Arsenic Adsorption Performance Research Articles

Influence of Phosphate on Arsenic Adsorption Behavior of Si-Fe-Mg Mixed Hydrous Oxide.

The arsenic adsorption performance of silicon (Si), iron (Fe), and magnesium (Mg) mixed hydrous oxide containing a Si: Fe: Mg metal composition ratio of 0.05:0.9:0.05 (SFM05905) was investigated. SFM05905 was synthesized by the co-precipitation method. Batch experiments on arsenic adsorption were conducted at various temperatures and concentrations. Adsorption isotherms models were represented by a linearized equations and were insensitive to temperature change. The anion selectivity of SFM05905 at single component was high for arsenite (III), arsenate (V), and phosphate (PO4), indicating that PO4 inhibits arsenic adsorption. The adsorption amount of As (III), As (V), and PO4 were compared using a column packed with granular SFM05905, and an aqueous solution was passed by a combination of several anions that are single, binary, and ternary adsorbate systems. As (III) had the highest adsorption amount; however, As (III) and PO4 were affected by each other under the ternary mixing condition. Although the adsorption amount of As (V) was smaller than that of As (III), it was not affected by other adsorbates in the column experiments. Finally, although the adsorption of both arsenic continued, the adsorbed PO4 gradually desorbed.

Evaluation of potassium ferrate activated Fe-N-modified carbons from bamboo shoot shells for arsenic removal

Fe-N-modified activated carbons (ACs) were prepared from bamboo shoot shells (BSS) by potassium ferrate activation for arsenic adsorption. BSS provided abundant nitrogen and carbon sources for ACs, while potassium ferrate significantly improved the pore volume and specific surface area (SSA), but also loaded iron particles. The highest SSA of AC was 1900 m2/g, with the iron content of 4.54–6.52% and nitrogen content of 2.88–3.35%. Based on the arsenic adsorption capacity, the optimized manufacturing process was activation temperature of 800 °C, activation time of 120 min, and activator ratio of 3.5. The optimized AC exhibited excellent arsenic adsorption performance and the maximum adsorption capacity was 9.18 mg/g. The good magnetism of AC was beneficial to recovery and reuse. The adsorption capability retention was still more than 50% after reusing for five times. This work showed that BSS had great potential for commercial development, and also provided a cost-effective production way for arsenic adsorbents.

Exceptional arsenic removal using novel mesoporous Mg-Al-Ti ternary composite oxide nanoparticles prepared via self-assembly templating method

Arsenic contamination of water through natural and anthropogenic activities is a grave problem today. One of the most efficient ways to remove arsenic from water is through adsorption. Porous nanomaterials show high adsorption capacities due to high surface area, and efficient mass transfer with plenty of active adsorption sites. Porous metal oxides have been successfully employed to remove arsenic from water previously. However, ternary metal oxide composites hold potential for novel adsorbent materials but have yet to be explored in depth. Mesoporous Mg-Al-Ti oxide composite oxide nanoparticles with varying compositions were synthesized via a low-cost, scalable, evaporation-induced self-assembly technique using P123 block copolymer as a soft template. All the compositions of synthesized ternary oxide nanoparticles exhibited exceptionally high arsenic adsorption capacities ranging from 543 to 1215 mg/g for As(V) and 359.6–919.4 mg/g for As(III) along with 96–98% removal of arsenic from real groundwater samples of up to 489.3 ppb. The composites show mesopores and high surface area ranging from 93-393.6 m2/g with very small particle size ranging from 8 to 12 nm. The nanoparticles have shown great selectivity towards arsenic and exceptional adsorption performance in a wide pH range. High volume-to-surface area ratio, an abundance of hydroxyl groups, interconnected mesoporous morphology, and high point of zero charge pH contribute to the high adsorption capacity of the composite oxides. Mesoporous Mg-Al-Ti ternary oxide composite nanoparticles have shown higher adsorption capacity towards arsenic than many existing adsorbent material materials and can be a very promising candidate for arsenic remediation from water.

