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INVENTION
Russian Federation Patent RU2164554
A method of separating precious metals from SOLUTION
Name of the inventor: Pickpockets VP .; Igumnov MS .; Draenkov AN .; Tatarintcev AN .; Kovalev VV .; Kleandrov VT .; Yurasova OV
The name of the patentee: Pickpockets Vladimir Pavlovich
Address for correspondence: 125167, Moscow, ul. Konstantin Simonov, 4, kv.90, Klimenko MA
Starting date of the patent: 2000.01.26
The invention relates to ferrous metallurgy and can be used for electrochemical recovery of precious metals. The aqueous solution is extracted after processing of precious metals such as raffinate after extraction of platinum and palladium, to neutralize the residual acidity of 20-30 g / l HC1. The solution was treated in an electrolytic cell on a planar titanium cathode at a current density of 1500-2000 A / m 2 and a voltage of 8-12 V. At an event in this process elektroflotokoagulyatsii formed hydroxides of base metals, which are adsorbed organic substances present in the solution. These include solvents, and extractants such as TBP and kerosene, octanol and others. The purified solution contains traces of organic and inorganic impurities. From this noble metals deposited on the three-dimensional flow of a graphite cathode material. process Result: The possibility of processing solution resulting from the extraction of precious metals processing, higher recovery and purity of the final product.
DESCRIPTION OF THE INVENTION
The invention relates to non-ferrous metallurgy and can be used for the electrochemical extraction of precious metals: gold, platinum, palladium, rhodium, iridium from dilute hydrochloric acid solutions, resulting from the extraction and processing of primary and secondary raw materials containing organic substances: extractants and diluents.
Processing solutions obtained by the extraction techniques extracting precious metals is very relevant and complex.
Firstly, these solutions (raffinates, washes, etc.) have a low concentration of precious metals.
Second, the impurities they contain base metals and organic substances - residues extractants and diluents, which form stable complexes with platinum metals.
Known method of separating precious metals from solutions of organic complexes (US patent 4201636, C 25 C 1/20, 1980).
The method comprises adjusting pH of the solution to a value ± 0,5 and removing the main quantity of alkali metals and amphoteric by filtration. The filtrate was heated to 70 o C and subjected to electrolysis while maintaining the temperature at 70 o C and pressure 8. During electrolysis complexes are destroyed, and the platinum metals are precipitated as hydroxides, which were filtered off.
The method has the following drawbacks: the presence of two filtrations and precipitating impurities base leads to loss of noble metal. Precious metals themselves are obtained in the form of hydroxides, which means that they may be contaminated with organic compounds and their subsequent release in a multistage metal.
Known and the method of allocation of precious metals from hydrochloric acid electrolysis solution (RF patent 2131485, C 25 C 1/20, 10.06.1999).
The method involves a two-step electrochemical processing solution.
The first step is precipitated noble metal on titanium cathode at a current density of 200-300 A / m 2. In the second step the deposition of noble metals from solutions with low concentration of lead to the three-dimensional flow graphite cathode at a current density of 20-60 A / m 2.
The disadvantage of the method is the closest analogue is the fact that the current efficiency and extraction of platinum metals, particularly rhodium, and iridium, is very low in the processing solutions produced during extractive separation of platinum group metals. The presence of organic substances. Tributyl phosphate (TBP), kerosene, octanol, sulfonium bases oil (HCO), etc., which form stable complexes with platinum group metals greatly increases the cathodic polarization of the platinum metals (at 0.8-0.9 V) and the cathode mostly hydrogen is released. Also in this case there is no removal of dissolved organics, extractants TBP, HCO, etc. and organic solvents -. Kerosene, etc. octanol.
Object of the invention - the creation of such a method for separating precious metals from solution as a result of which extend the functionality of the method by processing solutions, obtained in the extraction technology of extraction of precious metals, increases the purity of precious metals.
The problem is solved in that the precious metal recovery method of a hydrochloric acid solution comprising elktrohimicheskuyu processing solution and precipitating the noble metal on the cathode of the three-dimensional flow graphite material subjected to treatment the aqueous solution after the extraction and refining of precious metals are in its cathode current density of 1500-2000 A / m 2 and a voltage of 8-12 V.
The method and is characterized in that the solution treatment is carried out for 0.5-1.5 hours, and the solution is neutralized prior to treatment until the residual density of 20-30 g / l HCl.
In the treatment of the initial solution using a titanium cathode and a graphite anode at a current density of 1500- 2000 A / m 2 and a voltage of 8-12 V proceeds simultaneously several processes:
- Electrowinning recovery of platinum group metals and their hydrogen evolved at the cathode;
- Electrochemical oxidation of organic compounds with oxygen and chlorine produced at the anode;
- Stable and foam flotation associated with intensive bubbling (H 2, O 2, Cl 2) and the presence of organic substances in the solution;
- Change of pH of the solution from 0.1 to 7.0-8.5 by electrolysis of water according to the reaction K 2 H 2 O + 2e = H 2 + 2 OH -.
