New method removes heavy metals like uranium from water effectively
JOENSUU, FINLAND: Researchers at University of Eastern Finland have found a new and efficient method for the removal of uranium and other heavy metals from water. A Finnish chemicals company, Chemec Ltd, has purchased the rights in the invention and will introduce the method to the commercial markets. Binding metal ions to a solid material, the CH Collector method can be used within the mining industry, and also in the removal of emissions caused by the chemicals and metals processing industries.
Chemec’s CH Collector method is a potential solution to issues relating to the dangers and recovery of uranium. Uranium is a mildly radioactive and poisonous heavy metal, which is naturally occurring in some parts of the Finnish bedrock. When mining other metals such as gold, uranium may be present as an impurity in mining wastewaters. A complete removal of uranium from solutions is difficult due to the fact that uranium takes different forms depending on the acidity of the solution. The removal of other heavy metal emissions such as lead, mercury, cadmium and zinc from waters is also challenging.
Traditionally, metal ions are removed from solutions with the help of chemical coagulants or ion exchangers, which usually require adjustments to the solution’s pH or significant extra energy in order to function efficiently. Research group of Jouko Vepsalainen, Professor, University of Eastern Finland has developed a new method enabling an efficient removal of metal ions from solutions without the need to use any auxiliary substances. The CH Collector method is based on the use of a solid material which collects metal ions directly from the solution. University researcher Petri Turhanen had a central role in the development of the new method.
The solid material developed by the researchers belongs to the aminobisphosphonate family, which are also used in, for example, osteoporosis medications. The invention is unique, as no other metal absorbents working on the same principle are in use. “Ion channels are formed inside the material, in which the metal ions are collected from the solution. Unlike traditional methods, the CH Collector method also allows the recovery of metals occurring in very small concentrations,” explained Professor Vepsalainen.
The new material collects metal ions directly from the solution. The collection of metals does not require a separate precipitation step or any adjustments to the solution’s pH. For instance, an efficient recovery of uranium is possible from a very wide pH range and even in cases where the solution is rich in other naturally-occurring metal ions such as sodium, magnesium or calcium.
The new method enabled practically a complete removal of uranium from water samples taken from Finnish mines. There was no need to pre-process the samples even though they contained very high concentrations of other metals possibly disturbing the process. The efficiency of the method was also tested on an ore sample that contained scandium. The sample was dissolved and then treated with the new material. The two-phase process made it possible to recover 98 per cent of the scandium.
The new method is well-suited for the removal of metals not only from the wastewaters of the mining industry, but also from the wastewaters of the metals processing and chemical industries, which may contain heavy metals and uranium in particular.
R&D activities around the CH Collector method will continue. Chemec and the University of Eastern Finland are participating in Tekes’s Green Mining Programme which seeks to enhance the selective recovery of metals and to create a novel, optimised concept for the treatment of mining industry wastewaters and process waters.
“The goal is to create a toolkit for the selective recovery of different metals with the help of bisphosphonates. In the future, these kinds of methods could enable a targeted recovery of rare and valuable earth metals from complex mixtures containing metal ions,” said Professor Vepsalainen.