Dissolution Rate Of Oxide Research Articles

Electrochemically structured tantalum surfaces via anodization for core-shell nanostructures: Optimization and characterization of Zn-ZnO nanoparticle deposition using magnetron sputtering

This study explores the electrochemical anodization of tantalum surfaces to create nanostructured substrates for the deposition of Zn-ZnO nanoparticles (NPs) through magnetron sputtering. The anodization process, conducted at different potentials (25 V and 50 V), resulted in tantalum surfaces with distinct dimple structures. The formation of these nano-level dimples is attributed to the dynamic equilibrium between the continuous formation and dissolution of the anodic TaOx layer. The dimple diameter is observed to increase with applied potential, correlating with the dissolution rate of the anodic oxide. The NP deposition parameters were studied in two steps. First, the effect of the deposition conditions on the nanoparticle size and distribution was evaluated and optimized on silicon substrates. Second, the conditions that resulted in the optimum size and distribution of the nanoparticles were utilized in tantalum substrates and evaluated to which extent these conditions were reproduced onto the anodized Ta substrate. Comparisons of Zn-ZnO nanoparticle depositions on silicon and tantalum substrates reveal similar island growth trends, with differences in nanoparticle size and distribution attributed to substrate properties. Further investigation involves anodized tantalum substrates with varying dimple sizes, and deposition conditions are adjusted with bias voltage, pressure, and deposition time to control nanoparticle characteristics. Characterization of the Zn-ZnO nanoparticles deposited on anodized tantalum surfaces is performed using scanning electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, and energy-dispersive x-ray spectroscopy. The resulting core-shell structures are confirmed through structural analysis, revealing a core of hexagonal close-packed Zn and a shell of ZnO. The study demonstrates the influence of substrate properties and deposition conditions on the morphology and composition of Zn-ZnO nanoparticles, providing insights for applications in nanoelectronics and catalysis.

Mechanism of interaction between zirconium dioxide and fluoride melts

In this work, the mechanism of interaction between zirconium dioxide and fluoride melts was studied. Dissolution rates and maximum permissible oxide contents in the KF-AlF3 and NaF-AlF3 melts were determined under natural convection conditions at a temperature of 750 °C. The results of solubility measurement show that the limiting content of ZrO2 in the KF-AlF3 melt ([KF]/[AlF3] = 1.3) is 0.69 ± 0.10 mol. %, and in the NaF-AlF3 melt ([NaF]/[AlF3] = 1.3) at 800 °C it is 0.54 ± 0.04 mol. %. The calculated dissolution rate of zirconium oxide under these conditions in melts based on potassium fluoride and sodium fluoride is 0.022 mol/min and 0.017 mol/min, respectively. The influence of the cationic composition of the medium and the concentrations of additives on the liquidus temperatures of the melts was studied. It has been established that the increase in liquidus and solidus temperatures is facilitated by the addition of zirconium and aluminium oxides, as well as by the replacement of potassium fluoride with sodium fluoride while maintaining the molar ratio of the replaced cations. Analysis of thermal effects by differential scanning calorimetry (DSC) shows that, regardless of the molar ratio of the components, the onset of the thermal effect in melts based on potassium fluoride occurs at a temperature of 542 °C and in the systems with sodium fluoride additives at a temperature of 597 °C. Presumably, this dependence is associated with the melting of the KAlF4 and K2NaAl3F12 phases formed in the melts based on KF-AlF3 and KF-NaF-AlF3, respectively. It has been established that the melting of the KF-AlF3 mixture is accompanied with a mass loss of up to 1.3 wt. %, which is associated with partial evaporation of KAlF4.

Understanding the goethite role on stibnite oxidative dissolution and transformation: Spectroscopic and DFT study

