Lászloó Szekeres

Bio: Lászloó Szekeres is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 63 citations.

The role of Thiobacillus ferrooxidans in hydrometallurgical processes

Abstract: The present article illustrates the increased interest which is manifested in the microorganisms, Thiobacillus ferrooxidans, involved in the biohydrometallurgical extraction processes. The wide varieties of problems currently studied are very important in order to gain a better understanding about the factors which are governing the growth of microorganisms, and as a consequence, the metal dissolution phenomena. In several mining sites, the microbiological leaching techniques are currently practiced at industrial-scale, especially for recovery of copper and uranium from low-grade materials. However, an accurate assessment of further potential possibilities for the application of microorganisms in leaching metal sulfides requires a more fundamental knowledge about the interactions of the physical and chemical factors with the growth of T. ferrooxidans in pure and mixed cultures including heterotrophic and thermophilic cohabitants. Altogether, the future industrial exploitation of these microbiological leaching techniques are very attractive in many countries of the world.

Protocol for Quantitative Detection of Elemental Sulfur and Polysulfide Zero-Valent Sulfur Distribution in Natural Aquatic Samples

Abstract: A HPLC-based protocol has been developed for the determination of zero-valent sulfur (ZVS) speciation, including solid, colloidal elemental sulfur and individual inorganic polysulfides in natural aquatic samples. The protocol includes four experimental procedures: (1) determination of polysulfide speciation by rapid single-phase derivatisation with methyl trifluoromethanesulfonate; (2) determination of the sum of polysulfide and colloidal sulfur by reaction with hydrogen cyanide (cyanolysis); (3) determination of total zero-valent sulfur by treatment with zinc chloride followed by extraction with chloroform; and (4) chromatographic determination of polythionates without sample pre-treatment. With proper sampling and preservation techniques in the field or on board ship, this combination of methods allowed the quantitative determination of: (a) individual polysulfide species; (b) dispersed colloidal sulfur; (c) dispersed solid elemental sulfur; and (d) tetra-, penta- and hexathionates. With minor modification, the method could be expanded to include other polythionates. Sixteen various wet chemical and liquid chromatographic methods were tested on nine synthetic reference samples (including solid elemental sulfur, colloidal elemental sulfur, inorganic polysulfides and polythionates) to establish the optimal protocol. The protocol was further evaluated by analysing the zero-valent sulfur content in microbially-produced sulfur and in sulfur from two natural samples of sulfide-rich seawater from tidal flats pools of the Wadden Sea (Germany).

Capillary electrophoretic determination of thiosulfate, sulfide and sulfite using in-capillary derivatization with iodine.

Abstract: A new capillary electrophoresis (CE) method was developed for the rapid, simple and selective determination of thiosulfate, sulfide and sulfite species. The proposed method is based on the in-capillary derivatization of separated sulfur anions by mixing their zones with the iodine zone during the electrophoretic migration and direct UV detection of iodide formed. The optimal conditions for the separation and derivatization reaction were established by varying electrolyte pH, electrolyte counter-ion, concentration of iodine, and applied voltage. The optimized separations were carried out in 20 mmol/L Tris-chloride electrolyte (pH 8.5) using direct UV detection at 214 nm. All three sulfur species were well resolved in less than 4 min. The method gives repeatability comparable or even better than this obtained for sulfur anions using standard CE technique. The proposed CE system was applied to the monitoring of sulfur anions in spent fixing solutions during the electrolytic oxidation.