Abstract
Metallic wastes from the metal-mechanic industry represent a serious environmental problem. The possible strategies to reduce the metal content of these industrial wastes is their biotreatment by means of sulfur-oxidizing bacteria, such as Acidithioobacillus thiooxidans DSM 26636, which has been reported as an excellent metal-leaching microorganism by its capability to oxide sublimed sulfur and produce sulfuric acid in the presence of metallic burrs, and leach metals. The metallic composition of burrs was determined by ICP-OES before and after its exposure to biological treatment. The bioleaching process was kept for 21 days at 30 °C at an orbital shaking of 150 rev/min by using Erlenmeyer flasks of 125 mL containing 30 mL of Starkey-modified media added with 0.33 g (1% w/v) of sublimed sulfur and 0.33 g (1% w/v) of metal burrs, and 3 mL of inoculum at logarithmic phase. Results showed that A. thiooxidans was able to grow at these conditions with a maximum sulfate production of 11,028 mg/L, sulfuric acid corresponded to 0.16 M, but no statistical difference was observed for days 14 and 21. A reduction in pH was observed from 2.5 to 1.3 units. Metal bioleaching in mg/kg corresponded Fe (4658.5 ± 291), Cr (237 ± 46), Al (185 ± 12), Si (71 ± 10.3), Mo (63 ± 3.6), Mn (46 ± 3.3), V (18 ± 0.94), Mg (22.2 ± 3.7), Ni (15.8 ± 1.5), and Cu (5.7 ± 1.9). Results showed that A. thiooxidans DSM 26636 was able to grow in the presence of metal-containing wastes, and although metal removal was feasible, more studies are needed to enhance metal removal.
Highlights
During the production of metal-containing parts, such as structures or any other products, large amounts of metallic burrs are produced; in most of the cases, these wastes are disposed of in landfills; in fewer cases, they are recycled; the high amount of metallic wastes generated has created a serious environmental concern
A. thiooxidans DSM 26636 was able to grow in the presence of metal-containing wastes, and metal removal was feasible, more studies are needed to enhance metal removal
The present results report the potential use of A. thiooxidans DSM 26,636 to leaching metals contained in metal burrs in the presence of sublimed sulfur, both at 1% (w/v)
Summary
During the production of metal-containing parts, such as structures or any other products, large amounts of metallic burrs are produced; in most of the cases, these wastes are disposed of in landfills; in fewer cases, they are recycled; the high amount of metallic wastes generated has created a serious environmental concern. Metal burrs could result in environmental pollution derived from their heavy metal content, so the accumulation of these heavy metals leads to major ecological and health problems. As it has been reported, heavy metals can cause malfunctioning of the cellular processes via the displacement of essential metals from their respective sites. Its high level of toxicity is alarming, but the metallic resources represent a viable option before the depletion of natural reserves by its non-renewable nature. It is, imperative to search for alternatives for the Catalysts 2020, 10, 1230; doi:10.3390/catal10111230 www.mdpi.com/journal/catalysts
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
