/MMTNS are continually reactivated through photo-Fenton degradation. Additionally, the Fe-CS/MMTNS gel was found to be stable and the iron ions were hardly leached out because of the complexation between iron and chitosan (CS). The MB degradation occurred by two pathways: a part of MB was directly attacked by reactive radicals and gradually converted into inorganic substances while another part of MB was firstly adsorbed by Fe-CS/MMTNS gel and then degraded by reactive radicals. [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]

• Calcium ions improve malachite flotation at pH 6–11. • Calcium ions enhance fine malachite particles aggregation. • Ca(OH)+ and Ca(OH) 2 species inhibit malachite flotation at pH > 11. In this study, the effects of calcium ions on the flotation of malachite with octyl hydroxamate collector has been investigated using micro-flotation, zeta potential, contact angle, adsorption, and particle size measurements. Although the adsorption amount of collector and the hydrophobicity of malachite surface were not influenced by the addition of 1 × 10−2 mol/L CaCl 2 at the optimized flotation pH 9, it was found that the malachite flotation recovery was enhanced by the addition of CaCl 2 in the pH range of 6–11. In the presence of CaCl 2 , energy barrier between the malachite particles and the bubbles were lower, leading to the aggregation of malachite particles, and the enhanced malachite recovery. However, at pH > 11, the formation of Ca(OH)+ and Ca(OH) 2 species on malachite surface inhibited its flotation. [ABSTRACT FROM AUTHOR]