Many of us have not heard about Tellurium (Te), but the element is critical for solar panels, photo-voltaic cells, electronic devices, semiconductors, optical discs, various radiation ray detectors and lenses or fibers. It is added to stainless steel and copper to improve their application.
Global consumption of Te is estimated as follows: for photo voltaic cells — 40 percent, thermoelectric power generation — 30 percent, metallurgy – 15 percent and various other applications — 15 percent. Universally more than 90 percent of Te — a rare earth mineral — is produced from anode slimes collected from electrolytes formed in the copper refining process.
The anode slimes of copper and lead refineries normally contains about 2-23% tellurium. The estimated worldwide reserve of tellurium in copper resources alone has been estimated at 24,000 ton. An estimated total of Te is between 450-500 tons per annum.
The Indian Center for Scientific and Industrial Research (CSIR) developed new technology to recover tellurium easily from anode slimes. The CSIR lab, the Institute of Minerals and Materials Technology (IMMT), developed a process where Te can be extracted from the anode slime along with copper and lead through alkaline leaching-electrowinning route.
BK Mishra, director of IMMT, considers it an important innovation. According to Mishra, the IMMT has also created the basic engineering process package to produce 60 tons per annum of Te with a capital investment of around 2.5 million US dollars.
The US patent on the IMMT process for the recovery of Te from anode slime was published by the US Patent Office recently. The CSIR-IMMT is continuing efforts to transfer the technology to other primary products units of India such as Hindustan Copper Limited (HCL) and Sterlite Industries.
He is hopeful the present efforts upon successful implementation will transform India from an importer (about 0.55 million USD was spent in 2015 by India for imports on Te) to a major exporter of Te.