Novel ball-milled biochar-vermiculite nanocomposites effectively adsorb aqueous As(Ⅴ)

Ball milling was used to fabricate a nanocomposite of 20% hickory biochar (600 °C) and 80% expanded vermiculite (20%-BC/VE). This novel composite adsorbent had much higher removal of As(V) from aqueous solutions than ball-milled biochar and expanded vermiculite. Characterization of these adsorbents showed that the enhanced As(V) adsorption was ascribed to much larger surface area and pore volume (2-6 times), notable changes in crystallinity, activation of cations, and increased functional groups in the nanocomposite compared with the ball-milled products of their pristine counterparts. The As(V) adsorption process by the 20%-BC/VE fitted well with the pseudo-second-order kinetic model (R²= 0.990) and Langmuir isotherm model (R²= 0.989) with a maximum adsorption capacity of 20.1 mg g^-1. The 20%-BC/VE best performed at pH about 6. The adsorption efficiency was not sensitive to the competition of NO₃^-, Cl^-, SO₄^2-, as well as the coexistence of humic acid. However, the adsorption capacity for As(V) was significantly reduced by coexisting with PO₄^3-. The 20%-BC/VE composite can potentially serve as a superior low-cost adsorbent for As(V) removal in real-world applications.

Analytical Methodologies for the Determination of Organoarsenicals in Edible Marine Species: A Review

Setting regulatory limits for arsenic in food is complicated, owing to the enormous diversity of arsenic metabolism in humans, lack of knowledge about the toxicity of these chemicals, and lack of accurate arsenic speciation data on foodstuffs. Identification and quantification of the toxic arsenic compounds are imperative to understanding the risk associated with exposure to arsenic from dietary intake, which, in turn, underscores the need for speciation analysis of the food. Arsenic speciation in seafood is challenging, owing to its existence in myriads of chemical forms and oxidation states. Interconversions occurring between chemical forms, matrix complexity, lack of standards and certified reference materials, and lack of widely accepted measurement protocols present additional challenges. This review covers the current analytical techniques for diverse arsenic species. The requirement for high-quality arsenic speciation data that is essential for establishing legislation and setting regulatory limits for arsenic in food is explored.

Arsenolipids in the green alga Coccomyxa (Trebouxiophyceae, Chlorophyta)

Lipid-like compounds containing a dimethylarsinoyl group, i.e. Me₂As(O)-, have been identified by liquid chromatography/inductively coupled plasma mass spectrometry (LC/ICP-MS) and non-aqueous reversed-phase high-performance liquid chromatography (positive and/or negative high-resolution tandem electrospray ionization mass spectrometry (NARP-HPLC/HR-ESI^+(-)-MS/MS) from three strains of green algae of the genus Coccomyxa (Trebouxiophyceae, Chlorophyta). The algae were cultivated in a medium containing 10 g arsenic/L, i.e. 133.5 mmol/L of Na₂HAsO₄.7H₂O. After extraction by methyl-tert-butyl ether (MTBE), total lipids were analyzed by ICP-MS or ESI-MS without any further separation or fractionation. A total of 39 molecular species of arsenic triacylglycerols (AsTAG), 15 arsenic phosphatidylcholines (AsPC), 8 arsenic phosphatidylethanolamines (AsPE), 6 arsenic phosphatidylinositols (AsPI), 2 arsenic phosphatidylglycerols (AsPG) and 5 unknown lipids (probably ceramides) were identified. The structures of all molecular species were confirmed by tandem MS. Dry matter of the individual strains contained different amounts of total arsenolipids, i.e. C. elongata CCALA 427 (0.32 mg/g), C. onubensis (1.48 mg/g), C. elongata S3 (2.13 mg/g). On the other hand, there were only slight differences between strains in the relative abundances of individual molecular species. Possible biosynthesis of long-chain lipids with the end group Me₂As(O) has also been suggested.

Selective speciation of inorganic arsenic in water using nanocomposite based solid-phase extraction followed by inductively coupled plasma-mass spectrometry detection

The multi-walled carbon nanotubes-branched polyethyleneimine (MWCNTs-BPEI) adsorbent composite material was employed to separate and pre-concentrate As(V) in water samples. The characterization of MWCNTs-BPEI by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy showed successful modification of the composite. The MWCNTs-BPEI composite exhibited selective retention of As(V) in the presence of As(III) in water samples of pH 7 using 40 mg of composite as adsorbent. The pre-concentrated As(V) was quantified using inductively coupled plasma-mass spectrometry (ICP-MS). A limit of detection (LOD) of 0.0537 µg L^-1 and limit of quantification (LOQ) of 0.179 µg L^-1 were achieved along with pre-concentration factor of 23.3. A percentage recovery of 81.0% confirm the accuracy of the method. The As(V) concentrations in water were in the range of 0.0612-3.65 µg L^-1. The As(V) concentrations determined using solid-phase extraction (SPE) procedure were in good agreement with the concentrations obtained using high performance liquid chromatography hyphenated to inductively coupled mass-mass spectrometry (HPLC hyphenated to ICP-MS).

Arsinothricin, an arsenic-containing non-proteinogenic amino acid analog of glutamate, is a broad-spectrum antibiotic

The emergence and spread of antimicrobial resistance highlights the urgent need for new antibiotics. Organoarsenicals have been used as antimicrobials since Paul Ehrlich's salvarsan. Recently a soil bacterium was shown to produce the organoarsenical arsinothricin. We demonstrate that arsinothricin, a non-proteinogenic analog of glutamate that inhibits glutamine synthetase, is an effective broad-spectrum antibiotic against both Gram-positive and Gram-negative bacteria, suggesting that bacteria have evolved the ability to utilize the pervasive environmental toxic metalloid arsenic to produce a potent antimicrobial. With every new antibiotic, resistance inevitably arises. The arsN1 gene, widely distributed in bacterial arsenic resistance (ars) operons, selectively confers resistance to arsinothricin by acetylation of the α-amino group. Crystal structures of ArsN1 N-acetyltransferase, with or without arsinothricin, shed light on the mechanism of its substrate selectivity. These findings have the potential for development of a new class of organoarsenical antimicrobials and ArsN1 inhibitors.

Measurements of Strain and Bandgap of Coherently Epitaxially Grown Wurtzite InAsP-InP Core-Shell Nanowires

We report on experimental determination of the strain and bandgap of InAsP in epitaxially grown InAsP-InP core-shell nanowires. The core-shell nanowires are grown via metal-organic vapor phase epitaxy. The as-grown nanowires are characterized by transmission electron microscopy, X-ray diffraction, micro-photoluminescence (μPL) spectroscopy, and micro-Raman (μ-Raman) spectroscopy measurements. We observe that the core-shell nanowires are of wurtzite (WZ) crystal phase and are coherently strained with the core and the shell having the same number of atomic planes in each nanowire. We determine the predominantly uniaxial strains formed in the core-shell nanowires along the nanowire growth axis and demonstrate that the strains can be described using an analytical expression. The bandgap energies in the strained WZ InAsP core materials are extracted from the μPL measurements of individual core-shell nanowires. The coherently strained core-shell nanowires demonstrated in this work offer the potentials for use in constructing novel optoelectronic devices and for development of piezoelectric photovoltaic devices.

Homoarsenocholine - A novel arsenic compound detected for the first time in nature

The arsenic speciation was determined in macrofungi of the Ramaria genus with HPLC coupled to inductively coupled plasma mass spectrometry. Besides arsenic species that are already known for macrofungi, like arsenobetaine or arsenocholine, two compounds that were only known from marine samples so far (trimethylarsoniopropanate and dimethylarsinoylacetate) were found for the first time in a terrestrial sample. An unknown arsenical was isolated and identified as homoarsenocholine. This could be a key intermediate for further elucidation of the biotransformation mechanisms of arsenic.

