Selective Removal Of Arsenic Research Articles

Fundamental research on selective arsenic removal from high-salinity alkaline wastewater

The alkaline leaching process of arsenic-containing solid waste discharged during nonferrous metal smelting affords typical high-salinity alkaline arsenic-containing wastewater (HSAW). In this study, for the first time, Me (Ca2+ and Mg2+)–AsO43−–OH−–H2O and Me (Ca2+ and Mg2+)–AsO43−–CO32−–H2O systems are studied based on a thermodynamic equilibrium diagram and an arsenic removal experiment, proving that the removal of arsenic using single metal ions in the presence of CO32− is infeasible because of carbonate coprecipitation. Based on this observation, a new method that uses magnesium ammonium complex salts (MACSs) for HSAW treatment is proposed. Based on the thermodynamic calculations of the Mg2+–AsO43−–NH4+–CO32−–H2O system and the arsenic removal experiment, carbonate and arsenate can be selectively separated by the formation of magnesium ammonium arsenate (NH4MgAsO4·6H2O). In an arsenic solution containing 150-g/L Na2CO3, the arsenic removal rate and the arsenic grade of the precipitation product reach 90.16% and 27.13%, respectively, when the molar ratios of Mg2+/NH4+:As(V) are 1.8:1 and 2:1, respectively. The proposed method is successfully employed for treating a leaching solution of alkaline arsenic slag discharged during antimony smelting. The findings of this study will broaden the basic theory of HSAW treatment and lay a foundation for the resource treatment of arsenic-containing solid waste.

Application of chromium-silicon cluster for selective removal of arsenic and sulfide from wastewater

The development of industrialisation increases the abundance of heavy metals, anionic, and harmful gases in the environment. Several techniques are already being used for the removal of different kinds of contaminants, but most of them are far away from their optimum performance. Among different approaches, the capturing of water and air pollutants by functionalised materials has been investigated widely due to cost-effectiveness, and high efficiency. From this point of view, silicon-based nanoclusters have attracted much attention due to their outstanding performance in terms of sensing properties. In the present work, we have applied the CrSi14 cluster for selective capturing of environmental pollutants. To this end, the adsorptions of heavy metal ions (As3+, Pb2+, Cd2+, Hg2+), inorganic anions (CN−, S2−, NO2 −), and gas molecules (CO, N2, CH4, CO2, NO2, H2S) on the pristine CrSi4 cluster (PC) and the functionalised cluster (FC) by 1-ethyl-3-methyl imidazolium have been investigated using first-principles methods. The results indicate that PC is not only sensitive to capture As3+ but also acts highly selective so that other examined metals would not interfere with the arsenic removal. The PC also exhibits high sensitivity toward S2- and can be considered as a prominent sorbent for the removal of sulfide.

Selective removal of arsenic from crude antimony trioxide by leaching with nitric acid

The presence of arsenic (As) in crude antimony trioxide (Sb2O3) impedes the Sb recovery and results in an environmental issue. Selective As removal from crude antimony trioxide would therefore enable using this residue in commercial Sb2O3 production. This work uses a nitric acid leaching method to remove As from crude antimony trioxide. Arsenic oxide and antimony oxide are respectively converted to soluble H3AsO4 and insoluble antimony(III) oxide hydroxide nitrate Sb(III)OHN during HNO3 leaching. The As content in the crude antimony trioxide decreases from 3.0 wt% to 0.4 wt%. The As removal ratio reaches 86%, while the Sb leaching ratio is limited to 0.3%, confirming the high selectivity of HNO3 leaching. The leaching residue is composed of cervantite (Sb2O4) and Sb(III)OHN. By calcining the leaching residue in the air at 200 °C, it can be converted to a mixture of cervantite and valentinite (Sb2O3). Finally, cervantite is decomposed above 1070 °C in N2 into Sb4O6 that can be condensed as Sb2O3. A novel flowsheet is proposed for both As removal and Sb recovery from the crude antimony trioxide.

A novel scheme for safe disposal and resource utilization of arsenic-alkali slag

As solid waste posing a great threat to the environmental system, the disposal of arsenic-alkali slag has become the top priority in the development of the antimony industry. In this paper, a novel technological scheme combining the advantages of chemical precipitation and fractional crystallization is proposed for the safe disposal and resource utilization of arsenic-alkali slag. The scheme is mainly composed of three parts, namely, leaching of arsenic-alkali slag, selective removal of arsenic in the arsenic-alkali solution, and evaporation crystallization of alkali solution. In the leaching part, the optimum leaching parameters are determined by orthogonal tests. In the arsenic and alkali separation part, based on thermodynamic analysis, the selective removal of arsenic from arsenic-alkali solution is realized by forming ammonium magnesium arsenate (MgNH4AsO4) precipitation. In the evaporation crystallization part, the crystalline product with sodium carbonate (Na2CO3) content of 89.87% is obtained by the evaporation crystallization experiment. The whole process does not produce secondary pollution and realizes the reuse of wastewater. The final products are leaching residue, arsenic slag, and sodium carbonate with an arsenic content of 0.83%, 24.93%, and 0.18%, respectively.