The geochemical cycling of antimony (Sb) in aquatic system is primarily influenced by the dissolution and transformation of stibnite (Sb2S3) in the presence of iron minerals. Here, Sb2S3 oxidative dissolution and sequestration on goethite were investigated to mimic the environmental fate of Sb2S3. The results demonstrated that goethite accelerated the rate of Sb2S3 oxidative dissolution by a factor of 9.4 times under sunlight. The significant Sb2S3 oxidation on goethite was attributed to a heterogeneous electron transfer from Sb2S3 to goethite, as proved by XANES analysis. This electron transfer facilitated the generation of hydroxyl radicals (OH) on Sb2S3, and superoxide radicals (O2−) on goethite. Radical trapping experiments confirmed that O2− was the dominant oxidant for Sb(III) oxidation with 91 % contribution. Thus, goethite plays a dominant role in O2− generation and Sb2S3 oxidative dissolution. Meanwhile, the total dissolved Sb was decreased by 69 % in Sb2S3 and goethite coexisting system compared to a single Sb2S3 system, indicating the retention of dissolved Sb on goethite. Density functional theory (DFT) calculations deciphered that Sb(III) oxidation on mineral-water interfaces with O2− radicals was thermodynamically preferential to OH radicals. Additionally, the Sb was anchored on goethite as a bidentate binuclear structure with a favorable adsorption energy. Our findings shed the light to understand the geochemical cycles of Sb2S3 in natural environment.

Oxidative Dissolution of Cemented Tungsten Carbides in Molten Sodium Carbonate by Addition of Copper(I) Oxide as Oxidizing Agent for Tungsten Recycling

Due to the monopolized supply of tungsten resource, it is important to efficiently recycle tungsten scrap for use as a secondary resource. The recycling of tungsten from cemented carbide tools by the molten carbonate method was investigated using simulated hard and soft scrap (carbide tool tips and WC powder, respectively). The oxidative dissolution of tungsten was examined in molten Na2CO3 under Ar–O2–CO2 atmospheres at 1173 K. Based on the immersion potentials of Cu, W, Co, C, and WC–Co, Cu2O was suggested to work as an oxidizing agent for tungsten dissolution. The oxidative dissolution rate for carbide tool tips with 12.8 mol% Cu2O addition reached 57 mg h−1 for the reaction time of 2.5 h, equivalent to 0.32 mm h−1. The decrease in the dissolution rate after 2.5 h was attributed to the decrease in the Cu(I) ion concentration in the melt and the inhibition of ion diffusion by the deposited metallic Cu. No violent reaction leading to explosion was observed, even for the oxidative dissolution of fine WC powder with a large surface area. Thus, this method provides significant safety improvements compared to the molten nitrate method.Graphical

Analysing the impact of autocatalysis on the dissolution kinetics of uranium and plutonium mixed oxide powders by optical microscopy

Spent fuel dissolution is a key step in the recycling of nuclear fuel as it must ensure the production of a liquid solution consisted of concentrated nitric acid and the reusable fissile materials (uranium and plutonium), and decrease the fissile material hold-up in the system. This approach needs the understanding of chemical kinetic phenomena involved in the solid-liquid reaction. Optical microscopy was implemented to determine the dissolution rates of U-Pu-mixed oxides in nitric acid at different concentrations and temperatures for the first time. Mass transfer resistance was found negligible during dissolution indicating a process limited by the chemical reaction. Results showed a decrease in dissolution rate of the different oxides studied mainly due to the increment of plutonium content in the solids. Moreover, dissolution kinetics of solid U0.70Pu0.3O2 seems to improve when a catalyst is present in solution. Thus, the autocatalytic behaviour for the dissolution of spent fuel might occur for solids with 0% and up to 30%PuU+Pu of content.

Mechanical and electrochemical characterization of 3D printed orthodontic metallic appliances after in vivo ageing.

Three-dimensional (3D) printing technology is a promising technique for fabricating custom orthodontic metallic appliances. Aim of this study was to assess the effect of intraoral aging on the mechanical / electrochemical properties of 3D-printed orthodontic metallic appliances. Twelve molar orthodontic distalization appliances 3D-printed from cobalt chromium (Co-Cr) alloy were retrieved after intraoral use and twenty blocks fabricated under similar conditions were used as control. The samples' microstructural / elemental composition assessment was assessed with SEM/EDS, while their mechanical properties (modulus of elasticity [EIT], Martens hardness [HM] and the elastic index [ηIT]) were measured by instrumented indentation testing. Finally, the samples' electrochemical features were assessed with a potentiostat-connected cell arrangement in terms of open circuit potential (OCP), corrosion potential (Ez), current density (I300) and breaking potential (Epit). Results were analyzed by t-test / Mann-Whitney test (α=0.05). The used Co-Cr alloy was found to have a highly homogenous structure with no significant differences between retrieved and new specimens in HM (4037.7±215.6 vs 4090.9±259.8N/mm2), EIT (120.0±13.2 vs 123.8±12.9GPa), or nIT (28.4±2.6 vs 28.6±2.9 %) (P>0.05 in all instances). Metallic surfaces retained the same oxidation tendency and oxide dissolution rate in passive region in both groups (P>0.05 for OCP, Ez, and I300). However, intraorally-aged specimens had a significantly lower breakdown potential due to degraded protection efficacy of surface oxide (P=0.003 for Epit). The tested 3D-printed Co-Cr orthodontic appliances present clinically-acceptable mechanical properties that remained unaffected by intraoral ageing, which however degraded the protection of surface oxide against pitting corrosion.