Hydrogen bonding donor/acceptor active sites exposed on imide-functionalized carbon dots aid in enhancing arsenic adsorption performance

During the arsenic (As) adsorption process, amino-functionalization has been widely considered as one of the effective adsorbents optimization methods, while this study reveals that imide functional groups also play a non-negligible role. Herein, magnetic carbon dots (CDs) equipped with imide (FeCD-NH) or amino functional groups (FeCD-NH2) were synthesized to deduce the relationship between different configurations of amino-like functional groups and As. The results showed that FeCD-NH exhibited extraordinary As(V) adsorption behavior (with 97.80 % As(V) removal within 5 min), outperformed that equipped with amino functional groups (FeCD-NH2). An array of advanced characterization techniques and density functional theory (DFT) calculation collectively revealed a dual-configuration hydrogen bond synergistic mechanism of FeCD-NH toward As(V). Different from monomorphic hydrogen bond of amino functional group, imide functional group forms abundant adsorption sites through dual-configuration hydrogen bonds to realize the ultrafast adsorption of As(V). In addition, FeCD-NH can remove As(V) from other more complex water matrices to levels below the World Health Organization (WHO) drinking water standards and the Chinese surface water standards. Therefore, this work provides a promising strategy for As decontamination by fine-tune the surface chemistry of adsorbents.

Effect of aluminum modified mesoporous SBA-15 on surface properties and arsenic adsorption performance

Effect of aluminum modified mesoporous SBA-15 on surface properties and arsenic adsorption performance

Oxidative adsorption of arsenic from water environment by activated carbon modified with cerium oxide/hydroxide

Arsenic contamination at high concentration frequently occurs in nature water environments and poses a great risk to human health. In this study, a cerium oxide/hydroxide-modified activated carbon was synthesized via a simple co-precipitation process as an adsorbent for the removal of arsenic from aqueous systems. Analysis of the cerium oxide/hydroxide-modified activated carbon by field emission scanning electron microscopy and X-ray photoelectron spectroscopy showed that cerium was mainly coated on the surface of activated carbon as cerium (IV) hydroxide. The arsenic adsorption performance of the adsorbent was investigated via batchwise adsorption and using a chromatographic system with a fixed bed column. Neutral pH conditions were optimal for removal of arsenic. Kinetic experiment data were described by a diffusion–chemisorption model. The adsorption isotherm followed the Langmuir model, and the maximum adsorption capacity of cerium oxide/hydroxide-modified activated carbon was 0.220 and 0.284 mmol g−1 for As(V) and As(III), respectively. Regeneration trials showed that cerium oxide/hydroxide-modified activated carbon could be regenerated with 0.1 mol L−1 NaOH solution as regenerant. During adsorption, redox reactions occurred in the aqueous and solid phases. As(III) was oxidized to As(V) by reduction of surface functional groups (CO, C-O, and cerium oxide/hydroxide) in the solid phase and by dissolved organic matters and surface functional groups in the aqueous phase. Chromatographic treatment with a fixed bed column of cerium oxide/hydroxide-modified activated carbon showed high arsenic adsorption efficiency. The repeated use of cerium oxide/hydroxide-modified activated carbon by chromatographic operation was also achieved.

Strengthened arsenic adsorption over Ni-modified γ-Al2O3 under different operation conditions: An experimental and simulation study

