Arsenic Solution Research Articles

STUDY OF THE BEHAVIOR OF ARSENIC IN COPPER ELECTROLYTE

Abstract. In industrial wastewater, arsenic is most often present in the trivalent state. An analysis of existing purification methods shows that in all cases, with a few exceptions, the most complete removal of arsenic is observed from solutions in which it is in the pentavalent state. This is explained by the significantly lower solubility of arsenates of heavy and alkaline earth metals compared to the corresponding arsenites. The chemical oxidation of As(III) in the following systems was studied: As(III)-H2SO4-H2O, As(III)-MeSO4-H2O, As(III)–H2SO4–MeSO4–H2O (where Me is Cu, Ni, Co, Mn, Zn). The influence of temperature, the amount of transition metal ions, the duration of the experiment, and the concentration of sulfuric acid on the degree of transition of As(III) to As(V) was studied. The effect of catalytic oxidation of As(III) in sulfuric acid solutions was discovered. The maximum degree of oxidation of trivalent arsenic (55-60%) is observed when transition metal salts are introduced into an arsenic solution in the presence of a platinum plate. It has been established that the nature of the studied transition metal salts (Cu2+, Ni2+, Co2+, Mn2+, Zn2+), process duration and temperature do not have a significant effect on the degree of As(III) conversion. The results obtained largely explain the predominance of pentavalent forms of arsenic in production solutions of non-ferrous metallurgy. Key words: copper electrolyte, arsenic, transition metals, catalytic role, instant oxidation effect, activated oxygen.

Mechanism and kinetics of scorodite formation in arsenic-bearing solutions using Fe(OH)3 as a solid iron source

Recently, solid iron sources have been used for scorodite synthesis in arsenic-bearing wastewater from nonferrous metallurgy. Immobilising arsenic-solution as scorodite via iron hydroxide (Fe(OH)3) solid iron source is an important method for controlling arsenic pollution. The evolution behavior of scorodite during its formation in high arsenic solution have been rarely investigated. In this paper, the mechanism and kinetics of scorodite formation using Fe(OH)3 in arsenic-bearing solution were investigated. This work was divided into three parts. Firstly, the influencing parameters were investigated, revealing that the dissolution of Fe(OH)3 and scorodite generation accelerated at lower initial pH and higher reaction temperature. Increasing Fe/As ratio delayed scorodite crystallisation, which was in turn enhanced by elevating arsenic concentration. Secondly, the mechanism of scorodite formation was investigated, revealing that Fe(OH)3 underwent acidic dissolution to form a precursor. Subsequent scorodite formation had a ΔrGmθ ranging from −69.39 kJ·mol−1 to −15.64 kJ·mol−1. Residual As was absorbed and converted into Fe(OH)3@scorodite. Thirdly, the chemical kinetics were investigated, showing that activation energy (Ea) for Fe(OH)3 dissolution was 72.54 and 105.37 kJ·mol−1 at Stages I and II, respectively, whereas it was 105.97 kJ·mol−1 for residual As absorption-conversion at Stage III outweighing the Ea of As-Fe coprecipitation. The restrictive steps were Fe(OH)3 dissolution and residual arsenic absorption-conversion. This proposed method can be applied for environment-friendly treatment of 10－40 g/L of arsenic-bearing industrial effluent for scorodite formation. Overall, this research confirmed the formation of scorodite via Fe(OH)3 and can potentially provide feasible schemes for eliminating arsenic-bearing acidic waste, dust, and anode slime from nonferrous metallurgical processes.

Turning waste into wonder: Arsenic removal using rice husk based activated carbon

In this study, rice husk activated carbon (RHAC) was synthesized by physicochemical activation, which consists of heat treatment with CO2 gasification and KOH chemical treatment to eliminate arsenic (As) from the polluted water. Initial arsenic concentrations, solution pH, solution temperature and contact time are the parameters that have been tested in this study. The characterization study showed that RHAC has a high BET surface area (815.52 m2/g) and its pore structure was found to be mesoporous with an average pore diameter of 2.96 nm. Characterization studies, including X-ray diffraction analysis (XRD), Raman spectroscopy and scanning electron microscopy (SEM) were employed to determine the RHAC’s performance. The adsorption of As towards RHAC followed the Freundlich isotherm model and pseudo-first order with adsorption process was favorable at higher arsenic concentrations. The mechanism study also signified that the adsorption of As-RHAC was limited by film-diffusion. Thermodynamic studies indicated that the As-RHAC adsorption system was endothermic, random, spontaneous, feasible in nature and governed by the chemisorption process. Desorption and regeneration studies of RHAC showed that it can be utilized up to 5 cycles and is stable for the water treatment facilities.