Reactive Transport Modeling during Uranium In Situ Leaching (ISL): The Effects of Ore Composition on Mining Recovery

Unconsolidated sandstone uranium deposits exploited by the in situ leaching (ISL) method, contain complex tetravalent and hexavalent uranium compounds, mostly as UO2 and UO3 oxides that have different dissolution rates in sulfuric acid solutions. This work investigates a reactive transport model that takes into account the dissolution of both UO2 and UO3 in sulfuric acid solution together with possible interactions with rock minerals during the ISL uranium extraction. Several empirical reaction rate constants were determined during lab experiments on uranium extraction assays, including dissolution rates of tetravalent and hexavalent uranium oxides, and the dissolution rate of rock components by sulfuric acid solution. Effects on the recovery of solution flow rates and ratios between tetravalent and hexavalent uranium compounds are also investigated. The experimental dissolution constants were then used in the proposed reactive transport model to be applied to a real case study in Kazakhstan for comparing the 16 months history matching of an exploitation block consisting of 18 well injectors and 4 producers. The obtained numerical results show good agreement with empirical data gathered during exploitation.

New radiolysis-driven matrix dissolution operational model based on stationary UO2 voltametric experiments

In the framework of research on direct deep disposal of spent nuclear fuel, a new α radiolysis-driven matrix dissolution model is proposed. This model is based on an experimental stationary voltametric curve established using a UO2 rotating disk electrode in a neutral pH non-complexing solution under reducing conditions. Kinetic and chemical speciation calculations give access to the equilibrium redox potential of a simulated Callovo-Oxfordian pore water solution containing α-radiolysis products, which is used in the experimentally obtained current-potential relationship to estimate the oxidative dissolution rate. Comparison of model results with literature data show good agreement with previously established α−activity threshold values.

Analysis of anodic nanotubular oxide on homogeneous Ti-Si alloys for Li-ion battery anodes

The porous anodization of pure Ti and arc melted Ti2Si, and Ti4Si alloys were studied, aiming to produce novel anodes for lithium-ion batteries. The annealed and quenched Ti2Si alloys were homogeneous β-martensite, while Ti4Si close to the maximal Si solubility presented Ti3Si and Ti5Si3 precipitates. The alloys anodized in standard HF + NH4F electrolyte showed an increasing tendency to detach the oxide layer with the Si content increase. The slope of the cell voltage transient ∂E/∂t was used to evaluate each material's current efficiency. Si addition decreases the oxide's electronic conductivity and the oxygen evolution reaction but increases the oxide dissolution rate due to a higher Si dissolution rate. Consequently, higher current efficiency of oxide formation is observed during the barrier layer and a lower one during the porous layer formation. Nevertheless, the specific Li mass capacity increased by around 15% with 2 at% Si addition to Ti.

Role of ionic surfactants on the plasmonic oxidative dissolution of silver nanoparticles by ferric ions

Effects of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) on the optical sensing of AgNPs toward ferric ions were investigated spectrophotometrically in an aqueous media. Surface Plasmon resonance (SPR) intensity of AgNPs was decreases after addition of ferric ions at room temperature. CTAB and SDS, respectively, catalyzed and inhibited the oxidative dissolution rates of AgNPs. The redox reaction between AgNPs and Fe3+ ions proceeds through the complex formation. The reaction follows first-, and fractional-order kinetics with AgNPs and Fe3+ ions, respectively. CTAB catalytic role was explained with micellar pseudo-phase model, and associated parameters were estimated. The activation parameters (Ea, ΔH#, and ΔS#) were found to be 23.7 kJ/mol, 16.6 kJ/mol, −226 J/K/mol, and 16.5 kJ/mol, 13.5 kJ/mol, −238 J/K/mol for aqueous and CTAB assisted dissolution of AgNPs. SDS coordinated with Fe3+ through electrostatic interactions in pre-, and post-micellar region, which in turn reduces the electron gaining tendency of Fe3+, and overall rates of sensing reaction decreases.