Alkali circulating leaching of arsenic from copper smelter dust based on arsenic-alkali efficient separation

Leaching arsenic from solid waste selectively and removing arsenic from alkaline leachate efficiently are two key points in alkali treatment of copper smelter dust, and the latter is challenging. In this study, composite salt precipitation of magnesium ammonium arsenate (NH4MgAsO4·6H2O), similar to magnesium ammonium phosphate (NH4MgPO4·6H2O), was proposed to solve the difficult problem of separation arsenic from alkali. Based on the thermodynamic analysis, the selective leaching of arsenic from copper smelting dust was carried out in the NaOH-Na2S system. In the alkali leaching system, more than 80% arsenic can be leached out from the dust with the diffusion-controlled type in the Avrami model, while the leaching rates of valuable metals are less than 0.5%. For the strong alkaline leachate containing arsenic obtained by alkali leaching, the selective removal of arsenic was achieved by adding magnesium salt and ammonium salt. With the change of the amount of magnesium salt and ammonium salt, the sedimentation performance and composition of the arsenic slag changed accordingly. At the mole ratio of NH4+: As = 8:1 and Mg2+: As = 1.5:1, 96.38% of arsenic was removed, and the content of arsenic in the arsenic slag composed of MgNH4AsO4·6H2O reached 28.96%. On this basis, the circulating alkali leaching of copper smelter dust based on arsenic-alkali separation was successfully carried out. The whole scheme is not only economical and safe, but also achieves the reuse of wastewater without secondary pollution, which provides an alternative solution for the treatment of arsenic containing solid waste.

Enhanced removal of arsenic from water by using sub-10 nm hydrated zirconium oxides confined inside gel-type anion exchanger

Given high selectivity and excellent stability, zirconium oxides are very promising in selective removal of arsenic, fluorine, and phosphorus from water. Nevertheless, it remains challenging to prepare sub-10 nm zirconium oxides of ultra-high adsorptive reactivity. Herein, we prepared hydrated zirconium oxides (HZO) of 4.88 ± 1.02 nm by conducting in-situ precipitation of nanoparticles (NPs) inside the gel-type anion exchanger (GAE). GAE was swollen in water and contained lots of < 10 nm swollen pores, restricting excess growth of HZO NPs. In comparison, the NPs formed inside the macroporous anion exchanger (MAE) possessed an average diameter of 30.91 ± 8.98 nm. XPS O1s analysis indicated that the oxygen sites in the gel-type nanocomposite (HZO@GAE) possessed a much higher proportion (48.9%) of reactive terminal oxygen (-OH) than the macroporous nanocomposite (HZO@MAE, 21.2%). Thus, HZO@GAE exhibited significantly enhanced adsorption reactivity toward As(V)/As(III) than HZO@MAE. The exhausted HZO@GAE could be fully regenerated by alkali treatment for repeated use without any loss in decontamination efficiency. In column assays, the HZO@GAE column successively produced ~2400 bed volume (BV) clean water ([As]<10 μg/L) from synthetic groundwater, exceeding twice the amount produced by the HZO@MAE column. This study may shed new light on developing highly efficient nanocomposites for water decontamination.

A Comprehensive Research on Selective Arsenic Removal from High-Salt Alkaline Wastewater

A Comprehensive Research on Selective Arsenic Removal from High-Salt Alkaline Wastewater

Selective removal of arsenic in water: A critical review.

Selective removal of arsenic (As) is the key challenge for any of As removal mechanisms as this not only increases the efficiency of removal of the main As species (neutral As(III) and As(V) hydroxyl-anions) but also allows for a significant reduction of waste as it does not co-remove other solutes. Selective removal has a number of benefits: it increases the capacity and lifetime of units while lowering the cost of the process. Therefore, a sustainable selective mitigation method should be considered concerning the economic resources available, the ability of infrastructure to sustain water treatment, and the options for reuse and/or safe disposal of treatment residuals. Several methods of selective As removal have been developed, such as precipitation, adsorption and modified iron and ligand exchange. The biggest challenge in selective removal of As is the presence of phosphate in water which is chemically comparable with As(V). There are two types of mechanisms involved with As removal: Coulombic or ion exchange; and Lewis acid-base interaction. Solution pH is one of the major controlling factors limiting removal efficiency since most of the above-mentioned methods depend on complexation through electrostatic effects. The different features of two different As species make the selective removal process more difficult, especially under natural conditions. Most of the selective As removal methods involve hydrated Fe(III) oxides through Lewis acid-base interaction. Microbiological methods have been studied recently for selective removal of As, and although there have been only a small number of studies, the method shows remarkable results and indicates positive prospects for the future.

