Separation and preconcentration of arsenite and other heavy metal ions using graphene oxide laminated with protein molecules.

The graphene oxide surface was laminated with bovine serum albumin (BSA) followed by the directional flow through a membrane to prepare a free-standing PLGO (protein laminated GO) composite. BSA immobilization increased the interlayer spacing of GO and led to the formation of capillaries. The column packed with PLGO adsorbent permeated water faster as much as ca. 5 fold as compared to only GO packed column. The PLGO composite was used to develop a solid phase extraction method for the selective preconcentration of As(III) in the presence of As(V), prior to their determination. As(III) binding to sulfhydryl groups of BSA in PLGO plays a key role in the speciation. The coexisting heavy metal ions did not hinder the recovery of trace As(III). The method was advantageously employed for the preconcentration of As(III), Pb(II), Cd(II), Zn(II), Cu(II) and Ni(II) from water and food samples. A 3 mL of 1 M hydrochloric acid would be adequate for the complete desorption (recovery > 99%) of the adsorbed metal ions. The preconcentration limit achieved for As(III), Pb(II), Cd(II), Zn(II), Cu(II) and Ni(II) were 1.7, 2.0, 2.0, 2.0, 1.8 and 2.0 µg L-1 respectively, with an optimized sample flow rate of 10 mL min-1.

Dithiocarbamate-modified cellulose resins: A novel adsorbent for selective removal of arsenite from aqueous media.

We synthesized three new dithiocarbamate (DTC)-modified cellulose biomaterials (DMC-1, DMC-2, and DMC-4) to investigate their adsorption capabilities as mitigators of arsenite (AsIII) in aqueous media. The main novelty of the adsorbents was that, among two inorganic species of arsenic, arsenite and arsenate (AsV), DMCs were highly selective to AsIII in the pH range 2-7. The surface areas of the adsorbents were unified by supporting the DMCs on silica gel (designated SSDMC-1, SSDMC-2, and SSDMC-4, respectively) to investigate the effect of the length of the alkyl chains connecting cellulose and DTC groups on AsIII adsorption. The Langmuir model showed a good regression coefficient (R2 > 0.96), and the isotherm results revealed that longer chains might enhance the AsIII capture ability. The adsorbents were also capable of removing various heavy metals, and the coexisting ions, FeIII, MnII, PbII, and ZnII, had no significant impact on the removal of AsIII by the DMCs. Moreover, DMC-2 could remove 98.4 ±â€¯0.1% of AsIII from artificially contaminated river water.

Arsenite removal from groundwater by iron-manganese oxides filter media: Behavior and mechanism.

Arsenic, a common contaminant in groundwater environments, usually coexists with other contaminants, for example, ammonium, iron, and manganese. In our previous studies, an iron-manganese (Fe-Mn) oxides filter media was developed for catalytic oxidation removal of ammonium, iron, and manganese. In this study, batch oxidation/adsorption kinetic experiments revealed that the filter media could easily oxidize arsenite (As(III)) to arsenate (As(V)). And the sorption kinetics was found to follow the pseudo-second-order kinetic model. X-ray powder diffraction (XRD) and Fourier transform infrared spectra (FTIR) along with X-ray photoelectron spectroscopy (XPS) were used to analyze the surface change in the Fe-Mn oxides. Based on sorption and spectroscopic measurements, the mechanism of As(III) removal by the Fe-Mn oxides filter media was found to be an oxidation coupled with sorption approach. As(III) in the aqueous solution was firstly oxidized to As(V) on the surfaces of the Fe-Mn oxides filter media. Then the converted As(V) was attracted to the Fe-Mn oxides filter media surfaces and bounded with the active sites (-OH groups), through weak intermolecular H-bondings. Our results indicated that the novel Fe-Mn oxides filter media could be applied for the simultaneous removal of ammonium, iron, manganese, and As(III) in drinking water treatment and environmental remediation. PRACTITIONER POINTS: A novel iron-manganese oxides filter for efficient As(III) removal was established. The exhausted filter media could be easily regenerated by NaHCO3 solution. Mn(III) related to surface lattice oxygen species was responsible for As(III) oxidation. The oxidation and adsorption processes were involved in As(III) removal. The filter media could be successfully applied to simultaneous removal of ammonium, manganese, iron, and arsenic.

Calcium ion incorporated hydrous iron(III) oxide: synthesis, characterization, and property exploitation towards water remediation from arsenite and fluoride.

