Showing 7 results for Gold
Fotoohi B., No Parast M., Oliazadeh M.,
Volume 1, Issue 4 (12-2004)
Abstract
Gold deposits are varied regarding their geological and geochemical settings. Hence,their processing methods must be best organized for achieving the desired recovery of preciousmetals. In this research, two types of hard-rock gold ores, each with specific characteristics fromKouh-zar region (south of Damghan city) were subjected to mineral processing tests at thelaboratory scale. The reference (head) samples of both veins contained on average 3.5-4.5 ppmgold. According to mineralogical investigations no observable gold particles reported even inSEM analyses except for rare over-micrometer gold particles locked in the silica matrix.Therefore, the major (invisible) gold supposed to exist in sulfides" crystal structure. Flotationapplied to recover the gold interlocked within sulfides. The highest grades achieved were 49.2ppm @ R=77.61% for Baghu samples and 57.0 ppm @ R=61.00% for Darestan samples gold inthe sulfide concentrates. In the cyanidation diagnostic tests the optimum conditions of pH,particle size, cyanide concentration and leaching time were determined for both ores. High goldrecoveries (> 95%) were achievable for Baghu samples for the pH conditions between 10.5 and11, and cyanide and hydrated lime consumptions of 0.6 and 2.5 grams per kilogram of orerespectively. As it had been expected, direct cyanidation of Darestan samples (containing up to1.5% copper), couldn"t be established as an efficient procedure (due to cyanide consumption ofabout 20 times higher than for Baghu tests to achieve similar recoveries) and the preliminarycopper removal phase was determined as a necessity for better recovery of gold.
M. Banoee,z. Ehsanfar, N. Mokhtari,m. R. Khoshayand, A. Akhavan Sepahi, P. Jafari Fesharaki,h. R. Monsef-Esfahani,, A. R. Shahverdi,
Volume 7, Issue 1 (3-2010)
Abstract
Abstracts:
nanoparticles. All the extracts were used separately for the synthesis of gold nanoparticles through the reduction of
aqueous AuCl
gold ions to gold nanoparticles. The ethanol extract of black tea and its tannin free ethanol extract produced gold
nanoparticles in the size ranges of 2.5-27.5 nm and 1.25-17.5 nm with an average size of 10 nm and 3 nm, respectively.
The prepared colloid gold nanoparticles, using the ethanol extract of black tea, did not show the appropriate stability
during storage time (24 hours) at 4
showed no particle aggregation during short and long storage times at the same conditions. To the best of our
knowledge, this is the first report on the rapid synthesis of gold nanoparticles using ethanol extract of black tea and
its tannin free fraction.
In this research the ethanol extract of black tea and its tannin free fraction used for green synthesis of gold4¯. Transmission electron microscopy and visible absorption spectroscopy confirmed the reduction ofoC. In contrast, gold colloids, which were synthesized by a tannin free fraction
M. Aazami, H. Yoozbashizadeh, A. K. Darban, M. Abdolahi,
Volume 10, Issue 4 (12-2013)
Abstract
The orthogonal array design has been used to determine the optimum conditions for gold recovery from Zarshuran refractory gold sulfide ore (Iran) by direct cyanidation and roasting-cyanidation. The Taguchi method was used as the experimental design to determine the optimum conditions of dissolution behavior of gold with cyanidation and roasting-cyanidation from Zarshuran refractory gold ore . The experimental conditions were studied in the range of 10–12 for pH, 20-40 for time(h), 400-1200 for cyanide content (g/ton) and 30 -40 for percent solid(%). Orthogonal array (OA) L9 (34) consisting of four parameters each with three levels, was chosen. From this study for direct cyanidation the total optimum gold dissolution (30.11%) obtained at pH (10), Time (40 h), Cyanide content (800g/ton) and Percent solid (30%). Also for roasting- cyanidation the total optimum gold dissolution (34.96%) obtained at pH (12), Time (40 h), Cyanide content (1200g/ton) and Percent solid (35%).
M. Ghobeiti Hasab, F. Rashchi, Sh. Raygan,
Volume 11, Issue 2 (6-2014)
Abstract
In this paper, gold leaching of a refractory sulfide concentrate by chloride–hypochlorite solution was
investigated and effects of stirring speed, temperature and particle size on the leaching rate were reported.
Experimental data for leaching rate of gold were analyzed with the shrinking–core model. Results were consistent with
chemical reaction control mechanism in the first 1 h of leaching and diffusion control mechanism in the second 1 h.
Apparent activation energy also was found to be 22.68 kJ/mol in the first step and 3.93 kJ/mol in the second step of
leaching.
B.y.r. Surnam, B.s. Audit, A. Soopee,
Volume 14, Issue 3 (9-2017)
Abstract
In this study the use titanium and tungsten as alternatives to the noble metals in the jewellery industry was investigated. The degradation of titanium and tungsten were compared to that of gold, used as reference. Alternate immersion tests were performed in 3.5% sodium chloride and artificial perspiration. The metals’ abrasion resistance with respect to textile fabrics was determined.
In general, there is around 30% difference in pit density for titanium and tungsten as compared to that of gold. Pit depth and pit diameter showed a similar trend. From the abrasive test performed, it was observed that titanium and tungsten had insignificant changes in the surface reflectivity with time. Hence, it was deduced that titanium and tungsten products would have longer maintenance intervals than that of gold. New tools and techniques, however, would be required by jewellers to work with titanium and tungsten.
H. Esfandiar, S. M. Hashemianzadeh, S. Saffary, S. Ketabi,
Volume 15, Issue 3 (9-2018)
Abstract
Gold nanoparticles have become common in many applications of biotechnology due to their specific properties. Shape and size are important attributes which affect their solubility in water. In this study, the outcomes of Monte Carlo Simulation for the solvation of gold nanorods in aqueous solution with the different radii, in terms of solvation free energy, are discussed. Simulation results show a negative solvation free energy for all the samples with radii of 4 to 9Å. The results show that the absolute values of solvation free energy for gold nanorods with smaller radius are larger, which indicate the dependency between the gold nanorods solvation and their radius.
E. Mohammadi, M. Pourabdoli,
Volume 16, Issue 2 (6-2019)
Abstract
The effect of mechanical activation on the kinetics of ammoniacal thiosulfate leaching of a refractory oxide gold ore containing 2.8 ppm Au was investigated. The gold extraction of 99.81% was achieved by 16 h leaching of a sample mechanically activated for 60 minutes. The gold extraction observed for a similar reference sample without mechanical activation was only 55%. Studies revealed that leaching progresses at two different rates depending on the leaching time (0-2 h and 2-16 h). It was observed that diffusion through an ash layer as a dominant mechanism controls the leaching of samples mechanically activated up to 45 minutes during total leaching time, while reaction control and liquid film diffusion are dominant mechanisms for leaching of a sample mechanically activated for 60 minutes during 0-2 h and 2-16 h, respectively. The extraction observed during the ash diffusion step depends significantly upon mechanical activation time. Mechanical activation of 60 minutes results in high gold extraction in this step which when combined with subsequent chemical reaction gives close to 100% gold extraction in a 16 hour leach. Mechanical activation for up to 45 minutes leads to a modest improvement in overall gold extraction compared with the reference test without mechanical activation
