| JPH10265863 | METHOD FOR RECOVERING NOBLE METALS FROM SMELTING RESIDUE |
| WO/2023/212777 | PROCESSING MINED ORE |
| WO/1995/011319 | GOLD LIXIVIATION USING NITROGEN AND SULFUR HETEROCYCLIC AROMATIC COMPOUNDS |
ÇETİNER BURCU NILGÜN (TR)
AKTAS SERDAR (TR)
CETINER BURCU NILGUEN (TR)
| JP2012172182A | 2012-09-10 | |||
| JPH03131529A | 1991-06-05 | |||
| KR101925725B1 | 2018-12-05 | |||
| EP1118683A1 | 2001-07-25 |
| CLAIMS 1. A platinum recovery method comprising the process step of a) dissolving the platinum-containing scraps in the aqua regia and taking the platinum product into the solution, characterized in comprising the following process steps in order to obtain platinum with minimum 99.95% purity: b) precipitating and filtering potassium hexachloroplatinate by adding potassium chloride to the solution obtained, c) dissolving potassium hexachloro platinate in the potassium hydroxide solution by mixing, d) setting pH to 1-2 by adding the solution obtained to the HCI solution in the beaker located to the ice bath drop by drop and reprecipitating potassium hexachloroplatinate in a purer form than the previous process step, e) if sufficient purity cannot be reached, repeating the process steps c and d one after another until desired purity is achieved. 2. The platinum recovery method according to claim 1 , characterized in that the mixing process mentioned in the process step of c is performed for 1-2 hours. |
DESCRIPTION
Technical Field
The invention relates to a method for the recovery of the noble metals.
In particular, the invention relates to the platinum recovery method to obtain platinum with minimum 99.95% purity from platinum-containing scraps, the method comprises the process steps of precipitating and filtrating potassium hexachloro platinate by adding potassium chloride to the solution obtained by dissolving said scraps in aqua regia, dissolving potassium hexachloro platinate in potassium hydroxide solution by stirring and adding the obtained solution drop by drop to HCI solution to reprecipitate potassium hexachloro platinate in a purer form than the previous process step.
The Present State of The Art
Recently, the use of secondary resources is interesting due to the limited primary metal resources; however, its rate in recycling has been increasing in recent years. The metal content in the secondary sources is much higher than the primary sources. The base metal and the impurity rates vary in the primary or the secondary sources. Therefore, the process is adapted to the raw material. Particularly, in the case of PGM (platinum group metal) recovery from the secondary sources, the change in the concentration and the level of impurity are significantly related to the chemical reactions during the process.
In the present art, in order to obtain metallic values, they are precipitated by the conventional techniques after the treatment with the strong acids following the pre-treatment processes. Nevertheless, the problems occur in the selective precipitation by the use of these methods. After the dissolution by treating in the aqua regia, and then the precipitation with ammonium chloride (NH CI), rhodium, palladium and other impurities also precipitate with the platinum depending on the concentration and increase the purification steps of platinum. However, when it is considered theoretically, the precipitation with ammonium chloride is specific to platinum (IV) and other impurities should not precipitate. Though, since other impurities are dragged with the platinum and cannot be removed by washing, it significantly reduces the purity of platinum. The selective extraction of the noble metals such as iridium, palladium and rhodium in the solutions containing platinum was also researched in the studies conducted in the state of the art. Several methods can be applied to remove these impurities from the platinum-containing medium. One of the easiest methods applied is to use ammonium chloride for the precipitation. The platinum metal is dissolved in a combination of hydrochloric acid and nitric acid, generally referred to as aqua regia.
