SU1407994A1 - Electrochemical method of regenerating used alkali solutions for pickling copper - Google Patents

Abstract

The invention relates to the electrochemical regeneration of alkaline solutions for etching copper, mainly copper-ammonia or copper-monoethanolamine. The purpose of the invention is to obtain compact copper at the cathode and to reduce energy consumption. The method involves pre-dilution of the regenerated copper solution to a concentration of 40-50 g / l by adding a solution of ammonium salts with a concentration equal to their concentration in the initial pickling solution, and subsequent electrolysis of the resulting solution with separation of compact copper at the cathode and simultaneous oxidation of monovalent copper at the anode, carried out at a current density of 200-600 A / m and a temperature of 18-30 C to reduce the copper concentration in the solution, equal to 18-30 g / l, and for preliminary dilution of the solution It is used after electrolysis solution containing 18-30 g / l copper. 1 hp f-ly, 3 tab. € (L

Description

QD

;about

four

The invention relates to the regeneration of etching solutions, in particular, to electrochemical methods for the regeneration of alkaline solutions for etching copper, preferably copper ammonia or copper monoethanolamine.

The aim of the invention is to obtain compact copper at the cathode and reduce energy consumption. Table 1 presents examples 1-4 of using the proposed method.

Regeneration of solutions in accordance with examples 1 and 2 is carried out after etching, samples of printed circuit boards in solutions containing copper (II) chloride two-water in concentrations listed in Table 1, 25% ammonia solution the amount of 500 ml / l and ammonium chloride 100 g / l. The initial dilution of the solution is carried out with a solution containing 100 g / l of Ammoni chloride. The regeneration of the solutions in accordance with Example 3 is carried out after etching the samples in solutions containing copper (II) chloride two-water in the concentrations listed in Table 1, a 25% ammonia solution in an amount of 500 ml / l, ammonium chloride 100 g / l, ammonium nitrate 20 g / l, ammonium bicarbonate 60 g / l. The initial dilution is carried out with a solution containing 100 g / l of ammonium chloride, 20 g / l of ammonium nitrate and 60 g / l of ammonium bicarbonate.

The regeneration of the solutions in accordance with Example 4 was carried out after etching the samples in solutions containing copper (II) chloride two-water in the concentrations indicated in Table 1, monoethanolamine in an amount of 500 mg / l ammonium chloride 100 g / l. The initial dilution is carried out with a solution containing 100 g / l of ammonium chloride.

The criterion for regenerability in all examples is the rate of etching, chi in a freshly prepared and regenerated solution.

As can be seen from the data in Table 1, the regeneration of solutions under stable conditions begins with the 3rd cycle of each example. Under these conditions, the corrosion rate of copper is greatly reduced, and the possibility of deposition of compact copper on the cathode appears.

When implementing the proposed method, the volume of the solution to be

dilution and the degree of dilution must meet the ratios

Wed

Cj ((T)

g - g K (t) c. (a)

Wed

2e) ;: с) Op n (B) Cg (a)

five

0

5 0 5

0 5

where Or is the volume of the pickling solution to be diluted before electrolysis, l; Cp is the degree of dilution; C is the volume of the solution to be electrolyzed, l; CH (T) and

. —the concentration of copper in the pickling solution, respectively, before and after etching, g / l;

H (e) h

Sk (copper concentration in the regenerated solution, respectively, before and after electrolysis, g / l.

In accordance with the indicated ratios in Table 2, the calculated parameters of the method implementation for Cirsol 3 of each of the examples listed in Table 1 are given.

As can be seen from the data of Table 2, the calculated ratios have a good agreement with the practical ones.

According to the proposed method, it is advisable to start electrolysis with a higher cathode current density of 600-500 A / m and gradually reduce it as the copper solution becomes depleted. By using lower current densities, the potentials of the anode and cathode, the voltage drop in the electrolyte, and consequently, the voltage on the electrolyzer and the consumption of electrical energy, decrease.

As can be seen from Table 3, using the proposed method allows to obtain compact copper, which. it is possible to reuse, for example, in copper baths, to increase the regeneration rate of copper-ammonia solutions due to a higher current output and more rational use of the electrolyzer volume, to reduce energy costs by 2-3 times.

The technical and economic indicators of the proposed in table 3

31407994

The method is provided at the expense of reductions for copper etching, the advantage of the interelectrode distance of copper-ammonia or copper under the condition of obtaining a compact mono-ethanolamine, including deposition and maintaining a high bulk current density, i.e. the current passing through 1 l of the solution, as well as by reducing the specific energy consumption, as indicated above. In addition, the reduction in energy costs is also associated with the lack of a continuous flow of the solution and cooling, which is necessarily required when using high current densities.

The simplification of the proposed method in comparison with the known one is achieved by using a non-visible cathode and electrolyte, eliminating the need for cooling the cathode (solution) and the device for periodically removing the cathode with copper.

Claims (2)

1. Electrochemical method of regeneration of spent alkaline copper deposition at the cathode with simultaneous oxidation of monovalent copper at the anode, characterized in that, in order to obtain compact copper at the cathode and reduce energy consumption, the waste solution is pre-diluted by copper to concentrate. 40-50 g / l by adding a solution of ammonium salts with a concentration equal to their concentration in the initial pickling solution, after which the electrolysis is carried out at a current density of 200-600 A / m and a temperature of IS-BO C to reduce the concentration of copper in the solution, equal to 18 - 30 g / l. 25 2. The method of Claim 1, wherein the spent solution is pre-diluted in copper to a concentration of 40-50 g / l by adding a solution after electrolysis, containing 18-30 g / l of copper. Table I Temperature, С Current density, А / m Copper current output,% Characteristics of the cathode sediment Copper extraction rate, g / lh Electricity consumption for electrolysis, kW / h / kg copper table 2 Table 3 24 150 78 24 430 90 24 470 93 24 280 95 Compact powder compact compact lactation 4.5 5.8 6.5 4.0 4.0 2.2 2.0 1,3