Enhancement in Formation of Insoluble Arsenic Phases without Re-Leaching by Particle Size of Excavated Sediment with Iron Sulfate Heptahydrate

ABSTRACT Massive quantities of naturally arsenic-containing sediments are excavated for construction. Chemical immobilization is applied to such excavated materials for reuse. Appropriate physicochemical properties should be understood to enhance the formation of the insoluble arsenic phases without re-leaching. The up-flow column retention test flowing 10 mg L−1 of arsenic solution was conducted to understand how the retention of arsenic and the phases of arsenic immobilized by iron sulfate heptahydrate depend on the particle size of the excavated sediment. The amount of arsenic retained on the immobilization material (particle size of 0.5 mm) during the retention test was lower for the larger particle size of the excavated sediment. However, arsenic was more stably retained on the immobilization material for the large particle sizes (1.0–2.0 and 2.0–5.0 mm) and the amount of arsenic re-leached was 12% of that in the small one (<0.5 mm). The percentages of arsenic in fraction 3 of sequential extraction increased from 45% to 68% with increasing the particle size. These results indicate that the excavated sediment with a larger particle size than that of immobilization material retains less arsenic on the immobilization material, but the arsenic phases immobilized are more stable, resulting in less arsenic re-leaching. This study suggests that the use of excavated sediment with a particle size larger than that of the immobilization material is desirable for the application of immobilization technique without re-leaching.

Preparation of an adsorptive membrane of polyvinylidene fluoride incorporated functionalized boron nitride nanosheets for arsenic removal

Incorporating nanomaterials into membranes will enhance wastewater treatment efficiency with their unique characteristics, such as higher permeability, thermal stability, surface roughness, hydrophilicity, and fouling control. In this study, the surface modified boron nitride with phosphoric acid 2-hydroxyethyl methacrylate ester (PA/BN) was grafted with polyethylene glycol (PEG) via conventional grafting. The PEG grafted PA/BN (PEG-g-PA/BN) melt blended with polyvinylidene fluoride (PVDF) resin by using an internal mixer at different mass percentages (100% PVDF (PVDF), 3% PEG-g-PA/BN + 97% PVDF (97:3 BN), 5% PEG-g-PA/BN + 95% PVDF (95:5 BN), 7% PEG-g-PA/BN + 93% PVDF (93:7 BN), and 7% PEG-g-PA/BNNS + 93% PVDF (93:7 BNNS). Phase inversion technique was used to cast the blended mixture into a thin membrane. The prepared membranes were analyzed with different characterization techniques to determine chemical composition, crystallinity, morphology, and thermal properties. The prepared composite membrane was evaluated in terms of water permeability, anti-fouling resistance, and solute rejection efficiency with deionized water, bovine serum albumin, and arsenic solution as well. PVDF membranes show high water flux and porosity. The water flux and porosity of the blends decrease as the percentage of PEG-g-PA/BN increases. However, the highest removal capacity for arsenic was observed at 93:7 BN. The adsorption of arsenic ions takes place via complexation with PA/BN in the PVDF matrix. This was confirmed with field emission scanning electron microscopy–energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy analyses.