3Pt + 18HCI + 4HN0 3 ® 3H 2 [PtCI 6 ] (aq) + 4NO(g) + 8H 2 0
In the most known general process, the solid that is desired to be purified is treated with the aqua regia and boiled, and then the liquid phase is taken by solid/liquid separation. The liquid phase taken is then precipitated with ammonium chloride and platinum and other noble metals are precipitated. As a result of this process, some active metals remain in the solution, while platinum and other noble metals are also precipitated and the desired purity level in regard to platinum cannot be reached. This process must be repeated continuously in order to reach the desired purity value. Platinum must be continuously re-dissolved in the aqua regia and reprecipitated with ammonium chloride. This situation appears as an important problem in the platinum purification. Also, when the rhodium metal is above a certain concentration, it must be removed in advance by additional processes. Therefore, it is very important to remove impurities such as the rhodium metal beforehand in order to reach the desired purity level.
Techniques that have drawn attention in recent years are counted as the adsorption by ion exchangers or binder resins, the solvent extraction (SX), the resin/liquid impregnated membranes, and the reduction of precious metals with reagents. The pure metal binder resins or polymers with the adsorption selectivity and the high adsorption capacity have two components and the polymer matrix acts as a support while the functional group provides binding to other ions. Covalently bonded functional groups holding one or more donor atoms can easily be complexed with metal ions using them, and hereby are used for the recovery or the selective separation of the metal ions from the different weak and strong acid-based chemical solutions depending on the functional groups and donor atom. These techniques are not economically effective, and the installation costs of the enterprises are very high in order to operate such comprehensive systems in a functional way.
As well as all of these, currently in the industrial production of platinum, the precipitation process with ammonium chloride is applied. In the first stage, since the platinum will not precipitate purely, this yellow precipitate is sintered at 800Ό and a gray metallic platinum called platinum sponge is obtained. In the next step, this platinum is dissolved in the aqua regia and precipitated again with ammonium chloride. However, this method creates disadvantages in terms of both the number of processes and time.
In the patent application numbered EP2052092A1 , which is encountered in the literature related to the subject, a method for the recovery of noble metals is mentioned. The method is particularly related to the recovery of noble the metals such as gold, silver, palladium, for example from the materials to be recycled or disposed such as scraps of the power plants and the electrical and telephone control units, from the electronic fractionation, as well as from the production scraps and waste of the jewelry industry. In the present invention, materials containing metals to be recovered are treated with an aqueous solution containing potassium cyanide, sodium nitrobenzosulfonate and thallium sulphate.
As a result, there has been a need to make an innovation in the relevant technical field due to the negativities and deficiencies mentioned above.
The Object of the Invention
The present invention relates to a platinum recovery method that meets the above-mentioned requirements, eliminates all disadvantages and brings some additional advantages.
The main object of the invention is to obtain platinum with a minimum purity of 99.95% from platinum-containing scraps.
The object of the invention is to shorten the purification steps of platinum by preventing the precipitation of rhodium, palladium, and other impurities with platinum.
The object of the invention is to purify economically and to reduce the loss of platinum, which occurs as a process loss by being dragged during the purification process.
The object of the invention is to form a platinum recovery method that is economically effective, that can be operated functionally and that reduces the operating costs of enterprises.
The object of the invention is to enable platinum to be purified in a much easier and faster method than the existing applications.
In order to achieve the objects above, the invention is a platinum recovery method comprising a) dissolving the platinum-containing scraps in the aqua regia and taking the platinum product into the solution process step and consists of the following process steps in order to obtain platinum with minimum 99.95% purity: b) precipitating and filtering potassium hexachloroplatinate by adding potassium chloride to the solution obtained, c) dissolving potassium hexachloro platinate in the potassium hydroxide solution by mixing, d) setting pH to 1-2 by adding the solution obtained to the HCI solution in the beaker located to the ice bath drop by drop and reprecipitating potassium hexachloroplatinate in a purer form than the previous process step, e) if sufficient purity cannot be reached, repeating the process steps c and d one after another until a minimum purity of 99.95% is achieved.
The structural and characteristic features and all the advantages of the invention will be understood more clearly by means of the detailed description given below, and therefore the evaluation should be made by taking this detailed description into consideration.
