Guangxi's Liuzhou Water is a gold mine mesothermal gold-bearing iron ore type. In the flotation gold concentrate, gold and a small amount of silver are mainly recovered. Metal concentrate mainly pyrite minerals, ore containing small amounts of brass, galena, arsenopyrite, sphalerite, magnetite, siderite, limonite. Urea minerals quartz, silicate-based, containing a small amount of sericite, and graphite. Table 1  Concentrate multi-element analysis table Element name Au/ ( g·t -1 ) Ag/ ( g·t -1 ) Cu Pb Zn Fe S C Content /% 45.33 113.17 0.338 0.672 0.18 22.33 21.77 2.32 Element name As Mn CaO MgO Al 2 O 3 TiO 2 SiO 2 　 Content /% 0.11 0.084 0.88 1.9 9.07 0.78 30.87 Table 2  Carbon phase analysis table Phase C graphite C organic C inorganic C total Gold in concentrates /% 1.61 0.13 0.58 2.32 Relative content /% 69.4 5.6 25 100 In order to realize the one-step process of leaching-deposition, the gold in the leaching slurry can be extracted by the mud metal replacement method, the adsorption method and the solvent extraction method respectively in the acidic medium to reduce the concentration of Au[SC(NH 2 ) 2 ] 2 + ions. Since the standard potential of the Au[SC(NH 2 ) 2 ] 2 + /Au pair is +0.38 V, and the concentration of the ruthenium cation is low, the metal is replaced with a negatively charged metal. The greater the electronegativity of the metal, the greater its acid solubility. Therefore, the acid consumption of the metal replacement method and the consumption of the metal displacement electrode are relatively high, which increases the operating cost. Although there have been reports of solvent extraction of gold in recent years, it is still quite difficult to extract gold directly from the slurry. Although the adsorption method can use activated carbon or ion exchange resin as the adsorbent, its selectivity remains to be studied. Therefore, the industrial prospect in the one-step process is the thiourea leaching-electrowinning one-step method. When thiourea is immersed in gold, the leaching process is relatively simple because of the "one-step" process, so the leaching process is simple, and the specific process is as shown in the flow chart of FIG. [next] The main body of the expanded test process is a multi-tank combination immersion tank, the structure of which is shown in FIG. The plate portion in the tank is a replacement zone, and the agitating portion is a leaching zone. The entire tank and internal connecting screws are made of hard PVC, and the shaft and impeller are lined with epoxy. Continuous leaching ancillary facilities are: rectifiers and lifting plate travel mechanisms controlled by photoelectric semi-automatic procedures. Pellet Machine,Wood Pellet Machine,Feed Pellet Machine,Biomass Pellet Machine HUNAN JINSONG MACHINERY CO., LTD , https://www.sheller.nl
The majority of the gold in the concentrate is in the form of fine particles and fine particles. The grain-level gold is less than 0.01mm, accounting for 54.89%, and the gold in the concentrate is 11%, of which the urea-coated gold is 1.83%. Parcels accounted for 9.17%. The results of multi-element analysis of concentrates are shown in Table 1. The carbon phase analysis results are shown in Table 2. 
The leaching work procedure is: the gold concentrate is leached under constant stirring in the thiourea solution, and the gold is replaced by a lead plate with a negative potential, and the gold is loosely attached to the plate, starting from the first groove per hour. The plate in the tank is lifted up along the guide rail and sent to the washing tank to wash away the impurities. Finally, it is sent to the gold mud tank, and the plate brushed under the gold mud brush attached to the electrode plate is sent back to the original tank for replacement, and the washing is set. The purpose of the mud tank is to wash away the sulfide particles attached to the electrode plate to make the gold mud pure. The amount of miscellaneous amount to be washed does not exceed 2% of the amount of the dip, and after classification, the coarse particles are returned to the first tank for double immersion, and the fine particles can be treated as gold mud.
The thiourea leaching-electrowinning one-step gold extraction process has the advantages of short process, simple operation, simple control factors and low cost, and has good industrialization prospects, in addition to the pollution-free process inherent in thiourea gold extraction. As long as the amount of sulfuric acid, the amount of thiourea, the cell voltage, etc. are properly controlled, a satisfactory immersion rate and immersion rate can be obtained.
