Synthesis of TiO2 visible light catalysts with controllable crystalline phase and morphology from Ti-bearing electric arc furnace molten slag

TiO₂ visible light catalysts with different crystalline phases and morphologies were synthesized from titanium-bearing electric arc furnace molten slag (Ti-bearing EAF slag) by using a simple acidolysis process. The effects of the pH of the HCl solution, liquid to solid ratio (R_L/S, HCl solution to the residue ratio, mL/g) and acidolysis time on the micro-morphology and crystalline phase of as-prepared TiO₂ photocatalysts were systematically investigated. The results indicated that with decreasing pH in the HCl solution and increasing R_L/S, the crystalline phase and micro-morphology of the obtained TiO₂ nanostructures tended to transform from anatase type TiO₂ with spherical nanoparticle structures to rutile type TiO₂ with needle-like nanorod structures. The acidolysis time had little influence on the crystalline phase but great impact on the size of the obtained TiO₂. The growth mechanism of TiO₂ from Ti-bearing EAF slag during the acidolysis process was also discussed. In addition, the influence of R_L/S on the photocatalytic properties of the synthesized nanostructured TiO₂ was studied. The results showed that the photodegradation efficiency for Rhodamine B solution could reach 91.00% in 120 min when the R_L/S was controlled at 50:1.