Chlorination for degrading saxitoxins (paralytic shellfish poisons) in water

Chlorination was investigated as a treatment option for degrading and thus removing saxitoxins (paralytic shellfish poisons, PSPs) produced by cyanobacteria (blue-green algae) from water. It was found to be effective with the order of ease of degradation of the saxitoxins being GTX5 (B1) similar to dcSTX > STX > GTX3 similar to C2 > C1 > GTX2. However the effectiveness of chlorine was pH dependent. Degradation as a function of pH was not linear with the degree of degradation increasing rapidly at around pH 7.5. At pH 9 > 90% removal was possible provided a residual of 0.5 mg l(-1) free chlorine was present after 30 min contact time. The more effective degradation at higher pH was unexpected as chlorine is known to be a weaker oxidant under these conditions. The more effective degradation, then, must be due to the toxins, which are ionisable molecules, being present in a form at higher pH which is more susceptible to oxidation. The feasibility of using chlorine to remove saxitoxins during water treatment will therefore depend strongly on the pH of the water being chlorinated. Degradation may be improved by pH adjustment but may not be a practical solution. Although saxitoxins were degraded in that the parent compounds were not detected by chemical analysis, there is no indication as to the nature of the degradation products. However, acute toxicity as determined by the mouse bioassay was eliminated.

A galloylated cyanogenic glycoside from the Australian endemic rainforest tree Elaeocarpus sericopetalus (Elaeocarpaceae)

A cyanogenic glycoside -6'-O-galloylsambunigrin - has been isolated from the foliage of the Australian tropical rainforest tree species Elaeocarpus sericopetalus F. Muell. (Elaeocarpaceae). This is the first formal characterisation of a cyanogenic constituent in the Elaeocarpaceae family, and only the second in the order Malvales. 6'-O-galloylsambunigrin was identified as the principal glycoside, accounting for 91% of total cyanogen in a leaf methanol extract. Preliminary analyses indicated that the remaining cyanogen content may comprise small quantities of sambunigrin, as well as di- and tri-gallates of sambunigrin. E. sericopetalus was found to have foliar concentrations of cyanogenic glycosides among the highest reported for tree leaves, up to 5.2 mg CN g(-1) dry wt. (c) 2006 Elsevier Ltd. All rights reserved.

Surface-functionalized polymer nanoparticles for selective sequestering of heavy metals

Xanthate-mediated (reversible addition-fragmentation chain transfer) emulsion polymerization has been used to create novel polystyrene nanoparticles with functionalized surfaces (see Figure) for the selective sequestering of heavy metals from water below ppm levels. These nanoparticles show a high degree of selectivity for Hg-II over Co-II. This technology has potential for the selective remediation of heavy metals from the human blood system.