Silver is an inexpensive and valuable natural element used extensively in the manufacturing of coins, electrical equipments, photographic materials, electronics and jewelry. Although the metal is in high demand, silver mining and processing is expensive, less efficient and can cause depletion of silver reserves and increased environmental pollution. Silver recovery from jewelry scrap such as silver plates is an effective alternative for improving market supply of silver as the metal used in the making of silver plates is pure and of high quality.
Chemical Method For Silver Recovery
Wear the lab coat, put on nitrile gloves on the hand, protect your eyes with goggles and cover your face with a face shield before starting the procedure. Place the silver plate in a porcelain crucible and melt it using an acetylene torch. Cool the molten silver to form a silver ball.
Place the silver ball in a 50ml beaker and fill 3/4 of it with concentrated nitric acid in a fume hood. Cover the beaker with a 1000ml beaker turned upside down. Connect the beakers to a ventilation system and heat the acid to 176 degrees Fahrenheit. Toxic nitrogen dioxide gases released during the process are eliminated through the ventilation system.
Cool the acid solution and dilute it with distilled water. The volume of the distilled water should be three times the volume of acid. Upon standing, the solution appears yellow and slowly turns green.
Filter the solution using a Buchner funnel connected to a vacuum filtration flask. The filtered solution is called filtrate.
Take the filtrate in a beaker and add equal amounts of concentrated nitric acid and concentrated hydrochloric acid in a fume hood. Cover the beaker with a 1000ml beaker placed upside down. Attach the beaker to a ventilation system.
Heat the mixture on a hot plate until white silver crystals start to form at the bottom of the beaker. Place a copper wire inside the beaker and allow it to stand for 10 minutes. Pure silver will start precipitating on the copper wire.
Cool the acid solution and dilute it with distilled water. The volume of the distilled water should be three times the volume of acid.
Filter the solution using a Buchner funnel connected to a vacuum filtration flask.
Decant the filtrate. Rinse the white silver crystals with distilled water and dry in saw dust. Also, scrape off the silver precipitate from the copper wire using a wooden tongue depressor.
Estimate the silver precipitate using a weighing scale.
Remember to wear protective goggles, gloves, lab coat and face shield during the entire procedure. Vapors from acids are extremely corrosive and harmful to the lungs. Therefore, always use a fume hood when handling acids. Always keep a first aid kit at your side.
The silver recovery process using chemicals is extremely dangerous and should be handled only by professionals. Nitrogen dioxide generated during the process is an extremely poisonous gas and can cause instant death. Never inhale the gas.
- old silver plate image by Dumitrescu Ciprian from Fotolia.com