Calcium ion-incorporated hydrous iron(III) oxide (CIHIO) samples have been prepared aiming investigation of efficiency enhancement on arsenic and fluoride adsorption of hydrous iron(III) oxide (HIO). Characterization of the optimized product with various analytical tools confirms that CIHIO is microcrystalline and mesoporous (pore width, 26.97 Å; pore diameter, 27.742 Å with pore volume 0.18 cm3 g-1) material. Increase of the BET surface area (> 60%) of CIHIO (269.61 m2 g-1) relative to HIO (165.6 m2 g-1) is noticeable. CIHIO particles are estimated to be ~ 50 nm from AFM and TEM analyses. Although the pH optimized for arsenite and fluoride adsorptions are different, the efficiencies of CIHIO towards their adsorption are very good at pH 6.5 (pHzpc). The adsorption kinetics and equilibrium data of either tested species agree well, respectively, with pseudo-second order model and Langmuir monolayer adsorption phenomenon. Langmuir capacities (mg g-1at 303 K) estimated are 29.07 and 25.57, respectively, for arsenite and fluoride. The spontaneity of adsorption reactions (ΔG0 = - 18.02 to - 20.12 kJ mol-1 for arsenite; - 0.2523 to - 3.352 kJ mol-1 for fluoride) are the consequence of entropy parameter. The phosphate ion (1 mM) compared to others influenced adversely the arsenite and/or fluoride adsorption reactions. CIHIO (2.0 g L-1) is capable to abstract arsenite or fluoride above 90% from their solution (0 to 5.0 mg L-1). Mechanism assessment revealed that the adsorption of arsenite occurs via chelation, while of fluoride occurs with ion-exchange.

Removal of arsenite by reductive precipitation in dithionite solution activated by UV light.

This study investigates the removal of arsenite (As(III)) from water using dithionite activated by UV light. This work evaluated the removal kinetics of As(III) under UV light irradiation as affected by dithionite dose and light intensity, and characterized the nature of the precipitated solids using XPS and SEM-EDS. Photolysis of dithionite was observed by measuring dithionite concentration using UV absorbance at 315nm. This study also investigated the effect of UV light path length on soluble As concentrations to understand resolubilization mechanisms. Total soluble As concentrations were observed to decrease with reaction time due to reduction of arsenite to form solids having a yellow-orange color. The removal mechanism was found to be reductive precipitation that formed solids of elemental arsenic or arsenic sulfide. However, these solids were observed to resolubilize at later times after dithionite had been consumed. Resolubilization of As was prevented and additional As removal was obtained by frequent dosing of dithionite throughout the experiment. As(III) removal is attributed to photolysis of dithionite by UV light and production of reactive radicals that reduce As(III) and convert it to solid forms.

High efficiency removal of As(III) from waters using a new and friendly adsorbent based on sugarcane bagasse and corncob husk Fe-coated biochars.

Water contamination of As is a big issue in many areas around the globe. Therefore, cheap and efficient techniques are essential facing traditional treatment methods. Then, biochars (BC) emerged recently as material that can be used for As removal. However, research about efficiency of BC produced from local feedstock is still needed. The purpose of this study is to assess the efficiency of BC produced from sugarcane bagasse (SB) together with corncob husk (CH) with and without Fe(III) (BCFe) modification to be used for removal of As(III) from waters. The BC and BCFe produced at different pyrolysis temperatures were characterised using FTIR and SEM/EDS. Adsorption capacities of BC and BCFe were evaluated via batch adsorption, desorption and column tests and their performance was compared with adsorption using activated carbon. The results showed that Fe modification improve substantially the As(III) adsorption in a way that both BCFe-SB and BCFe-CH removed from 85% to 99.9% from 1000 µg/L As(III) solutions. Both materials fitted well in Langmuir model and the maximum adsorption capacity was 20 mg/g for BCFe-SB and 50 mg/g for BCFe-CH. The adsorption kinetics of BCFe was fast (≤ 30 min) and it had a better performance than activated carbon. The column tests showed that the process is efficient even at high As(III) concentrations. The fast removal process and good removal results make the BCFe-SB and BCFe-CH attractive for in situ and commercial (filters) use, since time and efficiency are required in new technologies.

Efficient photocatalytic oxidation of arsenite from contaminated water by Fe2O3-Mn2O3 nanocomposite under UVA radiation and process optimization with experimental design.