Alkalization leads to a reduction of solution stability of the complexes of platinum metals, coagulation and formation of hydroxides present in the noble metal solution:. Nickel, iron, lead, etc., which are adsorbed on the anode oxidized organic and inorganic components processed solutions. Thus, in electrochemical processing solution at the same time proceed electroextraction elektroflotokoagulyatsiya and platinum metals, by whom, and made the extraction of organic and inorganic components of the solutions. After the electrochemical machining (step 1), the solution was filtered and fed to the second step: the selection to waste noble metal concentration in an electrolytic cell with three-dimensional carbon cathodes of a material with cation exchange membranes. Processed hydrochloric acid solution containing trace amounts of noble metals, is circulated through the series-connected cathode chambers. The anode chamber is filled with sulfuric acid solution with a concentration of 5-10%. Electrochemical deposition is carried out at a current density of overall 20 - 60 A / m 2, an electrolyte circulation rate of 2.0 - 3.5 m 3 (m 2 · hr).
When the concentration of hydrochloric acid below 20 g / l in the pre-processed neutralization solutions, drops the particulate poorly filterable precipitate (a mixture of hydroxides and organic matter), which hinders further electrochemical machining due to the passivation of the electrodes. Increasing the acid concentration of more than 30 g / l leads to an increase of the electrochemical processing time, reduces the output current and extraction of platinum metals.
Reducing the current density at the first electrochemical processing step below 1500 A / m 2 and a voltage less than 8 reduces the degree of extraction of platinum metals and oxidation of organic components, thus badly filterable precipitates formed.
With increasing current density greater than 2000 A / m 2 and a voltage above 12 V power consumption increases, the electrolyte heats up and boils vigorously. With a decrease in the second stage of the electrochemical current density below 20 A / m 2 is reduced recovery of precious metals and their residual concentration exceeds the allowable content in the waste solution. Increasing the current density 60 A / m 2 in the second stage does not affect the electrolysis performance, but increases the power consumption.
High recovery of platinum group metals is achieved by the destruction of the complexes of platinum metals with organic ingredients TBP, VAT in the neutralization and electrochemical treatment (elektroflotokaogulyatsiya, electroextraction), but also the application of the second stage of the three-dimensional flow-through cathodes made of carbon material with a high surface area.
Examples of the method are given below.
example 1
Industrial-raffinate solution (10 liters), which is formed after the extraction process of extraction of impurities and base isolation of palladium and platinum containing, mg / l gold - <10 Silver - 90.5, platinum - 471, Pd - 2200, rhodium - 275, iridium - 540, nickel - 104, lead - 24.6, iron - 41.0;
extractants: TBP-200, NSO-1430;
solvents: kerosine -185, octanol - and hydrochloric acid 28 - 68 g / l pH was neutralized to 25 g / l HCl, was subjected to an electrochemical treatment at a current density of 1750 A / m 2, a voltage of 10 V for 1 hour and the precipitate formed is filtered. Once the first electrochemical processing and filtration, the solution contained, mg / l gold - 2.0 Silver - 7.1 Pt - 19.7 Pd - 2.5, rhodium - 2.6, iridium - 9.2 nickel iron and lead - less than 2.5, TBP, octanol - <10.0, kerosene - 22, HCO - 45.
The solution was then passed through two series-connected electrolytic chamber filtrpressnogo three-dimensional graphite cathode, where the noble metals carried electroextraction overall current density at 60 A / m 2 and electrolyte circulation rate of 2.0 m 3 / (m 2 · hr).
After the two-stage electrochemical machining with intermediate filtration, the solution consisted of: gold, silver, rhodium - <1 mg / l palladium - 1.3 mg / l, platinum - 2.9 mg / l and iridium - 3.8 mg / l TBP and octanol were found in the solution, kerosene - 12 mg / l HCO - 36 mg / l.
Other examples are given in the table .
These examples show that the method created a high degree of recovery of precious metals from solutions produced during the separation of the extraction of platinum metals containing organic matter and cleaning solutions from base impurities. Moreover, in electrochemical processing is significantly reduced concentration of toxic organic substances and HCO TBP in the waste solutions.
CLAIM
A method of isolating the precious metals from the hydrochloric acid solution, comprising an electrochemical treatment of solution and precipitation of the noble metals on the three-dimensional flow-through cathode of graphite material, characterized in that the treatment is subjected to the aqueous solution after extraction processing precious metals and lead it at a cathodic current density of 1500 - 2000 A / m 2 and a voltage of 8 - 12V.
A method according to claim 1, characterized in that the treatment solution is carried out for 0.5 - 1.5 hours.
A method according to claim 1 or 2, characterized in that before treatment the residual solution was neutralized to pH 20 - 30 g / l HCL.
print version
Publication date 05.12.2006gg
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