Electrochemical study of the dissolution of oxide films grown on type 316L stainless steel in molten fluoride salt

The corrosion behavior of oxide films grown on Type 316L stainless steel (SS) in molten FLiNaK (LiF-NaF-KF: 46.5−11.5−42 mol.%) salt was investigated. The results show that the oxide film formed on Type 316L SS is unstable and can only temporarily protect materials from corrosion in molten FLiNaK salt. Based on the electrochemical impedance spectroscopy, the oxide dissolution rate is calculated to be 0.85 nm/h at 700 °C in molten FLiNaK salt. After the oxide film dissolved, Cr and Fe are selective dealloyed from the steel, leading to intergranular corrosion of Type 316L SS in molten fluoride salt.

Oxidative dissolution kinetics of organic-rich shale by hydrogen peroxide (H2O2) and its positive effects on improving fracture conductivity

Maintaining the fracture network created by hydraulic fracturing remains challenging because unpropped fractures close during production, resulting in shale gas production decline. Chemical dissolution is being implemented to maintain unpropped fracture conductivity, and the effect of oxidative dissolution on organic-rich shale may have the potential to maintain these fractures. In this paper, the change of organic matter (OM) in crushed shale samples exposed to hydrogen peroxide (H2O2) or deionized water were characterized. Reaction kinetics experiments were run using sliced shale samples and H2O2 with a mass concentration of 2–10% at temperature of 40–80 °C. Stress sensitivity of fractured shale plugs after oxidation for 72 h was evaluated. Results show H2O2 can remove 56.87% of solid OM and 55.34% of extractable OM in the crushed sample. Total organic carbon in H2O2 filtrate after the reaction is 91.36 mg/L,while that of deionized water is 30.88 mg/L. A significant decrease of C–O according to the C1s and O1s spectra of the crushed samples after oxidation means that some of oxygen contained functional groups oxidized and cleaved. However, reaction rate of oxidative dissolution occurs slowly and significantly depends on the concentration and temperature. The relationship between reaction rate and concentration can be described as a power function, and the relationship between reaction rate and temperature can be described as an exponential function. Activation energy of oxidative dissolution ranges from 3.51 to 12.10 kJ/mol when H2O2 mass concentration ranges from 2% to 10%. Oxidative dissolution can increase fracture width judging by estimation based on the mass loss. Stress sensitivity coefficient of the plugs treated with deionized water are 0.52 and 0.59, while the plugs treated with H2O2 are 0.48 and 0.52. It indicates that oxidative fluids can play a role in maintaining unpropped fracture conductivity enhancing shale gas recovery.

In Situ Formation of Silver Nanoparticles (Ag-NPs) onto Textile Fibers

Silver nanoparticles (Ag-NPs) adhered/inserted on textile fibers have an effective antimicrobial role. However, their release due to low adherence and their fate in the natural settings have been questioned in terms of toxicity level. In order to overcome this recurrent problem of adherence, the in situ formation of Ag-NPs in five textile fibers (cotton (untreated and chemically bleached), sheep’s wool, polyamide, and polyester) was assessed. Herein, the fibers were first immersed in a silver ion solution (1 g/L of AgNO3) for ion saturation at room T for 24 h followed by draining fibers and their reimmersion this time in a strong chemical reducing solution (0.25 g/L of NaBH4) at room T for 24 h. This latter step leads to the in situ formation of Ag-NPs where size (5 nm < size < 50 nm), surface covering concentration, and aggregation degree depend on the textile fiber kind as deduced from FESEM images. This simple lab chemical method allows instantaneous in situ formation of Ag-NPs onto fibers without the requirement of additional thermal treatment. Moreover, for natural fibers, the formation of Ag-NPs inside of them is also expected as confirmed from FESEM images in cotton cross sections. In complement, all textile fibers containing Ag-NPs (sheep’s wool 10 mg/g > untreated cotton 2.3 mg/g > bleached cotton 1 mg/g > polyamide 0.62 mg/g > polyester 0.28 mg/g) were submitted to interact with strong oxidants in an aqueous media (7.5% v/v of H2O2, 0.5 and 0.05 M of HNO3 and ultrapure water as the control) using flow-through reactor experiments. Here, breakthrough curves reveal that the oxidative dissolution rate (given in mol/g min) of adhered Ag-NPs (ionic release) depends strongly on fiber nature, and nature and concentration of oxidant solution. In summary, this fundamental study suggests that Ag-NPs may be successfully adhered/inserted in natural fibers (wool and cotton) in a safety-design perspective with performant biocide properties as confirmed by using Bacillus subtilis.

