Leaching studies for tin recovery from waste e-scrap

Printed circuit boards (PCBs) are the most essential components of all electrical and electronic equipments,
which contain noteworthy quantity of metals, some of which are toxic to life and all of which
are valuable resources. Therefore, recycling of PCBs is necessary for the safe disposal/utilization of these
metals. Present paper is a part of developing Indo-Korean recycling technique consists of organic swelling
pre-treatment technique for the liberation of thin layer of metallic sheet and the treatment of epoxy resin
to remove/recover toxic soldering material. To optimize the parameters required for recovery of tin from
waste PCBs, initially the bench scale studies were carried out using fresh solder (containing 52.6% Sn and
47.3% Pb) varying the acid concentration, temperature, mixing time and pulp density. The experimental
data indicate that 95.79% of tin was leached out from solder material using 5.5 M HCl at fixed pulp density
50 g/L and temperature 90 C in mixing time 165 min. Kinetic studies followed the chemical reaction
controlled dense constant size cylindrical particles with activation energy of 117.68 kJ/mol. However,
97.79% of tin was found to be leached out from solder materials of liberated swelled epoxy resin using
4.5 M HCl at 90 C, mixing time 60 min and pulp density 50 g/L. From the leach liquor of solder materials
of epoxy resin, the precipitate of sodium stannate as value added product was obtained at pH 1.9. The Pb
from the leach residue was removed by using 0.1 M nitric acid at 90 C in mixing time 45 min and pulp
density 10 g/L. The metal free epoxy resin could be disposed-of safely/used as filling material without
affecting the environment.