Biooxidation of hydrogen sulfide to sulfur by moderate thermophilic acidophilic bacteria.

The copper industry utilizes significant amounts of sulfuric acid in its processes, generating sulfate as waste. While sulfate-reducing bacteria can remove sulfate, it produces hydrogen sulfide (H2S) as a byproduct. This study examined the capability of a consortium consisting of Sulfobacillus thermosulfidooxidans and Sulfobacillus acidophilus to partially oxidize H2S to S° at a temperature of 45 °C. A fixed-bed bioreactor, with glass rings as support material and sodium thiosulfate as a model electron donor, was inoculated with the consortium. Formation of biofilms was crucial to maintain the bioreactor's steady state, despite high flow rates. Afterward, the electron donor was changed to H2S. When the bioreactor was operated continuously and with high aeration, H2S was fully oxidized to SO42-. However, under conditions of low aeration and at a concentration of 0.26 g/L of H2S, the consortium was able to oxidize H2S to S° with a 13% yield. S° was discovered attached to the glass rings and jarosite. The results indicate that the consortium could oxidize H2S to S° with a 13% yield under low aeration and at a concentration of 0.26 g/L of H2S. The findings highlight the capability of a Sulfobacillus consortium to convert H2S into S°, providing a potential solution for addressing environmental and safety issues associated with sulfate waste generated by the mining industry.

[Biomass of Rhizopus oligosporus as an adsorbent for metal ions]. / Biomasa de Rhizopus oligosporus como adsorbente de iones metálicos.

The effect of different parameters on the adsorption of metal ions by Rhizopus oligosporus has been studied. The uranium sorption by dried biomass was rapid, reaching in 5 min around 95.% of the binding capacity. The uranium-binding capacity of the culture showed an inverse relation to the growth kinetic. The relationship between sorption and equilibrium concentration was similar to an adsorption isotherm. Using the Langmuir model, a maximum sorption capacity of 0.52 mmoles uranium/g dry biomass and an affinity constant of 101 l/mmol uranium at pH 4.15 were determined. The best capacity of the biomass to bind ions (UO2(2+), Cu2+, Cd2+ and Zn2+) was best at pH 4.5-5.5. By using hydrochloric acid as eluant a 18% uranium removal of the biomass-bound ions was obtained at pH 1.0. The presence of other cations inhibited uranium-binding in the following order: Cu2+ > Cd2+ > Zn2+ > Mg2+ > Ca2+.

Biosorption of metal ions byAzotobacter vinelandii.

Azotobacter vinelandii was better than eitherDerxia gummosa orRhizobium trifolii for sorption of UO 2 (2+) . Its maximum binding capacity was 0.25 mmol UO 2 (2+) /g dry biomass with an affinity constant of 333 l/mmol at pH 4.1 according to the Langmuir model. In a semisynthetic medium,A. vinelandii showed the highest sorption capacity in the early stationary phase. The binding of UO 2 (2+) , Cu(2+), Ca(2+) and Zn(2+) was affected by the pH of the solution. With HCl as eluent, virtually all the sorbed UO 2 (2+) was released. The presence of Cu(2+), Cd(2+), Ca(2+), and Zn(2+) inhibited the UO 2 (2+) biosorption whereas Mg(2+) and K(+) had no effect.