Case Study: Metal Recovery from E-Waste

• Pyrolysis and gravity recovery of metals from e-waste

With the ever-increasing use of electronic devices around the world such as computers, mobile phones and automation components there is an ever-increasing amount of electronic waste that is generated. Sepro has worked closely with electronic waste recyclers to develop innovative processes to recover gold and other metals, to produce metal concentrates which can be sold directly to refiners at a profit and to generate an environmentally clean waste stream that is free of toxic chemicals.

• Malleable metals like gold and copper have a tendency to smear, making direct grinding and gravity concentration difficult.
• Chemical leaching can be expensive and it can be difficult to separate various metals once they’re in solution.
• Flame retardants used on circuit boards can create toxic chemicals when heated, making thermal treatment difficult and dangerous.
• E-waste is typically sold to smelters which have to employ sophisticated gas scrubbing technology and are unable to buy the metals from e-waste at full value.

• Sepro was approached by a team of pyrolysis experts ask asked to develop an efficient method for recovery of metals from pyrolyzed e-waste. Pyrolysis is the process of applying high temperature in an inert atmosphere so that materials decompose rather than burn.
• Proper pyrolysis of e-waste decomposes the harmful circuit board chemicals as well as the fibreglass adhesives while melting solder and releasing the precious metals. All this is done while the gasses are captured and reused in the heating process.
• Sepro developed a separation process consisting of a brief milling stage followed by screening and two stages of gravity concentration. The process is simple, inexpensive and surprisingly effective.

• The process produces a coarse copper concentrate made up of foils from between the circuit boards as well as a fine metal concentrate.
• Gold recovery was >98%