Fluosilicate electrolyte

For electrolytic refining, an electrolyte is required that has a reasonable lead solubility, is stable, has a high electrical conductivity and will yield a smooth compact deposit of lead. Various organic acids have good lead solubility and conductivity but tend to be unstable. It was found during the early development of the process that fluosilicic acid, fluoboric acid and sulfamic acid were most suitable and fluosilicic acid was the least costly. Sulfamic acid systems were also used, but showed instability at high current densities. Consequently, most electrolytic refining operations are based on a fluosilicate electrolyte. 

Betts An electrolytic process for refining lead and recovering silver and gold from it. The electrolyte is a solution of lead fluosilicate and hydiofluosilicic acid. The other metals collect as a slime on the anode and are retained there. Developed by A.G. Betts in 1901, first operated at Trail, British Columbia, in 1903, and now widely used in locations having cheap electric power. 

Electrolytic refining of lead bullion is commonly employed in many modern plants to obtain high purity grade metal. Various separation processes for removal of individual metals are not required. In such refining (Betts process), a solution of lead fluosilicate is used as an electrolyte, while the anode consists of impure lead bullion and the cathode constitutes a thin sheet of pure lead. Lead deposits on to the cathode during electrolysis. Impurity metals remain undissolved and attached to the anode, forming a slime which may be removed after electrolysis and treated for recovery of these metals. 

Betts process. An electrolytic process for removing impurities from lead in which pure lead is deposited on a thin cathode of pure lead from an anode containing as much as 10% of silver, gold, bismuth, copper, antimony, arsenic, selenium, and other impurities. The electrolyte is lead fluosilicate and fluosilicic acid. The scrap anodes and the residues of impurities associated with them are either recast into anodes or treated to recover antimony lead, silver, gold, bismuth, etc. 

Electrolytic Section Cell room foundation H+, OCl , mechanical/ rubber-lined steel Concrete coated with fluosilicates of Zn or... 

In this case batteries are fully separated, metallic components are simply melted and drosses from that operation together with desulfurised battery pastes are subjected to hydrometaUurgical extraction of lead followed by electrowinning from the leach solution. As detailed in Chapter 9, solutions used for lead electrolytes are fluosilicates as used in the Betts refining process, fluoborates and chlorides. 

The disadvantage of the use of a chloride system is the production of lead powder or sponge at the cathode rather than a dense deposit as with fluosilicate and fluoborate electrolytes. In this case such an output would facilitate recycle to the leaching stage, but the bulk of the cathode deposit must be compressed by briquetting or roll extrusion prior to melting to minimise oxidation. 

The electrolyte is a solution of lead fluosilicate and free fluosilicic acid. The lead concentration is normally in the range of 75 to 120 g/L and the free fluosilicic acid 65 to 100 g/L. The total equivalent fluosilicic acid is close to twice the free acid amount. 

Electroplating Application of a coating by use of electric current. An anode (-I-) and cathode —) is immersed in an aqueous medium (electrolyte) through which current is passed. For instance, in chromium plating the electrolyte contains chromic acid, sulfuric acid, sodium fluoride and sodium fluosilicate. The bath is operated at 90° C at current densities up to 30A/cm. ... 

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