New Haven – A team of researchers at Yale University in New Haven has investigated the extent to which metals and semimetals can be recovered from wastewater as important raw materials. The question is which elements and processes are technically and economically suitable.
Computers, smartphones and other electronic devices contain a variety of different elements. These include copper, silicon, lithium, gold, platinum or rare earths. Often the mining of metals from their ores is very costly or geological deposits are limited, so their recovery is becoming increasingly important. Scientists from Yale University in New Haven, Connecticut, present possible methods in an article published in the journalNature Water.
A classic process is the deposition of a metal on the surface of an electrode. In this electrochemical process, an electrical potential is applied between two electrodes so that the positively charged metal ions migrate to the cathode and deposit there. This is an established process, especially for the recovery of copper.
Newer systems for separating metal ions use capacitive electrodes. After the known deposition of the metal, the solution is changed and during an appropriate discharge process, the metal ions now accumulate in the new solution. Membrane processes made of special plastics are also used to separate metal ions from wastewater. The pores of these membranes are permeable only to certain ions. To achieve membrane separations between similar metals, materials such as liquid crystals or porous frameworks are currently being investigated.
Since metal recovery from wastewater is very costly, it is only worthwhile to focus on metals that are geologically scarce and at the same time critical to important industries. eb