How to electrolyze gold

Traditional gold electrolysis has a large backlog of gold and low unit output, and the liquidity of gold under this process is not enough, which brings inconvenience to the turnover of enterprises. According to the essence of gold electrolysis, our company changed the electrolysis scheme, optimized the power quality and realized the low backlog and high efficiency electrolysis of gold. The electrolytic backlog can be reduced to about 3-5 kg per 100 kg, and 16 3000 ml beaker is used as electrolytic cell. 240 kilograms of gold can be electrolyzed every day (24 hours). After primary electrolysis and secondary electrolysis, the purity of gold is close to 99.999%, and the recovery rate is as high as that of ordinary electrolysis. This blog must have been written by following the actual work for a long time. Now it is roughly explained as follows (because the production unit is not allowed to take pictures, it is only described in words):

First, the relationship between the purity of gold and the content of primary crude gold in the same electrolytic cell. In practice, 99.9% gold can be obtained from about 90% crude gold by one electrolysis, 99.98% gold by one electrolysis, 99.994% gold by one electrolysis and 99.95-99.99% gold by one electrolysis.

Secondly, under the same gold content, the greater the electrode spacing in the same electrolytic cell, the higher the purity of gold, the higher the amplitude of DC voltage and superimposed pulse, and the lower the gold output;

Thirdly, under the same gold purity, the gold purity obtained by electrolysis in iodoauric acid medium is one order of magnitude higher than that in chloroauric acid medium;

Fourthly, under the same conditions, pulse superposition electrolysis is more efficient than pure DC electrolysis;

In actual production, we designed a digital pulse power supply, the working pulse frequency is about 38KHz, and the internal resistance of the power supply is about 0.068 Ω, thus realizing an electrolytic power supply with high power efficiency and strong load capacity, and its weight is one-fifth of that of the conventional electrolytic power supply with the same capacity, and all the key components are imported from Siemens. Power supply has automatic protection function.

Electrolyte is prepared by dissolving 500 grams of 99.995% gold in aqua regia in a beaker used as an electrolytic cell, diluting it to 2300 ml with about 30% hydrochloric acid, and continuously adding hydrochloric acid during electrolysis.

The electrolyzer uses a beaker with a thickness of 3000ml, which is placed in a specially ventilated kitchen and works in the way of "two negative electrodes and one positive electrode". The electrolytic cell leads are made of pure silver with a diameter of 5mm (7mm is recommended), the cathode hooks are made of 99.995% gold with a diameter of 4mm, the anode hooks are made of 4mm thick gold, and the cathode plate is made of 0.3mm thick, 120mm wide and 65438+. The hook is welded on the plate, molded on the cathode die and hung on the cup wall. The weight of the whole cathode is about 120g, the gold thickness of the anode is 15mm, the width is 120mm, the length is 150mm, and the ear semicircle diameter is 15mm, which is cast by high-density graphite mold. The weight is about 4.65 kg, the electrolytic crude gold content is about 99.3%, and the anode hook is 34 grams. Hang the anode on the anode hanging rod (timely glass rod), turn on the power supply, keep the current at 265A, brush the anode once in the third electrolysis, sink the silver chloride brush to the bottom of the cup, and continue the electrolysis to the end point for about 6 hours. The residual electrode weighs about 80 g, and each cup is 65,438. In order to reduce the backlog, several electrolytic cells should be left in the second round of electrolysis according to the calculation ratio, and the electrolyte used in this shift should be recovered and cast with the remaining electrodes for electrolysis, so that the extrusion amount of electrolytic gold per 100 kg is less than 3 kg. The generated electrogold is washed with hydrochloric acid in an electrolytic cell, then washed with water to form an acid-free ingot, and then subjected to secondary electrolysis under the same conditions. Boiling the obtained electrogold, washing with 2: 1 nitric acid for 20 minutes, washing with 2: 1 ammonia water for 20 minutes, and washing the ingot with water, the gold above 99.995% can be obtained.

From casting anode plate to casting finished gold ingot, the electrolytic loss of gold is 0.03%-0.05% once. We investigated the main reasons for this loss: most of them are the melting loss of cast plates or ingots, followed by the volatilization loss during electrolysis (which can be minimized by using self-condensing sealed ventilation kitchen), the leakage operation loss and the detection error of crude gold content.

Industrial production of gold refining: with the continuous opening of the market, the demand for high-purity gold has increased sharply, which has promoted the development of gold refining. Some refining friends seized the opportunity to upgrade their small factories to large refineries, but the complexity of raw gold in the market (from mines, jewelry, industrial raw materials to industrial waste and electronic waste refining materials, the content ranged from 75-99.95%, and impurity metals ranged from conventional nonferrous metals to raw gold containing various rare earth metals. It is difficult to produce 99.995% gold by one-time water method or electrolysis method. Friends who do batch alchemy know that some crude gold can be produced by water method with a content of more than 99.99% in a small batch (below 5 kg), but it cannot be produced by the same method in a large batch. Sometimes a batch or batches produce more than 99.99% gold, but it is difficult for similar materials to obtain more than 99.99% gold in the following batches by the same method, and so on. All these reflect the instability of water law, which is difficult to unify in industrial production! Although there is extractive refining, it is difficult to realize large-scale industrial production because of the limited capacity of extractant and huge amount of water (our practice is that extracting gold in platinum group metal refining is the most suitable method to extract impurity gold, which is not suitable for large-scale refining to produce gold). Here, we recommend that all gold containing more than 75% gold be refined into gold containing more than 99.995% gold by one-time water method and two-time electrolysis method. That is, more than 75% of crude gold is refined to about 99.95% by water method, and then about 99.995% of gold can be obtained by casting plate electrolysis. However, at this time, individual impurities in gold may not meet the requirements of national No.1 gold, and secondary electrolysis can be carried out, and the gold obtained is close to 99.999%. At this time, the content of main impurities is lower than that of Guoyijin, and the total loss is about 0.098% (loss is about 0.098%), which is labor-saving and efficient.