A unique arsenic speciation profile in Elaphomyces spp. ("deer truffles")-trimethylarsine oxide and methylarsonous acid as significant arsenic compounds

Arsenic and its species were investigated for the first time in nine collections of Elaphomyces spp. ("deer truffles") from the Czech Republic with inductively coupled plasma mass spectrometry (ICPMS) and high-performance liquid chromatography coupled to ICPMS. The total arsenic concentrations ranged from 12 to 42 mg kg-1 dry mass in samples of E. asperulus and from 120 to 660 mg kg-1 dry mass in E. granulatus and E. muricatus. These concentrations are remarkably high for terrestrial organisms and demonstrate the arsenic-accumulating ability of these fungi. The dominating arsenic species in all samples was methylarsonic acid which accounted for more than 30% of the extractable arsenic. Arsenobetaine, dimethylarsinic acid, and inorganic arsenic were present as well, but only at trace concentrations. Surprisingly, we found high amounts of trimethylarsine oxide in all samples (0.32-28% of the extractable arsenic). Even more remarkable was that all but two samples contained significant amounts of the highly toxic trivalent arsenic compound methylarsonous acid (0.08-0.73% of the extractable arsenic). This is the first report of the occurrence of trimethylarsine oxide and methylarsonous acid at significant concentrations in a terrestrial organism. Our findings point out that there is still a lot to be understood about the biotransformation pathways of arsenic in the terrestrial environment. Graphical abstract Trimethylarsine oxide and methylarsonous acid in "deer truffles".

A review of cinnabar (HgS) and/or realgar (As4S4)-containing traditional medicines

ETHNOPHARMOCOLOGICAL RELEVANCE

Herbo-metallic preparations have a long history in the treatment of diseases, and are still used today for refractory diseases, as adjuncts to standard therapy, or for economic reasons in developing countries.

AIM OF THE REVIEW

This review uses cinnabar (HgS) and realgar (As₄S₄) as mineral examples to discuss their occurrence, therapeutic use, pharmacology, toxicity in traditional medicine mixtures, and research perspectives.

MATERIALS AND METHODS

A literature search on cinnabar and realgar from PubMed, Chinese pharmacopeia, Google and other sources was carried out. Traditional medicines containing both cinnabar and realgar (An-Gong-Niu-Huang Wan, Hua-Feng-Dan); mainly cinnabar (Zhu-Sha-An-Shen Wan; Zuotai and Dangzuo), and mainly realgar (Huang-Dai Pian; Liu-Shen Wan; Niu-Huang-Jie-Du) are discussed.

RESULTS

Both cinnabar and realgar used in traditional medicines are subjected to special preparation procedures to remove impurities. Metals in these traditional medicines are in the sulfide forms which are different from environmental mercurials (HgCl₂, MeHg) or arsenicals (NaAsO₂, NaH₂AsO₄). Cinnabar and/or realgar are seldom used alone, but rather as mixtures with herbs and/or animal products in traditional medicines. Advanced technologies are now used to characterize these preparations. The bioaccessibility, absorption, distribution, metabolism and elimination of these herbo-metallic preparations are different from environmental metals. The rationale of including metals in traditional remedies and their interactions with drugs need to be justified. At higher therapeutic doses, balance of the benefits and risks is critical. Surveillance of patients using these herbo-metallic preparations is desired.

CONCLUSION

Chemical forms of mercury and arsenic are a major determinant of their disposition, efficacy and toxicity, and the use of total Hg and As alone for risk assessment of metals in traditional medicines is insufficient.

Enhancing As(V) adsorption and passivation using biologically formed nano-sized FeS coatings on limestone: Implications for acid mine drainage treatment and neutralization

The iron-reducing bacterium Acidiphilium cryputum JF-5 and a sulfate reducing bacterium (SRB) collected and purified from the mine drainage of a copper mine in the northwest of Sichuan Province, China, were used to biologically synthesize nano-sized FeS-coated limestone to remove As(V) from solution. The adsorption efficiency of As(V) is improved from 6.64 μg/g with limestone alone to 187 μg/g with the FeS coated limestone in both batch and column experiments. The hydraulic conductivity of the columns are also improved by the presence of the nano-sized FeS coatings, but the solution neutralization performance of the limestone can be reduced by passivation by gypsum and Fe(III) precipitates. Calculations for FeS-coated limestone dissolution experiments show that the process can be described as n_Ca.sol = At^1/2 - n_Ca,gyp. The results suggest that FeS-coated limestone may be an effective medium for remediating As(V)-bearing solutions such as acid mine drainage in systems such as Permeable Reactive Barriers.

Complete removal of arsenic and zinc from a heavily contaminated acid mine drainage via an indigenous SRB consortium

Acid mine drainages (AMD) are major sources of pollution to the environment. Passive bio-remediation technologies involving sulfate-reducing bacteria (SRB) are promising for treating arsenic contaminated waters. However, mechanisms of biogenic As-sulfide formation need to be better understood to decontaminate AMDs in acidic conditions. Here, we show that a high-As AMD effluent can be decontaminated by an indigenous SRB consortium. AMD water from the Carnoulès mine (Gard, France) was incubated with the consortium under anoxic conditions and As, Zn and Fe concentrations, pH and microbial activity were monitored during 94days. Precipitated solids were analyzed using electron microscopy (SEM/TEM-EDXS), and Extended X-Ray Absorption Fine Structure (EXAFS) spectroscopy at the As K-edge. Total removal of arsenic and zinc from solution (1.06 and 0.23mmol/L, respectively) was observed in two of the triplicates. While Zn precipitated as ZnS nanoparticles, As precipitated as amorphous orpiment (am-As^III₂S₃) (33-73%), and realgar (As^IIS) (0-34%), the latter phase exhibiting a particular nanowire morphology. A minor fraction of As is also found as thiol-bound As^III (14-23%). We propose that the formation of the As^IIS nanowires results from As^III₂S₃ reduction by biogenic H₂S, enhancing the efficiency of As removal. The present description of As immobilization may help to set the basis for bioremediation strategies using SRB.

The use of artificial neural network for modelling of phycoremediation of toxic elements As(III) and As(V) from wastewater using Botryococcus braunii

In the present study, a thorough investigation has been done on the removal efficiency of both As(III) and As (V) from synthetic wastewater by phycoremediation of Botryococcus braunii algal biomass. Artificial neural networks (ANNs) are practised for predicting % phycoremediation efficiency of both As(III) and As(V) ions. The influence of several parameters for example initial pH, inoculum size, contact time and initial arsenic concentration (either As(III) or As(V)) was examined systematically. The maximum phycoremediation of As(III) and As(V) was found to be 85.22% and 88.15% at pH9.0, equilibrium time of 144h by using algal inoculum size of 10% (v/v) and initial arsenic concentration of 50mg/L. The data acquired from laboratory scale experimental set up was utilized for training a three-layer feed-forward back propagation (BP) with Levenberg-Marquardt (LM) training algorithm having 4:5:1 architecture. A comparison between the experimental data and model outputs provided a high correlation coefficient (R(2)all_ANN equal to 0.9998) and exhibited that the model was capable for predicting the phycoremediation of both As(III) and As(V) from wastewater. The network topology was optimized by changing number of neurons in hidden layers. ANNs are efficient to model and simulate highly non-liner multivariable relationships. Absolute error and Standard deviation (SD) with respect to experimental output were calculated for ANN model outputs. The comparison of phycoremediation efficiencies of both As(III) and As(V) between experimental results and ANN model outputs exhibited that ANN model can determine the behaviour of As(III) and As(V) elimination process under various circumstances.

