Recovering precious metals from electronic scrap and catalytic converters from autos has become more profitable than ever before. That may explain why more and more specialized “niche” recyclers and refiners have sprung up and the sector has really surged over the past several years globally.
In a typical printed circuit board (PCB), maybe 2% of the weight is gold, 18-22% copper and small traces of silver, palladium and iron. M&K Recovery Group in Boston, has been recovering precious metals from electronic wastes for the last 30 years.
M&K uses a chemical refining method to recover gold, silver and platinum group metals from encapsulated and clad materials, and a cyanide strip method for gold-plated scrap products. Both processes are zero-discharge and emission-free.
In electronics recycling, the primary sources of precious metals are found in PCBs and integrated circuits (ICs) and vary in yields depending on size and type of the board or chip. The highest yields come from personal computers, laptops and cell phones in the form of motherboards, main boards, video and audio boards, network cards and related PCBs and ICs. Lower value PCBs are found in monitors, amplifiers, DVD players, printers, speakers, VCRs, MP3 players, cameras and the like. These usually contain copper and lead, but in much lower quantities of precious metals than computers.
After an electronic unit is manually stripped, PCBs and ICs and other precious metal-bearing components are set aside. An alligator shearing machine is used to trim off small precious metal-bearing pieces from PCBs such as ICs, fingers, connectors, plugs and pins. The small pieces are sent through chemical treatment process where the precious metals drop off the PCB fiberglass substrate and later cast into bars. The stripped PCB fiberglass is collected into 25,000 pound lots and sent out to a smelter where it is burned and scrubbed to remove and recover copper. There are scant amounts of precious metals in e-wastes, but more in catalytic converters.
PMR Catalytic Converter Recycling in Quebec specializes in recycling CCs the first step is to “decan” or remove the auto catalyst materials from the whole steel converter unit. This involves shearing open the steel or stainless steel case to release the bead or honeycomb ceramic biscuits. Since the recovery value is in the Platinum Group Metals (PGM) that coat the ceramic catalyst material, all the dust and small pieces are collected. The catalyst material is then crushed and milled into a uniform powder which is then assayed to determine the precious metal content.
Decanned catalysts are refined in submerged arc furnaces where the electrode tips are buried in the slag-charge and arcing occurs through the slag between a matte and an electrode. After the catalyst material is refined in the arc furnace, the extracted metal is called “PGM alloy” and it contains approximately 10% precious metals. The remaining ceramic material is of negligible value and is used for road fill. PGM alloy is sent to chemical refineries for final processing into 99.99% pure platinum, palladium and rhodium sponge. Techemet’s smelter generates no waste streams, nothing that is processed is discarded and everything is recycled.
Elsewhere in Brazil using pieces from all sorts of useless equipment, students at the Computer Recovery Centre in Porto Alegre have put 1,700 computers into operation in three years.
Rafael de Vasconcelos a student has transformed an old computer screen into an illuminated sign. “It took us two months to map out the electronic part, and then we plugged in the computer’s parallel port and made a programme to post words and letters,” he explained. The wooden parts of the slot machines will also be used to make stools, decorations and tables, in a new project this year to create new jobs and income.
In the back of CRC, electronic waste that cannot be returned to technological use is turned into art. The cover of an enormous, outdated IBM computer becomes a graffiti-covered work of art with an Easter theme. From its metallic parts emerged small figures of soccer players, painted and set in bases, which are used as trophies for this popular sport. When there are materials that CRC cannot re-use, the centre itself makes sure they are properly disposed of. Still in its early stages, a market is developing in Brazil in which companies collect electronic waste that comes from computers, electronics and cell phones.Sources: American Recycler/IPS Newsletter