Influence of acid type and concentration on the synthesis of nanostructured titanium dioxide photocatalysts from titanium-bearing electric arc furnace molten slag

In this paper, nanostructured titanium dioxide (TiO2) photocatalysts with different crystal structures and morphologies were successfully synthesized from titanium-bearing electric arc furnace molten slag (Ti-bearing EAF slag). The effects of different kinds of acid and acid concentrations during the acidolysis process on the crystal structures and morphologies of TiO2 were systematically studied. The TiO2 crystal phase transformation mechanism and morphology evolution in different acid systems and concentrations were discussed in detail. In addition, the photocatalytic properties of TiO2 obtained in different acid systems were investigated. It is shown that rutile and anatase type TiO2 were obtained in hydrochloric acid and sulfuric acid, respectively, while two types coexisted in nitric acid. With increasing sulfuric acid concentration, anatase would be apt to change to rutile. The growth mechanism of TiO2 from Ti-bearing EAF slag was also discussed. The TiO2 synthesized from sulfuric acid showed better photocatalytic activity than that from hydrochloric or nitric acid, and its photodegradation efficiency can reach 90.52% in 90 min for rhodamine B solutions.