Removal Arsenic Research Articles

Study on ultrasonic assisted intensive leaching of germanium from germanium concentrate using HCl/NaOCl

Ultrasonic radiation is widely used in the enhancement of leaching process with outstanding advantages in leaching efficiency. In this study, a germanium concentrate was leached with NaClO and the influence of factors such as ultrasound power and oxidant addition on the leaching efficiency of germanium from the concentrate were investigated. The leaching efficiency of germanium reached 96.8% at the initial concentration of hydrochloric acid of 8 mol/L, the oxidant dosage of 1.5 g/L NaClO, the liquid-solid volume/mass ratio of 6 mL/g, the ultrasonic power density of 13.3 W/cm3, and the stirring speed of 300 rpm for 30 min at 60 °C. The leaching efficiency was 4.50% higher at a shorter leaching time and lower temperature, than that of the conventional process, which was mainly attributed to the ultrasonic multiple effects and NaClO. Meanwhile, NaClO can effectively oxidize As(III) into non-volatile As(V), remove arsenic in germanium, facilitate the subsequent distillation, improve the leaching efficiency, and be more environmentally friendly.

Reduction of Toxic Metal Ions and Production of Bioelectricity through Microbial Fuel Cells Using Bacillus marisflavi as a Biocatalyst.

Industrialization has brought many environmental problems since its expansion, including heavy metal contamination in water used for agricultural irrigation. This research uses microbial fuel cell technology to generate bioelectricity and remove arsenic, copper, and iron, using contaminated agricultural water as a substrate and Bacillus marisflavi as a biocatalyst. The results obtained for electrical potential and current were 0.798 V and 3.519 mA, respectively, on the sixth day of operation and the pH value was 6.54 with an EC equal to 198.72 mS/cm, with a removal of 99.08, 56.08, and 91.39% of the concentrations of As, Cu, and Fe, respectively, obtained in 72 h. Likewise, total nitrogen concentrations, organic carbon, loss on ignition, dissolved organic carbon, and chemical oxygen demand were reduced by 69.047, 86.922, 85.378, 88.458, and 90.771%, respectively. At the same time, the PDMAX shown was 376.20 ± 15.478 mW/cm2, with a calculated internal resistance of 42.550 ± 12.353 Ω. This technique presents an essential advance in overcoming existing technical barriers because the engineered microbial fuel cells are accessible and scalable. It will generate important value by naturally reducing toxic metals and electrical energy, producing electric currents in a sustainable and affordable way.

Combined Electrodialysis and Electrocoagulation as Treatment for Industrial Wastewater Containing Arsenic and Copper.

In copper smelting processes, acidic effluents are generated that contain inorganic contaminants such as arsenic and copper. Nowadays, the treatment of wastewater is done by physicochemical methods without copper recovery. Electrodialysis is an alternative process that can recover copper. Moreover, when electrocoagulation is applied to remove arsenic from wastewater, a more stable final sludge of less volume is obtained. The present research studies the application of a combined electrodialysis and electrocoagulation process to (1) recover Cu and (2) precipitate and remove arsenic simultaneously in the same batch reactor, using synthetic wastewater that simulates wastewater from a copper smelter. Copper and arsenic could be removed and separated by the electrodialysis part, and the electrocoagulation of arsenic was verified. With electrodialysis, the arsenic and copper removals were 67% and 100%, respectively, while 82% of the arsenic arriving at the electrocoagulation part of the cell could be precipitated and removed by this process. Initial concentrations were around 815 mg L-1 Cu and 7700 mg L-1 As. The optimal current was found to be 1.36 A due to the shorter treatment times necessary to get removal percentages, recovery percentages and energy/removed copper mass ratios in the same ranges as the values achieved with a current of 1.02 A. In summary, the combined process is a promising tool for simultaneous copper recovery and arsenic removal.

What's in your water? A well-known risk for arsenic toxicity.

Arsenic cannot be tasted, seen or smelled and can vary in concentration between water wells even in condensed areas. American domestic well water is not regulated to meet the same drinking water standards as other types of water supplies and often contains arsenic. If arsenic is not detected in a well water sample, it is unlikely to be found later. Conversely, if it is detected in a new well, it is recommended to retest six months later as levels may fluctuate in the first months following well construction. It is up to the well owner to test their water and remove arsenic through commercially available water filters. If it is not detected and removed via filtration, a variety of serious, yet common, medical conditions may arise from chronic arsenic exposure, some of which are life-threatening. These include diabetes mellitus, hypertension, skin cancer, renal, bladder and lung cancers, polyneuropathy and cardiac QTc prolongation. Testing is best done through urine speciation if an initial total urine arsenic concentration is elevated. Consider a complete blood count, renal and liver function tests, an electrocardiogram as well as a urinalysis assessing for evidence of hematuria when examining patients with histories concerning for chronic arsenic exposure.

