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In the leaching of gold in solutions containing thiosulphate, ammonia and copper, the solution chemistry is constantly changing, making fundamental studies difficult. The rotating electrochemical quartz crystal microbalance (REQCM) measures mass in real time, allowing leach kinetics to be measured in minutes at essentially constant solution conditions. It was found that a sufficient concentration of copper II and ammonia are required to achieve appreciable gold leach rates. Using air to maintain copper II concentration catalyses the undesirable side-reaction between copper II and thiosulphate. The REQCM was also used in preliminary studies on gold cementation and electrowinning from gold I thiosulphate. It was found that the presence of both silver and copper enhances gold deposition, especially at low overpotentials. This is beneficial in cementation but can cause passivation of the cathode surface during electrowinning at higher overpotentials., In the leaching of gold in solutions containing thiosulphate, ammonia and copper, the solution chemistry is constantly changing, making fundamental studies difficult. The rotating electrochemical quartz crystal microbalance (REQCM) measures mass in real time, allowing leach kinetics to be measured in minutes at essentially constant solution conditions. It was found that a sufficient concentration of copper II and ammonia are required to achieve appreciable gold leach rates. Using air to maintain copper II concentration catalyses the undesirable side-reaction between copper II and thiosulphate. The REQCM was also used in preliminary studies on gold cementation and electrowinning from gold I thiosulphate. It was found that the presence of both silver and copper enhances gold deposition, especially at low overpotentials. This is beneficial in cementation but can cause passivation of the cathode surface during electrowinning at higher overpotentials.

Gold leach rates in cyanide, ammonia/thiosulphate and chloride/hypochlorite solutions were measured using a rotating electrochemical quartz crystal microbalance (REQCM). The aims of the study were to determine whether leaching behaviour of gold in the thiosulphate and chloride systems is affected by sample purity and to derive conditions under which the leaching rate in the alternative systems is similar to that of the cyanide system., Gold leach rates in cyanide, ammonia/thiosulphate and chloride/hypochlorite solutions were measured using a rotating electrochemical quartz crystal microbalance (REQCM). The aims of the study were to determine whether leaching behaviour of gold in the thiosulphate and chloride systems is affected by sample purity and to derive conditions under which the leaching rate in the alternative systems is similar to that of the cyanide system.

A rotating electrochemical quartz crystal microbalance was used to study the effect of experimental variables on the efficiency of the electrowinning process. The technique provided a useful means of differentiating between the cobalt deposition and hydrogen evolution reactions, which cannot be achieved using conventional methods. The major effects on the deposition reaction were found to be pH, temperature and Co concentration, whilst for H2 evolution temperature and pH were important. It was shown that current efficiency is highest at high pH values, due to a combination of inhibited H2 evolution and enhanced Co deposition. Of additives and impurities, Zn did affect Co deposition but only when present at more than 100 ppm., A rotating electrochemical quartz crystal microbalance was used to study the effect of experimental variables on the efficiency of the electrowinning process. The technique provided a useful means of differentiating between the cobalt deposition and hydrogen evolution reactions, which cannot be achieved using conventional methods. The major effects on the deposition reaction were found to be pH, temperature and Co concentration, whilst for H2 evolution temperature and pH were important. It was shown that current efficiency is highest at high pH values, due to a combination of inhibited H2 evolution and enhanced Co deposition. Of additives and impurities, Zn did affect Co deposition but only when present at more than 100 ppm.