Biotransformation of arsenic by bacterial strains mediated by oxido-reductase enzyme system

The present study deals with the enzyme mediated biotransformation of arsenic in five arsenic tolerant strains (Bacillus subtilis, Bacillus megaterium, Bacillus pumilus, Paenibacillus macerans and Escherichia coli). Biotransformation ability of these isolates was evaluated by monitoring arsenite oxidase and arsenate reductase activity. Results showed that arsenic oxidase activity was exclusively present in P. macerans and B. pumilus while B. subtilis, B. megaterium and E. coli strains showed presence of Arsenic oxido-reductase enzyme. The reversible nature of arsenic oxido- reductase suggested that same enzyme can carry out oxidation and reduction of arsenic depending upon the relative concentration of arsenic species. Lineweaver-Burk plot of the arsenite oxidase activity in P. macerans showed highest Km value (Km- 200 μM) and lower Vmax (0.012 μmol mg-1 protein min-1) indicating lowest affinity of the enzyme for arsenite. On the contrary, E. coli showed the lower Km value ( Km- 38.46 μM) and higher Vmax (0.044 μmol mg-1 protein min-1) suggesting for higher affinity for the arsenite. Lineweaver-Burk plot of arsenate reductase activity showed the presence of this enzyme in B. subtilis, B. megaterium and E. coli which were in the range of 200-360 μM Km and Vmax value between 0.256- 0.129 mmol mg-1 protein min-1. These results suggested that affinity of the as reductase enzyme is lowest for arsenate than that for the arsenite. Thus, arsenite oxidase system appears to be a predominant mechanism of cellular defense in these bacterial strains.

Selectively adsorptive extraction of phenylarsonic acids in chicken tissue by carboxymethyl α-cyclodextrin immobilized Fe3O4 magnetic nanoparticles followed ultra performance liquid chromatography coupled tandem mass spectrometry detection

Carboxymethyl α-cyclodextrin immobilized Fe₃O₄ magnetic nanoparticles (CM-α-CD-Fe₃O₄) were synthesized for the selectively adsorptive extraction of five phenylarsonic acids including p-amino phenylarsonic acid, p-nitro phenylarsonic acid, p-hydroxy phenylarsonic acid, p-acylamino phenylarsonic acid and p-hydroxy-3-nitro phenylarsonic acid in chicken tissue. Using ultra performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS), a highly sensitive analytical method was proposed for the determination of five phenylarsonic acids. It was shown that CM-α-CD-Fe₃O₄ could extract the five phenylarsonic acids in complex chicken tissue samples with high extraction efficiency. Under the optimal conditions, a high enrichment factor, ranging from 349 to 606 fold, was obtained. The limits of detection (LODs) (at a signal-to-noise ratio of 3) were in the range of 0.05–0.11 µg/kg for the five phenylarsonic acids. The proposed method was applied for the determination of five target phenylarsonic acids in chicken muscle and liver samples. Recoveries for the spiked samples with 0.2 µg/kg, 2.0 µg/kg and 20 µg/kg of each phenylarsonic acids were in the range of 77.2%–110.2%, with a relative standard deviation (RSD) of less than 12.5%.

Pharmacokinetic properties of arsenic species after oral administration of Sargassum pallidum extract in rats using an HPLC-HG-AFS method

Sargassum pallidum is one of the Traditional Chinese Medicine widely used for phlegm elimination and detumescence. Arsenic is present in high concentration in seaweed belonging to the genus Sargassum. Therefore, the consumption of S. pallidum is a route of exposure to arsenic. Since the toxicity of arsenic is highly dependent on its chemical speciation, the determination of total arsenic is not adequate to assess the risks. Here, a high performance liquid chromatography-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS) was developed for determination of the common arsenic species including arsenite [As(III)], dimethylarsinate (DMA), methylarsonate (MMA) and arsenate [As(V)] simultaneously. This method was applied to study the pharmacokinetic profile of these arsenic species in rats after oral administration of S. pallidum extract at different doses. The described assay was validated for limit of quantification, linearity, intra-day and inter-day precisions, accuracy, extraction recovery and stability according to the FDA validation guidelines. As(III) or MMA was not detected in any samples collected at all time points using the present HPLC-HG-AFS method. As(V) and DMA in the S. pallidum could be readily absorbed and eliminated in rats. A trend of dose-dependence was shown for DMA and As(V) in the drug concentration-time profiles. This study would be helpful for the apprehension of the action mechanism and clinical application of medicinal seaweeds.

Arsenic removal in a sulfidogenic fixed-bed column bioreactor

In the present study, the bioremoval of arsenic from synthetic acidic wastewater containing arsenate (As(5+)) (0.5-20mg/L), ferrous iron (Fe(2+)) (100-200mg/L) and sulfate (2,000 mg/L) was investigated in an ethanol fed (780-1,560 mg/L chemical oxygen demand (COD)) anaerobic up-flow fixed bed column bioreactor at constant hydraulic retention time (HRT) of 9.6h. Arsenic removal efficiency was low and averaged 8% in case iron was not supplemented to the synthetic wastewater. Neutral to slightly alkaline pH and high sulfide concentration in the bioreactor retarded the precipitation of arsenic. Addition of 100mg/L Fe(2+) increased arsenic removal efficiency to 63%. Further increase of influent Fe(2+) concentration to 200mg/L improved arsenic removal to 85%. Decrease of influent COD concentration to its half, 780 mg/L, resulted in further increase of As removal to 96% when Fe(2+) and As(5+) concentrations remained at 200mg/L and 20mg/L, respectively. As a result of the sulfidogenic activity in the bioreactor the effluent pH and alkalinity concentration averaged 7.4 ± 0.2 and 1,736 ± 239 mg CaCO3/L respectively. Electron flow from ethanol to sulfate averaged 72 ± 10%. X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses were carried out to identify the nature of the precipitate generated by sulfate reducing bacteria (SRB) activity. Precipitation of arsenic in the form of As2S3 (orpiment) and co-precipitation with ferrous sulfide (FeS), pyrite (FeS2) or arsenopyrite (FeAsS) were the main arsenic removal mechanisms.

Efficient removal of trace antimony(III) through adsorption by hematite modified magnetic nanoparticles

Hematite coated magnetic nanoparticle (MNP@hematite) was fabricated through heterogeneous nucleation technique and used to remove trace Sb(III) from water. Powder X-ray diffraction, transmission electron microscopy (TEM), and alternating gradient magnetometry were utilized to characterize the prepared adsorbent. TEM image showed that MNP@hematite particles were spherical with size of 10-30nm. With saturation magnetization of 27.0emu/g, MNP@hematite particles could be easily separated from water with a simple magnetic process in short time (5min). At initial concentration of 110μg/L, Sb(III) was rapidly decreased to below 5μg/L by MNP@hematite in 10min. Sb(III) adsorption capacity of MNP@hematite was 36.7mg/g, which was almost twice that of commercial Fe3O4 nanoparticles. The removal of trace Sb(III) was not obviously affected by solution pH (over a wide range from 3 to 11), ionic strength (up to 100mM), coexisting anions (chloride, nitrate, sulfate, carbonate, silicate, and phosphate, up to 10mM) and natural organic matters (humic acid and alginate, up to 8mg/L as TOC). Moreover, MNP@hematite particles were able to remove Sb(III) and As(III) simultaneously. Trace Sb(III) could also be effectively removed from real tap water by MNP@hematite. The magnetic adsorbent could be recycled and used repeatedly.

