Application of iron-oxidizing bacteria to hydrometallurgical flue dust treatment and H₂S desulfurization

Abstract

Flue dust produced from the Kosaka copper flashsmelting furnace contains metals such as Cu, Pb, Zn, Fc, As, Cd, etc. To recover these metals, the dust is treated in the hydrometallurgical plant. Previous iron oxidation by air blown at pH 5 and at 50°C for removal of iron from the leached solution has been superceded by bacterial iron oxidation and pecipitation processes. The advantages of this bacterial oxidation procedure are (i) low cost; (ii) clear separation of metals; (iii) improvement in settling and dewatering characteristics and smaller, stable of volume precipitate and (iv) possibilities of fixing arsenate to obtain inexpensive ferric ions. A new hydrogen sulfide gas treatment process has been developed to treat the gas from plants producing barium chemicals. Itydrogen sulfide (70% content) is absorbed on ferric iron solution, and is thus oxidized to elemental sulfur. After the sulfur has been separated, the iron‐ oxidizing bacteria are employed to regenerate the absorbing solution. In this plant, which produces 150 tons sulfur per month, the hydrogen sulfide content of sweet gas is kept under 10 ppm; equivalent to 99.99%,; of the hydrogen sulfide recovery. The advantages of this process are (i) high H 2S gas removal efficiency; (ii) low running cost; (iii) ease of operation and maintenance: (iv) no waste; (v) high H2S selectivity; and (vi) good flexibility overload fluctuations.

Differential gene expression in response to copper inAcidithiobacillus ferrooxidans analyzed by RNA arbitrarily primed polymerase chain reaction

“…According to Johnson [6], in 1998 the global market of the bioleaching industry and stirred reactor processes for valuable metal recovery was estimated to be around US$ 10 billion. In addition, A. ferrooxidans represents a less expensive and nonpolluting alternative for use in the degradation of chemical residues from processed minerals [7]. A. ferrooxidans can also remove sulfur from coal and fuel oil and, when present in biofilters, can scrub sulfur dioxide from various industrial emissions [8].…”

Chemolithoautotrophic Bacteria

“…The molar growth yield for formate of the bacterium (Y formate ) is 1.32 g (dry weight), while that for ferrous ion (Y Fe 2+ ) is 0.23 g (dry weight). Although the bacterium is sensitive to chloride ion, it becomes resistant to 140 μM chloride ion by training (Shiratori and Sonta, 1993). The growth of the bacterium is inhibited by benzoic acid, sorbate, and sodium laurylate (Onysko et al, 1984), and nitrate at 50 mM inhibits completely the oxidation of ferrous ion by the bacterium (Eccleston et al, 1985).…”

Analise de proteinas e genes envolvidos no metabolismo energetico e sistema antioxidante em Acidithiobacillus ferrooxidans LR

“…ferrooxidans possui também importância ambiental, pois pode ser utilizada na degradação de resíduos químicos provenientes de minerais processados. Os métodos convencionais geralmente apresentam custos elevados e o emprego de A. ferrooxidans é uma alternativa econômica e rápida, com benefícios para o meio ambiente (Shiratori & Sonta, 1993;Hubert et al, 1995). Além disso, a capacidade de metabolização de compostos sulfúricos possibilita a utilização de A. ferrooxidans em filtros para a eliminação do dióxido de enxofre, um importante poluente ambiental emitido por vários tipos de indústrias (Bonaventura & Johnson, 1997).…”