Novel iron-supported ZSM-5 molecular sieve remove arsenic from wastewater by heterogeneous nucleation with pH limit breaking

Molecular sieves have also been used for arsenic adsorption in recent years because of their special structure. In order to solve the problem of arsenic pollution in drinking water and/or industrial wastewater, ZSM-5/Fe adsorbent was prepared by loading iron on ZSM-5 molecular sieve. It is also used as an excellent adsorbent for removing arsenic and other heavy metal ions from industrial wastewater. At room temperature, the concentration of arsenic was reduced from 100 mg/L to 0.006 mg/L after the solution pH was adjusted to the range of weak acid to weak base (4–10) and 0.5 g of ZSM-5/Fe adsorbent was added for reacting 2 h. The adsorption capacity reached 40.00 mg/g, the adsorption efficiency reached 99.99%, reaching the national standard of drinking water. Adsorption thermodynamics, kinetics and isotherms showed that the adsorption mechanism of arsenic is heterogeneous nucleation adsorption (including electrostatic attraction and chemical precipitation). Moreover, ZSM-5/Fe adsorbent can adjust pH spontaneously by using non-skeleton Si–Al phase to achieve effective adsorption from weak acid to weak base. At the same time, ZSM-5/Fe adsorbent showed good reusability and stability in five cycles. This study provides an important idea for the application of ZSM-5 molecular sieve in many fields and the efficient removal of arsenic from drinking water and industrial wastewater.

New material for arsenic (V) removal based on chitosan supported onto modified polypropylene membrane.

This paper presents a new material easily synthesized and with low cost, with the possibility of remove arsenic and the potential capability for the remediate water bodies. In this work, the efficiency in removing arsenic of the chitosan, supported onto modified polypropylene membrane, was studied using an aqueous As(V) solution of 0.4 mg/L, achieving a removal efficiency of 75%, which corresponds to an adsorption capacity of 0.031 mg/g. The As(V) adsorption depends on pH and the degree of chitosan grafting on the polypropylene membrane. A pseudo-second-order equation describes the adsorption of the membrane, classifying it as a chemisorption process. The chitosan supported on the membrane was characterized by the analysis of wettability, FT-IR-ATR, SEM-EDS, XRD powder, and surface charge. The As ions coordinate to the chitosan polar groups, allowing their removal from the aqueous solution.

Separation of arsenic and tin from Cu–As alloy based on phase transformation in a vacuum to form Cu–Fe–S compounds

Cu–As alloy is viewed as one kind of secondary copper resources. It is difficult to simultaneously recover copper and remove arsenic using conventional processes. To separate arsenic and tin from Cu–As alloy (mainly Cu3As), an innovative methodology that uses vacuum distillation in the presence of pyrite to form new phase is proposed herein. The constituents, phases and morphology of the sample before and after vacuum distillation were investigated by chemical analysis, X-ray diffraction (XRD) analysis and electron probe microanalysis (EPMA) to interpret separation performances and volatilization mechanisms of arsenic and tin. Chemical analysis results showed that it is difficult to separate arsenic from Cu-As alloy by direct vacuum distillation, but arsenic and tin were effectively separated after introducing pyrite. The effects of several factors, such as temperature, pyrite dosage and distillation time, on separation performances of arsenic and tin were examined. Volatilization ratios of copper, arsenic and tin reached 0.84%, 96.29% and 88.70%, respectively. Results of XRD analysis and EPMA revealed that arsenic had strong affinity to copper in Cu-As alloy, which inhibited free volatilization of arsenic. After introduction of pyrite, formation of copper sulfides, such as mainly Cu5.433Fe1.087S4, Cu1.96S and Cu9S5, destroyed the alloy structure, which made elemental arsenic volatilize. Excessive sulfur also interacted with elemental arsenic to form mainly As4S3 that is also easily volatilized. Nevertheless, tin was only separated in the form of SnS. It is a promising method to achieve cleaner utilization of Cu-As alloy and effective control of arsenic pollution.

