Tin recovery from lacquered tinned iron sheet scrap - by heating, leaching with sodium hydroxide and electrolysing

摘要

Tin is recovered from lacquered tinned iron sheet scrap by heating the scrap at 230-300 degrees C for 10-35 min. then leaching for 30-60 min. in a soln. contg. 150-250 g/l of NaOH and 20-50 g/l of NaNO3 at 100-105 degrees C, and subjecting the resulting sodium stannate soln. (Sn content 30-80 g/l NaOH 60-100 g/l and Na2CO3 10-20 g/l) to a two-stage electrolysis at 80-90 degrees C. In the first stage the current density is 100-150 A/m2 and in the second stage 50-70 A/m2. The metallic tin is washed with water, and the washing water contg. 10-30 g/l of Sn is subjected to electrolysis at a current density of 50-100 A/m2 at 80-90 degrees C. The degree of tin recovery is increased compared with the known processes (by 30-40% in the case of one -side lacquered sheets, and by 90% in the case of two-side lacquered sheets). Cheap chemicals are used.