The efficiency of photocatalytic oxidation process in arsenite (As(III)) removal from contaminated water by a new Fe2O3-Mn2O3 nanocomposite under UVA radiation was investigated. The effect of nanocomposite dosage, pH and initial As(III) concentration on the photocatalytic oxidation of As(III) were studied by experimental design. The synthesized nanocomposite had a uniform and spherical morphological structure and contained 49.83% of Fe2O3 and 29.36% of Mn2O3. Based on the experimental design model, in photocatalytic oxidation process, the effect of pH was higher than other parameters. At nanocomposite concentrations of more than 12 mg L-1, pH 4 to 6 and oxidation time of 30 min, photocatalytic oxidation efficiency was more than 95% for initial As(III) concentration of less than 500 µg L-1. By decreasing pH and increasing the nanocomposite concentration, the photocatalytic oxidation efficiency was increased. Furthermore, by increasing the oxidation time from 10 to 240 min, in addition to oxidation of As(III) to arsenate (As(V)), the residual As(V) was adsorbed on the Fe2O3-Mn2O3 nanocomposite and total As concentration was decreased. Therefore, Fe2O3-Mn2O3 nanocomposite as a bimetal oxide, at low doses and short time, can enhance and improve the efficiency of the photocatalytic oxidation and adsorption of As(III) from contaminated water resources. Furthermore, the energy and material costs of the UVA/Fe2O3-Mn2O3 system for photocatalytic oxidation of 1  mg L-1 As(III) in the 1 L laboratory scale reactor was 0.0051 €.

Novel synergistic hydrous iron-nickel-manganese (HINM) trimetal oxide for hazardous arsenite removal.

A novel hydrous iron-nickel-manganese (HINM) trimetal oxide was successfully fabricated using oxidation and coprecipitation method for metalloid arsenite removal. The atomic ratio of Fe:Ni:Mn for this adsorbent is 3:2:1. HINM adsorbent was identified as an amorphous nanosized adsorbent with particle size ranged from 30 nm to 60 nm meanwhile the total active surface area and pore diameter of HINM area of 195.78 m2/g and 2.43 nm, respectively. Experimental data of arsenite adsorption is best fitted into pseudo-second order and Freundlich isotherm model. The maximum adsorption capacity of arsenite onto HINM was 81.9 mg/g. Thermodynamic study showed that the adsorption of arsenite was a spontaneous and endothermic reaction with enthalpy change of 14.04 kJ/mol and Gibbs energy of -12 to -14 kJ/mol. Zeta potential, thermal gravimetric (TGA) and Fourier transform infrared (FTIR) analysis were applied to elucidate the mechanism of arsenite adsorption by HINM. Mechanism of arsenite adsorption by HINM involved both chemisorption and physisorption based on the electrostatic attraction between arsenite ions and surface charge of HINM. It also involved the hydroxyl substitution by arsenite ions through the formation of inner-sphere complex. Reusability of HINM trimetal oxide was up to 89% after three cycles of testing implied that HINM trimetal oxide is a promising and practical adsorbent for arsenite.

Removal of arsenite by a microbial bioflocculant produced from swine wastewater.

This paper focused on the production and characteristics of a bioflocculant by using swine wastewater and its application in removing arsenite from aqueous solution. A series of experimental parameters including bioflocculant dose, calcium ions concentration, and solution pH value on arsenite uptake were evaluated. Results have demonstrated that a bioflocculant of 3.11 g L-1 was achieved as the maximum yield after 60 h fermentation, with a main backbone of polysaccharides. Maximum arsenite removal efficiency of 99.2% can be reached by adding bioflocculant in two stages: 3 × 10-3% (w/w) in the 1.0 min's rapid mixing (180 rpm) and 2 × 10-3% (w/w) after 2.0 min's slow mixing (80 rpm) with pH value fixed at 7. Negative Gibbs free energy change (ΔGo) indicated the spontaneous nature of arsenite removal. Arsenite was removed by the bioflocculant through bridging mechanisms.

A rapid monitoring method for inorganic arsenic in rice flour using reversed phase-high performance liquid chromatography-inductively coupled plasma mass spectrometry.