Direct removal of aqueous As(III) and As(V) by amorphous titanium dioxide nanotube arrays

Amorphous titanium dioxide nanotube arrays (TiO2 NTs) were prepared by a simple anodization process without subsequent calcination at high temperature, and the effectiveness of amorphous TiO2 NTs as adsorbents in removing arsenite (As(III)) and arsenate (As(V)) was investigated. The TiO2 NTs were not only effective for arsenic removal without a pre-oxidation of As(III) to As(V) and/or adjusting the pH value of water before the adsorption process, but also can be separated and recovered easily from the solution. The adsorption kinetics and adsorption capacity of the amorphous TiO2 NTs for As(III) and As(V) were studied separately by batch experiments. The apparent values for Langmuir monolayer sorption capacities were 28.9 mg/g for As(III) and 24.7 mg/g for As(V) at pH 7. Kinetics studies indicated that the adsorption process on TiO2 NTs followed a pseudo-second-order kinetics model. Arsenic adsorption of TiO2 NTs remains stable over a broad pH range. Moreover, the TiO2 NTs have excellent stability and regeneration, and they can be used repeatedly at least five times.

Determination of arsenic species in edible periwinkles (Littorina littorea) by HPLC-ICPMS and XAS along a contamination gradient

Arsenic is naturally found in the tissues of marine animals, usually as the non-toxic arsenical arsenobetaine, but exposure to elevated arsenic concentrations in the environment may alter the arsenic species distribution within tissues of the organism. This study examined the arsenic species in the tissues of the marine periwinkle (Littorina littorea) along an arsenic concentration gradient in the sediment. The arsenicals in L. littorea were examined using the complementary analytical methods high performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICPMS) and X-ray absorption spectroscopy (XAS). Total arsenic concentrations in the periwinkle tissues ranged from 56 to 840 mg·kg(-1) dry weight (equivalent to 13 to 190 mg·kg(-1) wet weight). Inorganic arsenicals were found to be positively correlated with total arsenic concentrations (R(2)=0.993) and reached 600 mg·kg(-1) dry weight, the highest reported to date in marine organisms. These high inorganic arsenic concentrations within this low trophic organism pose a potential toxicological risk to higher trophic consumers.

Application of advanced oxidation processes for cleaning of industrial water generated in wet dedusting of shaft furnace gases

The paper presents results of studies into advanced oxidation processes in 03 and 03/UV systems. An advanced oxidation process (AOP) was conducted to reduce the load of impurities in circulating waters from wet de-dusting of shaft furnace gases. Besides inorganic impurities, i.e. mainly arsenic compounds (16 g As L(-1) on average), lead, zinc, chlorides and sulphates, the waters also contain some organic material. The organic material is composed of a complex mixture that contains, amongst others, aliphatic compounds, phenol and its derivatives, pyridine bases, including pyridine, and its derivatives. The test results show degradation of organic and inorganic compounds during ozonation and photo-oxidation processes. Analysis of the solutions from the processes demonstrated that the complex organic material in the industrial water was oxidized in ozonation and in photo-oxidation, which resulted in formation of aldehydes and carboxylic acids. Kinetic degradation of selected pollutants is presented. Obtained results indicated that the O3/UV process is more effective in degradation of organic matter than ozonation. Depending on the process type, precipitation of the solid phase was observed. The efficiency of solid-phase formation was higher in photo-oxidation with ozone. It was found that the precipitated solid phase is composed mainly of arsenic, iron and oxygen.

Microbial arsenic reduction in polluted and unpolluted soils from Attica, Greece

Indigenous soil microorganisms often affect the mobility of heavy metals and metalloids by altering their oxidation state. Under anaerobic conditions, the microbial transformation is usually reduction and may cause the mobilization of contaminants, as happens in the case of arsenic, which is much more stable in the pentavalent state compared to the reduced trivalent form. The aim of this work was to investigate the occurrence of such a microbial activity in representative Greek soils. Five soil samples, with As levels varying between 14 and 259 mg/kg, were examined. The samples were artificially contaminated, by adding 750 mg of As(V) per kg of soil. Initial sorption of As(V) ranged between 70 and 85%. Microbial reduction of arsenic was observed in three of the examined soils, without any obvious correlation with pre-existing levels of contamination. Reduction reached high percentages, i.e. up to 99%, and was accompanied by the corresponding release of reduced As in the aqueous solution. A simultaneous iron reducing activity was also observed in four of the five soil samples.

[Mineralogical characteristics of biogenic schwertmannite amended with different pretreatment methods and the effects on As(III) absorption]

Biogenic schwertmannite has better absorption performance for As(III) than other adsorbents, but there is obvious agglomeration of mineral particles due to the polysaccharides secreted by the bacteria during the synthesis of schwertmannite. The aim of this study was to find out a best pretreatment method to further reduce the agglomeration of mineral particles and enhance the As(III) absorption capacity by comparing the effects of different pretreatment methods on the mineralogical characteristics and adsorption performance of schwertmannite. The pretreatment methods of the biogenic schwertmannite induding the treatments with NaOH, NaCl, thermal activation at 200 degrees C and ethanol-ultrasound. The results showed that the mineral phases were not altered after pretreatment, however, different physical and chemical properties of schwertmannite were found after different pretreatment methods were used. Compared with the original mineral, the mineral surface area, Fe/S molar ratio, SEM image and As(III) adsorption were significantly changed. The highest As(III) sorption capacity was obtained for the pH 12 NaOH treated schwertmannite with the maximum absorbance at room temperature increased from 101.9 mg x g(-1) to 143.3 mg x g(-1), and the surface area enhanced from 45.63 m2 x g(-1) to 325.18 m2 x g(-1). Besides, aggregation of mineral particles was remarkably decreased.

Toxicity of so-called edible hijiki seaweed (Sargassum fusiforme) containing inorganic arsenic

The UK Food Standards Agency and its counterparts in other countries have warned consumers not to eat hijiki (Sargassum fusiforme; synonym Hizikia fusiformis), a Sargasso seaweed, because it contains large amounts of inorganic arsenic. We investigated dietary exposure of hijiki in weaning male F344/N rats fed an AIN-93G diet supplemented with 3% (w/w) hijiki powder for 7 weeks, compared with those fed only an AIN-93G diet. Body weight, body temperature, blood and tissue arsenic concentrations, plasma biochemistry and hematological parameters were measured. We found that feeding rats a 3% hijiki diet led to a marked accumulation of arsenic in blood and tissues, and evoked a high body temperature and abnormal blood biochemistry including elevated plasma alkaline phosphatase activity and inorganic phosphorus, consistent with arsenic poisoning. These findings should prompt further investigations to identify the health hazards related to consumption of hijiki and related Sargassum species in humans.

Preparation and certification of hijiki reference material, NMIJ CRM 7405-a, from the edible marine algae hijiki (Hizikia fusiforme)

A certified reference material, NMIJ CRM 7405-a, for the determination of trace elements and As(V) in algae was developed from the edible marine hijiki (Hizikia fusiforme) and certified by the National Metrology Institute of Japan (NMIJ), the National Institute of Advanced Industrial Science and Technology (AIST). Hijiki was collected from the Pacific coast in the Kanto area of Japan, and was washed, dried, powdered, and homogenized. The hijiki powder was placed in 400 bottles (ca. 20 g each). The concentrations of 18 trace elements and As(V) were determined by two to four independent analytical techniques, including (ID)ICP-(HR)MS, ICP-OES, GFAAS, and HPLC-ICP-MS using calibration solutions prepared from the elemental standard solution of Japan calibration service system (JCSS) and the NMIJ CRM As(V) solution, and whose concentrations are certified and SI traceable. The uncertainties of all the measurements and preparation procedures were evaluated. The values of 18 trace elements and As(V) in the CRM were certified with uncertainty (k = 2).