Fabrication and characterization of copper (II) oxide/iron (III) oxide thin film heterostructures for trace arsenic (III) removal in water

In this study, nano-heterostructures based on copper (II) oxide/iron (III) oxide (CuO/α-Fe2O3) thin films were fabricated by a dip-coating technique using aqueous solutions. The heterostructures were deposited on fluorine-doped tin oxide glass substrates varying the CuO film thickness. From a detailed characterization using Fourier transform-infrared and X-ray diffraction the formation of CuO (tenorite)/α-Fe2O3 (hematite) was demonstrated. Atomic force microscopy provided valuable information on the growth of α-Fe2O3 crystals in the heterostructure with a conical-shaped surface. Meanwhile, the field emission scanning electron microscopy cross-section images confirm the formation of well-defined CuO layers under the α-Fe2O3 layers. The optical band gap energies for the heterostructures obtained were estimated from the diffuse reflectance spectra and ranged from 1.41 to 1.51 eV. Photoluminescence analysis revealed an improved separation and faster transfer of photogenerated electrons and holes for the heterostructures. The removal arsenic from an aqueous solution was achieved through the direct adsorption for As(III) and visible light oxidation to As(V). An enhancement of removal efficiency of As(III) for the heterostructures fabricated compared to pristine oxides was obtained.

Recovery of Gallium from Simulated GaAs Waste Etching Solutions by Solvent Extraction

Gallium arsenide is used in semiconductor industries worldwide. Numerous waste etching solutions are produced during the processes of GaAs wafer production. Therefore, a complete and eco-friendly technology should be established to recover gallium as a gallium chloride solution and remove arsenic ion from waste GaAs etching solution. In this study, the gallium trichloride and arsenic trisulfide powders were dissolved in ammonia solutions to prepare the simulated solutions, and the pH value was adjusted to pH 2 by nitric acid. In the extraction step, the GaAs etching solutions were extracted using 0.5 M Cyanex 272 solutions in kerosene at pH 2 and 0.1 O/A ratio for 5 min. The extraction efficiency attained 77.4%, which had an optimal ratio of concentration, and the four steps extraction efficiency attained 99.5%. After extraction, iron sulfate heptahydrates were added into the raffinate, and the arsenic ions were precipitated. The removed rate attained 99.9% when the Fe/As ratio was 10. In the stripping step, the organic phase was stripped with 0.5 M hydrochloric acid at 1 O/A ratio for 3 min, and 97.5% gallium was stripped. Finally, the purity of gallium chloride solution was 99.95% and the gallium was seven times the concentration of the etching solutions.

Element Distribution in Oxygen-Enriched Bottom-Blown Smelting of High-Arsenic Copper Dross

An oxygen-enriched bottom-blown smelting process has been proposed to extract valuable metals and remove arsenic from high-arsenic copper dross. PbO, PbS, Cu2S, and Cu5As2 were the main components of the copper dross. Iron scrap, calcium carbonate, coke, and silica were added as flux in the smelting process. Mineralogical analysis revealed that the smelting products were ferrous calcium silicate slag, lead copper matte (PbS and Cu2S), speiss (Cu3As), crude lead (Pb), and dust. Approximately 35% of copper distributed to lead copper matte, while 56% of copper and 75% of arsenic reported to speiss. The Cu concentrated in economical products for further extraction reached 91%, 87% of Pb was directly recovered to crude lead, and the As removed to dust was 4–6%. The technology was first developed and applied in industry by Henan Yuguang Gold and Lead Group Co., LTD, providing an efficient approach and production experience for copper dross recycling.

Adsorption properties of arsenic on sulfated TiO2 adsorbents

Adsorption technologies are considered to be cost-effective solutions for the removal of toxic residues. In the present study, two types of sulfated TiO2 adsorbents, sulfated–TiO2(A) and sulfated–TiO2(B), were prepared by the wetness impregnation method, and tested for how effectively they could bind to, and hence, remove arsenic. These adsorbents were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The interaction of the arsenic with the sulfate group at the surface of the adsorbent can be deduced by the reduction in the peak intensity of the SO bond at 1219 cm−1, corresponding to the SO42− group. In particular, the number of Lewis and Brønsted acid sites was enhanced in the sulfated–Ti(OH)4 adsorbents, which modulated the surface acidity of titania by controlling the electron density and facilitated the adsorption of arsenic. Our results confirmed that sulfated–TiO2(B) is 20% more efficient at removing arsenic, as compared to TiO2 (60%) and Ti(OH)4 (64%).

