Transformation of arsenobetaine and growth of bacteria on zeolitic tuffs

Abstract

Arsenobetaine (AsB) is a known organoarsenical of harmless toxicity. It is formed mainly by the metabolization of arsenate in marine organisms such as fish, mollusks and crustaceans. Preliminary investigations have shown that AsB can be degraded in contact with zeolites used as feed additives. Employing high-performance liquid chromatography (HPLC) combined with simultaneous parallel electrospray ionization (ESI) and inductively coupled plasma mass spectrometric (ICP-MS) detection, the formation of degradation products was monitored over fifty days in batch reactors containing AsB and clinoptilolites in an aqueous solution. After a 50-day contact with different natural Mexican zeolites, the AsB concentration decreased by 37 to 100 %. In contrast, no degradation products of AsB were detected after contact with a synthetic clinoptilolite. The formation of dimethyl (1-carboxymethyl) arsine and arsenate proceeded with different yields in the set of four natural zeolites. To search for the presence of bacteria on the zeolites as an alternative explanation for the metabolism of AsB in our experiments, the growth of microorganisms was studied on two natural clinoptilolites from Hungary and Mexico after severe acid wash. After 10 days of cultivation in iron and sulfur media, almost a threefold increase of the microbial population was observed. In further experiments on the retention of inorganic arsenic, one sample retained, for example, 25 μ/g As(V) and 2.5 μ/g As(III) from a 400 μ/L arsenic solution. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.