A new rapid monitoring method by means of high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) following the heat-assisted extraction was developed for measurement of total inorganic arsenic species in rice flour. As(III) and As(V) eluted at the same retention time and completely separated from organoarsenic species by an isocratic elution program on a reversed phase column. Therefore, neither ambiguous oxidation of arsenite to arsenate nor the integration of two peaks were necessary to determine directly the target analyte inorganic arsenic. Rapid injection allowed measuring 3 replicates within 6min and this combined with a quantitative extraction of all arsenic species from rice flour by a 15min HNO3-H2O2 extraction makes this the fastest laboratory based method for inorganic arsenic in rice flour.

A comparative evaluation of different ionic liquids for arsenic species separation and determination in wine varietals by liquid chromatography - hydride generation atomic fluorescence spectrometry.

The application of different ionic liquids (ILs) as modifiers for chromatographic separation and determination of arsenite [As(III)], arsenate [As(V)], dimethylarsonic acid (DMA) and monomethylarsonic acid (MMA) species in wine samples, by reversed-phase high performance liquid chromatography coupled to hydride generation atomic fluorescence spectrometry detection (RP-HPLC-HG-AFS) was studied in this work. Several factors influencing the chromatographic separation of the As species, such as pH of the mobile phase, buffer solution concentration, buffer type, IL concentration and length of alkyl groups in ILs were evaluated. The complete separation of As species was achieved using a C18 column in isocratic mode with a mobile phase composed of 0.5% (v/v) 1-octyl-3-methylimidazolium chloride ([C8mim]Cl) and 5% (v/v) methanol at pH 8.5. A multivariate methodology was used to optimize the variables involved in AFS detection of As species after they were separated by HPLC. The ILs showed remarkable performance for the separation of As species, which was obtained within 18min with a resolution higher than 0.83. The limits of detection for As(III), As(V), MMA and DMA were 0.81, 0.89, 0.62 and 1.00µg As L(-1). The proposed method was applied for As speciation analysis in white and red wine samples originated from different grape varieties.

Inorganic arsenic speciation by differential pulse anodic stripping voltammetry using thoria nanoparticles-carbon paste electrodes.

Two novel thoria (ThO2) nanoparticles-carbon paste electrodes were used to evaluate an anodic stripping voltammetric method for the direct determination of arsenite and total inorganic arsenic (arsenite plus arsenate) in water samples. The effect of Ag((I)), Cu((II)), Hg((II)), Sb((III)) and Se((IV)) ions on the electrochemical response of arsenic was assayed. The developed electroanalytical method offers a rapid procedure with improved analytical characteristics including good repeatability (3.4%) at low As((III)) concentrations, high selectivity, lower detection limit (0.1 µg L(-1)) and high sensitivity (0.54 µA µg(-1) L). The analytical capability of the optimized method was demonstrated by the determination of arsenic in certified reference materials (trace elements in natural water, trace elements in water and coal fly ash).

Production of bioflocculants prepared from formaldehyde wastewater for the potential removal of arsenic.

A novel bioflocculant (MBF-79) prepared using formaldehyde wastewater as carbon resource was investigated in the study. The optimal conditions for bioflocculant production were determined to be an inoculum size of 7.0%, initial pH of 6.0, and formaldehyde concentration of 350 mg/L. An MBF-79 of 8.97 g/L was achieved as the maximum yield. Three main elements, namely C, H, and O, were present in MBF-79 with relative weigh percentages of 39.17%, 6.74%, and 34.55%, respectively. The Gel permeation chromatography analysis indicated that the approximate molecular weight (MW) of MBF-79 was 230 kDa. MBF-79 primarily comprised polysaccharide (71.2%) and protein (27.9%). Additionally, conditions for the removal of arsenic by MBF-79 were found to be MBF-79 at 120 mg/L, an initial pH 7.0, and a contact time 60 min. Under the optimal conditions, the removal efficiencies of arsenate (0.5 mg/L) and arsenite (0.5 mg/L) were 98.9% and 84.6%, respectively. Overall, these findings indicate bioflocculation offers an effective alternative method of decreasing arsenic during water treatment.

Development of Mag-FMBO in clay-reinforced KGM aerogels for arsenite removal.