Exploration on the removal of arsenic in silicon under electron beam melting condition

Arsenic is one of the main impurity elements in silicon. Electron beam melting (EBM) is considered an effective method for the purification of silicon. The removal of arsenic from silicon is performed by electron beam solidification furnace in this paper. The results demonstrated that arsenic could be removed effectively by EBM process with the average removal efficiency up to 95.4% and show the morphology of silicon ingot is less essential to distribution of arsenic impurities in the silicon ingot. The evaporation behavior of arsenic atoms is more important in the process of arsenic removal by EBM. The relationship between the evaporation coefficient of arsenic impurities and temperature was deduced. It provides a reference for further research on removal arsenic in silicon by EBM.

Anaerobic digestion to reduce biomass and remove arsenic from As-hyperaccumulator Pteris vittata

The lack of efficient methods to treat As-rich biomass is a drawback for phytoremediation technology. In this study, we applied anaerobic digestion to reduce biomass and remove As from As-rich Pteris vittata biomass. P. vittata biomass including control (3.1 mg kg−1 As) and As-rich (2665 mg kg−1 As), together with positive and negative controls, was anaerobically digested at 35 °C for 35 d. Arsenic partitioning among gas, liquid and solid phases after anaerobic digestion was determined. Methane index potential assay was used to assess methane yields whereas liquid-displacement method was used to measure methane gas production. After 35 d, As partitioning in the liquid, solid and gas phases was 79, 30 and 1%, respectively. Besides, volatile solid was decreased from 91 to 12–17% total solid, while P. vittata biomass was decreased by 73–83%. Moreover, anaerobic digestion solubilized 76% As from P. vittata biomass, with 90% soluble As at 4.95 mg L−1 being recovered by As-Mg precipitation. Finally, methane production after 35 d was 197–212 LNCH4/kg volatile solid, showing slight As inhibition. Effective As removal from P. vittata biomass prior to disposal can improve the phytoremediation process.

Adsorption kinetic and species variation of arsenic for As(V) removal by biologically mackinawite (FeS)

Biologically mackinawite was synthesized by FRB and SRB culture solutions, which had been shown a crucial role in removal arsenic under anaerobic environment. To investigate the changes of arsenic species in aqueous by As(V) sorption onto biologically FeS, As(III/V) in aqueous were detected by HPLC-AFS. And the solid phase was characterized by XRD, XPS, and BET. The adsorption envelope of As(T) shown the high uptake occurred at pH 5. The adsorption kinetics followed the pseudo- second- order model and the isotherm followed by Langmuir equilibrium for different solid/solution ratios. The maximum sorption capacities were 237.45 mg/g (0.05 g/L FeS), 160.45 mg/g (0.1 g/L FeS), and 56.71 mg/g (0.2 g/L FeS), respectively. The results showed that sorption for As(V) sorption by FeS decreased with increased in solid/solution ratios. Our results showed that As(V) was reduced to As(III) or lower valences in As(V) sorption experiments. The results showed that the As(others) dominated in the batch experiments and the As(V) was the main state in the column experiments. The XPS date suggested that the FeS particles were effective for reduce As(V) and the As(others) were possibly As-S and As-As complexes.

Removal of Arsenic from Groundwater Using Nano-Metal Oxide Adsorbents

Arsenic can be found in groundwater that is harmful to human beings. In this research, we present the potential uses of ZnO microparticles, ZnO and TiO2 nanoparticles to removal arsenic in groundwater. The experiments of %arsenic removal upon using ZnO microparticles ZnO and TiO2 nanoparticles were conducted in 25 mL of sample volume with 0.05 g of nanoadorpbents at pH 6. We found that the efficiency of arsenic adsorption increased with a reduction of particle size of theadsorbents. Upon using nanoadsorbents to remove arsenic from the solutions with the concentrations of 200-2000 ppb, we found that the %removal of arsenic decreased from 100% to 84% for ZnO nanoparticles and 100% to 97% for TiO2 nanoparticles. Adsorption capacities upon using ZnO and TiO2 nanoparticles were 0.85 and 0.99 mg of arsenic/g of sorbents, respectively. TiO2 nanoparticles exhibited a better adsorption ability to arsenic than that ZnO because TiO2 nanoparticles had a smaller average particle size and larger surface area allowed the adsorption of hydroxyl groups on the surface that could bond with in coming HAsO42- via hydrogen bonding resulting in a better arsenic adsorptive capacity.

