DE720663C - Production of zinc powder from zinc salt solutions - Google Patents

Description

Production of zinc powder from zinc salt solutions The representation of Zinc powder. Is electrolytically made from non-alkaline zinc salt solutions to the use of high current densities (up to about 5oooA, 'm ° -) and not too high a metal concentration bound in the electrolyte, with r the temperature of the electrolysis solution additionally can be changed.- Here you only get coarse-grained to flaky Products. Finer powders are made almost exclusively from an alkaline zincate solution generated. Also known is the electrolyte substances: organic or foreign metals to add.

It has now been found that weakly acidic zinc salt solutions, the still foreign salts, e.g. B. The alkalis, contain zinc in fine powder form can get. if you check the acidity (pH value) of the solution during electrolysis and keeps the current density within certain narrow limits. This can be done by applying different concentration of the electrolyte as well as the temperature the desired powdered products obtained.

Of particular importance for this type of zinc dust extraction is the pH of the solution. From an acidic solution, e.g. B. PH 3, o, the zinc only as solid metal, deposited on the cathode. Even with pH values of .1 to 4.5 are known to be coherent precipitates and no zinc powder obtain. At a pH of z. B. over 6, o is obtained with normal Temperature from a zinc chloride solution, a heavily contaminated by hydroside Metal sponge. Flawless zinc powder precipitates were made obtained only in the range from above PH 45 to 5.8, preferably PH 5, o to 5.5. Of the p11 value must not be higher than the value at which the hydrolysis of the relevant Zinc salt (e.g. with zinc chloride PH = 5.8) is used. The zinc powder will be like this finer, the lower the acidity of the electrolyte. The cathodic current density is held at a value from goo to iooo A, lm °.

It has also been found that, taking into account the most favorable pii range to achieve economical production (favorable energy yield), instead of reducing the zinc content of the solution, it is better to give the solution the desired pH value and high conductivity by adding buffer salts. By using salts of the same ion, the effective zinc ion concentration is reduced to a desired level. Mau will therefore add the cheap table salt to the electrolysis of a zinc chloride solution. Use of higher temperatures for electrolysis is an advantage. Here, too, the desired grain fineness can be achieved by adjusting the p1.1 value with the current densities not being too high. Embodiments i. A zinc powder was obtained from a zinc chloride solution at a pH of 5.5 and a cathodic current density of 100A / m = 5% grain 0.3 to 0.6 mm , 330/0 from 0.15 to 0.3 mm , 3 i oio contained from 0.075 to 0.15 n-im and 3 i% below 0.075 mm.

2. A zinc chloride solution turned into a. obtain a zinc powder, ii, 5% grain from 0.3 to o, 6mm, 3% i o, 1 5 to 0.3 mm - pH-value of 4.9 and a cathodic current density of 98o A / m ° , contained 29.5% of o, o to 075, 1 5 mm and 27.2% of O, 075 mm. The rest was larger than 0.6 mm.

The grain fineness can be influenced by changing the current density, because. at higher current densities at the same pH value, finer powder is produced.

By using diaphragms, insoluble Anodes the anodic products, e.g. B. chlorine, from chloride solution; won. will.

Claims (3)

PATENT CLAIMS: i. Process for the production of zinc powder from zinc salt solutions, which may contain other salts, characterized in that at. one relatively high cathodic current density from goo to ioooA / m = 'and possibly at a slightly higher temperature, the acidity of the solution is within the limits of pH = 4.5 up to the pH value at which hydrolysis of the corresponding zinc salt occurs, z. B. with zinc chloride solutions up to about 5.8, is held, depending on the Acidity a zinc powder of different fineness is achieved. 2. Procedure, according to Claim i, characterized in that by adding salts with common Anion, e.g. B. in zinc chloride solutions of sodium chloride, with a simultaneous increase the conductivity the effective zinc ion concentration and / o: the pH value of the Solution is brought to the desired value. 3. The method according to the claims i and 2: characterized in that to influence the degree of fineness of the Zinc powder current density and / or temperature can be changed.