• Enhanced electron transfer among Al 2 O 3 , NiO and As 2 O 3 boosts adsorption performance. • NiO reduces TS energy barrier of physically adsorbed As 2 O 3 into chemisorption state. • Stronger attraction forces promote desorption temperatures of Ni-modified γ-Al 2 O 3 . • Bond stretch of Ni-O helps to capture more As 2 O 3 molecules at higher temperatures. • Experiments of arsenic adsorption are consistent with DFT/MD simulation results. Variations of operation conditions have negative effects on arsenic adsorption of γ-Al 2 O 3 . Therefore, it is necessary to modulate γ-Al 2 O 3 for better arsenic adsorption performances under complex industrial conditions. In this study, besides complete experiments used to characterize arsenic adsorption features of Ni-modified γ-Al 2 O 3 , density functional theory (DFT) calculations and molecular dynamics (MD) simulations are also wielded to investigate arsenic adsorption enhancement mechanisms in microscale and mesoscale, respectively. As to DFT calculations, it is revealed that the strengthened electron transfer between As 2 O 3 and the adsorbent is the principal factor for 24.59–63.14 % higher adsorption energies. What is more, transition state (TS) energy barriers of physisorption structures being transformed into chemisorption are curtailed by 24.93–54.23 % and negative effects of high temperatures on dissociation of adsorption structures are also partially impaired. As far as MD simulations are concerned, stronger attraction forces of the adsorbent to arsenic molecules and the As 2 O 3 aggregation effect are leading factors for capturing 26.75 % more As 2 O 3 , which counters adverse effects of variable operation conditions. Regarding experiments, it is manifest that the arsenic adsorption amounts over Ni-modified γ-Al 2 O 3 are averagely 24.28–32.55 % higher than those over pure γ-Al 2 O 3 , which is consistent with DFT and MD results. Analyses of above three aspects would provide significant information for Ni-modified γ-Al 2 O 3 being used in real industries to remove arsenic from flue gas.

Gaseous Arsenic Capture in Flue Gas by CuCl2-Modified Halloysite Nanotube Composites with High-Temperature NOx and SOx Resistance.

Gaseous arsenic emitted from coal combustion flue gas (CCFG) causes not only severe contamination of the environment but also the failure of selective catalytic reduction (SCR) catalysts in power plants. Development of inexpensive and effective adsorbents or techniques for the removal of arsenic from high-temperature CCFG is crucial. In this study, halloysite nanotubes (HNTs) at low price were modified with CuCl2 (CuCl2-HNTs) through ultrasound assistance and applied for capturing As2O3(g) in simulated flue gas (SFG). Experiments on arsenic adsorption performance, adsorption mechanism, and adsorption energy based on density functional theory were performed. Modification with CuCl2 clearly enhanced the arsenic uptake capacity (approximately 12.3 mg/g) at 600 °C for SFG. The adsorbent exhibited favorable tolerance to high concentrations of NOx and SOx. The As2O3(III) was oxidized and transformed into As2O5(V) on the CuCl2-HNTs. The Al-O bridge had the highest adsorption energy for the O end of the As-O group (-2.986 eV), and the combination formed between arsenic-containing groups and aluminum was stable. In addition, the captured arsenic could be stabilized in the sorbent at high temperature, making it possible to use the sorbent before the SCR system. This demonstrates that CuCl2-HNTs is a promising sorbent for arsenic oxidation and removal from CCFG.

Novel design of amine and metal hydroxide functional group modified onto sludge biochar for arsenic removal.

This study involved novel-designed sludge biochar (SB) adsorbed for arsenic removal with lower operating costs and higher adsorption efficiency properties. Generally, biochar only relies on micropores for pollutant adsorption, but physical adsorption is not highly efficient for arsenic removal. Therefore, in order to improve the removal efficiency of arsenic by SB, diethylenetriamine (DETA) and FeCl3 were used in this study to modify the surface of SB by an immersion method. The objectives of this research are to obtain optimum operation conditions by assessing the effect of different Fe content, pH and initial concentration on adsorbing arsenic. This study is the first to use Density Functional Theory (DFT) to simulate and verify the adsorption mechanism of arsenic by SB. Results showed the presence of amine/iron oxyhydroxides functional groups greatly promoted SB surface activity and its arsenic adsorption potential. The surface area, pore volume and pore size of the SB were estimated to be 525 m2 g-1, 0.35 cm3 g-1 and 8.71 nm, respectively. The DFT model result is the same as the result of arsenic adsorption performance with high adsorption energy (-246.3 kJmol-1) and shorter bond distances (1.42 Å), indicating strong chemical adsorption between arsenic and material. The reaction mechanism is divided into four pathways, including oxidation-reduction, complexation, electrostatic adsorption and pore adsorption.

