Abstract: The present paper reports a new fluoride-free and energy-saving lead electrolytic refining process in order to solve the serious problems of the existing Betts lead electrorefining process, such as low production efficiency, high energy consumption and fluorine pollution. In the process, a mixed solution of perchloric acid and lead perchlorate (HClO₄-Pb(ClO₄)₂) with the additives of gelatin and sodium lignin sulfonate is employed as the new electrolyte. The cathodic polarization curves show that HClO₄ is very stable, and there is no any reduction reaction of HClO₄ during the electrolytic process. The redox reactions of lead ions in HClO₄ solution are very reversible with an ultrahigh capacity efficiency, so the HClO₄ acts as a stable support electrolyte with higher ionic conductivity than the traditional H₂SiF₆ electrolyte. The results of the scale-up experiments show that under the optimal conditions of 2.8 mol·L^-1 HClO₄, 0.4 mol·L^-1 Pb(ClO₄)₂ and electrolysis temperature of 45℃, the energy consumption is as low as 24.5 kW·h·(t Pb)^-1, only about 20% of that by Betts method at the same current density of 20 mA·cm^-2, and the purity of the refined lead is up to 99.9992%, much higher than that specified by Chinese national standard (99.994%, GB/T 469-2013) and European standard (99.99%, EN 12659-1999).

Key words: Lead refining, Perchloric acid, Fluoride-free, Electrorefining process

摘要： The present paper reports a new fluoride-free and energy-saving lead electrolytic refining process in order to solve the serious problems of the existing Betts lead electrorefining process, such as low production efficiency, high energy consumption and fluorine pollution. In the process, a mixed solution of perchloric acid and lead perchlorate (HClO₄-Pb(ClO₄)₂) with the additives of gelatin and sodium lignin sulfonate is employed as the new electrolyte. The cathodic polarization curves show that HClO₄ is very stable, and there is no any reduction reaction of HClO₄ during the electrolytic process. The redox reactions of lead ions in HClO₄ solution are very reversible with an ultrahigh capacity efficiency, so the HClO₄ acts as a stable support electrolyte with higher ionic conductivity than the traditional H₂SiF₆ electrolyte. The results of the scale-up experiments show that under the optimal conditions of 2.8 mol·L^-1 HClO₄, 0.4 mol·L^-1 Pb(ClO₄)₂ and electrolysis temperature of 45℃, the energy consumption is as low as 24.5 kW·h·(t Pb)^-1, only about 20% of that by Betts method at the same current density of 20 mA·cm^-2, and the purity of the refined lead is up to 99.9992%, much higher than that specified by Chinese national standard (99.994%, GB/T 469-2013) and European standard (99.99%, EN 12659-1999).

关键词: Lead refining, Perchloric acid, Fluoride-free, Electrorefining process