Selective Arsenic Removal from Groundwaters Using Redox-Active Polyvinylferrocene-Functionalized Electrodes: Role of Oxygen.

In this work, we investigate selective sorption of arsenic from simulated groundwaters at pH 8 by a redox-active polyvinylferrocene (PVF)-functionalized electrode using a modified double potential step chronoamperometry (DPSC) method. Our results show that effective and sustainable As(III) removal can be achieved at 0 V once the electrode is activated via anodic polarization. During activation, ferrocene (Fc) in PVF is oxidized to the ferrocenium ion (Fc+) with the latter facilitating As(III) sorption and subsequent oxidation as well as As(V) sorption. The high affinity of Fc+ to As and weak attraction to competing anions at 0 V ensure high selectivity of As over Cl-, SO42-, and NO3- at concentrations typical of groundwaters. Following the removal process, efficient regeneration of the electrode is achieved at -1.2 V wherein Fc+ is reduced to Fc thereby facilitating As desorption from the electrode surface. Our results further show that O2 and associated generation of hydrogen peroxide during the regeneration step drive the oxidation of Fc to Fc+, thereby maintaining the constant generation of Fc+ required to achieve As(III) removal in subsequent cycles. Our results show that 91.8 ± 0.6% of As(III) could be selectively removed from simulated groundwater over 10 cycles at an ultralow energy consumption of 0.12 kWh m-3.

Studying Kinetics of Arsenic Recovery from Copper Dross by Alkaline Sulfide Leaching

Copper dross are produced by rough decopperizing of blast furnace lead bullion. During liquation separation of copper dross from lead bullion most of arsenic and copper are concentrated in copper dross, arsenic content is approximately 4% As. Currently the processes for arsenic recovery from copper dross are understudied. In this work the focus is given to studying kinetics of the process for recovering arsenic from copper dross by alkaline-sulfide leaching. Alkaline sulfide leaching allows carrying out selective removal of arsenic into solution, keeping at this non-ferrous and precious metals in leaching residue. The studied method of alkaline sulfide leaching of copper dross provides backgrounds for developing technology that would allow processing of copper dross with selective arsenic removal from lead production cycle. By minimizing circulation of this harmful impurity in lead production it is possible to lessen destructive effect of its aggressive compounds on smelting-units refractory. Kinetics of alkaline sulfide leaching of copper dross was understudied up to date. This work is an attempt to fill the gap.

Polysaccharide-derived hydrogel water filter for the rapid and selective removal of arsenic

A low-cost furfuraldehyde–chitosan cross-linked hydrogel (FCH) has been designed and synthesized as a smart bio-adsorbent for the selective removal of As(v) from an aqueous solution using a solid liquid extraction (SLX) technique.

Selective removal of arsenic from arsenic-containing copper dust by low-temperature carbothermal reduction

ABSTRACT To selectively separate arsenic from arsenic-containing copper dust, this paper reports a new method of treating the dust by carbothermal reduction and roasting it with coke powder at low temperatures. The effects of different roasting temperatures, coke powder additions and roasting times are discussed. Optimum conditions were obtained to selectively separate arsenic from other valuable metals. The volatilization rate of arsenic was 97.02% and the content of arsenic in the slag was 0.31%. Other valuable metals were not volatile under the conditions of a 350°C roasting temperature, coke powder addition of 30%wt, coke powder particle size of 0.15–1 mm, and a roasting time of 150 min.

Sorption of Arsenic from Desalination Concentrate onto Drinking Water Treatment Solids: Operating Conditions and Kinetics

Selective removal of arsenic from aqueous solutions with high salinity is required for safe disposal of the concentrate and protection of the environment. The use of drinking water treatment solids (DWTS) to remove arsenic from reverse osmosis (RO) concentrate was studied by batch sorption experiments. The impacts of solution chemistry, contact time, sorbent dosage, and arsenic concentration on sorption were investigated, and arsenic sorption kinetics and isotherms were modeled. The results indicated that DWTS were effective in removing arsenic from RO concentrate. The arsenic sorption process followed a pseudo-second-order kinetic model. Multilayer adsorption was simulated by Freundlich equation. The maximum sorption capacities were calculated to be 170 mg arsenic per gram of DWTS. Arsenic sorption was enhanced by surface precipitation onto the DWTS due to the high amount of calcium in the RO concentrate and the formation of ternary complexes between arsenic and natural organic matter (NOM) bound by the polyvalent cations in DWTS. The interactions between arsenic and NOM in the solid phase and aqueous phase exhibited two-sided effects on arsenic sorption onto DWTS. NOM in aqueous solution hindered the arsenic sorption onto DWTS, while the high organic matter content in solid DWTS phase enhanced arsenic sorption.

