Hexavalent chromium continues to contaminate water sources around the world, with one US company fined just this February for having put employees at risk. Hexavalent chromium is considered to be extremely toxic, especially when inhaled or ingested, and its use is regulated in Europe and in many countries around the world. It is thought to be genotoxic, leading to DNA damage and the formation of cancerous tumors.
Now, chemists at EPFL are developing energy efficient processes for removing contaminants, this time hexavalent chromium, from water. The results are published in the Journal of Materials Chemistry A.
The EPFL scientists are developing sponge-like materials that can collect specific substances from solution. Their materials are actually crystals, called metal-organic frameworks (MOF), and the scientists are tailoring these crystalline structures to capture a particular substance.
The materials are extremely porous and the contact surface area contained in one gram of these MOFs can be as large as that of a football field. The target substance then enters these pores and sticks to the internal surface area in a process called adsorption.
The scientists have previously shown that their materials can efficiently adsorb other substances dissolved in solution, like gold, mercury and lead. For instance, 1 gram of MOF yields almost 1 gram of gold. Now the team has demonstrated the extraction of hexavalent chromium from water. With hexavalent chromium, a relatively light substance, the MOFs can extract approximately 208 milligrams per gram of MOF. Also, if you shine light on the MOF, it then transforms the highly toxic hexavalent chromium into a relatively nontoxic trivalent chromium.
Further developments are required in order to implement the technology for decontaminating water outside of the laboratory.
News Source: EPFL
