RU2116362C1 - Method of recovering precious metals from exhausted catalysts - Google Patents

Abstract

FIELD: precious metal recovery. SUBSTANCE: catalyst is treated by freshly prepared mixture of concentrated hydrochloric acid and hydrogen peroxide under static, dynamic, or circulation conditions at 0 to 100 C and atmospheric pressure. Filtered solution is combined with that obtained after washing precipitate with water on filter. Combined solution is treated by sorbent 10-hydroxy- (perhydro-1,3,5-dithiazine)-5 yl-ethane in quantity 5-10 g per 1 g of metal to be recovered, treatment being carried out at 0 to 100 C and atmospheric pressure for 2 to 10 h until traces of precious metals are no longer found in solution. Sorbent exhibits high sorption capacity toward precious metals so its intake is 10-12- fold lower, whereas recovery reaches 95-98%. EFFECT: enhanced precious metal recovery efficiency. 1 tbl

Description

 The invention relates to the field of hydrometallurgy, in particular to methods for the extraction of metals from spent catalysts.

 Known hydrometallurgical processes for the extraction of precious metals from spent catalysts.

The main stages of the known processes are:
dissolution of metals using an oxidizing agent in an acidic environment; the most effective systems are: a solution of chlorine in hydrochloric acid; [1, 2, 3];
- extraction of precious metals from solution using reagent precipitants, etc .; [4, 5, 6];
- separation of precious metals from the reagent concentrate - calcination of sediment, etc. [4, 5, 6].

 The dissolution of metals according to methods 1-3 is equally effective, however, in the case of using nitric acid as an oxidizing agent, toxic and difficult-to-utilize nitrogen oxides appear as process wastes; the use of chlorine under pressure requires increased attention to safety issues and a high production culture; the most successful combination of environmental friendliness and manufacturability in the case of using a mixture of hydrochloric acid with hydrogen peroxide. In this embodiment, the process can be carried out under relatively mild conditions and is characterized by the absence of gas emissions.

 Extraction of precious metals from solution using precipitants such as hydrazine and other reducing agents leads to the formation of a finely dispersed precipitate that is difficult to catch on filters. The extraction of precious metals compounds with organic solvents subsequently requires additional reextraction operations, which increases the value of precious metals losses; the latter also applies to the use of ion exchangers.

 Reducing the loss of precious metals allows you to achieve the technique used by Ron-Pulenk Industries [9]: the sorbent-ion exchanger saturated with precious metals is not subjected to a reverse exchange, but is burned, reducing the number of operations and immediately obtaining pure metal.

The process closest in technical essence to the claimed, includes the stages of dissolution of the essence to the claimed, includes the stages of dissolution of precious metals with an acid-oxidative mixture, extraction of precious metals from solution by adsorption on Duolit A 101 D anion exchange resin and burning of the sorbent concentrate at a temperature of 880 ^o C to obtain pure metals. The process provides a high degree of metal recovery due to the reduced number of operations.

 The disadvantage of this method is the high consumption of the sorbent-ion exchanger per unit mass of the extracted metal, since the sorbent is irretrievably lost during combustion.

 The reason for the high consumption of the sorbent is the low capacity of the sorbent in relation to the extracted metals: up to 50 g per 1 g of precious metal.

 The authors proposed a method that reduces the consumption of the sorbent due to the capacity in relation to the extracted precious metals.

 The task is carried out using 1-hydroxy-2- (perhydro-1,3,5-dithiazine) -5-yl-ethane (hereinafter OPDE) as a sorbent.

 The use of OPDE allows to reduce the consumption of sorbent in the process up to 5-10 g per 1 g of recoverable metal.

The proposed process for the extraction of precious metals from spent catalysts includes the following stages:
- dissolution of precious metals with a mixture of hydrochloric acid with hydrogen peroxide;
- sorption extraction of precious metals from solution using 1-hydroxy-2- (perhydro-1,3,5-dithiazine) -5-yl-ethane;
- the allocation of precious metals from the sorbent concentrate by ashing at 600-650 ^o C.

 The proposed process allows to achieve high degrees of extraction (95-98%) of precious metals from spent catalysts based on silica gel, aluminum oxide.

The process was carried out as follows: the spent catalyst was treated with a freshly prepared mixture of conc. hydrochloric acid and hydrogen peroxide (30% aqueous solution) in ratios (weight) from 5: 1 to 1: 2, in quantities from 1.2 g to 3.6 g of a mixture of the mass of catalyst, in static, dynamic or circulating modes, at a temperature of from 0 to 100 ^o C and atmospheric pressure.

 The filtered solution was combined with the solution obtained by washing the filter cake with water in an amount of 1.0 g to 4.8 g per 1 g of catalyst.

 The washed precipitate did not contain precious metals.

The combined solution containing precious metals was treated with a sorbent -1-oxy-2- (perhydro-1,3,5-dithiazine) -5-yl-ethanane in an amount of 5-10 g per 1 g of recoverable metal at a temperature of 0-100 ^o C and atmospheric pressure, in static or dynamic mode, in the mode, for 2-10 hours until the complete absence of traces of precious metals in the solution.

The sorbent concentrate filtered and washed with water was dried and calcined in an oven at a temperature of 600 - 650 ^o C, the recoverable metal was obtained in a reduced form with a yield of 95-98%.

 A distinctive feature of the process is the use of 1-hydroxy-2- (perhydro-1,3,5-dithiazine) -5-yl-ethane as an sorbent for the extraction of gold and platinum group metals from solution.

 The advantage of the OPDE sorbent over the well-known sorbent “Duolit A 101 D” in the processes of precious metals extraction consists in a significantly higher sorption capacity with respect to recoverable metals, reaching 0.1-0.2 g of metal per 1 g of sorbent mass. The increase in capacity entails a decrease in reagent consumption by 10-20 times compared with the consumption of the sorbent "Duolit A 101 D".

 The invention is illustrated by the following examples.

 Example 1. A sample of 5 g of a catalyst containing 0.22% gold and 0.56% palladium was placed in a column type reactor equipped with a filtrate in the lower part and a drain valve located below the filter, and, with the valve closed, 6 g were introduced into the reactor a mixture of a 30% solution of hydrogen peroxide and concentrated hydrochloric acid, taken in equal quantities. The reaction mixture was kept at room temperature for 8 hours, after which the lower valve was opened and the solution was poured into reactor No. 2, which was a container with a stirrer and a filter in the lower part. The solid phase remaining in reactor No. 1 was washed with water, filling the reactor three times with water and then draining the washing water also into reactor No. 2, after which the washed solid phase was discarded.

390 mg of 1-hydroxy-2- (perhydro-1.3,5-dithiazin-5-) yl-ethane was added to reactor N 2 containing a solution of gold and palladium at room temperature, stirred for 6 h, after which the precipitate was filtered off, the precipitate was washed with water on the filter until the washings were neutral, dried and calcined in a muffle furnace at a temperature of 600 ^o C for 2 hours. The ash contained 10.5 mg of gold, 272 m of palladium (yield, respectively, 98.5% gold and 97, 1% palladium).

 The results of the remaining examples are presented in the table.

Claims (1)

 A method of extracting precious metals from spent catalysts, including dissolving precious metals with an acid-oxidizing mixture, sorbing precious metals from a solution and separating them from the sorbent concentrate by ashing, characterized in that 1-hydroxy-2- (perhydro-1,3- is used as a sorbent 5-dithiazine) -5-yl-ethane.

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