Abstract
The interaction of biofilms with metallic surfaces produces two biologically induced degradation processes of materials: microbial induced corrosion and bioleaching. Both phenomena affect most metallic materials, but in the case of noble metals such as gold, which is inert to corrosion, metallophilic bacteria can cause its direct or in direct dissolution. When this process is controlled, it can be used for hydrometallurgical applications, such as the recovery of precious metals from electronic waste. However, the presence of unwanted bioleaching-producing bacteria can be detrimental to metallic materials in specific environments. In this work, we propose the use of single-layer graphene as a protective coating to reduce Au bioleaching by Cupriavidus metallidurans, a strain adapted to metal contaminated environments and capable of dissolving Au. By means of Scanning Tunneling Microscopy, we demonstrate that graphene coatings are an effective barrier to prevent the complex interactions responsible for Au dissolution. This behavior can be understood in terms of graphene pore size, which creates an impermeable barrier that prevents the pass of Au-complexing ligands produced by C.metallidurans through graphene coating. In addition, changes in surface energy and electrostatic interaction are presumably reducing bacterial adhesion to graphene-coated Au surfaces. Our findings provide a novel approach to reduce the deterioration of metallic materials in devices in environments where biofilms have been found to cause unwanted bioleaching.
Highlights
When microorganisms adhere to surfaces, they secrete extracellular polymeric substances (EPS) to form biofilms which result in a highly effective protection strategy against external influences such as temperature, pH or biocides agents [1]
Nanoscale morphological characterization of graphene-coated and uncoated Au substrate after C. metallidurans exposure was mainly carried out using scanning tunneling microscopy (STM), a powerful tool for nondestructive topographical and morphological testing with high spatial resolution, that it has not been previously reported for the study of this type of biodegradation process
Graphene grown on Cu presents sharp first-order bond stretching G band centered at ~1589 cm−1 and the two-phonon 2D band centered at ~2683 cm−1, with a 2D/G intensity ratio of 2.47, which is expected for single layer graphene [67,68]
Summary
When microorganisms adhere to surfaces, they secrete extracellular polymeric substances (EPS) to form biofilms which result in a highly effective protection strategy against external influences such as temperature, pH or biocides agents [1]. Controlled bioleaching processes are mainly used in these ganisms in biofilms exhibit extreme tolerance to hostile environments such as acidic and biohydrometallurgy applications [35,36,37] and for metal recovery from e-waste [38,39], alkaline pH, low and higher temperatures, as well as pressure gradients, and as consethe presence of unwanted bioleaching-producing bacteria on metallic surfaces can be quence, MIC has been found in power plants [18], oil and gas pipelines [19], public water detrimental for specific environments This is the case for the International Space Station supply systems [20], sewers [21], marine engineering infrastructure water cooled heat (ISS), where bioleaching-producing bacteria have been found at its[22], Potable. Nanoscale morphological characterization of graphene-coated and uncoated Au substrate after C. metallidurans exposure was mainly carried out using scanning tunneling microscopy (STM), a powerful tool for nondestructive topographical and morphological testing with high spatial resolution, that it has not been previously reported for the study of this type of biodegradation process
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