Titania has recently been identified as a new and effective nonlight-driven catalyst for degradation of organic pollutant with the use of H₂O₂ as an oxidant; however, either relatively low surface area or lack of diversity in chemical composition largely limits its catalytic performance. In this work, a series of transition-metal ion (Mn²⁺, Co²⁺, Ni²⁺, and Cu²⁺)-doped titania nanomaterials with regular flower-like morphology, good crystallinity (anatase), and large specific surface areas (71.4–124.4 m² g^–1) were facilely synthesized and utilized as catalysts for methylene blue (MB) degradation in the presence of H₂O₂ without light irradiation. It was revealed that the doping of transition-metal ions (especially Mn²⁺) into titania could significantly improve the catalytic efficiency. At 30 °C, 10 mL of MB with a concentration of 50 mg L^–1 could be completely degraded within 60–100 min for these doped samples, whereas the removal rate was only 35.1% within 100 min with the use of pure flower-like titania. Temperature-dependent kinetic studies indicated that the presence of transition-metal ion dopants could markedly lower the activation energy and thus resulted in enhanced catalytic performances. Test of reusability exhibited that these doped catalysts could well keep their original catalytic activities after reuse for several cycles, indicating their excellent catalytic durability.

Geopolymer-TiO₂ nanocomposites were prepared by two different techniques, namely the two-step acidification calcination treatment and one-step adding method. The potential photocatalytic activities of geopolymer-TiO₂ nanocomposites prepared by the two different methods were tested and compared. Nanocomposites prepared via the one-step process showed better photocatalytic activity. The amount of TiO₂ particles loaded on the surface of the foaming materials was investigated by XRD and SEM-Mapping. By comparing with the sample obtained from two-step treatment, the TiO₂ particles were distributed uniformly on the surface of the foaming materials for the sample obtained from the one-step method in this study. Results showed that the specific surface area of the geopolymer-TiO₂ prepared by the one-step treatment process (28.67 m²/g) was significantly lower than the two-step acidification calcination process (215.04 m²/g), while the photocatalytic efficiency with methylene blue trihydrate (MB) was better. This is due to the more stable structure of geopolymer-TiO₂ nanocomposites, the better dispersion and more loading of TiO₂ particles on the foaming materials surfaces, leading to the enhanced photocatalytic activity.