Biomineralization based remediation of As(III) contaminated soil by Sporosarcina ginsengisoli

Arsenic is a highly toxic metalloid and has posed high risk to the environment. As(III) is highly mobile in soil and leached easily into groundwater. The current remediation techniques are not sufficient to immobilize this toxic element. In the present study, an As(III) tolerant bacterium Sporosarcina ginsengisoli CR5 was isolated from As contaminated soil of Urumqi, China. We investigated the role of microbial calcite precipitated by this bacterium to remediate soil contaminated with As(III). The bacterium was able to grow at high As(III) concentration of 50mM. In order to obtain arsenic distribution pattern, five stage soil sequential extraction was carried out. Arsenic mobility was found to significantly decrease in the exchangeable fraction of soil and subsequently the arsenic concentration was markedly increased in carbonated fraction after bioremediation. Microbially induced calcite precipitation (MICP) process in bioremediation was further confirmed by ATR-FTIR and XRD analyses. XRD spectra showed presence of various biomineralization products such as calcite, gwihabaite, aragonite and vaterite in bioremediated soil samples. The results from this study have implications that MICP based bioremediation by S. ginsengisoli is a viable, environmental friendly technology for remediation of the arsenic contaminated sites.

Co2+-exchange mechanism of birnessite and its application for the removal of Pb2+ and As(III)

Co-containing birnessites were obtained by ion exchange at different initial concentrations of Co(2+). Ion exchange of Co(2+) had little effect on birnessite crystal structure and micromorphology, but resulted in an increase in specific surface areas from 19.26 to 33.35 m(2)g(-1), and a decrease in both crystallinity and manganese average oxidation state. It was due to that Mn(IV) in the layer structure was reduced to Mn(III) during the oxidation process of Co(2+) to Co(III). The hydroxyl groups on the surface of Co-containing birnessites gradually decreased with an increase of Co/Mn molar ratio owing to the occupance of Co(III) into vacancies and the location of large amounts of Co(2+/3+) and Mn(2+/3+) above/below the vacant sites. This greatly accounted for the monotonous reduction in Pb(2+) adsorption capacity, from 2538 mmol kg(-1) for the unmodified birnessite to 1500 mmol kg(-1) for the Co(2+) ion-exchanged birnessite with a Co/Mn molar ratio of 0.16. The amount of As(III) oxidized by birnessite was enhanced after ion exchange, but the apparent initial reaction rate was greatly decreased. The present work demonstrates that Co(2+) ion exchange has great influence on the adsorption and oxidation behavior of inorganic toxic metal ions by birnessite in water environments.

Reduction of As(V) to As(III) by commercial ZVI or As(0) with acid-treated ZVI

Zero-valent iron (ZVI) consists of an elemental iron core surrounded by a shell of corrosion products, especially magnetite. ZVI is used for in situ removal or immobilization of a variety of contaminants but the mechanisms for removal of arsenic remain controversial and the mobility of arsenic after reaction with ZVI is uncertain. These issues were addressed by separately studying reactions of As(V) with magnetite, commercial ZVI, and acid-treated ZVI. Strictly anoxic conditions were used. Adsorption of As(V) on magnetite was fast with pH dependence similar to previous reports using oxic conditions. As(V) was not reduced by magnetite and Fe(II) although the reaction is thermodynamically spontaneous. As(V) reactions with ZVI were also fast and no lag phase was observed which was contrary to previous reports. Commercial ZVI reduced As(V) to As(III) only when As(V) was adsorbed, i.e., for pH<7. As(III) was not released to solution. Acid-treated ZVI reduced As(V) to As(0), shown using wet chemical analyses and XANES/EXAFS. Comparisons were drawn between reactivity of acid-treated ZVI and nano-ZVI; if true then acid-treated ZVI could provide similar reactive benefits at lower cost.

Synthesis, characterization and kinetic of a surfactant-modified bentonite used to remove As(III) and As(V) from aqueous solution

In this study, organobentonites were prepared by modification of bentonite with various cationic surfactants, and were used to remove As(V) and As(III) from aqueous solution. The results showed that the adsorption capacities of bentonite modified with octadecyl benzyl dimethyl ammonium (SMB3) were 0.288 mg/g for As(V) and 0.102 mg/g for As(III), which were much higher compared to 0.043 and 0.036 mg/g of un-modified bentonite (UB). The adsorption kinetics were fitted well with the pseudo-second-order model with rate constants of 46.7 × 10(-3)g/mgh for As(V) and 3.1 × 10(-3)g/mgh for As(III), respectively. The maximum adsorption capacity of As(V) derived from the Langmuir equation reached as high as 1.48 mg/g, while the maximum adsorption capacity of As(III) was 0.82 mg/g. The adsorption of As(V) and As(III) was strongly dependent on solution pH. Addition of anions did not impact on As(III) adsorption, while they clearly suppressed adsorption of As(V). In addition, this study also showed that desorbed rates were 74.61% for As(V) and 30.32% for As(III), respectively, after regeneration of SMB3 in 0.1M HCl solution. Furthermore, in order to interpret the proposed absorption mechanism, both SMB3 and UB were extensively characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses.

Scorodite encapsulation by controlled deposition of aluminum phosphate coatings

A new stabilization process for scorodite (FeAsO(4).2H(2)O) solids based on the concept of encapsulation by controlled deposition of mineral coatings immune to pH or redox potential variations is described. The stability of the encapsulated scorodite with aluminum phosphates under simulated anoxic and oxic environments is demonstrated. Encapsulation experiments were carried out at 95 degrees C using 50 g/L scorodite in acidic sulphate solution containing 0.16 mol/L of P(V) with Al(III) to P(V) molar ratio of 1 and precipitation pH of 1.7. The encapsulated particles were characterised by XRD, SEM, TOF-SIMS and TOF-LIMS. The coating was crystalline AlPO(4).1.5H(2)O ranging in thickness from 2.5 to 3.5 microm. Encapsulation of scorodite particles with hydrated aluminum phosphate appears to be effective in controlling/suppressing the release of arsenic under both oxic and anoxic conditions by more than one order of magnitude.

[Speciation analysis and toxicity of arsenic in realgar bioleaching solution]

OBJECTIVE

To analyze speciation and toxicity of arsenic in realgar bioleaching solution, and to explore its possible relation between speciation and toxicity.

METHODS

Capillary zone electrophoresis (CZE) can be used quickly and simply onto the simultaneous separation and quantitative determination of the speciation of arsenic in realgar bioleaching solution. The effects of three different realgar bioleaching liquids on the acute toxicity level of rat were also investigated as well. Parallel experiments with traditional processing realgar via gastric irrigation were conducted for comparison.

RESULTS

There are three different arsenic species in realgar bioleaching solution (iAs(III), iAs(V) MMA(V)), and the processing method largely affected speciation and toxicity of arsenic of it. It was found that the toxicity level was decreased through increasing the amount of MMA(V).

CONCLUSION

These results indicate that the species of arsenic may be tightly relationship to its toxicity in realgar bioleaching solution.