To seek high-efficient, convenient and robust methods to decontaminate water polluted by arsenite are critically in demand. Here, we developed a series of magnetic konjac glucomannan (KGM) aerogels as adsorbents for arsenite removal. These adsorbents were fabricated based on sodium montmorillonite (Na(+)-MMT) reinforced KGM matrix with magnetic Fe and Mn oxides (Mag-FMBO) inside. The obtained aerogels adsorbents were characterized by using compression test, thermo gravimetric analysis (TGA), vibrating sample magnetometer (VSM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). The characteristic results showed that the composite aerogels possessed strong mechanical and magnetic property, excellent thermal characteristic and tunable pore structure. Batch adsorption tests were used to evaluate arsenite removal capacity. The adsorption results exhibited that the arsenite removal process was pH-dependent, followed a pseudo-second-order rate equation and Langmuir monolayer adsorption. The maximum arsenite uptake capacity of magnetic aerogels M1.5 reached 16.03mgg(-1) according to Langmuir isotherm at pH 7 and 323K. Besides, the magnetic composite aerogels can be repeatedly used after the treatment of regenerant (NaOH/NaCl/NaClO solution).

Anabaena sp. mediated bio-oxidation of arsenite to arsenate in synthetic arsenic (III) solution: Process optimization by response surface methodology.

Blue green algae Anabaena sp. was cultivated in synthetic arsenite solution to investigate its bio-oxidation potential for arsenic species. Response surface methodology (RSM) was employed based on a 3-level full factorial design considering four factors, viz. initial arsenic (III) concentration, algal dose, temperature and time. Bio-oxidation (%) of arsenic (III) was considered as response for the design. The study revealed that about 100% conversion of As (III) to As (V) was obtained for initial As (III) concentration of 2.5-7.5 mg/L at 30 °C for 72 h of exposure using 3 g/L of algal dose signifying a unique bio-oxidation potential of Anabaena sp. The dissolved CO2 (DCO2) and oxygen (DO) concentration in solution was monitored during the process and based on the data, a probable mechanism was proposed wherein algal cell acts like a catalytic membrane surface and expedites the bio-oxidation process. Bioaccumulation of arsenic, as well as, surface adsorption on algal cell was found considerably low. Lipid content of algal biomass grown in arsenite solution was found slightly lower than that of algae grown in synthetic media. Toxicity effects on algal cells due to arsenic exposure were evaluated in terms of comet assay and chlorophyll a content which indicated DNA damage to some extent along with very little decrease in chlorophyll a content. In summary, the present study explored the potential application of Anabaena sp. as an ecofriendly and sustainable option for detoxification of arsenic contaminated natural water with value-added product generation.

Production of a bioflocculant from methanol wastewater and its application in arsenite removal.

A novel bioflocculant (MBF83) prepared using methanol wastewater as nutrient resource was systematically investigated in the study. The optimal conditions for bioflocculant production were determined to be an inoculum size of 8.6%, initial pH of 7.5, and a methanol concentration of 100.8mgL(-1). An MBF83 of 4.61gL(-1) was achieved as the maximum yield. MBF83 primarily comprised polysaccharide (74.1%) and protein (24.2%). The biopolymer, which was found to be safe in zebrafish in toxicity studies, was characterized using Fourier-transform infrared spectroscopy and elemental analysis. Additionally, conditions for the removal of arsenite by MBF83 were found to be MBF83 at 500mgL(-1), an initial pH of 7.0, and a contact time of 90min. Under the optimal conditions, the removal efficiency of arsenite was 86.1%. Overall, these findings indicate bioflocculation offers an effective alternative method of decreasing arsenite during wastewater treatment.

Improving the Reactivity of Zerovalent Iron by Taking Advantage of Its Magnetic Memory: Implications for Arsenite Removal.

Premagnetization was employed to enhance the reactivity of zerovalent iron (ZVI) toward As(III) sequestration for the first time. Compared to the pristine ZVI (Pri-ZVI), the rate of As(III) elimination by the premagnetized ZVI (Mag-ZVI) was greater over the pHini range of 4.0-9.0 and increased progressively with increasing intensity of the magnetic field for premagnetization. Mag-ZVI could keep its reactivity for a long time and showed better performance than Pri-ZVI for As(III) removal from synthetic groundwater in column tests. The Fe K-edge XAFS analysis for As(III)-treated ZVI samples unraveled that premagnetization promoted the transformation of ZVI to iron (hydr)oxides and shifted the corrosion products from maghemite and magnetite to lepidocrocite, which favored the arsenic sequestration. The arsenic species analysis revealed that premagnetization facilitated the oxidation of As(III) to As(V). ZVI pretreated with grinding was very different from Mag-ZVI with regard to As(III) removal, indicating that the improved reactivity of Mag-ZVI should not be associated with the physical squeezing effect of the ZVI grains during magnetization. The positive correlation between the remanence of Mag-ZVI and the rate constants of total arsenic removal indicated that the enhanced reactivity of Mag-ZVI was mainly ascribed to its magnetic memory, i.e., the remanence kept by Mag-ZVI.