Adsorption and estimation of As (III) from wastewater using cross linked Chitosan-STPP nanoparticles with voltammetric analysis computrace, isotherms, and kinetic study

Chitosan (CS) is a naturally occurring polycationic linear amino polysaccharide produced commonly through the deacetylation of chitin. This study describes the synthesis of Chitosan (CS) modified with sodium tripolyphosphate (STPP) using an efficient coated Cross-linked method. The study investigated the efficacy of chitosan-tripolyphosphate (CS-STPP) nanoparticles for the efficient adsorption of As (III) ions from a wastewater solution. The effect of initial Arsenic (III) ion concentration, solution pH, and temperature on adsorption efficiency was thoroughly investigated. The highest adsorption capacity of CS-STPP nano adsorbents for As (III) was found to be 39.8 mg/g and 39.6 mg/g, respectively, at pH 5.5, and a temperature of 30 °C. The FESEM, SEM, HRTEM, XRD, FTIR, DLS, and TGA results indicated that the adsorption process of As (III) was chemically dominating. As (III) Determine with the anodic linear sweep voltammetry 797 VA Computrace (Metrohm). The Langmuir parameters of 40.9 mg/g and 1000 L/mg were found for maximum adsorption capacity, which indicated monolayer adsorption on a homogeneous site, Freundlich isotherm is applicable for multilayer adsorption onto heterogeneous sites. The thermodynamic study showed that the adsorption of As (III) by CS-STPP was spontaneous, feasible, and exothermic at temperatures ranging from 30 °C to 50 °C. The kinetic model indicated that the adsorption processes persist well to the pseudo-second-order kinetics model. The reaction is suitable for a pseudo-second-order model, it indicates an inclination for chemisorption. Adsorption-desorption processes are determined efficiency of bio adsorbent by several physicochemical cycles. All results indicate that the prepared CS-STPP nanoparticles might be considered a cost-effective adsorbent for removing As (III) from wastewater.

Comprehensive recovery of arsenic and valuable metals from lead smelting flue dust: Process optimization and mechanism investigation

The comprehensive recovery of arsenic and valuable metals from lead smelting flue dust have received widespread attention due to its extremely high toxicity and economic value. In this research, a clean process which consisted of pressure oxidation leaching, preferential separation of Zn and Cd, reduction of As(Ⅴ) and recovery of indium was proposed. Thermodynamic calculation of leaching process suggested that the increasing of temperature reduces the redox potential required for the oxidation of As3+ to As5+, and the optimal conditions were found to be at acid concentration of 100 g/L, oxygen pressure of 2.0 MPa, temperature of 170 °C, L/S of 10 mL/g, leaching time of 2.5 h and agitating speed of 500 r/min. Under the selected conditions, the leaching extents of As, Cd, In, Sb and Zn are 99.17 %, 98.96 %, 92.68 %, 40.23 % and 96.63 %, respectively, while lead remained in the leaching residue. The separation of arsenic and other valuable metals in leachate is the most difficult and critical section of the process, where As2S3 was particularly added to the acid solution in certain manner to preferentially precipitate Zn and Cd in the forms of ZnS and CdS, subsequently reduce As(Ⅴ) to As(Ⅲ). Experiments by adding arsenic filter cake furtherly confirmed the reducibility of As2S3 and realized simultaneous extraction of arsenic in arsenic cake and acid leaching solution. Eventually, arsenic was recovered as As2O3 with a high purity of 98.56 % and the total extraction extent of indium is 93.76 %.

Arsenate and cadmium ions removal from multicomponent solutions of ionic polymers using mesoporous activated biocarbons

Activated biocarbons (AC) obtained in the process of simultaneous pyrolysis and activation of lemon balm (LB) and mint (MT) herbs with H3PO4 were used to purify aqueous solutions of cadmium, arsenate, polyethylenimine (PEI) and poly(acrylic acid) (PAA). The metals show high toxicity in the whole range of their concentrations, whereas the polymers are cytotoxic at high concentrations.The efficiency of As(V) removal from an aqueous solution depends on the pH value, while the Cd(II) adsorption on the activated biocarbons surface is independent on this parameter. The maximum adsorbed amounts are 135.8 mg/g for Cd(II) and 109.6 mg/g for As(V), respectively. The removal of metals ions and polymers from binary systems is lower in comparison to the one-component solutions. This is a consequence of the formation of polymer-metal complexes, that tend to remain in the solution. Additionally, the surface charge density, zeta potential, the size of activated biocarbons aggregates in the aqueous suspensions and the influence of toxic metal ions on the determination of the concentration of polymers in water samples was investigated. The obtained results proved that the PEI concentration can be effectively determined in the presence of metal ions, whereas the procedure of PAA determination requires additional validation.

