Recovery of Tin Metal from Soldering Alloy by Electro Refining Process

Electro refining is a unique method for the extraction and recovery of pure metal from their alloys and it is an environmentally benign process. This method has been utilized worldwide to get pure form of metals from an impure alloy.  The process involved on the extraction of tin from the secondary sources of alloy and also the separation of some noble metals by using Electro refining and cementation processes.

The soldering dross, a mixed alloy contains certain amount of copper, lead  and silver, is used as the raw material. Due to less purity, the above alloy does not have high cost in the market and the presence of minor constituents of silver, gold and lead cause difficulties in the direct usage in electronic and food industries. Taking in to account, the alloy has to be refined and to extract pure metals such as tin and silver from the alloy. The method for the separation of these valuable metals such as Sn and Ag  is being done by electro refining process.

For the separation of pure metals, the soldering alloys were made in to sheets and  they were used as electrodes (anodes). Then the electro refining process was carried out at controlled electrochemical potential and the pure metallic tin was deposited at the cathode. The slime accumulated at the anode were collected and leached with suitable acids. The electrolyte solution contained the metals like silver and other valuable metals were separated by cementation process.

1. Tin 

• Tin is an important metal which is mostly used for tin plating on mild steel substrate and in electronic industries. It acts as a protective coating in acidic environment. The coated steel foils and sheets are used in keeping food items and beverages in canes and drums.
• Tin is also used to produce low melting soldering alloy which is widely used in electrical and electronic industry.
• Tin is used as an alloying element in the preparation of a variety of bronzes and copper based alloys. They are used in the fabrication heat exchanger tubes, heat transfer equipments, architectural and metallurgical applications.

2. Lead

• Lead is mostly used as electrode material in lead acid batteries alloyed with tin, antimony and silver. It is also used as a soldering alloy with tin and silver etc.
• Lead and its alloys are also used in the fabrication of tubes, valves and sanitary wares for the transport of saline and corrosive liquids.

3. Silver

• Silver is mostly used in chemical industry, photography, ornamental items, Jewelries and soldering alloy in electronics.

• Reutilization of tin for tin plate and electronic industries and reduce the import of tion from aboard.
• Silver is recovered it can be used jewelry and electronics.
• The above process is low cost and eco-friendly