FR2810681A1 - Recovery of precious metal, notably gold, from a variety of wastes involves electrolytic dissolution of gold and electrolytic deposition of gold from solution on an electrode - Google Patents

Abstract

Recovery of precious metals, notably gold, from various waste products and articles is achieved by using a new system of reverse electrolysis comprising two electrolysis chambers and two rinsing chambers. The first electrolysis chamber is a gold dissolution chamber containing alkali cyanide electrolyte and equipped with an immersion heater with probe protection. The second electrolysis chamber is used for the recovery of gold from the alkali bath, and is equipped with 3 cathodes and 4 anodes. The gold contained in the alkaline bath is deposited as flakes on the electrode or is amalgamated on a gold electrode. The bath of the second chamber and the articles treated in the gold dissolution chamber are transferred to the third chamber for static rinsing. The small amount of gold remaining on the articles is dissolved in the static rinsing chamber and is recovered in a new operation in the second electrolysis chamber. A second rinsing phase takes place in the fourth chamber. The bath is readjusted for cyanide content, in order to prepare a new working solution for a new cycle. An ion-exchanger assembly for the treatment of water necessary for the chambers comprises a mobile, strongly cationic exchanger, a mobile, weakly anionic exchanger, a cartridge filter, and a circulation pump second rinsing phase takes place in the fourth chamber.

Description

The invention which is the subject of this patent makes it possible to recover the precious metal which covers various materials (spectacle frames, buttons, printed circuits, various waste, etc.) by a new process of reverse electrolysis.

Its operation is relatively simple since it consists in extracting the gold metal fixed on certain materials immersed in two electrolytic baths constituted by two tanks, and two other rinsing tanks.

Traditionally the recovery of gold from debris or waste was preceded by a crushing and melting stage in an oven over 1000.

This method also required at least one tonne of products or waste.

At the end of this merger ingots of 100 to 200 kilos were recovered and entrusted to a refiner who brought them up in temperature in an oven at the limit of fusion and made ooze the drops of gold contained in this ingot.

This important implementation had a high cost barely offset by the recovery of the precious metal.

The process described in the present invention is therefore much more flexible, less expensive and faster. I1 overcomes the disadvantages of the old method of recovering gold from debris or waste.

The first tank (1) in Figure 1, known as deduction in an alkaline oxidizing cyanide medium, is made of special P.P.H. plastic. 10 mm thick equipped with a plunger with probe cover.

The pieces to be deducted are immersed in this first tank which has a cyanide bath crossed by an electrolytic current, the gold to be recovered is dissolved in the bath.

This bath is then transferred to the second electrolysis tank (2) in Figure 1, which is equipped with 3 cathodes and 4 anodes.

When this second electrolysis tank is put into operation, the gold contained in the solution will deposit in flakes on the chosen electrode, which it suffices to recover.

If this electrode is itself gold, the deposit will be all the easier. It will then suffice to recover the gold to melt this electrode.

In order not to lose anything of the gold particles which may have remained on certain pieces, during the cleaning operation in the first tank, the bath from the second tank (2) is transferred to the third tank (3) called static rinsing, as well as the parts having been treated a first time for the cleaning in the first tank. The little gold that may have remained on said coins is dissolved in the so-called static rinsing bath.

This gold will be recovered during a new operation, in the second electrolysis tank.

As for the fourth tank (4) it corresponds to the second rinsing phase, and recycling of the bath which will be checked, then readjusted as to the cyanide content in order to prepare a new operational solution for a new cycle.

Once this bath has been finalized, it will be transferred to the first tank (1) to start a new operation.

The water treatment exchanger, necessary for the tanks, is composed of - a cationic mobile exchanger with a capacity of 50 liters; - a weak anionic mobile exchanger of 50 liters; - a strong anion exchanger of 50 liters; - a cartridge filter, - a circulation pump

Claims (1)

1) Method for recovering precious metal or gold, characterized by a new reverse electrolysis system comprising two active cells and two rinsing cells, the first cell (1) known as scrubbing in cyanurized alkaline medium being equipped with a heat sink with probe protector in which the gold is dissolved by electrolysis, and the second electrolysis tank (2) the gold which is in the alkaline bath is recovered, This second tank being equipped with 3 cathodes and 4 anodes, the gold contained in the alkaline bath being deposited in flakes on the electrode or being amalgamated on a gold electrode.