Preparation and Characterization of Ferrihydrite: Application in Arsenic Removal from Aqueous Solutions

Arsenic pollution is a public health hazard in Burkina Faso due to its impact on human health and water resources. To mitigate this pollution, ferrihydrite material has been synthesized and characterized to be used as adsorbent for arsenic removal in aqueous solutions. This study aimed to contribute to improve of access to clean drinking water by removing arsenic from water using ferrihydrite. Arsenic species such as As(III) and As(V) were removed through batch adsorption. Experiments were carried out in batch mode using arsenic aqueous solutions. The characterization of ferrihydrite using Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDX), X-ray Diffraction (XRD), Infrared (IR), and Brunauer Emmett Teller (BET) showed that an amorphous and microporous 2-line ferrihydrite. The total specific surface area and pH at point of zero charge (pHpzc) were 184.518 m²/g and 9.41, respectively. The optimal adsorbent doses were 4 g/L for As (V) and 8 g/L for As (III). The optimum pH range for the adsorption of As (V) and As (III) was between 2 and 10, The maximum adsorption capacity was 15.07 mg/g for As(V) and 13.01 mg/g for As(III) with increasing concentration between 2 and 16 mg/L. Equilibrium time for As (V) and As (III) on ferrihydrite was found to be 720 min and 960 min, respectively. The adsorption of As(V) and As(III) was consistent with the Langmuir monolayer model on ferrihydrite. Arsenic adsorption was occurred according to spontaneous chemical reaction. Arsenic removal was occurred on a monolayer following the pseudo-second order kinetic.

Assessing the Long-Term Effectiveness of Sustainable Rural Water Treatment Technologies in Mitigating Arsenic Contamination of Groundwater in Afghanistan

Arsenic contamination in groundwater is a pressing global concern, impacting more than fifty million individuals across seventy-plus countries. Various sources contribute to this contamination, including human activities, geological processes, and natural biological factors. Afghanistan, where groundwater serves as the primary drinking water source, faces a critical need for sustainable arsenic removal solutions. Currently, 78% of the population relies on household tub wells for safe drinking water, highlighting the urgency of addressing arsenic contamination. Recent studies have revealed alarming arsenic levels, with approximately 61% of water samples exceeding World Health Organization standards.This study aims to assess and compare existing arsenic removal technologies to determine their suitability for Afghan households. Three commonly used methods—Sono Sand Filter, Kanchan Arsenic Removal, and Arsenic Bio Sand Filter—will be evaluated based on their efficacy and practicality. Preliminary findings indicate that the Arsenic Bio Sand Filter exhibits the highest efficiency, achieving a removal rate of 95%. Furthermore, this method offers additional benefits such as reducing pathogens, bacteria, iron, and turbidity levels. The ultimate goal of this research is to provide insights to policymakers and stakeholders, enabling them to develop effective mitigation strategies. By addressing arsenic-related health risks, these strategies can contribute to improving public health outcomes in Afghanistan

PSF/GO filtering membrane fabricated by electro-spinning applied on arsenic contaminated underground water

The excess arsenic content in groundwater sources threatens more than 50 million people worldwide. Current water treatment projects use polysulfone nanofiltration membranes (NFM). However, the inherent hydrophilicity of polysulfone nanofiltration membranes causes the membrane fouling problem. This study addresses this problem by improving the hydrophilic and anti-pollution properties by doping graphene oxide (GO) particles in polysulfone(PSF) membranes. Microstructure, morphology, and hydrophilicity of PSF/GO membranes were analyzed by field emission scanning electron microscope (FEFEM), contact angle, and BET surface area analysis. X-ray diffraction (XRD), zeta potential, Energy Dispersive Spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used to analyze the results of the phase structure and element distribution. Permeation tests and adsorption of arsenic experiments were used to study the filtration performance of PSF/GO membranes. The results showed that PSF/GO with high porosity enlarged the specific surface area significantly. The contact angle decreased by only about 7°. Still, the water flux increased from 33.26 L/m2/h to 183.62 L/m2/h, which weakened the effect caused by membrane contamination of the arsenate solution and GO doping on the arsenate adsorption rate of PSF/GO nanofiltration membrane was discussed. The results showed that solution pH was crucial in As (V) adsorption onto PSF/GO and obtaining higher adsorption capacity at higher pH. In an alkaline environment, The adsorption rate increased from 26.71% of pure PSF fiber membrane to 79.83%.