Removal of rhodamine B (a basic dye) and thoron (an acidic dye) from dilute aqueous solutions and wastewater simulants by ion flotation

The present work deals with removal, by ion flotation, of two dyes: a basic dye (rhodamine B (RB)) and an acidic one (thoron (TH)) from dilute aqueous solutions and simulated wastewaters. These dyes are widely used for analytical and biological staining purposes. Besides, RB is commonly used in dyeing of various industrial products. Therefore, wastewaters emanating from chemical and radiochemical laboratories, and biomedical and biological research laboratories may be contaminated with RB and TH. Ion flotation of these dyes has been investigated over a wide range of pH using the anionic surfactant, sodium lauryl sulfate (NaLS) and the cationic surfactant, cetyltrimethylammonium bromide (CTAB) as collectors. Successful removals could be achieved for RB and TH with the anionic collector, NaLS, and the cationic collector, CTAB, respectively. In addition to the effects of pH and type of collector on the efficiency of removal of each dye, the effects of collector and dye concentrations, frother dosage, ionic strength, bubbling time period and presence of foreign salts were investigated and the optimal removal conditions have been established. Removals exceeding 99.5 % and 99.9% could be achieved for RB and TH, respectively. The results obtained are discussed with respect to dissociation of dye, type of collector, ionic strength and sign and magnitude of charge of added foreign ions. Kinetics of flotation were also studied. Further studies demonstrate that under optimum conditions the developed flotation processes can be applied for the treatment of dye-contaminated wastewaters simulated to those generated at dyeing industries and radiochemical laboratories.

Biological extraction of realgar by Acidithiobacillus ferrooxidans and its in vitro and in vivo antitumor activities

Acidithiobacillus ferrooxidans is a Gram-negative, chemolithoautotrophic bacterium involved in metal bioleaching. It is used for the extraction of coarse medical realgar, which is converted into an aqueous solution. To prove its feasibility as an anticancer drug candidate, extracted realgar (ER/Af) was evaluated for its antitumor activities both in vitro and in vivo. In cytotoxicity tests, ER/Af displayed significant inhibition on cell proliferation of HepG2, SMMC7721, and H22 cells in a time and dose dependent manner. Remarkable tumor growth inhibition and survival time prolongation effects, along with no obvious toxicity, were observed in antitumor experiments against H22 cell-bearing mice. Apoptosis induction was also confirmed as one of the mechanisms involved in the efficacy of ER/Af both in vitro and in vivo. The most important observation is that ER/Af showed high selective affinity to tumor tissues with about eight-fold higher arsenic accumulations at the tumor site of mice than those of the arsenic trioxide (ATO)-treated group at the same dose (57.8 +/- 3.34 microg/g dry tissue vs. 7.6 +/- 0.88 microg/g dry tissue). In conclusion, A. ferrooxidans could be successfully used for the extraction of realgar and ER/Af was proved to be a promising anticancer drug candidate, which is valuable for further study and clinical trials.

Risk assessment and management of arsenic in source water in China

As part of our efforts to identify effective ways and means to keep source water safe, the concept of risk assessment and management is introduced in this paper to address the issue of risk assessment and management of arsenic in source water in China. Carcinogenic and non-carcinogenic risk are calculated for different concentrations of arsenic in source water using the corrective equation between potential health risk and concentration of arsenic in source water with purification process taken into consideration. It is justified through analyses that risk assessment and management is suitable for China to control pollution of source water. The permissible content of arsenic in source water should be set at 0.01 mg/L at present in China, and necessary risk management measures include control contaminated sources and improvement of purification efficiency.

Natural attenuation potential of phenylarsenicals in anoxic groundwaters

The extensive production of chemical warfare agents in the 20th century has led to serious contamination of soil and groundwater with phenyl arsenicals at former ammunition depots or warfare agent production sites worldwide. Most phenyl arsenicals are highly toxic for humans. The microbial degradation of phenylarsonic acid (PAA) and diphenylarsinic acid (DPAA) was investigated in microcosms made of anoxic groundwater/sediment mixtures taken from different depths of an anoxic, phenyl arsenical contaminated aquifer in Central Germany. DPAA was not transformed within 91 days incubation time in any of the microcosms. The removal of PAA can be described by a first order kinetics without a lag-phase (rate: 0.037 d(-1)). In sterilized microcosms, PAA concentrations always remained stable, demonstrating that PAA transformation was a biologically mediated process. PAA transformation occurred under sulfate-reducing conditions due to sulfate consumption and production of sulfide. The addition of lactate (1 mM), a typical substrate of sulfate-reducing bacteria, increased the transformation rate of PAA significantly up to 0.134 d(-1). The content of total arsenic was considerably reduced (> 75%). Intermediates of PAA transformation were detected by high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). Experiments with a pure strain and sterile controls of Desulfovibrio gigas spiked with PAA showed that the elimination process is linked to the presence of sulfide formed through bacterial activity. Phenyl arsenicals were likely immobilized in the sedimentthrough sulfur substitution and a subsequent sulfur bond under the prevailing sulfate reducing condition. The results of this study indicate that PAA can undergo microbiologically mediated transformation in anoxic aquifers, leading to reduced concentrations in groundwater, which indicate a (enhancend) natural attenuation potential.

Thermal behaviour of arsenic trioxide adsorbed on activated carbon

The thermal stability and desorption of arsenic trioxide (As(2)O(3)) adsorbed on activated carbon (AC) was investigated as this phenomenon is expected to influence the arsenic release during low temperature pyrolysis of chromated copper arsenate (CCA) wood waste. Firstly, a thermogravimetric (TG) experiment with arsenolite, an allotropic form of As(2)O(3), was performed. The sample starts to sublime at temperatures lower than 200 degrees C with a sublimation peak temperature of 271 degrees C. Subsequently, TG experiments with samples of As(2)O(3) adsorbed on AC revealed that only very little (max. 6+/-3 wt%) As(2)O(3) was volatilized at temperatures below 280 degrees C, while still 41.6 (+/-5)wt% of the original arsenic concentration was retained at 440 degrees C and 28.5 (+/-3)wt% at 600 degrees C. The major arsenic volatilization occurred between 300 degrees C and 500 degrees C. The kinetic parameters of desorption, activation energy of desorption (E(d)) and pre-exponential factor (A), were determined by fitting an Arrhenius model to the experimental data, resulting in E(d)=69 kJ/mol, A=1.21 x 10(4)s(-1). It can be concluded that the adsorption of As(2)O(3) on AC can contribute to the thermal stabilisation of As(2)O(3). Consequently, during low temperature pyrolysis of CCA wood arsenic release may be prevented by adsorption of As(2)O(3) on the coal-type product formed during the thermal decomposition of the wood.

Separation and preconcentration of inorganic arsenic species in natural water samples with 3-(2-aminoethylamino) propyltrimethoxysilane modified ordered mesoporous silica micro-column and their determination by inductively coupled plasma optical emission spectrometry

A simple and sensitive method using micro-column packed with 3-(2-aminoethylamino) propyltrimethoxysilane (AAPTS) modified ordered mesoporous silica combined with inductively coupled plasma optical emission spectrometry (ICP-OES) for the speciation of inorganic arsenic (As(III) and As(V)) has been developed. The adsorption behaviors of As(III) and As(V) on AAPTS modified ordered mesoporous silica were investigated. It was found that As(V) can be selectively adsorbed on the micro-column within pH of 3-9, while As(III) could not be retained in the studied pH range and passed through the micro-column directly. Total inorganic arsenic was extracted after the oxidation of As(III) to As(V) with 50.0 micromol L(-1) KMnO(4). The assay of As(III) was based on subtracting As(V) from total As. The effect of various parameters on the separation/preconcentration of As(III) and As(V) have been investigated and the optimal experimental conditions were established. The adsorption capacity of AAPTS modified ordered mesoporous silica for As(V) was found to be 10.3 mg g(-1). The detection limit of the method for As(V) was 0.05 microg L(-1) with an enrichment factor of 100, and the relative standard deviation (R.S.D.) was 5.7% (n=7, C=1.0 microg L(-1)). In order to validate the developed method, a certified reference material GSBZ50004-88 environmental water sample was analyzed and the determined values were in good agreement with the certified values. The proposed method was successfully applied to the speciation analysis of inorganic arsenic in natural water samples.