Figures Clarifying Understanding of the Invention
Figure-1 : XRF spectrum recovered with the present invention
Detailed Description of the Invention
In this detailed description, the platinum recovery method, which provides a much easier and faster purification/recovery compared to the existing applications, is described only for a better understanding of the subject and without any limiting effect.
The invention relates to obtaining of platinum with a minimum purity of 99.95% from platinum- containing scraps. The most important feature of the invention is that the purification is economically performed. The platinum recovery method from the platinum-containinp scraps: a) Platinum-containing scraps are dissolved in the aqua regia and the platinum product is taken into solution,
Pt (solid) + Aqua regia (aq)®H 2 PtCl 6 (aq) + N0 2 (g) + NO x CI (g)
3Pt + 18HCI + 4HNO 3 ® 3H 2 [PtCI 6 ] (aq) + 4NO(g) + 8H 2 0 b) the yellow potassium hexachloroplatinate is precipitated and filtered by adding potassium chloride to the solution obtained,
HsPtCle (aq) + 2KCI (aq)®K 2 PtCI 6 (s) + 2HCI (I) c) Potassium hexachloro platinate is dissolved in hot and concentrated potassium hydroxide solution by stirring,
K 2 PtCI 6 (s) + 6 KOH (aq)®K 2 Pt (OH) 6 (aq) + 6 KCI (aq) d) pH is set to 1 -2 by adding the solution obtained to the HCI solution in the beaker located to the ice bath drop by drop and potassium hexachloroplatinate is reprecipitated in a purer form than the previous process step, e) If sufficient purity cannot be reached, the process steps c and d are repeated one after another until a minimum purity of 99.95% is achieved.
In the process step a of the method according to the invention, while nitric acid contained in the aqua regia is consumed for the oxidation of platinum, complex nitrogen-containing gases come off as a result of the reaction and in the process step b, potassium chloride is added to the solution instead of ammonium chloride.
In case of precipitation with ammonium chloride, ammonia gas is formed as a result of treatment with potassium hydroxide and leaves the system. Since there is potassium in the reaction medium, KCI is formed as a side product. Thus, the precipitation occurs during the reacidification. If NH 4 PtCl 6 is dissolved in sodium hydroxide, the precipitation will not occur during the reacidification. There is no precipitation when sodium chloride is used instead of potassium chloride. The best of the afore-mentioned precipitation agents is potassium chloride. Because it does not leave the system as in the case of NH CI. The presence of potassium is also necessary for the precipitation of platinum.
At the end of the process step c of the method of the present invention, the noble metal complexes, especially platinum, are obtained in a basic environment, and some of the products that tend to precipitate together such as rhodium are removed.
In the process step d of the method of the invention, the reaction should be carried out in a cold environment as much as possible. The reason for this is that the acid-base reactions are always exothermic, and heat occurs. With increasing reaction medium temperature, the undesired metal compounds can also be dragged.
The mixing process mentioned in the process step a of the method of the invention is carried out for 24 hours above 100Ό, and the mixing proces s in the process step c is carried out for 1 -2 hours.
With the method of the invention, a much easier and faster purification/recovery was provided without the need for sintering of platinum precipitate in the existing processes and without the need for more than one dissolution step with aqua regia in the process steps. This result was proven by-the laboratory-scale tests. The X-ray fluorescence analysis of the product recovered by the method of the invention was performed in the "Precious Metals" mode by a Thermo Scientific Niton XL brand portable XRF (X-ray fluorescence) device. The result of the component analysis (verification certificate) obtained as a result of the XRF analysis of the product is given in table 1. In Figure-1 , the XRF spectrum of the product recovered by the method of the invention is given.
Table-1 : Component analysis result obtained as a result of XRF analysis of the product recovered by the method of the invention If the potassium hexachloro platinate precipitate, checked by XRF analysis, does not contain impurities, it is possible to produce the desired platinum compound as well as to obtain a platinum sponge by sintering.