The Study On Selective Extraction Behavior Of Indium In Rotary Hearth Furnace Dust

A large amount of blast furnace dust,containing Zn,Pb,K,Na and other metallic elements,is produced as a by-product with the development of iron and steel industry.However,it is difficult to recover and reutilize due to the characteristics of small particle size,strong hydrophobicity and complex mineral composition.The rotary hearth furnace process,as the representative technology of pyrometallurgy to recover blast furnace dust in steel industries,has important application potential.It is mainly to recover Fe,C and to enrich Zn,Pb,K,Na,In,Bi and other metals in rotary hearth furnace dust.Rotary hearth furnace dust is an important secondary resource,it will not only waste metal resources,but also bring economic and environmental pressure to enterprises and society if not comprehensive recycled.In is a rare and precious metal with a market value of more than one million RMB per ton,which is widely used in high-tech technologies such as information industry,and has great strategic significance.Therefore,it is of great value to research how to develop and utilize the metal resources in rotary hearth furnace dust,especially the rare and precious metal of In.In this paper,according to the characteristics of samples in rotary hearth furnace dust,the multi-step joint process of"sulfuric acid leaching–atmospheric pressure oxidation leaching–room temperature extraction"was studied to recycle In by using hydrometallurgical technologies.The influence of different factors on the leaching and extraction of In were analyzed,and the suitable experimental parameters to each process were obtained.As a result,a high comprehensive recovery rate of In was obtained.The main findings are as follows:(1)The element and phase analysis by XRD,SEM adn ICP on the rotary hearth furnace dust showed that the content order of main metallic elements was Zn>Na>K>Pb,and the content order of main non–metallic elements was O>Cl>S.The mass fraction of In was 0.0208%,which mainly existed in the form of oxides and sulfides.(2)The behavior of metal ions in direct leaching of rotary hearth furnace dust with H₂SO₄ was studied by single factor variable method.The suitable conditions of influence factors in H₂SO₄ leaching were determined by 180 g/L of H₂SO₄,7 mL/g of the liquid–solid ratio and 500 rpm of the stirring speed at 90?for 3 h.The leaching rate of In was36.82%,and Zn,K and Na were largely dissolved in the filtrate,while Pb and Bi were largely precipitated in the filter residue.(3)The H₂O₂ and HNO₃ were added into the leaching system of fillter residue and H₂SO₄ respectively to carry out the secondary oxidation leaching of In at room temperature.The common suitable experimental conditions include the 180 g/L of H₂SO₄,7 mL/g of H₂SO₄ liquid–solid ratio,300 rpm of the stirring speed for 3 h.The suitable liquid–solid ratio of H₂O₂ and HNO₃were 3 mL/g and 1mL/g respectively.The results show that the leaching rate of In in the oxidation process of H₂O₂ is only 18.13%,while that in the oxidation process of HNO₃ is up to 60.37%,and the leaching rates of Bi and Pb were only 1.84%and 0.15%,indicating obvious selectivity in the oxidation process.(4)The D2EHPA(P₂₀₄)was used to extract In³⁺in the filtrate at room temperature from direct leaching of H₂SO₄.The suitable conditions of experimental factors include30%volume concentration of D2EHPA,4/1 of organic phase/water phase(A/O),0.7 of the initial pH and 300 rpm of the oscillation frequency for 8 min.The experimental results showed that the extraction rate of In³⁺was 89.30%after three-stage extraction.In has the obvious selectivity to extract other metal ions.The In in filtrate at room temperature from HNO₃ oxidation leaching was extracted directly in this experimental conditions,and the results showed that the In³⁺extraction rate of 93.38%could be achieved by only one–stage extraction.(5)According to the experimental results of each process,the comprehensive recovery rate of In in rotary hearth furnace dust was calculated in the whole process.The content of In in 100 g rotary hearth furnace dust is only 0.0208 g,and the mass of In can be obtained by the whole process is 0.01426 g,therefore,the comprehensive recovery rate can reach 68.56%.