Mechanically activated rutile and its sorption properties with regard to gallium and germanium

To improve sorption properties, titanium dioxide in the rutile form was mechanically activated (MA) in the high energy planetary ball mill. The resulting material was analyzed by an X-ray diffraction and BET methods, the authors studied its capacity to sorb gallium (III) and germanium (IV) from a water solution. It is shown that during MA a crystal modification of titanium dioxide is not changed, average sizes of rutile crystal grains decrease to 15 nm within 150 min of MA. It is found that MA of rutile combined with ultrasonic machining significantly increases a sorption degree of germanium up to 97% (рН 4–10) and gallium up to 99% (рН 3–4) from artificial water solutions, containing 5 mg/dm3 of gallium and germanium. The authors determined the sorption capacity of 5 mg/dm3 of gallium at рН 3, when the solution contains 2- to 200-fold excessive shares of aluminum (III), lead (II), zinc (II), iron (III), as well as the sorption capacity of 5 mg/dm3 of germanium at рН 6 and the same excessive shares of lead (II), zinc (II), and iron (III). All metals under study, excluding iron, have a minor influence on the sorption capacity of gallium and germanium, it is 90%. Iron in solutions decreases the sorption capacity of germanium almost by twice, and almost fully prevents from gallium sorption. The authors obtained gallium and germanium sorption isotherms. They are adequately described by the Tot equation, indicating the sorbent surface energy heterogeneity. The sorption capacity limit value, obtained for mechanically activated rutile by the Tot equation, for germanium is 38.7 mg/g, for gallium is 27.4 mg/g, exceeding relevant values for nanosized anatase by 2.0 and 3.3 times. The research was carried out as part of project 18-10-3-28 of the Program of the Ural Branch of the Russian Academy of Sciences “New materials and technologies” using equipment of the Common Use Center “Ural M” of the Institute of Metallurgy, the Ural Branch of RAS, and the Common Use Center “Composition of substances” of the Institute of High Temperature Electrochemistry, the Ural Branch of RAS, with the financial support by Resolution No. 211 of the Russian Government, Contract No. 02.A03.21.0006.