Interaction of metals and protons with algae. 2. Ion exchange in adsorption and metal displacement by protons

Abstract

maxima of these species should have been found near the oxic/anoxic interface, which is around 80-m depth. The relatively low concentrations of sulfite and thiosulfate near the surface suggest that other factors, such as bacterial activities, may be important in controlling their distribution, and that both sulfite and thiosulfate are turned over rapidly in these waters.The reasons for the gradual increase in concentrations of sulfite and thiosulfate with depth (down to ~2000 m) are not clear. It is possible that some sulfite could have formed by air oxidation of sulfide during sampling, since there was a brief exposure to air (<30 s) just prior to derivatization. However, from kinetic considerations, this brief exposure was not likely to have given rise to the observed high concentrations in the deep samples ( 14). Furthermore, the sulfite depth profile closely parallels that of thiosulfate, which has a much slower formation rate than that of sulfite during air oxidation of sulfide in Black Sea water ( 14). An earlier work reported more than 20 µ concentrations of thiosulfate in the Black Sea waters deeper than ~300 m and attributed bacterial processes for its formation ( 15). The similarity of sulfite and thiosulfate profiles to that of sulfide suggests a common origin of these species in bacterial sulfate reduction. In fact, studies by Millet using radiolabeled sulfate revealed that sulfite was formed as an intermediate in the conversion of sulfate to sulfide (16). Since sulfite as well as thiosulfate are also formed as intermediates in the oxidation of sulfide to sulfate (17,18), it is likely that the reverse reactions occur during sulfate reduction. Our results imply that both sulfite and thiosulfate are probably intermediates in bacterial sulfate reduction.

Effects of Environmental Factors and Nutrient Availability on the Biochemical Composition of Algae for Biofuels Production: A Review

“…The cell surfaces of algae contain a number of functional groups with high affinity for metal ions and that carry a net negative charge mainly due to carboxylic, sulfhydryl, and phosphatic groups [199]. These groups are binding sites that transport metal ions across the cell membrane and into the cell.…”

Advances in the biosorption of heavy metals

“…Recent research work has indicated that ion exchange may be the predominant metal ion binding mechanism in biosorption (Crist et al, 1990;Fourest and Roux, 1994;Kratochvil et al, 1995;Spinti et al, 1995). The classical ion exchange concept based on exchange equilibrium constants and separation factors (Shallcross et al, 1988;Vermeulen et al, 1973) can be applied to this case.…”

Sargassum seaweed as biosorbent for heavy metals

“…Carboxylate groups of alginate have been identi®ed as the main metal binding site. Other negatively charged functional groups such as the sulphonate groups of fucoidan also contribute to heavy metal complexation (Crist et al, 1990;Fourest and Volesky, 1996). Fucoidan is a branched polysaccharide sulfate ester with L-fucose building blocks which are predominantly a(1 4 2) linked (Percival, 1970;Percival and McDowell, 1967b), however it is dicult to evaluate the absolute role these polymers play in determining the ultimate heavy metal uptake.…”

“…Copper would not desorb completely, most likely due to the enhanced covalent character of its binding (Crist et al, 1990). The use of calcium salts at pH=3, or HCl, resulted in the best desorption eciencies.…”