Effect of salinity on the kinetics of pyrite dissolution in oxygenated fluids at 60 °C and implications for hydraulic fracturing

Shale hydraulic fracturing involves the injection of oxygenated acidic fluids which trigger redox driven and acid driven reactions, in particular with pyrite and carbonates. These reactions alter the shale pore and fracture network and mobilize potentially harmful elements. Hence, understanding the kinetics of pyrite oxidation at shale reservoir conditions is critical. Here, we investigate the effect of salinity on the rate of pyrite oxidative dissolution by fluids of pH 1 at 60 °C, and 0–3.4 mol L−1 NaCl. We determine a pyrite dissolution rate of about 1.2 × 10−9 mol m−2 s−1 in non-saline oxygenated acidic fluids at 60 °C, consistent with previously established rate equations, considering an activation energy of 57 kJ mol−1. Our results suggest the following correlation between the pyrite dissolution rate r (in mol m−2 s−1) at 60 °C and Eh (0.580–0.700 V), log(r) = 4.47 Eh – 12.03. This reaction order is lower than that established in previous studies involving pyrite reaction with Fe3+ enriched fluids in the presence of dissolved O2. Furthermore, we calculate that the pyrite oxidation rate varies from 0.8 × 10−10 to 1.3 × 10−10 mol m−2 s−1 at 25 °C, based on salinity-determined dissolved oxygen content. The mixed flow reactor experimental results suggest a dependence of pyrite oxidation rate on Cl− activity aCl (in mol kg−1) at 60 °C for fluids with 0.6–3.4 mol L−1 NaCl and Eh of 612 ± 8 mV as follows, log(r) = −0.58 log(aCl) – 9.42. The pyrite oxidation rate varies within less than half an order of magnitude for the salinity range tested, and hence, the impact of salinity is less important than the Eh and temperature. The improved understanding of factors controlling pyrite oxidation kinetics may help in predicting environmental and engineering impacts of injection of hydraulic fracturing fluids in shale.

Kinetic modelling of Cr2O3 growth on a Ni-30Cr alloy in silicate melts

Corrosion tests of Ni-30Cr alloy were performed in three simplified soda-silicate and borosilicate melts in order to follow the evolution of the protective chromia layer. A complete identification of the corrosion mechanisms enables the establishment of a kinetic model based on the oxide formation and dissolution rates. The dissolution kinetics is strongly dependent on the chromium solubility limit and diffusivity, which are related to the basicity and viscosity of the melts. This new modelling of the oxide growth is in good agreement with the experimental results.

Mechanistic study for stibnite oxidative dissolution and sequestration on pyrite

Stibnite (Sb2S3) dissolution and transformation on mineral surfaces are the fundamental steps controlling the fate of antimony (Sb) in the environment. The molecular-level understanding of Sb2S3-mineral-water interfacial reactions is of great importance. Herein, Sb2S3 oxidative dissolution and sequestration on pyrite (FeS2) were explored. The results show that FeS2 accelerated the rate of Sb2S3 oxidative dissolution by a factor of 11.4-fold under sunlight due to heterogeneous electron transfer. The electron transfer from Sb2S3 to FeS2 separated photogenerated hole (h+) and electron (e−) pairs, facilitating the generation of hydroxyl radicals (OH) on Sb2S3 and FeS2, and superoxide radicals (O2-) on FeS2. Surface O2- was the dominant oxidant for Sb(III) oxidation with 91% contribution, as evidenced by radical trapping experiments. OH was preferentially adsorbed on Sb2S3, but was released with Sb2S3 dissolution, and subsequently contributable to Sb(III) oxidation in solution. The Sb(III) oxidation and sequestration on FeS2 surface coupled Fe2+/Fe3+ cycling and inhibited FeS2 dissolution, as evidenced by X-ray absorption near edge structure and X-ray photoelectron spectroscopy. The insights gained from this study further our understanding of Sb2S3 transformation and transport at the environmental mineral-water interfaces.