Arsenic removal from aqueous solution using PWN-type zeolite membrane: A theoretical investigation

Arsenic contamination in drinking water is a global health concern due to its extreme toxicity. This study explores the efficacy of PWN-type zeolite membranes in selectively removing dissolved arsenic ions. Molecular dynamics simulations analyze the permeation of aqueous arsenic solutions through the zeolite membrane under pressure-driven flow (5 to 600 MPa over 5 ns). The goal is to assess PWN-type zeolites as nanofiltration membranes for arsenic removal. The zeolite's nanoporous structure immobilizes arsenic ions while permitting water transport. Remarkably, the membrane exhibits high ion rejection, even at pressures up to 600 MPa. These findings underscore the potential of PWN-type zeolite membranes for separating As (III) ions from water supplies. With ultra-high porosity and selectivity, these nanoengineered membranes enable effective mechanical filtration processes for arsenic removal. In summary, this theoretical investigation highlights the significant promise of PWN-type zeolites as high-performance membranes for arsenic decontamination, crucial for safeguarding human health.

Isotopic Tracer Study of Initiation of Porosity in Anodic Alumina Formed in Chromic Acid.

In this paper, we focused on the initiation of porosity in the anodic alumina under galvanostatic conditions in chromic acid, using an 18O isotope tracer. The general concept of the initiation and growth of porous anodic oxide films on metals has undergone constant development over many years. A mechanism of viscous flow of the oxide from the barrier layer to the pore walls has recently been proposed. In this work, two types of pre-formed oxide films were analysed: pure Al2O3 formed in chromic acid, and a film containing As ions formed in a sodium arsenate solution. Both were anodized in chromic acid for several different time durations. Both pre-formed films contained the oxygen isotope 18O. The locations and quantities of 18O and As were analysed by means of ion accelerator-based methods supported by transmission electron microscopy. The significant difference observed between the two oxide films is in the 18O distribution following the second step of anodization, when compared with galvanostatic anodization in phosphoric or sulfuric acid reported in previous works. From the current experiment, it is evident that a small amount of As in the pre-formed barrier layer appears to alter the ionic conductivity of the film; thus, somehow, it inhibits the movement of oxygen ions ahead of advancing pores during anodization in chromic acid. However, anodising pure alumina film under these conditions does not enhance oxygen movement within the oxide layer. In addition, the tracer stays in the outer part of the growing porous oxide film. A lower-than-expected value for pure alumina enrichment in 18O in the pre-formed films suggests, indirectly, that the pre-formed film may contain hydrogen species, as well as trapped electrons, since no Cr is detected. This may lead to the presence of space charge distribution, which has a dual effect: it both retards the ejection of Al3+ ions and prevents O2- ions from migrating inward. Thus, the negative- and positive-charge distributions might play a role in the initiation of pores via a flow mechanism.

Need for external replication trials in homeopathic basic research: presenting research on three duckweed test systems as an example

One of the main aims in homeopathic basic research is to find reliable test systems that are externally replicable. In face of the replication crisis in research in general and the specificities that are necessary to include in homeopathic basic research, it is of great importance to encourage high-quality replication trials. One way to achieve that is to build up a register or a data base for test systems in homeopathic basic research that are already developed to the point that external replication trials are possible. Such a register offers the opportunity to include not just the published information but also helpful insight such as material lists and time frames for easier planning and conduction of replication trials. Additionally, further information on critical environmental parameter, unpublished negative results, etc. could be included.&#x0D; The general frame work of such a register/ data base is demonstrated with the example of three different duckweed test systems developed in our working group since 2001. The growth rate of duckweed (Lemna gibba L., clone number 9352) was investigated in randomised and blinded settings, using either untreated plants or plants pre-treated with a stressor (arsenic solution or calcium deficiency in the growth medium). Within the original trials, potentised substances in the range of 14x-33x were compared to water control groups (succussed and unsuccussed water). The stability of the test systems was investigated in parallel systematic negative control (SNC) experiments. All original trials revealed a significant influence of some potencies on the growth rate of duckweed and stable test systems as shown with SNC experiments. Four internal replication trials for two of the three test systems were conducted. The replication trials showed effects of homeopathic preparations with some differences in effect size and effect direction compared to original studies.

