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Scarcer water resources, stricter water regulations, decline in ore grade and increasing controversy on water use between local communities and mining operators have raised awareness of good water stewardship as being vital to running commercially viable mining operations. Water footprint assessment (WFA) is a holistic methodological framework that allows detailed quantification of direct and indirect water use in different sectors at various spatial and temporal scales. The ultimate aim of this study is to identify water footprint (WF) reduction targets, formulate response strategies to minimize water consumption and pollution and therefore improve the environmental, social and economic sustainability of the mining processes. The assessment will eventually serve as a model for other mines in northern China with water scarcity issues. The paper describes the preliminary WFA of copper cathodes, with particular emphasis on the methodology, approach, degree of details and areas for consideration. It focuses from ore extraction to final discharge to the river. Significant WF contribution is found in the process rather than the supply chain. The explorative approach applied in this real case scenario and the findings contribute to the literature body of the WFA field. This case study can provide helpful guidance for WFA practitioners when applying this methodological framework in addressing particular issues in mining processes.

The dissolution of gold-bearing pyrite plays an important role in bioleaching of gold. This paper describes a fundamental study on the electrochemical behavior and reaction mechanisms of gold-bearing pyrite leaching in the form of Carbon Paste Electrode (CPE) with and without microorganisms using Cyclic Voltammetry (CV) and polarization curve. A two step process was suggested from Cyclic voltammetry. Electrode passivation by elemental sulphur was observed below 700mV (vs. SCE), elemental sulphur was then oxidized to sulphate when the electrode potential further increased from 700mV. The polarization current density of CPE and the oxidation rate of pyrite are further enhanced by the presence of microorganisms. Analyses of EDS and XPS confirmed the formation of elemental sulphur and sulphate. This electrochemical method successfully showed its simplicity and reliability to measure oxidation rate of gold bearing pyrite.

Low-grade, finely disseminated refractory sulfide gold ores associated with high arsenic are ubiquitous resources all over the world. Since heap bio-oxidation is an economic and promising biotechnology to recover gold, low grade, high organic carbon and arsenic bearing gold ores from Zhesang Mines in China were chosen for this purpose to study the key factors that would affect biooxidation. Pyrite and arsenopyrite (particle size 0.002-0.22 mm) were the main minerals from Mineral Liberation Analysis (MLA). Column biooxidation and cyanidation of mineral size < 10 mm were evaluated for its potential for gold extraction. Results showed that temperature was the main factor influencing sulfide oxidation. 58-67 % of sulfide was oxidized at 35-45°C after > 240 days of biooxidation with mixed mesophiles, while higher sulfide-S dissolution (77%) was obtained at 60°C. Sulfide-S fraction distribution revealed higher mineral decomposition, finer fractions and eventually higher sulfide oxidation at 60°C. Jarosite and scorodite were found from the residues at 60°C by SEM and EDX, which implies higher temperature accelerated arsenic precipitation. No elemental sulfur was detected during the biooxidation at 35-60°C. After bio-oxidation, column cyanidation was successfully demonstrated recovery of gold from the residues, with gold extraction rate reaching 66%.