1 sulfuric acid dosage. The acidity, conductivity and electrode potential of the leached pulp increase with the increase of the amount of sulfuric acid. However, the gradient of the increase in the anode potential is larger than the cathode potential. When the anode potential is increased to a certain value, the thiourea will be oxidized, and as the anode potential is increased, the current density of the anode is also increased, the oxygen overvoltage is also increased, and the slurry temperature is significantly increased, causing the thiourea to thermally decompose. At the same time, due to the increased oxygen evolution rate of the anode, a viscous carbon foam layer is formed on the slurry surface, which is not conducive to operation. Therefore, the thiourea leaching-dielectric index begins to increase with increasing sulfuric acid usage, but has a peak. Generally, the pH of the slurry is preferably 1.0 to 1.3.
2 thiourea dosage. Under certain acidity conditions, the leaching-electroformation index increased significantly with the increase of the amount of thiourea. However, the parameters such as conductivity, pH and electrode potential of the slurry are basically constant. Therefore, under certain acidity conditions, thiourea is mainly present in the mineral state in the mineral state. Increasing the amount of thiourea will increase the leaching diffusion power and accelerate the leaching process. [next]
3 slot voltage. When other conditions are fixed, the electrode potential and current density increase significantly with the increase of the cell voltage, especially the increase of the anode potential, resulting in an increase in the acidity and temperature of the slurry. When the cell voltage is high, a carbon foam layer will also be formed on the slurry surface, which will affect the operation. Therefore, the tank voltage should not be too high during operation. When the acidity of the pulp is high, it can be reduced (about 3V), and when the acidity is slightly lower, it can be improved (about 5V).
4 electrode potential. The electrode potential is mainly related to the cell pressure and the acidity of the slurry. As the cell voltage and the amount of sulfuric acid increase, the cathode potential gradually becomes negative, and the anode potential gradually becomes positive, but the gradient of the anode potential changes greatly, and the gradient of the cathode potential changes is small. The deposition of gold in the cathode is mainly related to the cathode potential. When the cathode potential is -5 mV (for a saturated calomel electrode), the gold can be satisfactorily precipitated. Therefore, measuring the cathode potential is a convenient method of controlling the process.
5 grinding fineness. The effect of re-grinding of flotation gold concentrate re-grinding is very obvious. After re-grinding, the surface of the electro-deposited tank does not form a stable carbon foam layer, but the re-grinding increases the dissociation degree of acid-consuming substances (such as calcite , sericite, etc.). The amount of sulfuric acid needs to be multiplied to ensure the acidity of the leached pulp. For the test sample, it is better to not grind. At this time, the content of -300 mesh was 55.45%, and more than 50% of the gold was distributed in the -360 mesh size.
6 cathode plate material. In the test medium, the potentials of lead, iron, and copper cathodes were significantly different when they were not energized. However, under the same electrowinning conditions, the potentials of cathode plates of different materials are almost the same. Therefore, the cathode plate material has no significant effect on the electrodeposition of gold. However, from the viewpoint of corrosion resistance, it is preferable to use a lead, copper or silver plate to form a cathode plate and a Pb-Ag alloy plate as an anode, and it is preferable to place them in parallel. This reduces the current density and the overvoltage of oxygen.
7 oxidants. When leaching gold concentrate with thiourea, Fe 2+ and Fe 3+ ions are inevitably transferred into the leaching solution. During the electrowinning process, the anode continuously evolves oxygen, which can continuously regenerate Fe 3+ and dissolve oxygen concentration in the slurry. It can be kept constant. Therefore, no additional oxidizing agent is required for leaching an electrowinning, and although the initial velocity of leaching with only thiourea is almost the same as the initial leaching speed of the leaching-electrowinning process, the leaching-electrowinning process maintains a high leaching rate.
8 stirring strength. In general, when leaching, the stirring is beneficial to the suspension of the ore particles, and a certain inhalation is required to increase the concentration of dissolved oxygen in the slurry. Since the anode continuously oxidizes oxygen when leaching, the stirring speed can be lower. In order to reduce the scouring effect of the slurry on the cathode plate, the stirring zone and the deposition zone can be separated, which is more favorable for parameter adjustment.
Guangxi Longshui Gold Mine