In situ preconcentration and determination of trace arsenic in botanical samples by hydride generation-graphite furnace atomic absorption spectrometry with Pd–Zr as chemical modifier

Arsenic adsorption by iron-aluminium hydroxide coated onto macroporous supports: Insights from X-ray absorption spectroscopy and comparison with granular ferric hydroxides

This paper evaluates the arsenic adsorption characteristics of a macroporous polymer coated with coprecipitated iron-aluminium hydroxides (MHCMP). The MHCMP adsorbent-composite fits best with a pseudo-second order model for As(III) and a pseudo-first order kinetic model for As(V). The MHCMP shows a maximum adsorption capacity of 82.3 and 49.6 mg As/g adsorbent for As(III) and As(V) ions respectively, and adsorption followed the Langmuir model. Extended X-ray absorption fine structure showed that binding of As(III) ions were confirmed to take place on the iron hydroxides coated on the MHCMP, whereas for As(V) ions the binding specificity could not be attributed to one particular metal hydroxide. As(III) formed a bidentate mononuclear complex with Fe sites, whereas As(V) indicated on a bidentate binuclear complex with Al sites or monodentate with Fe sites on the adsorbent. The column experiments were run in a well water spiked with a low concentration of As(III) (100 μg/L) and a commercially available adsorbent (GEH(®)102) based on granular iron-hydroxide was used for comparison. It was found that the MHCMP was able to treat 7 times more volume of well water as compared to GEH(®)102, maintaining the threshold concentration of less than 10 μg As/L, indicating that the MHCMP is a superior adsorbent.

Arsenite adsorption on cryogels embedded with iron-aluminium double hydrous oxides: possible polishing step for smelting wastewater?

Arsenic is among the most toxic elements and it commonly exists in water as arsenite (As(III)) and arsenate (As(V)) ions. As(III) removal often requires a pre-oxidation or pH adjustment step and it is a challenge to adsorb As(III) at circumneutral pH. In this study, iron-aluminium double hydrous oxides were synthesized and incorporated into cryogels. The resulting composite cryogels were evaluated for As(III) adsorption. Initial experiments indicated that the adsorbent showed similar adsorption kinetics for both As(V) and As(III) ions. The adsorption of As(III) best fit the Langmuir isotherm and the maximum adsorption capacity was 24.6 mg/g. Kinetic modeling indicated that the mechanism of adsorption was chemisorption, making the adsorbent-adsorbate interactions independent of charge and hence allowing the adsorbent to function equally efficient across pH 4-11. A Swedish smelting wastewater was used to evaluate the adsorption performance in continuous mode. The studies showed that the adsorbent was successful in reducing the arsenic concentrations below the European Union emission limit (0.15 mg/l) in a smelting wastewater collected after two precipitation processes. The arsenic removal was obtained without requiring a pH adjustment or a pre-oxidation step, making it a potential choice as an adsorbent for As(III) removal from industrial wastewaters.

Speciation analysis of inorganic form of arsenic in ground water samples by hydride generation atomic absorption spectrometry with insitu trapping in graphite tube

This paper presents the results of a study on the optimization of the determination of total arsenic and its species using the absorption atomic spectrometry method combined with hydride generation and in-situ concentration on the inner walls of the graphite tube. To ensure a maximum efficiency of the in-situ analyte concentration on the graphite tube walls, a palladium modifier subjected to preliminary thermal reduction was used. The limits of detection (3σ) were 0.019 ng/mL for total As and 0.031 ng/mL for As(III) at the preliminary analyte concentration for 60s. The optimised procedure of the analyte concentration on the inner walls of the atomiser (graphite tube) was applied for determinations of arsenic in samples of ground water. The content of arsenic in the samples studied varied from 0.21 ng/mL to 0.80 ng/mL for As(III), and from 0.19 ng/mL to 1.24 ng/mL for As(V).