Bioleaching of cadmium and nickel from synthetic sediments by Acidithiobacillus ferrooxidans

Abstract

The microbial leaching process was evaluated for the treatment of synthetic sediments contaminated with cadmium and nickel sulfides. A series of batch leaching experiments was conducted to compare metal solubilization in sediment inoculated with Acidithiobacillus ferrooxidans -inoculated sediments to that in sterile control sediment. The rate and extent of metal solubilization were significantly higher in A. ferrooxidans -inoculated reactors than in acidified sterile reactors. The efficiency of cadmium (Cd) solubilization (80) in the bioleaching process was higher than that of nickel (Ni) solubilization (60). The performance of leaching reactors containing only culture supernatants was comparable to that of A. ferrooxidans -inoculated reactors, indicating that indirect non-contact leaching by the products of microbial metabolism is the predominant mechanism for metal solubilization rather than direct microbial sulfide oxidation. Moreover, the similar (60-75%) extents of Cd(2+) leaching with A. ferrooxidans , cell-free filtrate, and Fe(3+) suggest that abiotic oxidation of CdS by Fe(3+) controls the overall leaching rate, and the role of A. ferrooxidans is most likely not to oxidize CdS mineral directly but to regenerate Fe(3+) as an oxidant.

Enzymatic bioleaching of metals from printed circuit board

“…These results are in accordance with previous reports by Kim et al (2005), Liang et al (2010), Velgosova et al (2013), and Jadhav and Hocheng (2014a). These authors suggested that Fe(III) plays a vital role in solubilization of metals.…”

“…Fe(III) is a strong oxidizing agent. It can solubilize the metals as per following reaction (Kim et al 2005):…”

“…During Fenton process, Fe(III) ions are also produced along with hydroxyl radicals (Karimi et al 2012;Sekaran et al 2013). In past several researchers showed role of Fe(III) in metal solubilization (Kim et al 2005;Liang et al 2010;Velgosova et al 2013;Jadhav and Hocheng 2014a). Hence Fenton process can be used to treat metal-containing solid waste.…”

Bioleaching of copper from waste printed circuit boards by bacteria-free cultural supernatant of iron–sulfur-oxidizing bacteria

“…Jadhav and Hocheng (2013) investigated silver extraction from spent silver oxide-zinc button cell battery using Acidithiobacillus ferrooxidans, and considered indirect non-contact leaching was the predominant mechanism for metal solubilization. Kim et al (2005) demonstrated indirect non-contact leaching performed better than direct leaching in bioleaching of cadmium and nickel from synthetic sediments.…”

Bioleaching of spent Ni–Cd batteries by continuous flow system: Effect of hydraulic retention time and process load

“…Most of the metals dissolution needed relative short time in the initial 5-10 days. It can be inferred that at the initial bioleaching the predominant mechanism responsible for the solubilization of metals from the spent Ni-Cd batteries was non-contact mechanism (acid dissolution) [21]. And the longer HRT was advantageous for the dissolution of some materials difficult to dissolve such as metallic phases.…”