As2O3 adsorption enhancement over Ni-modified γ-Al2O3 in complex flue gas constituents

Arsenic adsorption capacities of γ-Al2O3 are easily affected by some flue gas constituents (e.g. SO2, NOx) based on previous studies. Therefore, promotion of arsenic adsorption performances under effects of different flue gas constituents is necessary. In this study, γ-Al2O3 plays a role of the raw adsorbent and nickel nitrate acts as the modifying agent for γ-Al2O3. Then, Ni-modified γ-Al2O3 is used as the adsorbent for arsenic adsorption experiments. Besides experiments, molecular dynamics (MD) simulations and density functional theory (DFT) calculations are performed to reveal mesoscopic and microscopic adsorption mechanisms, respectively. As to DFT calculations, the average arsenic adsorption energies are promoted by 77.5 kJ/mol, which means that nearly all adsorption structures belong to stable chemisorption. For MD simulations, the adverse molecular collision and aggregation are weakened to make the total arsenic adsorption efficiencies increase by 15.8 % averagely. As far as experiments are concerned, the arsenic adsorption amounts of Ni-modified γ-Al2O3 are averagely 0.033 mg/g bigger than those of pure γ-Al2O3 (i.e. 16.5 % in adsorption efficiencies) under some conditions, consistently corresponding to results of DFT and MD calculations. The whole understanding of this study from above three aspects can provide valuable information for applying Ni-modified γ-Al2O3 to removing arsenic in real industries.

Arsenic adsorption enhancement performances of Mn-modified γ-Al2O3 with flue gas constituents involved

Some flue gas constituents have negative effects on As2O3 adsorption of γ-Al2O3 so promoting arsenic adsorption performances under complicated flue gas conditions is necessary based on previous studies. In this study, γ-Al2O3 is modified with manganous nitrate and then Mn-modified γ-Al2O3 is used as the adsorbents in experiments. Besides, molecular dynamics (MD) simulations and density functional theory (DFT) calculations are performed to explore mechanisms of how loadings of Mn enhance arsenic adsorption features of γ-Al2O3 when being affected by flue gas constituents in microscale and mesoscale, respectively. As for DFT calculations, it is uncovered that electron transfer/interaction among As2O3, flue gas constituents and Mn-modified γ-Al2O3 mostly influences arsenic adsorption. For MD simulations, it is expounded that the collision and aggregation of As2O3 and flue gas constituent molecules have most impact on arsenic adsorption. As far as experiments are concerned, they are conducted to show the macroscopic characterizations of arsenic adsorption performances, corresponding to results of DFT calculations and MD simulations. The understanding of these three different aspects could supply significant references for utilization of Mn-modified γ-Al2O3 in real industries to remove arsenic under complex flue gas conditions.

Performance of CO2 and Fe-modified lignin char on arsenic (V) removal from water

Biochar was produced by the pyrolysis of Kraft lignin at 600 °C followed by modification with CO2 at 700 and 800 °C and impregnation with FeOx. The physicochemical properties and arsenic (V) adsorption performance of biochar were evaluated. The characteristics of the lignin biochar before and after CO2 modification and FeOx impregnation were analyzed using the following methods: proximate and ultimate analysis, specific surface area (Brunauer–Emmett–Teller (BET) surface area), porosity, scanning electron microscopy and energy dispersive spectroscopy mapping, Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. The specific surface area and porosity of biochar were improved significantly after CO2 modification. However, impregnation of FeOx in CO2-modified biochar showed a 50%–60% decrease of BET surface area and porosity due to pore blocking of FeOx. The batch adsorption of arsenic (V) showed that FeOx-LC-800 (FeOx impregnation lignin char modified with CO2 at 800 °C) had the highest adsorption efficiency among the biochars tested because of its highest Fe–O intensity and large surface area. The Langmuir adsorption model was suitable for the curve fitting arsenic (V) adsorption. The theoretical equilibrium adsorption amount (qe) was calculated to be 6.8 mg/g using a pseudo-second-order kinetic model.

