Dissolution of PCB Metals Using Surfactant-Producing Bacteria

PCB metalsAs PCBs experience accelerated advancements leading to improved and more affordable materials used in pcb fabrication, the problem with eliminating electronic scrap safely and cheaply continues to be problematic. In fact, electronic scrap currently represents one of the fastest-growing types of waste in the world, with over 50,000 tons of PCB scrap generated annually in the US and the UK and only about 20 percent of that scrap subjected to various recycling techniques.

PCB fabrication involves the use of many precious metals, copper, nickel, lead, polymers and ceramic compounds and PCB scrap is primarily incinerated or simply disposed of through landfills. Toxic properties of PCB components are associated with brominated flame retardants, heavy metals and PVC plastics that contaminate soil and ground water. Alternately, incinerating PCBs allows the release of byproducts into the air, such as furans, dioxins, aromatic hydrocarbons and polybrominated organics emitted by burning plastics, epoxy resins and BFRs.

PCB metalsBioleaching Technology Bioleaching is a relatively new technology addressing the safe elimination of PCB waste by utilizing specialized bacteria to corrupt metallic substances from their ores. Advantages of environmentally friendly bioleaching over incineration or landfill disposal include its mechanic simplicity, reduced energy output and minimal requirement for skilled labor.

Surfactant bacteria are microorganisms capable of decreasing the surface tension surrounding liquids that prevent them from being degraded and eventually, eliminated. Studies evaluating the viability of toxic PCB scrap elements--specifically, cadmium, lead, chromium, zinc, nickel and copper--being effectively dissolved by applying biosurfactant bacteria cultures combined with suphur-oxidizing bacteria found that all these metals were removed from PCB scrap, with lead showing the most resistance to the process (less than 0.5 percent). According to studies, aerating bacteria cultures treated with biosurfactant and sulphur and increasing temperature during the process further instigated the dissolution of all PCB metals.

PCB metalsBioleaching Instead of Recycling Saves Time, Money and the Environment Not everyone recycles PCBs and other electronic devices. Instead, they are sent to landfills, bypassing recycling plants where PCBs are manually dismantled and their parts reused, if possible. Additionally, components made of toxic substances may be only partially removed in recycling facilties, especially when small waste electrical and electronic equipment (WEEE) is involved. Unfortunately, this also means that significant amounts of potentially hazardous waste are forwarded to plants where mechanical crushing techniques are used, leading to significant distribution of ground and water pollutants and reduced quantities of valuable, recycled materials.