Materials Technology

DiaKhem's original foothold into the mining industry was on the basis of the unique properties its resins offer. With the exception of gravity recovery of gold and silver, the extraction of precious metals from ores is a hydrometallurgical process. To that end, the separation of the metals from the processing stream is an inherent step in the operation. Whether the metals targeted for removal are the focus or the waste, DiaKhem can offer a solution.

Often, base metals such as copper and zinc are present in the streams, competing with the precious metals for ligands. In the necessary pre-concentration step, often activated carbon adsorption, these base metals also compete for adsorption sites. DiaKhem resin has been proven to specifically adsorb these base metals in solution at the exclusion of a majority of the precious metals. This means it could be immediately utilized to increase the extraction efficiency of a process that is already established.

An environmental concern is also raised by the presence of base metals in tailings ponds. Cyanide will naturally, though slowly, degrade in the environment. However, when these base metals are present in the waste, the cyanide that is bound to them will replace the cyanide that decays. In that way, these metals act as cyanide reservoirs. Again, these metals and the cyanide that is bound to them can be effectively removed by DiaKhem resin.

Based on their chemistries, these patented resins exhibit preferences for the adsorption of certain metals. One particular resin will absorb nickel from solution and will also adsorb zinc at nearly the same quantity from solution. However, in a solution of both metals, the resin can pick up almost exclusively nickel; attractive if separation is desired. Because of the chemistry of this resin, pH provides another "knob to turn". Thus, at another pH, the resin will pick both metals indiscriminately; useful if the adsorption of both species is what is desired.

Nickel mining, for example, often involves a product stream of nickel and cobalt, which are notoriously difficult to separate. While there are methods to achieve this goal, they are either expensive from the cost of reagents, or expensive due to the cost of energy-intensive steps. It would be much simpler if a selective resin were able to remove one of the species.

Environmental Remediation

Any industrial process will generate waste and corporations who seek to be good stewards of the environment can often minimize waste before the fact by intelligent design. Unfortunately, this consideration has not always existed, and in some places it still does not. Whether the reason is a lack of foresight or simply ignorance of matter, the result is the same. Run-off from long-abandoned operations can continue to threaten environmental quality of surrounding regions and without a solution such as DiaKhem, producers may strive, but just miss, meeting environmental requirements. In the United States, recognition of these problems has resulted in both regulation of current industries and identification of problem areas. In some under-developed countries, these problems are still ignored.

Whether it is heavy metals that must be removed from an effluent stream or holding ponds in need of remediation, the high capacity of DiaKhem resins can be harnessed to effectively remove these pollutants. The presence of metals is not the only potential threat, but cyanide, mercury and arsenic are also hazardous at very low levels. In addition to its appetite for various metals, it has been found that DiaKhem resin will adsorb free cyanide ions, making it especially appropriate for mining applications.

New Competency

In some sectors of the mining industry, radiation exposure is a critical occupational health issue. DiaKhem Technologies, LLC has recently developed a process for reducing and/or eliminating the presence of radioactive metals from mine tailings.

Process Technology

DiaKhem has experience both in the chemistry and the process engineering aspects of precious and base metals extraction. While there are very basic approaches - cyanide, for example - not all ores respond to this kind of leaching. Additionally, cyanide is an increasingly frowned-upon lixiviant, particularly in the United States. It is expected that the number of ores that can be processed in traditional ways will decline as those sources are depleted. Alternative leaching, potentially mine-specific techniques, will be necessary. The rise in prices will also increase the probability that previously treated ores are revisited for gold that is economical today. To that point, DiaKhem has recently developed an extraction approach for a previously processed zinc ore. Though the ore contained gold, it did not respond to cyanidation so once the zinc was extracted, the ore was simply discarded. In tests to date, DiaKhem has found a relatively simple method that can effectively remove the gold. DiaKhem has also uncovered processing aids that can be used to increase the effectiveness of leaching from traditionally difficult clay-based ores.

DiaKhem has also begun research into new hydrometallurgical techniques for treating base metal ores that may or may not also contain precious metals. The concept behind this technology is to continually drive the extraction toward an equilibrium state, harnessing Le Chatelier's Principle. The objective is to use chemistry involved is more innocuous, and more selective, than the traditional acid or cyanide based systems. Finally, for processes that are already in place, DiaKhem has the engineering background to understand the overall process, taking into account factors like leaching kinetics, and to optimize the extraction output by improved selection of operating parameters.