| Titanium-bearing blast furnace slag(Ti-BFS)is a by-product of iron smelting process as metallurgical solid waste.Because of the large consumption of iron in modern society,the yield of Ti-BFS is quite huge and accumulates more than 3 million tons every year.However,Ti-BFS with low content of Ti(10～25 wt.%)is hard to utilized as raw material for Ti manufacture,and concentrating Ti by previously developed strategies,such as acid leaching,alkali molten salt calcining,carbonization-chlorination and high-temperature enrichment,due to the low efficiency and high cost.As such,most of the Ti-BFS are disposed directly without further treatment,which causes the waste of Ti-containing secondary resource and suffers the potential risk of environmental hazardousness,so developing facile and efficient approaches to recycle the Ti-BFS has become a critical issue need to be seriously concerned.In this work,a strategy of heat treatment-alkali precipitation has been developed to seperatte and recycle Ti-containing metallur-gical solid waste,and the influence of experimental paramters on the recovrying efficiency was well investigated,together with application of obtained LDH in photocatalytic degradation of pollutant and adsorption of heavy metal ions.In addition,extended research of as-proposed stretagy in recycling of steel slag has also be conducted,which provides a new idea for the effective recovery and high-value utilization of various waste slag.The main research results are as follows:(1)Ammonium sulfate was mixed with Ti-BFS and reacted at thrmal condition,then the roasted product was filtered through water leaching to separate Si and Ca elements in the slag.Then the p H of obtained supernatant was adjusted to 10 using 2mol/L Na OH solution,and resulted in Ti-embedded hydrotalcite product.By investigating the influence of experimental paramters on the recovrying efficiency of obtained prodcuts,the optimized parameters were well determined.As such,the content of Si and Ca in obtained CSS achieved 93.26%,while the content of Ti,Mg and Al in TMA-LDH was 92.55%.Importantly,the overall recovery efficiency beyond 85%could be achieved for each element.Furthermore,a two-step precipitation process was developed to enrich Ti in a separated phase with content of 98.19%,and high recoverying efficiency beyond 90%was still preserved for Mg and Al.(2)Structure investigation reveals that as-obtained brucite product was assembled by loosely aggregated nanosheets as building blocks,and specific surface area was further determined to be about 135.76 m~2/g.Furthermore,visible light response distinctly different from that of pristine MA-LDH was observed and could be ascribed to the Fe doping inherited from initial slag.With the synergistic effect of these factors,as-obtained product exhibits significantly enhanced performance in heavy metal ions adsorption and visible-light-driven photocatalysis.When TMA-LDH was employed as the photocatalyst,TC degradation of 88%of the initial concentration could be achieved within 60 min reaction,which is about 2.9 times higher than that of Ti-BFS,and 44%increase in efficiency than that of Ti-excluded LDH.Mechanism investigation suggests that Ti incorporation regulates the electronic structure of pristine LDH with more active sites,and favors the formation of·OH and h~+radicals with improved oxidative ability for photocatalysis;(3)Heat treatment-alkali precipitation strategy was further adopted to recycle steel slag solid waste by formation of products including the Si-Ca compound and Fe Mg Al-LDH,respectively.Because of high Fe content in initial slag,as-obtained hydrotalcite product exhibited much high response to visible light,and larger specific surface area of the nanosheets provide more active sites for photocatalytic reactions.As a result,Fe Mg Al-LDH presented enhanced visible-light-driven photocatalytic activity,and 92%degradation of the initial concentration of TC could be achieved within 60 min reaction. |
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