Simultaneous extraction of arsenic and selenium species from rice products by microwave-assisted enzymatic extraction and analysis by ion chromatography-inductively coupled plasma-mass spectrometry

A microwave-assisted enzymatic extraction (MAEE) method was developed for the simultaneous extraction of arsenic (As) and selenium (Se) species in rice products. The total arsenic and selenium content in the enzymatic extracts were determined by inductively coupled plasma mass spectrometry (ICP-MS), while the speciation analysis was performed by ion chromatography coupled to inductively coupled plasma-mass spectrometry (IC-ICP-MS). The main factors affecting the enzymatic extraction process were evaluated in NIST SRM-1568a rice flour. The optimum extraction conditions were 500 mg of sample, 50 mg of protease XIV, and 25 mg of alpha-amylase in aqueous medium during 40 min at 37 degrees C. The extraction recoveries of total As and Se reached 100 +/- 3 and 80 +/- 4%, respectively. The species stability study during the MAEE process did not show transformation of the target species in rice products. The results of As speciation obtained for SRM-1568a were in agreement with previous studies of As speciation performed on the same reference material. The proposed method was applied to the determination of As and Se species in rice and rice-based cereals. Arsenite [As(III)], arsenate [As(V)], dimethylarsinic acid (DMA), and selenomethionine (SeMet) were the predominant species identified in rice products.

[Study on water processing conditions of Realgar]

OBJECTIVE

To optimize the water processing (shui-fei) condition of Realgar.

METHODS

The processing conditions were optimized by L9 (3)4 orthogonal design with three factors as water dose, process times and dryness temperature. The content of dissolved arsenic As(III) in Realgar was tested by High Performance Liquid Chromatography-hydride generation on-line coupled with atomic fluorescence spectrometry (HPLC-HG-AFS).

RESULTS

The optimized conditions were 15 times quantity of water, 8 times for processing and dryness temperature of 40 degrees C.

CONCLUSION

The method is accurate and effective,which can be used to evaluate the quality of processed products of Realgar.

Analysis of accumulation, extractability, and metabolization of five different phenylarsenic compounds in plants by ion chromatography with mass spectrometric detection and by atomic emission spectroscopy

Phenylated arsenic compounds occur as highly toxic contaminants in former military areas where they were formed as degradation products of chemical warfare agents. Some phenylarsenic compounds such as roxarsone and aminophenylarsonic acids were applied as food additive and veterinary drugs in stock-breeding and therefore pose an environmental risk in agricultural used sites. Very few data exist in the literature concerning uptake and effects of phenylarsenic compounds in plants growing on contaminated soils. In this study, the accumulation, extractability, and metabolization of five different phenylarsenic compounds, phenylarsonic acid, p- and o-aminophenylarsonic acid, phenylarsine oxide, and 3-nitro-4-hydroxyphenylarsonic acid called roxarsone, by the terrestrial plant Tropaeolum majus were investigated. Ion chromatography coupled to inductively coupled plasma mass spectrometry was used to differentiate these arsenic compounds, and inductively coupled plasma atomic emission spectroscopy was used for total arsenic quantification. All compounds considered were taken up by the roots and transferred to stalks, leaves, and flowers. The strongest accumulation was observed for unsubstituted phenylarsonic acid followed by its trivalent analogue phenylarsine oxide that was mostly oxidized in soil whereas the amino- or nitro- and hydroxy-substituted phenylarsonic acids were accumulated to a smaller degree. The highest extraction yield of 90% for ground leaf material was achieved by 0.1M phosphate buffer, pH 7.7, in a two-step extraction with a total extraction time of 24h. The extraction of higher amounts of arsenic (50-70% of total arsenic present in leaves depending on arsenic species application) from non-ground intact leaves with deionized water in comparison with the buffer (20-40% of total arsenic) is ascribed to osmotic effects. The arsenic species analysis revealed a cleavage of the amino groups from the phenyl ring for plants treated with aminophenylarsonic acids. A further important metabolic effect consisted in the production of inorganic arsenate and arsenite from the phenylated arsonic acid groups.

An effective adsorbent developed from municipal solid waste and coal co-combustion ash for As(V) removal from aqueous solution

A new adsorbent was developed from waste ash resulting from municipal solid waste and coal co-combustion power plant. The ash was firstly subjected to hydrothermal treatment for zeolite synthesis, and then modified with iron(II) ions by agitation (ISZ) or ultrasonic (UISZ) treatment. The effect of operating factors such as pH, contact time, initial As(V) concentration and adsorbent dosage was investigated and the optimum operating conditions were established. The adsorption capacity for As(V) onto UISZ and ISZ were 13.04 and 5.37 mg g(-1), respectively. The adsorption isotherm data could be well described by Langmuir isotherm model. The optimum initial pH values for As(V) removal were 2.5 and 2.5-10.0 by ISZ and UISZ, respectively. The results indicated that ultrasound treatment scattered the particles of the adsorbent uniformly, which was in favor of impregnating iron ions into pores. Leaching of hazardous elements from the used adsorbents was very low. Accordingly, it is believed that the adsorbents developed in this study are environmentally acceptable and industrially applicable for utilization in arsenic-containing wastewater treatment.

Gastroenteritis exhumed

Nature of presenting symptoms and even signs of disease can lead to a diagnosis that seems routine but is in fact erroneous because a sufficient index of suspicion is not generated in the mind of the physician dealing with the case. A young girl of about 16 years was brought to the Casualty Department, DHQ Hospital Bannu on 12 Sep 2004 with complains of severe vomiting and diarrhoea; the casualty medical officer diagnosed her as a case of acute gastroenteritis.

Arsenic release from iron rich mineral processing waste: Influence of pH and redox potential

This paper presents the effect of pH and redox potential on the potential mobility of arsenic (As) from a contaminated mineral processing waste. The selected waste contained about 0.47 g kg(-1) of As and 66.2 g kg(-1) of iron (Fe). The characteristic of the waste was identified by acid digestion, X-ray diffraction and sequential extraction procedures. Less than 2% of the total As was acid extractable with the remaining 98% associated with Fe-oxyhydroxides and oxides. Batch leaching tests at different pH conditions showed a strong pH dependence on arsenic and iron leaching. Arsenic leaching followed a "V" shaped profiles with significant leaching in the acidic and alkaline pH region. Acid extractable phases dissolved at acidic pH, while desorption of arsenic due to increase in pH resulted in high arsenic concentration at alkaline pH. Under aerobic conditions and pH 7, As solubility was low, probably due to its precipitation on Fe-oxyhydroxides. Maximum As solubilization occurred at pH 11 (3.59 mg l(-1)). Similarity in the As and Fe leaching profiles suggested that the release of As was related to the dissolution of Fe in the low pH region. In general, redox potential did not play a significant role in arsenic or iron solubilization. It was thus concluded that for this solid waste, desorption was the predominant mechanism in arsenic leaching. A simple thermodynamic model based on arsenic and iron redox reactions was developed to identify the more sensitive redox couple.

On the First Polyarsenic Organic Compound from Nature: Arsenicin A from the New Caledonian Marine SpongeEchinochalina bargibanti

Reported here is the first polyarsenic compound ever found in nature. Denominated arsenicin A, it was isolated along a bioassay-guided fractionation of the organic extract of the poecilosclerid sponge Echinochalina bargibanti collected from the north-eastern coast of New Caledonia. In defining an adamantine-type polyarsenic structure for this compound, deceptively simple NMR spectra were complemented by extensive mass spectral analysis. However, it was only the synthesis of a model compound that provided the basis to discriminate structure 4 from other spectrally compatible structures for arsenicin A; to this end, a comparative ab initio simulation of IR spectra for the natural and the synthetic compounds was decisive. Arsenicin A is endowed with potent bactericidal and fungicidal activities on human pathogenic strains. All this may revive pharmacological interest in arsenic compounds while prompting us to rethink the arsenic cycle in nature.

