Maghemite nanoparticles for As(V) removal: desorption characteristics and adsorbent recovery.

Maghemite (gamma-Fe2O3) nanoparticles are potential adsorbents for arsenate removal from drinking water. Arsenate, As(V) oxoanion, removal is crucial due to arsenate's serious effects on health and its existence in water worldwide. The aim of the present study was to investigate the adsorbent properties of maghemite nanoparticles by observing their stability, desorption and regeneration ability. Arsenate batch desorption and regeneration experiments were carried out with two different kinds of maghemite - a commercial product and a laboratory-synthesized one using the sol-gel process. The best alkaline desorption solution was determined from five different alkaline solutions: NaOH, Na2CO3, Na2HPO4, NaHCO3 and CH3COONa.3H20 (NaAc). Desorption kinetics were also examined. NaOH was observed to be the best desorption solution at a concentration of 1 M with >95% desorption efficiency achieved for both adsorbents. The arsenate adsorption-desorption process was reversible and maghemite recovery was efficient at successive cycles. The laboratory-synthesized maghemite maintained more than 95% of its initial uptake capacity after six cycles for initial As(V) concentrations of 500 and 1000 microg/l, while the achievement with the commercial product was two to four cycles. In addition, iron dissolution from adsorbents was negligible. Thus, it is possible to regenerate the maghemite nanoparticles for repeated adsorption of As(V).

As(V) adsorption on maghemite nanoparticles.

In this study a novel adsorbent, maghemite nanoparticles (gamma-Fe(2)O(3)), is used for As(V) removal. Maghemite nanoparticles are an exceptional adsorbent material due to its magnetic properties and a good adsorption capacity. The aims of the study were to investigate the suitability of maghemite nanoparticles for As(V) adsorption and to compare properties of different maghemites and their As(V) adsorption efficiency. Maghemite nanoparticles were characterized by XRD, XPS, TEM, VSM, BET and Zeta potential analyzers. Size of the particles varied from 3.8 to 18.4 nm. Adsorption experiments were carried out with three different kinds of maghemite nanoparticles: (i) commercially available, (ii) homemade with mechanochemical method and (iii) homemade with sol-gel process. All three different kinds of maghemite nanoparticles were successful in removing As(V) from water, one of them reached as high adsorption capacity as 50mg/g.

Determination of pesticide residues in red wines with microporous membrane liquid-liquid extraction and gas chromatography.

A sample pretreatment method based on microporous membrane liquid-liquid extraction (MMLLE) was developed for the subsequent gas chromatographic determination of pesticides in wine. MMLLE provided efficient and selective extraction with enrichment factors in the range 3-13. The gas chromatographic separation was carried out using on-column injection and flame ionization detection. The method was linear, repeatable and sensitive. The limits of quantification were better than 0.006 mg/L for all the analytes except for iprodione (0.37 mg/L). The method was applied to the determination of pesticides in several red wines of different origin.