Abstract
In this work, a strategy of heat treatment-precipitation has been developed to recycle Ti-containing metallurgical solid waste by forming Ti-embedded MgAl layered double hydroxide (TMA-LDH). This facile and simple route is featured by the dedicated utilization of the composition of slag with high overall recovery efficiency. Importantly, as-obtained product exhibits visible light response distinctly different from that of pristine MA-LDH ascribed to the Fe doping inherited from initial slag. Its mesoporous nanostructure also provides more microchannels for mass and carrier transfer. As such, excellent photocatalytic activity towards degradation of tetracycline hydrochloride is achieved, and 88% removal could be obtained in 60 min. Furthermore, 44% increase in efficiency than that of Ti-excluded LDH also indicates the synergistically promoting effect of Ti incorporation. Mechanism investigation suggests that Ti incorporation regulates the electronic structure of pristine LDH with more active sites, and favors the formation of radicals with improved oxidative ability for photocatalysis.
Highlights
Titanium-containing blast furnace slag (Ti-BFS) is a by-product of the iron smelting process as metallurgical solid waste, and mainly composed of perovskite and aluminosilicates of calcium and magnesium, respectively [1]
In order to efficiently recover Ti-BFS, ammonium sulfate was firstly adopted to react with metal cations including Ti, Ca, Mg and Al in Ti-BFS, and corresponding sulfates generated during the thermal treatment process, which facilitates the elemental separation in the following immersing process considering their different solubility in water
Soluble Ti, Mg and Al cations were further precipitated by adjusting the pH of the solution to alkaline state, which results in the formation of Ti embedded MgAl-Layered double hydroxide (LDH)
Summary
Titanium-containing blast furnace slag (Ti-BFS) is a by-product of the iron smelting process as metallurgical solid waste, and mainly composed of perovskite and aluminosilicates of calcium and magnesium, respectively [1]. The mostly available route for Ti-BFS utilization is used as a whole for building materials considering its high content of CaO and SiO2 , but excessive TiO2 (>10%). In Ti-BFS would suppress the polymerization degree of building materials and result in a negative effect on its volume stability [7]. Most of the Ti-BFS is disposed directly without further treatment, which causes the waste of Ti-containing secondary resource and poses a risk to the environment; developing facile and efficient approaches to recycle
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