Method for reducing content of tetravalent stannum in stannous mono-sulphate

Abstract

The invention discloses a method for reducing the content of tetravalent stannum in stannous mono-sulphate. The method for reducing the content of the tetravalent stannum in the stannous mono-sulphate comprises the following steps that a stannum granular layer is laid in the bottom of a stannous mono-sulphate electrolytic tank; a deoxidant is added into a dilute sulphuric acid, and the treated dilute sulphuric acid is obtained; the treated dilute sulphuric acid is added into the stannous mono-sulphate electrolytic tank till the liquid level of the treated dilute sulphuric acid is higher than a cathode by 2-4 cm, and the voltage of the electrolytic tank is controlled to be lower than 2.4 V; when the content of stannum ions in an electrolyte at the bottom of the stannous mono-sulphate electrolytic tank is greater than or equal to 85 g / L, the electrolyte is discharged out of the tank from an outlet, and the treated dilute sulphuric acid is supplement into the tank to maintain the liquid level of tank liquid to be an original height while the electrolyte is discharged; when the content of the stannum ions in the electrolyte at the bottom of the stannous mono-sulphate electrolytic tank is decreased to 80 g / L, discharging of the electrolyte and supplementing of the treated dilute sulphuric acid are stopped; and the electrolyte is subjected to condensation crystallization, obtained crystals are eluted by using an eluting agent and then dried, and the stannous mono-sulphate is obtained.

Description

technical field [0001] The invention belongs to the field of preparation of stannous sulfate, and in particular relates to a method for reducing the content of tetravalent tin in stannous sulfate. Background technique [0002] Stannous sulfate is a white or light yellow crystalline powder, which can be dissolved in water and dilute sulfuric acid. It is widely used in many industries such as acid electroplating of metals, alloys and non-metallic materials, electrolytic oxidation and coloring of aluminum alloys, hydrogen peroxide remover and mixed with nickel salts as sealing agents, and printed circuit boards. [0003] The stability of divalent tin in stannous sulfate is poor, and it is easily oxidized to tetravalent tin by oxygen in the air. The presence of tetravalent tin will make the stannous sulfate product yellow and harden, and shorten the shelf life of the product. The accumulation of tetravalent tin in use will cause the aging of the bath, the increase of precipitat...

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Problems solved by technology

Therefore, the tetravalent tin content seriously affects its storage validity period and product appearance

[0004] Domestic scholar Wei Qing (Journal of Wuyi University, 2000, 14, 55-59) once reported that the current density needs to be controlled to suppress tetravalent tin when preparing stannous sulfate in the laboratory, but this method is obtained by intermittent electrolysis under laboratory conditions. In the process of large-scale industrial production, the anode area is constantly changing, and the current density is difficult to accurately control, which is not suitable for large-scale continuous production; The impact of oxidation into tetravalent tin, but the paper does not consider the impact of dissolved oxygen in the electrolyte on the generation of tetravalent tin; Chinese patent 201410846701.7 describes the method of adding organic antioxidants to prolong the shelf life of stannous sulfate products, but this method is added to the product Adding foreign matter affects product quality; Du Jianzhong (Food Science: 2005, 26, 397-399) introduced the test method of tetravalent tin

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