Study On Photocatalytic Activity And Modification Of Masteel Self-circulating Zn-bearing EAF Dust

Zn-bearing electric arc furnace dust(Zn-EAFD)has significant resource attributes due to its considerable content of iron and zinc.The research on the materialization of Zn-EAFD with high value-added has gradually become a hot spot,but the research on its own functionality is rarely reported.Iron and zinc mainly exist in the form of oxides and composite oxides in the Zn-EAFD,and these oxides have good photocatalytic properties.This work takes the self-circulating Zn-EAFD from Masteel as the object,and its composition,phase structure and electrochemical properties were systematically studied.The influences of washing,ball grinding and heat treatment modification on its photocatalytic activity were explored,which provided new ideas and data support for the research of high value-added utilization of this secondary resource.It is found that the Zn-EAFD from Masteel's self-circulating is mainly composed of Fe OOH,Zn Fe₂O₄and Fe₃O₄,with a small amount of Zn O and other trace impurities.The micromorphology is spherical particles with an average particle size of 452.9 nm.Zn-EAFD itself has certain photoelectricity response and the ability of photocatalytic degradation of organic pollutants in water.When irradiated by visible light for 7 h,the degradation rate of acid orange?(AO?)by Zn-EAFD reached 90.46%,and the degradation rates of three cycles are 90.46%,88.29%and 86.26%respectively,indicating its good stability in cyclic degradation.The Zn-EAFD was modified by water washing and ball milling(water as dispersing medium).The washing time was 0.5 h,1 h,3 h and 20 h,respectively.The ball mill speed was 500 r/min,and the time was 2 h,5 h and 10 h respectively.It was found that both water washing and ball milling did not significantly change the main phase composition of the Zn-EAFD,but both reduced the content soluble impurities.Ball milling not only reduced the particle size of Zn-EAFD,but also tended to intensify the agglomeration of particles.Compared with untreated Zn-EAFD,water washing and ball milling reduced the photocatalytic degradation rate of AO?over Zn-EAFD within irradiation of 7 h by about 5%and 20%respectively,while the effect of washing time and milling time on the photocatalytic activity of Zn-EAFD was not significant.The results show that water washing and ball milling can inhibit the photocatalytic activity of Zn-EAFD.Based on the results of TG-DSC analysis,the roasting modification of the Zn-EAFD was studied(roasted at 260,510,650,770 and 1000°C for 5 h).The results show that the main phases of the roasted Zn-EAFD are still Zn Fe₂O₄and Fe₃O₄,the Fe OOH gradually decreases with the increase of the roasting temperature and disappears at 510°C,and the content of Zn O also decreases with the increase of the roasting temperature.However,the main phases of the roasted Zn-EAFD are still Zn Fe₂O₄and Fe₃O₄,with a small amount of Zn O.The average particle size of the Zn-EAFD roasted at 260,510,650,770 and 1000°C was 449.9 nm,555.9 nm,755.0 nm,444.2 nm and 527.7 nm,respectively.With the increase of roasting temperature,the micromorphology of the sample changed from spherical to irregular spherical and finally to the block shape.The photocatalytic performance test found that roasting at260°C can significantly improve the photocatalytic activity of Zn-EAFD,and the photocatalytic degradation rate of AO?in 7 h reached 95.92%with good cycling degradation stability.When the roasting temperature was further increased,the photocatalytic activity of the Zn-EAFD decreased.