Study and analysis of arsenic adsorption during sludge incineration

This paper studies the mechanism of arsenic adsorption by different adsorbents during sludge incineration. The mechanism of arsenic adsorption in the sludge incineration process was studied in a vertical furnace. The arsenic adsorption performance of CaCO3 and Fe2O3 at different temperatures was studied. When the temperature is 900°C, the overall adsorption performance is the best. Therefore, the arsenic adsorption performance of Al2O3, molecular sieve and its metal load at 900°C is further studied for comparison. The research results show that: the optimal adsorption temperature of CaCO3 is 900°C, the optimal adsorption temperature of Fe2O3 is 800°C, and the adsorption performance of CaCO3 is better than Fe2O3. Ca2+: Al3+=0.5 and Fe3+: Al3+=0.4 are close to the adsorption saturation state when Al2O3 adsorbs arsenic at 900°C. When the molecular sieve adsorbs arsenic at 900°C, the adsorption effect is best when the molecular sieve is 10X, Ca2+: Al3+=0.8 and Fe3+: Al3+=0.6 are close to the adsorption saturation state.

Facile synthesis of zirconium-organic frameworks@biomass-derived porous graphitic nanocomposites: Arsenic adsorption performance and mechanism

This work describes the preparation of novel adsorbents based on a natural biomass-derived porous graphic carbon (PGC) as a backbone for the interfacial growth of zirconium–organic framework (UiO-66) using an in situ synthetic route for the adsorption of total arsenic from water. The pristine UiO-66 and their PGC loaded nanocomposites (UiO-66@PGCx%, where x = (5, 10, 20, and 50) % (wt/wt), were tested for the adsorption of As (III)/As(V) and batch adsorption results show that the UiO-66@PGC20% nanocomposite achieves superior removal efficiencies for As(III)/As(V), compared with other developed nanocomposites and pristine UiO-66. The developed adsorbents are highly pH dependent and selective in common co-existing anions except for F−, PO43− and humic acid. The adsorption data was fitted using Langmuir isotherm and pseudo-second-order kinetic models. The adsorption mechanism was revealed through FTIR and XPS analysis, and the chemisorption of As(III)/As(V) on the surface of the UiO-66@PGC20% nanocomposite was explored. The UiO-66@PGC20% nanocomposite exhibits better chemical stability under the adsorption–desorption process and ~500 and 651 bed volumes of As(III)/As(V) contaminated water were treated in continuous fixed-bed column, also reduced the As(III)/As(V) concentration to <10 μg/L, which indicates that the UiO-66@PGC20% nanocomposite is a practical adsorbent in the field of arsenic remediation.

Rapid Preparation of TiO2-x and Its Photocatalytic Oxidation for Arsenic Adsorption under Visible Light.

A rapid preparation method of TiO2-x by thermal treatment using H2TiO3 as the precursor was proposed compared with the static hydrogenation thermal treatment process. Its adsorption properties of arsenic under visible light were explored and investigated as well. Various colors of TiO2-x were prepared and characterized via XRD, TEM, BET, and so on. The results indicate that the method of rapid preparation is feasible. The TiO2-x exhibits a larger particle size that varied from 10 nm to 2 μm, and deeper color products were obtained as the treatment temperature increased from 600 to 900 °C. Light yellow TiO2-x was prepared after increasing the temperature from 600 to 900 °C, Ti4O7 and Ti6O11 with a dark color were formed under a H2 atmosphere at 1500 °C. The arsenic adsorption performances of some samples under visible light were tested, and reveal a high efficiency of TiO2-x in the photocatalytic oxidation arsenic adsorption under visible light, the conversion ratio of As(III) photocatalytic oxidation fluctuates around 2.85 mgAsg-1 h-1. In the absence of visible light, the adsorption capacities for As(III) and As(V) are 3.7 and 42.7 mg/g, respectively, at pH = 3. Under visible light condition, the adsorption capacity of As(III) increases sharply to 15.6 mg/g, which provides the foundation for a new application of TiO2-x in the field of arsenic adsorption.