Selective removal of arsenic(V) from natural water using N-methyl-d-glucamine functionalized poly(propylene) membranes

Functionalized membranes for As(V) removal were synthesized by grafting glycidyl methacrylate in the fibrous and microporous host substrates, and subsequently reacting these precursor membranes with N-methyl-d-glucamine (NMDG). These membranes have been characterized and studied for As(V) removal from aqueous solution by the permeation method using dense membranes and flow-through method using fibrous membranes. In the permeation experiment, it was observed that As(V) could be transferred 60% from feed (ground water) to receiver compartment (NaOH) using the dense NMDG-membranes. The lower transfer of As(V) from feed to receiver compartment was due to counter transport of OH− ions from a receiver to a feed compartment. To address this problem, the removal of As(V) by sequential flow-through cycles of the feed and receiver across the fibrous NMDG-membrane was studied. In this mode, 92% of As(V) was sorbed in the fibrous NMDG-membrane in one cycle of 7.5min for 15mL feed. As(V) was deloaded to 66% by a single cycle of 0.3molL−1 NaOH. The HPLC method was also developed for quantifying As(V) content preconcentrated in a receiver solution. This method could be used for coupling desorption flow through cycle directly to the HPLC system. The reusability experiments showed that the membranes developed in the present work is highly stable and can be regenerated without affecting their As(V) removal efficiency.

Selective arsenic removal from enargite by alkaline digestion and water leaching

Copper concentrates with elevated enargite content are not apt to be treated by the current technology of smelting/converting because of the high risk of pollution with toxic arsenic compounds. Therefore, these copper–high arsenic concentrates must be pretreated to remove the arsenic before smelting and the traditional method of pretreatment is roasting. In this work, an alternative hydrometallurgical method for selective removal of arsenic from enargite is presented. The process consists of alkaline digestion with a concentrated Na2S–NaOH solution followed by water leaching. The experimental results obtained using high grade enargite showed that the alkaline digestion is very effective for rapid and selective removal of arsenic from enargite. The copper in the solid residues remains as digenite (Cu9S5). More than 97% of the arsenic was removed in 12min of digestion at 80°C, 100% excess of Na2S and 2M of NaOH. The kinetics of the digestion reaction was analyzed by a shrinking particle kinetic model and the determined activation energy was 22.1kJ/mol for the temperature range of 70–90°C. This activation energy is consistent with a mass transfer kinetic control.

Removal of arsenic from Laminaria japonica Aresch juice using As(III)-imprinted chitosan resin

An As(III)-imprinted chitosan resin (As-ICR) was successfully prepared to selectively remove arsenic from Laminaria japonica Aresch (LJA) juice. Batch adsorption experiments and column adsorption experiments were performed to evaluate the adsorption conditions, selectivity, and reusability. The results showed that the minimum total arsenic concentration of the juice was 4.16 mg/L at pH 6.0, 40 °C, with equilibrium time 4 h. The selectivity of As-ICR for arsenic was much higher than that of non-imprinted chitosan resin. As-ICR could be reused for 10 times with only about 13% regeneration loss. FTIR spectra demonstrated that the adsorption of As-ICR for arsenic occurred on amino and hydroxyl groups. Total arsenic concentration of the juice decreased significantly, while the other metal ions decreased except Zn2+ insignificantly. This suggests that As-ICR is a very promising sorbent for selective removal of arsenic from the juice.

Selective removal of arsenic(V) from a molybdate plant liquor by precipitation of magnesium arsenate

Precipitation of Mg 3(AsO 4) 2 for the removal of arsenic (As) from a molybdenum oxide processing plant liquor containing 70.9 g/L Mo(VI) and 469 mg/L As(V) was performed. The Stabcal software was used to model the speciation and solubility equilibria, and to identify the pH conditions at which optimum precipitation can be carried out. The optimum pH range for As(V) removal is between pH 7.5 and 10.2. This avoids the need to adjust the liquor pH to affect the precipitation. By adding magnesium chloride or sulphate at a Mg:As molar ratio of at least 2:1, As(V) could be removed to less than 5 mg/L at pH 10.2 resulting in a pure Mo(VI) liquor from which a high purity product of 99.9% MoO 3 could be produced by acidification.

Removal of arsenic from drinking water by anion exchangers

Selective removal of arsenic(V) from drinking water was carried out with strong-base anion-exchange resins. The influence on the efficiency of the process of parameters such as type of anion-exchange resin and water composition was investigated. Recycling of the sodium chloride regenerant solution was carried out by precipitating the As with FeCl 3.