Characterization of gold ore from Babakan Loa Sub-District and leaching study in cyanide solution

Research on the characterization of gold ore from Babakan Loa sub-district and studies of leaching in cyanide solution has been carried out. This research was conducted to determine the characteristics of gold ore from Babakan Loa and the leaching behavior in cyanide solution. The preparations carried out were crushing and grinding to obtain several size fractions. The ore characterization was carried out through XRD, XRF, SEM-EDX, and wet chemical analysis. XRD analysis results show that the main mineral phases are quartz, hematite, goethite, kaolinite, montmorillonite, and berlinite. The main constituents of the ore were Si (60.96%), Fe (10.71%), K (5.47%), and Al (19.53%). The Au content was 7.8 ppm, and the results of SEM-EDX analysis show that the gold grain size is smaller than 10µm. The leaching process showed that the highest percent gold extraction data of 92.7% was obtained in experiments with 1000 ppm sodium cyanide concentration, 10% solids percent, and 104-149µm grain size. Increasing the percentage of solids and the reduction in grain size led to a decrease in the percentage of gold extraction. The clay content was suspected to be the cause of the ineffectiveness of the leaching process in this study.

Cyanides and Their Attenuation in Wastewaters Using Green Chemistry

Cyanides, though naturally occurring, are environmental pollutants when not treated properly. Some methods used to attenuate cyanides in waste waters from industrial processes are based simply on changing the physico-chemical properties of the waste water such as the pH and temperature. The effectiveness of these methods are based on hydrolysis of the cyanide and volatilization of the hydrogen cyanide formed. Another reaction which takes place simultaneously is ultraviolet-catalysed oxidation which converts the cyanide to bicarbonates and carbonates.The changes in the cyanide degradation rate approaches a minimum faster if the cyanide solution is maintained at a higher than ambient constant temperature.

Recovery of Copper and Cyanide from Copper-cyanide Solution by Direct Electrolysis

Using direct electrolysis method, the recovery of copper and cyanide from high concentration copper cyanide solution was researched. The distribution of copper cyanide species was calculated by stability constants and balance equation. The results showed that the cupric ion was confirmed to generate at low potential (<0.4V) on the titanium electrode coated with iridium and tantalum oxides during the electrolysis process, which led to the oxidation of cyanide and the precipitate obtained on the anode was proved to be cupric hydroxide by XRD at high potential. The copper was recovered by direct electrowinning, the recovery of copper increased with increasing temperature, which reached 80% at 70°C; but the loss of cyanide was serious, the free cyanide concentration was significantly lower than original value.

Effects of Maturity of Coconut Shells on Gold Adsorption Efficiencies of Derived Activated Carbons

Coconut shells are used as precursors for preparation of activated carbons. The shells could vary in terms of their maturity. The influence of the maturity of the shells on gold adsorption efficiencies of derived activated carbons (ACs) from gold di-cyanide solution was investigated. The shells were pyrolysed at 900 ºC and the resulting chars were activated in steam at the same temperature for different durations. Assessment of the properties of the derived ACs revealed that; the hardness, gold adsorption capacities and rates of gold adsorption of the ACs depended on the maturity of the shells. The more matured the shells the harder the AC. The relative hardness and gold adsorption rates of the mature coconut shells activated carbons, HMand RM, respectively and those of the less mature shells, HLand RL, respectively were in the order of HM >HL and RM >RL. The relative hardness of the ACs derived from the more mature and less mature shells after 3 hrs activation were 99.3% and 94.0%, respectively and the gold adsorption rates were 5.78 mg Au/hr/gand 4.95 mg Au/hr/g, respectively. The adsorption rates and relative hardness depended on the duration of activation, where longer activation times resulted in increase in the adsorption rates and a decrease in relative hardness of the derived ACs. Keywords: Adsorption, Activated Carbon, Coconut Shells, Maturity, Relative Hardness

The Importance of Mineralogical Knowledge in the Sustainability of Artisanal Gold Mining: A Mid-South Peru Case

Mineralogy and gold processing techniques from several mining areas of the Nazca-Ocoña gold belt, Mid-South Peru, were investigated to assess the efficiency of gold extraction methods in relation to their mineralogy. The deposits from this belt are intrusion gold related to mineralization in quartz veins. Native gold occurs as micrometric grains encapsulated in pyrite and in minor amounts in other sulfides and quartz. Electrum is found mainly in fractures of pyrite and attains up to 35 wt. % Ag. In addition to these occurrences, gold tellurides also occur and they are abundant in San Luis. Gold processing is carried out by amalgamation with mercury and/or cyanidation. The comparison of the gold grade in the mineralizations and in the residual tailings indicates that a significant amount of gold is not recovered using the mercury amalgamation process and also, in the case of the gold recovery by cyanidation, except when cement was added to the cyanide solution. This was due to an increase in the pH that favours the dissolution of the gold matrix. In the cyanidation process carried out in tailings previously treated with mercury, part of the mercury retained in them is released to the atmosphere or to the cyanidation fluids.

Gold sorption from cyanide media by ANS-3 anionite

Research results were presented for gold sorption from cyanide solutions by ANS-3 macroporous anionite based on styrene-divinyl benzene copolymer. Equilibrium data on gold sorption from a model cyanide solution agreed with the modified Langmuir-Freundlich equation within the studied gold concentrations. Gold stripping results with alkaline cyanide solution were given. Optimal structure of polymer matrix provides high mechanical and osmotic strength of ANS-3 anionite. The anionite is not subjected to an osmotic shock in alkaline solution allowing its application in hydrometallurgical processes including sorption from pulps.

A closed-loop electrogenerative recycling process for recovery of silver from a diluted cyanide solution

A closed-loop process for the complete recovery of silver from a diluted silver cyanide solution has been constructed based on an electrogenerative process.