Sustainable removal of arsenic from waters by adsorption on blue crab, Portunus segnis (Forskål, 1775) chitosan-based adsorbents

Chitosan is the common name of a linear, copolymer of β-(1−4)-linked d-glucosamine and N-acetyl-d-glucosamine whose molecular structure comprises a backbone linked through glycosidic bonds. This polysaccharide has received a lot of attention due to its potential to remove heavy metals. In this context, this work was carried out with the aim of studying the efficacy of blue crab, Portunus segnis (Forskål, 1775) chitosan produced previously by the authors via a studied biological process to remove arsenic from aqueous solutions and therefore to be promoted in the environmental sector as effective ingredients for water decontamination. Batch experiments were performed to examine the effects of multiple parameters. Equilibrium isotherms were fitted using the Langmuir and Freundlich equation and finally, column experiments based on adsorption capacity were applied to better describe the adsorption process. The adsorption efficiency of powder from blue crab by-products, biological chitosan (BC) and commercially available chitosan (CC) was compared with that of magnetic chitosan (BMC) which was also prepared by a cross-linking reaction using glutaraldehyde (GTA) in the presence of magnetite. Features of each chitosan forms were analyzed by a field emission-scanning electron microscopy (FE-SEM). The BMC has been found to be effective in removing arsenic. Indeed, both BMC and CC showed improved adsorption behavior of arsenic after the addition of magnetic nanoparticles. The arsenic removal behavior of most materials can be explained by a pseudo-second-order kinetic model mechanism. The pH of the arsenic solution depends on the acid-base state of the adsorbent, which further influences the adsorption performance.

Regulation and mechanism of pyrite and humic acid on the toxicity of arsenate in lettuce

Pyrite and humic acid are common substances in nature, and the combined effects of pyrite and humic acid on arsenic phytotoxicity are more widespread in the actual environments than that of a single substance, but have received less attention. In this study, the interaction between pyrite and humic acid in arsenate solution was studied, and the effects of pyrite and humic acid on plant toxicity of arsenate were evaluated. The results showed that arsenate + pyrite + fulvic acid (V-PF) treatment immobilized more arsenic by forming chemical bonds such as AsS and Fe-As-O and reduced the migration of arsenic to plants. Compared to the arsenate + fulvic acid (VF), arsenate + pyrite (VP) and arsenate (V) group, the inorganic arsenic content of lettuce leaves in the V- PF group was reduced by 19.8 %, 13.4 % and 13.4 %, respectively. In addition, the V-PF group increased the absorption of Ca, Fe and Cu in plant roots, and improved the activity of superoxide dismutase (SOD) in plant leaves. Compared to the VF group, SOD and MDA in the V-PF group increased by 34.1 % in 30 days and decreased by 47.3 % in 40 days, respectively. The biomass of lettuce in V-PF group was increased by 29.3 % compared with that in VF group on day 50. The protein content of the V-PF group was 58.3 % higher than that of the VF group and 23.1 % higher than that of the VP group. Furthermore, metabolomics analysis showed that the V-PF group promoted glycolysis by up-regulating glyoxylic acid and dicarboxylic acid metabolism, thus reducing carbohydrate accumulation. Phosphocreatine metabolism was also up-regulated, which decreased the oxidative damage in lettuce induced by arsenic. This study will provide new ideas for scientifically and rationally assessing the ecological environmental risks of arsenic and regulating its toxicity.

