Biological ferrous sulfate oxidation by A. ferrooxidans immobilized on chitosan beads

Immobilization of Acidithiobacillus ferrooxidans on cotton gauze for biological oxidation of ferrous ions in a batch bioreactor

The ability of Acidithiobacillus ferrooxidans to oxidize ferrous iron has been extensively studied in bioleaching to recover metal resources. Although immobilization of A. ferrooxidans is of great importance to achieve high bioleaching performance in practical application, the reported approaches of immobilization of A. ferrooxidans are still limited. This paper is attempting to develop a novel method to immobilize A. ferrooxidans by a less-costly effective carrier from zeolite, activated carbon, and cotton gauze. The results showed that cotton gauze was the most suitable carrier to immobilize A. ferrooxidans cells in comparison with zeolite and activated carbon. Acidithiobacillus ferrooxidans immobilized on the cotton gauze by gravity dehydration could achieve an average ferrous iron oxidation rate of 0.73 g/(L·h). Furthermore, the ferrous iron oxidation ratio attained in the bioreactor under batch operation was maintained above 97.83%. All results indicated that cotton gauze could be an efficient carrier for immobilizing A. ferrooxidans cells for the biooxidation of ferrous ions.

Immobilization of Acidithiobacillus ferrooxidans on Cotton Gauze for the Bioleaching of Waste Printed Circuit Boards

The bioleaching parameters of metal concentrates from waste printed circuit boards by Acidithiobacillus ferrooxidans immobilized on cotton gauze in a two-step reactor were investigated in this study. The results indicated that an average ferrous iron oxidation rate of 0.54 g/(L·h) and a ferrous iron oxidation ratio of 96.90 % were obtained after 12 h at aeration rate of 1 L/min in bio-oxidation reactor. After 96 h, the highest leaching efficiency of copper reached 91.68 % under the conditions of the content of the metal powder 12 g/L, the retention time 6 h, and the aeration rate 1 L/min. The bioleaching efficiency of copper could be above 91.12 % under repeated continuous batch operation. Meanwhile, 95.32 % of zinc, 90.32 % of magnesium, 86.31 % of aluminum, and 59.07 % of nickel were extracted after 96 h. All the findings suggested that the recovery of metal concentrates from waste printed circuit boards via immobilization of A. ferrooxidans on cotton gauze was feasible.

Bioremediation of mine water

Caused by the oxidative dissolution of sulfide minerals, mine waters are often acidic and contaminated with high concentrations of sulfates, metals, and metalloids. Because the so-called acid mine drainage (AMD) affects the environment or poses severe problems for later use, treatment of these waters is required. Therefore, various remediation strategies have been developed to remove soluble metals and sulfates through immobilization using physical, chemical, and biological approaches. Conventionally, iron and sulfate-the main pollutants in mine waters-are removed by addition of neutralization reagents and subsequent chemical iron oxidation and sulfate mineral precipitation. Biological treatment strategies take advantage of the ability of microorganisms that occur in mine waters to metabolize iron and sulfate. As a rule, these can be grouped into oxidative and reductive processes, reflecting the redox state of mobilized iron (reduced form) and sulfur (oxidized form) in AMD. Changing the redox states of iron and sulfur results in iron and sulfur compounds with low solubility, thus leading to their precipitation and removal. Various techniques have been developed to enhance the efficacy of these microbial processes, as outlined in this review.

Immobilization of Acidithiobacillus ferrooxidans on sulfonated microporous poly(styrene-divinylbenzene) copolymer with granulated activated carbon and its use in bio-oxidation of ferrous iron

The immobilization efficiencies of Acidithiobacillus ferrooxidans cells on different immobilization matrices were investigated for biooxidation of ferrous iron (Fe(2+)) to ferric iron (Fe(3+)). Six different matrices were used such as the polyurethane foam (PUF), granular activated carbon (GAC), raw poly(styrene-divinylbenzene) copolymer (rawSDVB), raw poly(styrene-divinylbenzene) copolymer with granular activated carbon (rawSDVB-GAC), sulfonated poly(styrene-divinylbenzene) copolymer (sulfSDVB) and sulfonated poly(styrene-divinylbenzene) copolymer with granular activated carbon (sulfSDVB-GAC). The sulfSDVB-GAC polymer showed the best performance for Fe(2+) biooxidation. It was used at packed-bed bioreactor and the kinetic parameters were obtained. The highest Fe(2+) biooxidation rate (R) was found to be 4.02 g/L h at the true dilution rate (Dt) of 2.47 1/h and hydraulic retention time (τ) of 0.4 h. The sulfSDVB-GAC polymer was used for the first time as immobilization material for A. ferrooxidans for Fe(2+) biooxidation.

Biological degradation of simazine by mixed-microbial cultures immobilized on sepiolite and tepojal beads

Simazine degradation by mixed microbial cultures was carried out in biological reactors with tepojal and sepiolite beads. The inoculum used is derived from a biotechnological product applied to plant roots, which contains mixed microbial cultures. This inoculum presented a stable adherence to the microorganism support throughout the experiment. In this research, the supports were evaluated in relation to both biofilm formation and simazine removal. For this study, hydraulic and mass starting-up parameters were established for simazine degradation and for the use of these reactors in the two types of supports. Tepojal had never been used before as a microbial support in any previous research paper. Tepojal demonstrated to be more efficient than sepiolite. Statistical analysis was done for the relationship among the parameters of chemical oxygen demand, colony formation units, total suspended solids, and volatile suspended solids.