Boosting Stability and Activity of Oxygen Evolution Catalyst in Acidic Medium: Bimetallic Ir−Fe Oxides on Reduced Graphene Oxide Prepared through Ultrasonic Spray Pyrolysis

AbstractElectrolysis of water in acidic media generally requires noble metals (oxides) to enhance the catalyst activity and durability in the oxygen evolution reaction (OER). Bimetallic Ir−Fe supported on reduced graphene oxide (IFG) is prepared by ultrasonic spray pyrolysis, followed by acid and/or heat treatment. Physical and electrochemical methods are used to elucidate the effect of the physical and chemical properties of the IFG catalysts modified by spray pyrolysis and post treatment on the OER activity and stability under harshly oxidizing conditions in 0.1 M HClO4. The IFG‐AHT catalyst synthesized via ultrasonic pyrolysis followed by acid and heat treatment exhibits superior OER activity among the IFG catalysts. The mass activity was two‐fold higher and the stability is superior to that of the commercially available Ir catalyst, indicating that the metal (oxide) dissolution rate and the interaction between Ir and the hybrid support affect the cost and lifetime of OER catalysts.

Correlation between the rate of silver nanoparticle oxidation and their biological activity: the role of the capping agent

The correlation between the chemical nature of capping agents used to prepare colloidal silver dispersions and kinetic characteristics of the process of oxidation of the dispersed phase (spherical silver nanoparticles, 2–50 nm in diameter) by hydrogen peroxide was studied for the first time. The well-pronounced correlation between the oxidative dissolution rate and the biological activity of silver dispersions was revealed with respect to the inhibition of the growth of the Saccharomyces cerevisiae yeast. The biological activity of nanosilver dispersions was found to be primarily controlled by the rate of generation of silver ions while the chemical nature of the capping agent defined the rate of generation of silver ions, thus showing an effective way to control the biological action of medications based on silver nanoparticles by varying the nature of the capping agent.

Electrolytes and its additives used in aluminum reduction cell: a review

The electrolyte is considered to play the role of blood in an aluminum reduction cell and performs several vital functions as the charge transfer, the mass dissolution and transfer, the electrode products separation and the electrical work dissipation. The proper performance of listed functions is completely determined by the physical and chemical properties, which namely are the electrical conductivity, the viscosity, the vapor pressure, the liquidus and solidus temperatures, the density, the surface tension, the solubility and the dissolution rate of oxides, aluminum, carbon and the various connections and by operating conditions, which namely are the temperature, the current density, the anode-cathode distance, etc. The electrolyte affects the current efficiency and the cell voltage, which determines the specific energy consumption and the total cost of aluminum. This is the reason why different electrolytes and additives have been in the spotlight of the researchers and the enterprises for decades. This article presents the brief information about the influence of additives in the cell utilizing traditionally used sodium cryolite and different low-temperature electrolytes on physical-chemical properties and concentrates on the latest works which have not been included in widely known textbooks. The article also contains new experimental results obtained by the authors and devoted to the effective electrical conductivity of suspended unconventional electrolytes.

Biogenic Cyanide Production Promotes Dissolution of Gold Nanoparticles in Soil.

Gold nanoparticles (Au NPs) are often used to study the physiochemical behavior and distribution of nanomaterials in natural systems because they are assumed to be inert under environmental conditions, even though Au can be oxidized and dissolved by a common environmental compound: cyanide. We used the cyanogenic soil bacterium, Chromobacterium violaceum, to demonstrate that quorum-sensing-regulated cyanide production could lead to a high rate of oxidative dissolution of Au NPs in soil. After 7 days of incubation in a pH 7.0 soil inoculated with C. violaceum, labile Au concentration increased from 0 to 15%. There was no observable dissolution when Au NPs were incubated in abiotic soil. In the same soil adjusted to pH 7.5, labile Au concentration increased up to 29% over the same time frame. Furthermore, we demonstrated that Au dissolution required quorum-sensing-regulated cyanide production in soil by inoculating the soil with different cell densities and using a quorum-sensing-deficient mutant of C. violaceum, CV026. Au NP dissolution experiments in liquid media coupled with mass spectrometry analysis confirmed that biogenic cyanide oxidized Au NPs to soluble Au(CN)2-. These results demonstrate under which conditions biologically enhanced metal dissolution can contribute to the overall geochemical transformation kinetics of nanoparticle in soils, even though the materials may be inert in abiotic environments.