High-tech metals germanium and gallium from the deep sea

Two met­als that are of great impor­tance for mod­ern high tech­nolo­gies are ger­ma­ni­um and gal­li­um. Both are impor­tant raw mate­ri­als for the semi­con­duc­tor indus­try, for fiber optic cables and for pho­to­voltaics. They are thus essen­tial com­po­nents for shap­ing elec­tro­mo­bil­i­ty and the ener­gy tran­si­tion. Using new ana­lyt­i­cal meth­ods, the research group “Crit­MET: Crit­i­cal Met­als for Enabling Tech­nolo­gies” led by Dr. Michael Bau, Pro­fes­sor of Geo­chem­istry at Jacobs Uni­ver­si­ty in Bre­men, Ger­many, has stud­ied the dis­tri­b­u­tion of ger­ma­ni­um and gal­li­um in iron-man­ganese crusts in the deep sea. The results have now been pub­lished in two renowned journals.

In 2020, 66 per­cent of glob­al ger­ma­ni­um pro­duc­tion came from Chi­na; for gal­li­um, Chi­nese mar­ket dom­i­nance is even greater at 97 per­cent. Because of this depen­dence and the asso­ci­at­ed risks to raw mate­r­i­al sup­plies, both the U.S. gov­ern­ment and the Euro­pean Union have includ­ed these met­als in their lists of crit­i­cal raw mate­ri­als. A great deal of effort is being put into search­ing for deposits around the world, espe­cial­ly since demand for these met­als is expect­ed to increase dra­mat­i­cal­ly in the com­ing years. But the search for raw mate­ri­als is prov­ing dif­fi­cult, and so uncon­ven­tion­al deposits are also com­ing under the spotlight.

One way to secure the world’s sup­ply of crit­i­cal raw mate­ri­als could be deep-sea min­ing. Although it is con­tro­ver­sial on the one hand because of its unclear impact on the envi­ron­ment, on the oth­er hand it could sup­ply a vari­ety of met­als with­out which, for exam­ple, cli­mate pol­i­cy goals such as the ener­gy turn­around can­not be real­ized. Recy­cling is not yet a solu­tion for crit­i­cal raw mate­ri­als in the fore­see­able future, as these met­als have not yet been used in large quantities.

The research group, which is based at Jacobs Uni­ver­si­ty in the Earth and Envi­ron­men­tal Sci­ence and Tech­nol­o­gy study pro­gram, is inves­ti­gat­ing both poten­tial raw mate­r­i­al sources and the envi­ron­men­tal behav­ior of crit­i­cal raw mate­ri­als such as rare earths, ger­ma­ni­um and gal­li­um. The arti­cles now pub­lished sum­ma­rize the research find­ings of the group led by Katha­ri­na Schi­er and David Ernst, Pro­fes­sors Michael Bau and Dieter Garbe-Schön­berg, and nation­al and inter­na­tion­al collaborators.

The iron-man­ganese crusts stud­ied form very slow­ly on the seafloor of the deep sea. In the process, they trap and accu­mu­late a vari­ety of met­als dis­solved in sea­wa­ter. Using new ana­lyt­i­cal meth­ods, the work­ing group suc­ceed­ed in reli­ably deter­min­ing the con­cen­tra­tions of gal­li­um and ger­ma­ni­um in such crusts. The results are of great impor­tance for basic geo­chem­i­cal research, because they help to bet­ter under­stand the trans­port of met­als from the main­land to the oceans.

For applied research, how­ev­er, they are rather sober­ing: the con­tents of gal­li­um and ger­ma­ni­um are too low to make the crusts a source of raw mate­ri­als for these met­als in the fore­see­able future. But the results also have a pos­i­tive side, because the researchers were able to show how effec­tive­ly gal­li­um and ger­ma­ni­um are attached to iron oxides and that they can thus be effec­tive­ly removed from the water and thus from the envi­ron­ment. As all crit­i­cal met­als are released into the envi­ron­ment, and thus into rivers, lakes and ground­wa­ter, in ever-increas­ing quan­ti­ties due to dra­mat­ic increas­es in their use, meth­ods to pre­vent this or to clean up the water are becom­ing increas­ing­ly impor­tant. The use of iron oxides could be a sim­ple and rel­a­tive­ly inex­pen­sive solu­tion here for ger­ma­ni­um and gallium.