Study of the Viscosity of Arsenic Acid Solutions

Study of the Viscosity of Arsenic Acid Solutions

Cellular uptake and biotransformation of arsenate by freshwater phytoplankton under salinity gradient revealed by single-cell ICP-MS and CT-HG-AAS

Environmental context Freshwater phytoplankton are involved in the biogeochemical cycling of arsenic within aquatic ecosystems via uptake processes. Rather than determining the mean arsenic content in a population of freshwater phytoplankton, we investigate the heterogeneity of arsenic uptake by single-cell ICP-MS. Our data show that arsenic distribution within a cell population may be highly heterogeneous, measured at the femtogram per cell level, and are affected by species and salinity. Rationale An advanced technique has been developed for analysing intracellular elements at the single-cell level using single-cell inductively coupled plasma mass spectrometry (SC-ICP-MS). Compared with conventional inductively coupled plasma mass spectrometry (ICP-MS) analysis, SC-ICP-MS provides uptake data with greater biological relevance. In this study, the use of SC-ICP-MS enabled the quantification of metal concentrations on an individual cell basis down to the femtogram (fg) per cell level. Methodology Three freshwater phytoplankton cells, namely Staurastrum paradoxum (S. paradoxum), Pediastrum duplex (P. duplex) and Scenedesmus acutus (S. acutus), were incubated in 0.1 µmol L−1 arsenate (AsV) solution for 14 days at varying salinity. Cold trap hydride generator atomic absorption spectrometry (CT-HG-AAS) was used to investigate the biotransformation of arsenate under varying salinity conditions. Results The results reveal that cellular arsenic levels decreased as salinity increased in P. duplex and S. paradoxum but increased in S. acutus. The SC-ICP-MS data, which show uptake of AsV by freshwater phytoplankton, were in good agreement with those produced using ICP-MS analysis. Various arsenic management strategies were seen in the phytoplankton species: P. duplex converted it to methylated forms; S. acutus produced organoarsenicals; and S. paradoxum reduced arsenate (AsV) to arsenite (AsIII) and excreted it. Our study also showed changes in the physiological status of phytoplankton following salt stress and arsenic exposure. Discussion Our results confirm the efficacy of SC-ICP-MS in precisely determining arsenic distribution at the single-cell level and reveal differences in intraspecies mechanisms for arsenic cycling in freshwater ecosystems.

An efficient and affordable hydrometallurgical process for co-treatment of copper smelting dust and arsenic sulfide residue

We developed a novel method for comprehensive treatment of copper smelting dust (CSD) and arsenic sulfide residue (ASR) using three processes: leaching CSD by sulfuric acid, Cu precipitation with ASR, and FeSO4·7H2O/O2 co-oxidizing and precipitating As. The novel method not only realizes the recovery of valuable metals from dust, but also removes and solidifies As in CSD and ASR in the form of scorodite to achieve harmless treatment. With sulfuric acid as leaching agent, the leaching efficiencies of Cu, Zn and As reached 87.23%, 93.07% and 95.21%, respectively, under the optimum conditions. Subsequently, Cu in CSD leaching solution was precipitated in the form of CuS by ASR, and the Cu precipitation percentage reached 97.39% and 94.86 wt. % of As in ASR entered the solution under the optimum conditions. Finally, FeSO4·7H2O/O2 was used to co-oxidize As(III) and simultaneously precipitate the As in the form of scorodite. The oxidation percentage and precipitation percentage of arsenic reached 98.73% and 96.77%, respectively. The leaching concentration of As in the arsenic precipitate residue (APR) was only 0.17 mg/L in the toxicity characteristic leaching procedure (TCLP). The arsenic precipitate solution can be directly used to recover Zn.

Photochemical Hydride Generation in Sulfite Medium: Sample Introduction into an Inductively Coupled Plasma Mass Spectrometer for the Determination of Ultratrace Inorganic Arsenic.

This Technical Note reports a new UV photochemical hydride generation (PHG) of As(III/V) in a sulfite medium. Combining PHG for sample introduction with sector field inductively coupled plasma mass spectrometry (SF-ICPMS) for detection, we established a novel and ultrasensitive approach for the determination of total inorganic As. Arsine was generated simply by exposing arsenic solutions containing 2 mM of sodium sulfite to UV irradiation for 10 s with 1 mM of sodium formate for sensitivity enhancement. An impressive limit of detection of 0.2 ng/L for As, suitable for the quantitation of inorganic arsenic at ultratrace levels, was readily achieved. Formation of hydrated electrons and hydrogen radicals was experimentally validated, and this may be responsible for the reduction of the high-valent arsenic species. The PHG may also provide a new and useful alternative to conventional hydride generation and photochemical vapor generation for the determination of other trace elements, such as Se(VI) and Te(VI), and by other atomic spectrometric techniques.