Facile inverse micelle fabrication of magnetic ordered mesoporous iron cerium bimetal oxides with excellent performance for arsenic removal from water

In this study, magnetic ordered mesoporous Fe/Ce bimetal oxides (OMICs) were successfully synthesized via the modified sol-gel-based inverse micelle method. The textural/structure properties, surface chemistry and adsorption behavior of OMICs could be easily adjusted by using the calcination temperature. The sintering of samples would decrease the surface area, while expand the pore and crystallite size, which resulted in the formation of highly ordered inner-connected structure. Compared with pure mesoporous iron oxides (MI) and mesoporous cerium oxides (MC), this ordered mesoporous iron-cerium bimetal oxides (OMIC-3, 450 °C) exhibited remarkable arsenic adsorption performance. The maximum adsorption capacities of As(III) and As(V) for OMIC-3 were 281.34 and 216.72 mg/g, respectively, and both As(III)/As(V) adsorption kinetics were well described by the pseudo-second order. The ionic strength and coexisting ions (except SiO32− and PO43-) did not affect arsenic removal, while humic acid (HA) significantly influenced on the arsenic removal even at a lower concentration. The adsorption mechanism study revealed that both the surface charge and surface M-OH groups of OMIC-3 were played the key roles in arsenic removal. The reusable property suggested that this magnetic OMIC-3 was a promising excellent adsorbent for decontamination of arsenic-polluted (especially As(III)-polluted) wastewater.

Removal of Arsenic Using a Cationic Polymer Gel Impregnated with Iron Hydroxide.

In this work, we prepared an adsorbent composed of a cationic polymer gel containing iron hydroxide in its structure designed to adsorb arsenic from groundwater. The gel we selected was the N,N-dimethylamino propylacrylamide methyl chloride quaternary (DMAPAAQ) gel. The objective of our preparation method was to ensure the maximum content of iron hydroxide in the structure of the gel. This design approach enabled simultaneous adsorption by both the polymer structure of the gel and the iron hydroxide component, thus, enhancing the adsorption capacity of the material. To examine the performance of the gel, we measured reaction kinetics, carried out pH sensitivity and selectivity analyses, monitored arsenic adsorption performance, and conducted regeneration experiments. We determined that the gel undergoes a chemisorption process and reaches equilibrium at 10 h. Moreover, the gel adsorbed arsenic effectively at neutral pH levels and selectively in complex ion environments, achieving a maximum adsorption volume of 1.63 mM/g. The gel could be regenerated with 87.6% efficiency and NaCl could be used for desorption instead of harmful NaOH. Taken together, the presented gel-based design method is an effective approach for constructing high-performance arsenic adsorbents.

Adsorption of arsenite and arsenate on binary and ternary magnetic nanocomposites with high iron oxide content

