Morphology Regulation Mechanism Of α-Fe₂O₃/ZnFe₂O₄ Prepared From Zinc Bearing Metallurgical Dust By Wet Chemical Route

In order to deal with the resource and ecological problems caused by the over-exploitation of natural minerals,the high value-added materialization of industrial solid waste is becoming a hot research topic.Existing studies mostly focus on the materialization of major elements in solid waste,and the role of trace elements is often ignored.The previous study of our research group found that trace elements in zinc-bearing dust have a significant effect on morphology regulation of the products derived from zinc-bearing dust by wet-chemical,but the specific details and mechanism are not clear.In this paper,FeSO₄·7H₂O and ZnSO₄·7H₂O were used to prepare the base solution.Si,Al,Mg and Cl were introduced into the reaction base solution with a certain amount of SiO₂·xH₂O,Al₂（SO₄）₃·18H₂O,MgSO₄,NaCl or HCl and H₂SO₄,respectively.α-Fe₂O₃/ZnFe₂O₄samples or doped samples were prepared by constant temperature reflux homogeneous precipitation method in glycol-water mixture solution system.The effects of Si,Mg,Al,Cl and related ions on the structure,morphology and photocatalytic performance of the products were systematically studied.The influencing factors on the morphology ofα-Fe₂O₃/ZnFe₂O₄prepared from zinc-bearing dust and mud acid hydrolysate were explained and the related mechanisms were discussed.The results showed that Al and Mg had no obvious effect on the composition and morphology of the products.When the molar ratio of Fe:Si=26:1,the product with the best morphology was obtained under the control of Si,but the morphology of the product was far less obvious than that of the product prepared by acid hydrolysis solution.The formation ofα-Fe₂O₃/ZnFe₂O₄by the combination of Siwith Al and Mg in pairs or in triplets is similar to that of Sialone.SO₄^2-was added into the initial reaction solution in the form of 3 mol/L H₂SO₄.The results showed that increasing the concentration ofSO₄^2-ions in the reaction system had no significant effect on the microstructure of the product,but it would induce the gelation of the suspension of the reaction system.Using NaCl and HCl as Cl sources,the effect of Cl on the morphology of the products was investigated.The results showed that the addition of Cl in two different forms had no effect on the phase composition of the products,but both of them could make the product microspheroidized to different degrees,and the addition of Cl in the form of HCl had a more obvious adjustment effect on the product morphology.Further study showed that Siand Cl had a significant synergistic effect on the regulation of product morphology.Compared with Siand Cl alone,the products with Siand Cl added to the initial reaction solution at the same time have better microspherical morphology.The experimental results show that the optimal molar ratio of Siand Cl is Fe:Cl:Si=26:2:1.In the experimental range,the morphology of the products are gradually optimized with the increase of Cl content.In order to reveal the influence of morphology regulation on the photocatalytic properties of the products,the photocatalytic activities of the products prepared by introducing different elements were characterized and compared with those prepared by acidolysis solution.The capability for photocatalytic degradation of methylene blue（MB）was used as a criterion to evaluate the photocatalytic activity of the product.The photocatalytic activity of the products are characterized by its photocatalytic degradation of organic pollutants,and the substrate was methylene blue（MB）.The photocatalytic activity of the prepared product was better when the Sicontent was closer to the value of zinc-bearing dust acid solution and the Cl content was higher,and the degradation rate of MB was 94.59%.The photocatalytic degradation rate of MB over the product prepared by zinc-bearing dust acid hydrolysis solution is 95.79%,which is better than the photocatalytic performance of the product prepared by reagent.This is attributed to the fact that the morphology of the product prepared by zinc-bearing dust acid hydrolysis solution is much better than that of the product prepared by reagent.The morphology of microspherical layered structure has a positive effect on the photocatalytic performance of the product.The results show that the Siand Cl elements in the acidysis solution have a certain regulation effect on the morphology ofα-Fe₂O₃/ZnFe₂O₄composite prepared by homoiothermic reflux homogeneous precipitation method,and the synergistic effect of Siand Cl is more significant.Trace elements Al and Mg in acidolysis solution had no obvious influence on the morphology evolution of the product.Under the experimental conditions,although it is clear that Siand Cl have a certain regulation effect on the morphology of the product,the same morphology as that of the product prepared by zinc-bearing dust acid hydrolysis solution cannot be obtained by adding Si,Cl,Al and Mg alone.These results indicate that there are still unknown factors in zinc-bearing dust acidolysis solution that have significant regulation effect on product morphology,which needs to be further studied.