A Study On Low-Grade Pyrite Slag Producing Iron With New Beneficiation Method

Pyrite cinder is the production of sulfuric acid sludge produced by roasting pyrite, it is a solid industrial pollutant. However, the content of iron is generally 30～50%, it is an important secondary resource. It has a study on producing iron with pyrite cinder many years ago in our country, In general, we treat pyrite cinder with reelection, magnetic separation, flotation or the joint of magnetic separation and reelection and so on to achieve the purpose of advancing the content of iron and reducing the content of sulfur. But the structure of pyrite cinder is complex, so the recovery rate of iron is very low and it is difficult to remove sulfur, which impact on the comprehensive utilization of pyrite slag. To develope and utilize such renewable mineral resource rationally, the pyrite cinder is provided by the chemical plant in Xiang Xi, Hunan province in this experiment. The content of iron of the pyrite cinder is only 38%, and the content of sulfur is no less than 8%. Under this situation, we adopt three kinds of ways to deal with it, and gain iron concentrate with high-content iron and low-content sulfur. The main content and innovations are as follows:(1) With fusion-acid leaching treat the pyrite cinder, this technics divide into two part—the melting and acid leaching process. Fusion is a process that mixed slag and lye, treat the impurities such as silicate turns into soluble compounds at high temperature, and then elute with water. The acid leaching process mainly rich the grade of iron and reduce the content of sulfur. We optimize the conditions of technics in trial and establish the best qualification. The appearance and structure of samples are characterized by SEM and XRD. After separation, the grade of iron concentrate can attain 65.01%, the content of sulfur can be reduced below 0.1% and the recovery is 82.12%.(2) With hydrothermal-acid leaching technics treat the pyrite cinder, which content of iron is only 38%. Hydrothermal can accelerate the reaction between lye and silicate ion. We discuss several factors about hydrothermal and acid leaching in these experiments, and characterize the treated-slag with XRD and SEM. After separation, the content of iron can attain 61.19%, the content of sulfur can be reduced 0.10% and the recovery is 86.34%.(3) With ball grinder-acid leaching technics treats pyrite cinder, this way carries out the possible treating slag under room temperature. Ball grinder can be explained with the theoretics of mechanical milling, interface reaction and diffusion-reaction. We discuss every factor about ball grinder and acid leaching processes in this experiment, and characterize the treated-slag with SEM and XRD. After separation, the content of iron can attain 57.25%, the content of sulfur can be reduced 0.17% and the recovery is about 90.98%.(4) To achieve the comprehensive utilization of pyrite cinder, zeolite 4A is synthesized using the alkali leaching filtrate, and the product structures are characterized by SEM, XRD, and their performance are analyzed by measuring the whiteness and calcium exchange capacity. The results show that the aging process is controlled at 60℃for 12h; the crystallization process is controlled at 90℃for 24h, it can produce qualified 4A zeolite, the Ca2+ index>295mg/g, which reaches a requirements with commodity 4A Zeolite-level product.