Microbially Influenced Corrosion of Stainless Steel by Acidithiobacillus ferrooxidans Supplemented with Pyrite: Importance of Thiosulfate

ABSTRACT Microbially influenced corrosion (MIC) results in significant damage to metallic materials in many industries. Anaerobic sulfate-reducing bacteria (SRB) have been well studied for their involvement in these processes. Highly corrosive environments are also found in pulp and paper processing, where chloride and thiosulfate lead to the corrosion of stainless steels. Acidithiobacillus ferrooxidans is a critically important chemolithotrophic acidophile exploited in metal biomining operations, and there is interest in using A. ferrooxidans cells for emerging processes such as electronic waste recycling. We explored conditions under which A. ferrooxidans could enable the corrosion of stainless steel. Acidic medium with iron, chloride, low sulfate, and pyrite supplementation created an environment where unstable thiosulfate was continuously generated. When combined with the chloride, acid, and iron, the thiosulfate enabled substantial corrosion of stainless steel (SS304) coupons (mass loss, 5.4 ± 1.1 mg/cm2 over 13 days), which is an order of magnitude higher than what has been reported for SRB. There results were verified in an abiotic flow reactor, and the importance of mixing was also demonstrated. Overall, these results indicate that A. ferrooxidans and related pyrite-oxidizing bacteria could produce aggressive MIC conditions in certain environmental milieus. IMPORTANCE MIC of industrial equipment, gas pipelines, and military material leads to billions of dollars in damage annually. Thus, there is a clear need to better understand MIC processes and chemistries as efforts are made to ameliorate these effects. Additionally, A. ferrooxidans is a valuable acidophile with high metal tolerance which can continuously generate ferric iron, making it critical to copper and other biomining operations as well as a potential biocatalyst for electronic waste recycling. New MIC mechanisms may expand the utility of these cells in future metal resource recovery operations.

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Robots in recycling and disassembly

Industrial Robot the international journal of robotics research and application ◽

10.1108/ir-03-2019-0053 ◽

2019 ◽

Vol 46 (4) ◽

pp. 461-466 ◽

Cited By ~ 1

Author(s):

Robert Bogue

Keyword(s):

Research Effort ◽

Electronic Waste ◽

Waste Recycling ◽

Content Type ◽

Research Activities ◽

Wide Range ◽

Electronic Waste Recycling ◽

Product Disassembly ◽

Insight Into

Purpose This paper aims to illustrate the growing role robots are playing in recycling and product disassembly and provide an insight into recent research activities. Design/methodology/approach Following a short introduction, this first considers robotic waste sorting systems and then describes two systems for the disassembly of electronic products. It then provides details of some recent research activities. Finally, brief conclusions are drawn. Findings Robotic systems exploiting artificial intelligence combined with various sensing and machine vision technologies are playing a growing role in the sorting of municipal and industrial waste, prior to recycling. These are mostly based on delta robots and can achieve pick rates of 60-70 items/min and be configured to recognise and select a wide range of different materials and items from moving conveyors. Electronic waste recycling is yet to benefit significantly from robotics although a limited number of systems have been developed for product disassembly. Disassembly techniques are the topic of a concerted research effort which often involves robots and humans collaborating and sharing disassembly tasks. Originality/value This provides an insight into the present-day uses and potential future role of robots in recycling which has traditionally been a highly labour-intensive industry.

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