Sorption of As(V) from waters using chitosan and chitosan-immobilized sodium silicate prior to atomic spectrometric determination

Abstract

Keywords:As(V) As(III) Sorption Chitosan Chitosan-immobilized sodium silicate a b s t r a c t A natural biosorbent containing amine functional groups, chitosan, and a novel sorbent, chitosanimmobilized sodium silicate, were prepared and utilized for the selective sorption of As(V) from waters prior to its determination by atomic spectrometric techniques, namely, hydride generation atomic absorption spectrometry (HGAAS) and inductively coupled plasma mass spectrometry (ICP-MS). Chitosan was synthesized from chitin and sodium silicate was used as the immobilization matrix due to its straightforward synthesis. Through sequential sorption studies, it was shown that chitosan-immobilized sodium silicate has exhibited a better chemical stability than the chitosan itself which demonstrates the advantage of immobilization method. Both chitosan and chitosan-immobilized sodium silicate were shown to selectively adsorb As(V), arsenate, from waters at pH 3.0 at which neither chitin nor sodium silicate displayed any sorption towards As(V). The sorption of arsenate by chitosan is supposed to have electrostatic nature since pH of 3.0 is both the point at which the amino groups in chitosan are protonated and also the predominant form of As(V) is H 2 AsO 4 − . A pre-oxidation step is required if both As(III) and As(V) are to be determined. Desorption from the sorbents was realized with 1.0% (w/v) l-cysteine prepared in a pH 3.0 solution adjusted with HCl. Among the possible interfering species tested, only Te(IV) and Sb(III) were shown to cause a decrease in the sorption capacity especially at high interferant concentrations. High concentrations of Sb(III) also resulted in gas phase interference during hydride generation.The validity of the method was checked both via spike recovery experiments and also through the analysis of a standard reference material. Spike recovery tests were carried out with four different types of water; namely, ultra-pure, bottled drinking, tap, and sea water; and percent recovery values were found to be 114 (±4), 112 (±2), 43 (±4), and 0 (±1), respectively. It was concluded that the proposed methodology can be applied efficiently to low-to-medium ionic strength solutions, such as most drinking waters. The accuracy of the method was additionally investigated through the analysis of a standard reference material and a good correlation was found between the determined (26.6 ± 2.4 g L −1 ) and the certified (26.67 g L −1 ) value.

Synthesis, characterization and application of a novel mercapto- and amine-bifunctionalized silica for speciation/sorption of inorganic arsenic prior to inductively coupled plasma mass spectrometric determination

“…On the other hand, (NH 2 )silica demonstrates selectivity only towards As(V), and this response is indicative of the affinity of amine functionality to arsenate ion. The nature of sorption at pH 3.0 has been suggested, in a previous study, as being electrostatic attraction between the protonated amine groups of (NH 2 )silica and H 2 AsO 4 − ion, which is the main species at this pH [32]. As can be deduced from Fig.…”

“…The sorption of (NH 2 + SH)silica was not affected by the temperature increase and was quantitative even at 75 • C. These results verifies the robust nature and the applicability of the bifunctional (NH 2 + SH)silica even at such relatively unusual conditions. In addition to the sorption studies with As(III) and As(V), the capacity of the sorbents was determined via Dubinin-Radushkevich (D-R) isotherm model, as explained in a previous study [32]. The model was applied at pH 1.0, 3.0 and 9.0 for As(III) and pH 3.0 for As(V).…”

“…The affinity of mercapto functionality to lower [30,31] and amine functionality to higher [32] oxidation state of arsenic has evoked the search for a bifunctional sorbent with both groups. From this point of view, the main purpose of the present study was to synthesize a novel bifunctional solid phase extraction sorbent with both mercapto and amine functional groups and to use the sorbent for selective sorption of arsenic species.…”

Preparation, Characterization and Optimization of Chitosan Nanoparticles as Carrier for Immobilization of Thermophilic Recombinant Esterase

“…Chitosan was synthesized from chitin by the method of Rigby and Wolfrom with some modification described by Boyacı et al (19). In the procedure, 15.0 g chitin was treated with 720.0 mL of 40.0% (w/w) aqueous NaOH solution at 115…”

Chitosan fiber-supported zero-valent iron nanoparticles as a novel sorbent for sequestration of inorganic arsenic

“…It was reported that chitosan flakes do not show any affinity for As(III) over the wide range of pH values, whereas the same sorbent has the highest As(V) sorption at pH 3.0. 60 However, at low pH values, the dissolution problem of chitosan precludes the possibility of its usage as a sorbent material for arsenic removal. As seen in Fig.…”