Improved chromatographic separation of thio-arsenic compounds by reversed-phase high performance liquid chromatography-inductively coupled plasma mass spectrometry

A new group of arsenic species, thio-arsenicals, have recently been reported in several natural samples such as molluscs, algae, and urine. These compounds are the sulfur analogues of oxo-arsenicals, a large group of naturally-occurring compounds, whereby the arsinoyl (As=O) group is substituted by an arsinothioyl group (As=S). The most common separation technique for oxo-arsenicals is anion-exchange HPLC with polymer-based columns, but under these conditions the thio-arsenicals show strong retention, resulting in unacceptably long analysis times and broad peaks. We report the development of a reversed-phase HPLC method, with ICPMS detection, which allows separation of the known thio-arsenicals within 15 min with significantly improved peak shapes. The detection limit is about 0.6 microg As/L based on 10 microL injection volume. Further, we have applied the method to the identification and quantification of thio-arsenic species in two standard reference materials, BCR 710 oyster tissue and NIES 18 human urine.

Development of a rapid extraction procedure for speciation of arsenic in chicken meat

A rapid extraction procedure has been developed for speciation of arsenic in chicken tissue. Water, methanol-water (1:1), and methanol-chloroform (1:1) were tested as extraction media. Individual use of an ultrasonic bath, a microwave oven, or an ultrasonic probe was not sufficient for quantitative recovery of As(III), dimethylarsinate, monomethylarsonate, As(V), and arsenobetaine in spiked samples of chicken tissue. A new extraction procedure using a methanol-water mixture and a microwave oven then an ultrasonic probe enabled extraction of the arsenic species in 7 min with efficiencies ranging from 80 to 100%. HPLC-UV-HG-AFS was used for the determinations. The extraction procedure was 100% efficient when applied to real samples of chicken tissue. AsB (48+/-5 microg As kg (-1)) and one containing-arsenic feed additive, Nitarsone (227+/-5 microg As kg (-1)) were detected.

Evaluation of a focused sonication probe for arsenic speciation in environmental and biological samples

Arsenic speciation analysis suffers in general from high sample handling time required by sample preparation. In a previous work, ultrasonic probe has been proved to reduce sample treatment time for arsenic extraction in rice to only a few minutes. Base upon the obtained results, here several extraction media for chicken, fish and soil samples (SEAS G6RD-CT2001-00473) have been studied and evaluated employing the same technique. Chicken sample needed an enzymatic treatment in order to liberate the species linked to the protein matrix. Extraction of the major species in fish, AsB, was quantitatively achieved in water in 1 min. Also 1 min was enough to leach about 85% of species present in soils and sediments, mainly the inorganic ones, using H(3)PO(4). In all cases, no inter-conversion among As species was observed. The five species found in those samples were separated using an improved HPLC-ICP-MS method in only 11 min, with detection limits at the ng l(-1) level. The proposed methods were validated by analysing several Certified Reference Materials: SRM 1,568 a rice flour, CRM-627 tuna fish tissue, SOIL-7 soil and MURST-ISS-A1 Antarctic sediment.

Unexpected arsenic compounds in low-rank coals

Nine low-rank coal samples from three different coal basins (Velenje and Trbovlje basins, Slovenia, and Sokolov basin, Czech Republic) were analyzed for their elemental composition and the presence of arsenic compounds. Total arsenic concentrations in the samples were 1.59-5.77 microg g(-1) with one exception, 142 microg g(-1) for a sample from the Sokolov basin. A methanol/water mixture (1:1) extracted 15.1 - 38.7% of the total arsenic from Velenje basin samples but only 2.2-7.1% from Sokolov and Trbovlje basin samples. Extracts from the Velenje basin samples contained mainly the tetramethylarsonium ion (0.14 - 0.92 microg g(-1)) with considerable amounts of arsenate (0.15 - 0.85 microg g(-1)) and monomethyl arsonic acid 0.04 - 0.27 microg g(-1)). In methanol/water extracts from samples from the Sokolov and Trbovlje basins inorganic arsenic (arsenate) prevailed (0.26 - 37.1 microg g(-1)), but at least trace amounts of organic arsenic compounds were found as well. It is likely that biogeochemical degradation of organic material is related to the unexpected organoarsenic compounds found in low-rank coals. However, it should also not be ruled out that abiogenic synthesis could have taken place in the carbon-rich environment under the harsh conditions present (elevated temperature and pressure).

Combined use of photocatalyst and adsorbent for the removal of inorganic arsenic(III) and organoarsenic compounds from aqueous media

A novel method for the removal of inorganic arsenic(III) (As(III)), monomethylarsonate (MMA), and dimethylarsinate (DMA) from aqueous media, was proposed and investigated. This method involves the combined use of TiO2-photocatalyst and an adsorbent, which has a high ability of As(V) adsorption, under photo-irradiation. When an aqueous solution of As(III) was stirred and irradiated by sunlight or xenon lamp in the presence of TiO2 suspension, the oxidation of As(III) into As(V) was effectively attained. By use of the same photocatalytic reaction, MMA and DMA were also degraded into As(V), while the total organic carbon (TOC) in the aqueous phase was decreased. When an aqueous solution of As(III) was stirred with a mixed suspension of TiO2 and an adsorbent for As(V) (activated alumina) under sunlight irradiation, the arsenic removal reached 89% after 24 h. By use of the same photocatalyst-adsorbent system, 98% of MMA and 97% of DMA were removed. The mechanism of the removal of arsenic species by the photocatalyst-adsorbent system was discussed.

Anaerobic microbial mobilization and biotransformation of arsenate adsorbed onto activated alumina

Due to the enactment of a stricter drinking water standard for arsenic in the United States, larger quantities of arsenic will be treated resulting in larger volumes of treatment residuals. The current United States Environmental Protection Agency recommendation is to dispose spent adsorbent residuals from arsenic treatment into non-hazardous municipal solid waste (MSW) landfills. The potential of microorganisms to alter the speciation affecting the mobility of arsenic in the disposal environment is therefore a concern. The purpose of this paper was to evaluate the potential of an anaerobic microbial consortium to biologically mobilize arsenate (As(V)) adsorbed onto activated alumina (AA), a common adsorbent used for treating arsenic in drinking water. Three anaerobic columns (0.27 l) packed with 100 g dry weight of AA containing 0.657 mg adsorbed As(V) (expressed as arsenic) per gram dry weight were continuously flushed with synthetic landfill leachate for 257 days. The fully biologically active column was inoculated with methanogenic anaerobic sludge (10 g volatile suspended solids l(-1) column) and was operated with a mixture of volatile fatty acids (VFA) in the feed (2.5 g chemical oxygen demand l(-1) feed). At the end of the experiment, 37% of the arsenic was removed from the column, of which 48% was accounted for by arsenical species identified in the column effluent. The most important form of arsenic eluted was arsenite (As(III)), accounting for nearly all of the identified arsenic in periods of high mobilization. Additionally, two methylated metabolites, methylarsonic acid and dimethylarsinic acid were observed. Mobilization of arsenic is attributed to the biological reduction of As(V) to As(III) since literature data indicates that As(III) is more weakly adsorbed to AA compared to As(V). Batch and continuous assays confirmed that VFA, present in landfill leachates, served as an electron donating substrate supporting enhanced rates of As(V) reduction to As(III). Two control columns, lacking inoculum and/or VFA in the feed displayed low mobilization of arsenic compared to the fully biologically active column. Therefore, leachates generated in MSW landfills could potentially result in the biologically catalyzed mobilization of arsenic from As(V)-laden drinking water residuals.