Simultaneous photooxidation and sorptive removal of As(III) by TiO2 supported layered double hydroxide.

The present study focused on the enhanced removal of As(III) by the simultaneous photooxidation and removal process using TiO2 nanoparticles supported layered double hydroxide (TiO2/LDH). The TiO2/LDH nanocomposites were synthesized using a flocculation method, and nanosized (30-50 nm) TiO2 particles were well-distributed on the LDH surface. The XPS and DLS data revealed that the TiO2/LDH nanocomposites were both chemically and physically stable in the aquatic system. The optimum ratio of TiO2 was 20 wt.% and the calcination process of LDH enhanced the removal capacity of As(III) by the reconstruction process. In the kinetic removal experiment, UV irradiation improved the removal rate of As(III), based on the continuous conversion of As(III) to As(V), and that the removal rate was faster under alkaline conditions than acidic and neutral conditions due to the abundance of oxidants and negative charged As(III) species (pKa: 9.2). The main mechanism of As(III) photooxidation is the direct oxidation by [Formula: see text] , which is generated by supported TiO2 nanoparticles. X-ray near edge structure results also confirmed that the As(III) was completely oxidized to As(V). Consequently, the simultaneous photooxidation and removal process of As(III) by TiO2/LDH nanocomposites may be the effective removal option in As(III) contaminated water.

Enhanced As(III) oxidation and removal by combined use of zero valent iron and hydrogen peroxide in aerated waters at neutral pH values.

The oxidation and removal of As(III) by commercially available micro-scale zero-valent iron (mZVI) was studied in aerated synthetic groundwater with initially 6.7 µM As(III) at neutral pH values. Batch experiments were performed to investigate the influence of ZVI and H2O2 concentrations on As(III) oxidation and removal. Oxidation and removal kinetics was significantly increased by increasing ZVI concentration or by adding H2O2 in micromolar concentrations slightly higher than that of initial As(III). Observed half-lifes for arsenic removal without added H2O2 were 81-17 min at ZVI concentrations of 0.15-2.5 g/L, respectively. X-ray absorption spectroscopy (XAS) confirmed that almost all As(III) was converted to As(V) after 2 h of reaction in the pH range 5-9. Addition of 9.6 µM H2O2 to 0.15 g/L ZVI suspensions diminished half-lifes for arsenic removal from 81 to 32 min and for As(III) oxidation from 77 to 8 min, i.e., by approximately a factor of 10. The increased rate of As(III) oxidation is attributable to enhanced formation of oxidants by the Fenton reaction with higher initial concentrations of H2O2. In practice, results of this study suggest that addition of small amounts (<1 mg/L) of H2O2 in various forms (e.g. stable and widely available Na-percarbonate) to water prior to treatment could significantly enhance As(III) oxidation and removal with ZVI.

Hybrid flow system for automatic dynamic fractionation and speciation of inorganic arsenic in environmental solids.

An integrated flow analysis system and protocol are proposed for the first time for automatic dynamic flow-through fractionation of inorganic arsenic (arsenite and arsenate) in environmental solids in combination with its real-time speciation. Four extractants (i.e., (1) 0.05 M ammonium sulfate, (2) 0.05 M ammonium dihydrogen phosphate, (3) 0.2 M ammonium oxalate, and (4) a mixture of 0.2 M ammonium oxalate and 0.1 M ascorbic acid at 96 °C) are applied sequentially to the sample to measure bioaccessible inorganic arsenic associated with (1) nonspecifically sorbed phases, (2) specifically sorbed phases, (3) amorphous plus poorly crystalline hydrous oxides of iron and aluminum, and (4) well-crystallized hydrous oxides of Fe and Al, respectively. The kinetic extraction profiles of arsenite and total inorganic arsenic are obtained for each extractant by automatic collection of a given number of its aliquots (subfractions) exposed to the solid sample. Arsenite and total inorganic arsenic in each subfraction are converted to arsine sequentially by hydride generation at pH 4.50 and in 1.14 M hydrochloric acid, respectively. Arsine is absorbed into a potassium permanganate solution, the discoloration of which is related to the concentration of the corresponding arsenic species. The proposed method is successfully validated by analyzing a soil reference material (NIST 2710a) and a sediment sample.