Bare maghemite nanoparticles (Nps), binary, and ternary magnetic nanocomposites prepared with titanium dioxide (TiO2) and graphene oxide (GO) were synthesized by a facile and cheap co-precipitation chemical route, and used as magnetic nanoadsorbents to remove arsenite (As(III)) and arsenate (As(V)) from water. The structural, morphological, magnetic and surface properties were analyzed by XRD, TEM microscopy, FTIR and Raman vibrational spectroscopy, Mössbauer technique and N2 adsorption-desorption measurements. It was found that materials were composed of maghemite nanoparticles with crystallites diameters varying from 9 to 13 nm for bare Nps, binary and ternary nanocomposites, these nanocomposites contain a high percentage of maghemite phase (80%). The presence of TiO2 and GO in the binary and ternary materials was also confirmed. All the samples were found to show magnetic properties and a slight porosity, with a specific surface area that increases up to 82 m2/g when the metal oxides Nps were supported on GO. The aqueous arsenic adsorption performance was studied from kinetic and equilibrium point of view, and the pH adsorption capacity dependence was evaluated aiming to explain the adsorption mechanism. The three nanocomposites prepared in this work exhibit high adsorption capacity for arsenic species, with values of maximum adsorption capacity ranging from 83.1 to 110.4 mg/g for As(III) and from 90.2 to 127.2 mg/g for As(V) from bare to ternary nanocomposites, being possible to be separated with a permanent magnet of neodymium (Nd) in less than 10 min. Therefore, these nanosystems can be proposed as good adsorbents for both arsenic species from water.

Adsorption Behavior and Removal Mechanism of Arsenic from Water by Fe(III)-Modified 13X Molecular Sieves

Presented are the synthesis and characterization of Fe(III)-modified 13X molecular sieves and their application as a novel adsorbent for removing arsenic from aqueous solutions. Batch experimental results showed that Fe(III) adsorption by 13X molecular sieves matched well with the Langmuir adsorption isotherm. The adsorption kinetics of arsenic on the Fe(III)-modified molecular sieves fit well with a pseudo-second-order model. The Langmuir adsorption isotherms of arsenic adsorption indicated the highest adsorption capacities of 1167.79 for As(V) at pH 4 and 731.56 mg/kg for As(III) at pH 9. The Fe(III)-modified 13X molecular sieves removed much more As(V) than As(III) at equivalent arsenic concentrations, regardless of the pH conditions. After As(V) removal, the Fe(III)-modified 13X molecular sieves were characterized by PXRD, SEM-EDX, and ATR-FTIR to analyze the morphology and arsenic speciation. The results of PXRD and SEM-EDX spectroscopy indicated that the material was physically stable after As(V) adsorption. ATR-FTIR spectroscopy showed that the formation of inner-sphere surface complexations between Fe hydroxide on the surface of the molecular sieves and As(V) could be a plausible mechanism for the uptake of arsenic by the Fe(III)-modified 13X molecular sieves. Therefore, the relatively low cost and remarkable arsenic-adsorption performance make the title material a promising absorbent for the treatment of arsenic in wastewater.

In Situ Oxidation and Efficient Simultaneous Adsorption of Arsenite and Arsenate by Mg–Fe–LDH with Persulfate Intercalation

Inorganic arsenic occurs mainly in As(III) and As(V) states in water environment, but arsenite is more toxic and difficult to remove than arsenate by usual adsorption processes. To achieve the in situ oxidation of As(III) and simultaneous removal of both As(III) and As(V) in water, a novel-layered double hydroxide (Mg–Fe–S2O8–LDH) with the intercalation of persulfate has been designed and synthesized by a calcination-reconstruction method. The arsenic adsorption performances and removal mechanism with the Mg–Fe–S2O8–LDH material were studied. The experimental result showed that, since the strong oxidation ability of the exchangeable persulfate ions from the LDH, the As(III) species in water were almost completely oxidized to the As(V) state and simultaneously adsorbed onto the Mg–Fe–S2O8–LDH. It was found that the maximum adsorption capacity for As(III) and As(V) in single-pollutant system was 75.00 and 75.63 mg·g−1, respectively. When the adsorbent dosage was 0.5 g·L−1 for a mixed As(III) and As(V) solution, the batch experiment showed that the residual arsenic concentration can be reduced from 1 mg·L−1 to lower than the limit value of drinking water standard recommended by WHO. It indicated that the synthesized Mg–Fe–S2O8–LDH is a potential attractive adsorbent for simultaneous removal of As(III) and As(V) in water.