Conversion of CaTi_1–xMn_xO_3–δ-Based Photocatalyst for Photocatalytic Reduction of NO via Structure-Reforming of Ti-Bearing Blast Furnace Slag

Abstract

In this work, a novel low-cost and robust approach is developed to covert Ti-bearing blast furnace slag (Ti-slag) to the main feed stock of photoassisted NH3 selective catalytic reduction (Photo NH3-SCR) of NO with high performance. The CaTi1–x Mn x O3−δ catalyst was directly extracted from the Ti-bearing slag with MnO2 in situ modification and Na2CO3 reformation followed by dilute hydrochloric acid leaching and water washing. Various methods were employed to characterize the structure changes of the slag in the preparation processes of MnO2 in situ doping, Na2CO3 reforming, and leaching. Mn element can be incorporated into the perovskite CaTiO3 with 0.16 to 1.79 wt % depending on the amount of MnO2 added in Ti-slag at 1500 °C. It is interesting to note that the amount of Mn incorporated into the perovskite decreases remarkably with increasing the additional amount of MnO2 in the in situ doped modification, which reaches a maximum of 9.54 wt % for the reformed slag of 5 wt % MnO2 addition. Moreover, most of the Si has been transferred to the sodium aluminum oxide instead of diopside, which is easily removed in the following leaching stage. Further semiquant crystalline analysis shows that there is 99 wt % of perovsvkite CaTi1–x Mn x O3−δ with 1 wt % hexamagnesium manganese­(IV) oxide in the slag after leaching with 5 wt % MnO2 addition, and the catalyst shows more than 93% NO removal efficiency at 300 °C in photoassisted NH3-SCR performance. The present study proposes a new route for the high value-added recycling of silicate minerals and wastes via structure-reforming with in situ optimization of secondary resources.

Fabrication of hollow flower-like magnetic Fe3O4/C/MnO2/C3N4 composite with enhanced photocatalytic activity

“…However, while the narrow band gap increases the usage of visible light, it is also accompanied by the rapid recombination of photo-generated electrons and holes. The low photocatalytic efficiency restricts pure MnO 2 for practical applications [37][38][39] .Coupling MnO 2 with other semiconductors to build a heterojunction is an effective method to prevent the recombination of photo-generated carriers. Wang et al 40 first reported that g-C 3 N 4 could decompose water to generate hydrogen by visible light irradiation.…”

“…However, while the narrow band gap increases the usage of visible light, it is also accompanied by the rapid recombination of photo-generated electrons and holes. The low photocatalytic efficiency restricts pure MnO 2 for practical applications [37][38][39] .…”

Building heterogeneous nanostructures for photocatalytic ammonia decomposition

“…TiO 2 is one of the most common photocatalysts; it has good performance in many photocatalytic applications, such as water splitting, hydrogen production, carbon dioxide reduction, nitrogen oxide reduction, nitrogen xation, pollutant degradation, organic reactions, and ammonia synthesis and decomposition. 31,42,[65][66][67][68][69][70][71][72][73][74] Three crystal types of TiO 2 , including anatase type, rutile type and plate titanium type, exist in nature, with bandgap widths of 3.0, 3.2 and 3.25 eV, respectively. 75 Bare TiO 2 shows lower photocatalytic activity in ammonia decomposition due to the reactive energy barrier.…”

An approach to prepare high-purity TiSi2 for clean utilization of Ti-bearing blast furnace slag

“…The ineffective use of Ti-bearing blast furnace slag wastes Ti resources and causes environmental pollution. 4 Many methods have been proposed for the clean utilization of Ti-bearing blast furnace slag, which include two routes: non-Ti extraction and Ti extraction. In non-Ti extraction routes, Ti-bearing blast furnace slag can be used as a photocatalytic degradation material, 5 compound fertilizer, 6 foam glass-ceramic, 7 and building materials (concrete 8 and sintered slag bricks 9 ); however, the most valuable element in Ti-bearing blast furnace slag, Ti, is not utilized effectively, and much of it is wasted; therefore, to make better use of Ti, the extraction of Ti from Ti-bearing blast furnace slag has been investigated.…”