| Raman spectroscopy has been a useful technology for fundamental studies in the mining industry. Surface changes through oxidation and reduction reactions can be monitored in-situ, allowing the changes to be monitored in real time. In conjunction with cyclic voltammetry, to change the conditions at which a mineral surface is subjected to, reaction and reaction conditions can be identified. The results can then be plotted to create a map similar to that of an EH-pH diagram.;In this study, the copper arsenic sulfide mineral, enargite (Cu 3AsS4) was subjected to a series of tests. Relatively pure samples were obtained from Butte, MT and Quirivilca, Peru and used to create mineral electrodes. The electrodes were cycled over an EH range of -1000 to +1000 mV (vs SHE) at pH values ranging from 1 to 13. Changes to the surface of the mineral were identified by comparing Raman spectra to a mineral Raman database. Plotted results were then compared against mass-balanced EH-pH diagrams for the Cu-As-S-H2O system, created using the STABCAL thermodynamic calculation program. Ultimately, the EH-pH diagram is modified based on the results, and an updated version was created.;The mass-balanced methodology is applied, in conjunction with Gibbs' phase rule, to an aqueous quaternary system. Variations in EH-pH diagrams of the Cu-As-S-H2O system based on slight changes in concentrations of copper, arsenic and sulfur are examined.;Finally, a novel nano-graphene material was tested for its ability to adsorb arsenic. Arsenic remediation, downstream of an enargite leach, remains an unsolved issue. The nano-graphene platelets were not able to successfully reduce arsenic levels in solution below the EPA-required limitation of 10 ppb. A thermodynamic evaluation of the adsorption characterized the process as physisorption, and likely unsuitable for long-term arsenic storage. A functionalized version of the nano-graphene may enhance results. |
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