Schwertmannite Adherence to the Reactor Wall during the Bio-Synthesis Process and Deterioration of Its Structural Characteristics and Arsenic(III) Removal Efficiency

Schwertmannite, a kind of iron oxyhydrosulfate mineral, can removal arsenic(III) from arsenic(III)-bearing groundwater by the adsorption process. In this study, schwertmannite was bio-synthesized by Acidithiobacillus ferrooxidans LX5 in shaking flasks (160 rpm) containing a 0.16 mol/L FeSO4 liquid solution. After bio-synthesis, 25.5% of the bio-synthesized schwertmannite adhered to the reactor wall (designated as adhered-sch) and the remainder was suspended in the system (designated as suspended-sch). Particles of adhered-sch exhibited a fractured structure with a small specific surface area (4.36 m2/g) and total pore volume (3.13 × 10−2 cm3/g). In contrast, suspended-sch had a spiny structure (similar in appearance to a hedgehog), and a larger specific surface area (9.62 m2/g) and total pore volume (8.01 × 10−2 cm3/g). When 0.25 g/L of adhered-sch was used as an adsorbent for arsenic(III) removal from 1 mg/L arsenic(III)-bearing waters (at pH 7.5), the arsenic(III) removal efficiency was 43.2% after 4 h of adsorption. However, this efficiency could be increased by 50% by using suspended-sch as the adsorbent. Furthermore, by adding 13.3 g/L and 26.7 g/L additional schwertmannite into the reactor system prior to schwertmannite bio-synthesis, all synthesized schwertmannite remained suspended in the bio-synthesis systems, and the ferrous ions’ bio-oxidation efficiency was improved to a certain extent. Due to the friction effect between the introduced schwertmannite and the reactor wall, adhered-sch was eliminated. The outcomes of this study will provide the necessary data for schwertmannite bio-synthesis and arsenic(III) removal from arsenic(III)-bearing groundwater.

Natural soil helps remove arsenic, fluoride

Natural soil helps remove arsenic, fluoride

RESEARCH ON SURVEY AND ASSESSMENT OF THE CONDITIONS AFFECTING ARSENIC ADSORPTION AND REMOVAL BY STEEL SLAG IN WATER

This paper presents the results of this research which utilizes solid waste resources in the environment, namely steel slag, to adsorp and remove arsenic in water. The study conducted empirical processes based on the processes in the experimental conditions affecting arsenic adsorption and removal by steel slag in contaminated water: concentration, steel slag size, steel slag weight, pollution concentration, temperature, symbiotic ions. The research results show: The lower initial solution concentration is, the more easily adsorption equilibrium can achieve, the higher initial concentration is, the longer it takes to reach adsorption equilibrium; the smaller steel slag particle is, the more easily adsorption equilibrium can reach; the larger particle size, the longer the time to reach adsorption equilibrium; the more increasing the number of steel slag particles, the greater the pollutant adsorption, the higher the removal efficiency; initial pH concentration affects As adsorption of steel slag (III); influence of temperature on As adsorption of steel slag (III) is not clear; different ions (NO3-, Cl‑, F-, SO42- and PO43-) intervene in As adsorption of steel slag (III) in solution. Thus, the choice of steel slag as the material to adsorb and remove arsenic in water is the optimal method, bringing economic efficiency, environmental protection and practical application.

Removal of arsenic by magnetic biochar prepared from pinewood and natural hematite

There is a need for the development of low-cost adsorbents to removal arsenic (As) from aqueous solutions. In this work, a magnetic biochar was synthesized by pyrolyzing a mixture of naturally-occurring hematite mineral and pinewood biomass. The resulting biochar composite was characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDS). In comparison to the unmodified biochar, the hematite modified biochar not only had stronger magnetic property but also showed much greater ability to remove As from aqueous solution, likely because the γ-Fe2O3 particles on the carbon surface served as sorption sites through electrostatic interactions. Because the magnetized biochar can be easily isolated and removed with external magnets, it can be used in various As contaminant removal applications.

Research on Influences of "A Test of Different Initial pH from the Reaction" with Properties of Environment Materials on Distribution of Arsenic Speciation Arsenic-Ferric Precipitation

The distribution of arsenic speciation can be applied to elucidate the mechanism of removal arsenic during treatment the water containing arsenic with molysite. In this study, the effect of initial pH on the distribution of arsenic speciation in arsenic-ferric precipitation was determined by a five-step sequential extraction procedure. And then further explore the mechanism of arsenic removal with molysite. This experimental results showed that the main mechanisms governing the arsenic removal with ferric chloride were specific adsorption and coprecipitation. Besides, as pH increased from 5 to 9, the arsenic-ferric coprecipitation played a more and more important role in mechanism of arsenic removal with molysite. At the same time, the water soluble state As and the non-specific adsorption As were barely detectable, which suggested that physical absorption had almost no effect on arsenic removal.