The methods mainly used are;
A) Chemical method and
B) Electrolytic method.
Note: Information and process recovery details are mentioned by doing research on related field to the best of our knowledge.
So, request to all is to be cautious during the recovery since you are dealing with all type of basic as well as hazardous chemicals. So you will be held responsible if the method goes wrong. So take care when you proceed.
A) CHEMICAL METHOD:
1) Determine gm/lit of fixer solution using Silver Estimation Paper (Litmus paper).
2) Take 5 lit. Fixer Solution and to it add approximate amount sodium sulphide (Na2S) and caustic soda (Noah). Using common ion effect we can remove silver from it.
3) Using the proper proportion as per the upper estimation add proper amount of sodium sulphide (Na2S) and caustic soda (Noah) to all the solution.
(Around 200g to 250g of Caustic soda & same amt of Sodium Sulphide for 5ltrs of Fixer)
4) We get black residue at bottom due to reaction and the solution at the top becomes yellow in color. Filter the solution and retain the black residue. Dry the residue using filter paper. Get it melted and molded into bricks by Goldsmith. While melting we can use Borax / Na2CO3 / CaCO3 etc. In this way shiny silver metal is recovered from black silver residue.
B) ELECTROLYTIC METHOD:
Silver can be extracted from hypo using semi automatic or fully automatic machines. The most appropriate model of such machine can be selected according to our working and financial capacity.
Anode used in such machine is made up of carbon or graphite and Cathode is mostly made up of large stainless steel or other alloy plates. By filling the waste solution into the machine and connecting to the electricity mains, machine starts working. Silver present in the solution starts depositing over silver collecting plates.
The machine should be operated till all the silver present in the solution gets deposited on cathode plates as black flakes. The process time can be estimated by checking silver availability using silver estimation paper time to time during operation.
It is not essential to attend the machine continuously while operating. Machine can be operated with full tank / half tank /quarter tank filled. No special training, industrial process, power, load line or license is required for this operation.