The Investigation Of Synthesis Of Fe₃O₄ Magnetic Powder From Spent Pickling Liquors

Steel and iron often become rusty during the processes of storage in the air.Therefore,acid pickling is a prerequisite step treatment of steel rolling in order to remove the rust and emerge a clean surface.They also generate dissolution of iron and acid solution.If the spent pickling liquors discharge directly,not only cause severe environmental pollution,but also cause the waste of resources.Comprehensive utilization of iron and steel pickling waste liquor processing,therefore,recycling of spent pickling liquors is the development of steel industry must solve the problem.In this paper,using spent picking liquors as raw materials,Fe₃O₄ with high coercivity magnetic powder was prepared via a simple,practical and environmental method.Firstly,impurity of spent picking liquors was removed.Secondly,picking liquors was prepared via oxidation.Then the effects of reaction pH,reaction temperature,reaction concentration and air flow rate on the preparation of Fe₃O₄powder have been studied.The results showed that the purification conditions were:adding 0.5%Fe in spent picking liquors,purification pH 5.5,purification temperature70°C.The optimum reaction conditions were:the reaction concentration 0.5mol/L,the reaction temperature 80-90°C,reaction pH 9,the air flow rate 0.03m³/h,Fe³⁺/Fe²⁺1.6-1.8.Then the pure black Fe₃O₄ powder product with particle size 250-300 nm which coercivity was 101G were obtained.Fe₃O₄ magnetic powder with high coercivity has a wide application in magnetic recording materials.In addition,Fe₃O₄ nanoparticles were prepared using spent picking liquors as raw material.The effects of reaction pH and reaction temperature on the preparation of Fe₃O₄ nanoparticles have been studied.The results showed that the optimum conditions were:reaction pH 8,the reaction temperature 25°C.Fe₃O₄ nanoparticles were obtained by H₂O₂ oxidation.Fe₃O₄ nanoparticles with particle size 250-300 nm which coercivity was 22 G can be used in magnetofluid.This work broke the traditional mode of waste disposal and introduced the preparation techniques of materials,at the same time solved the harmfulness of heavy metal irons.In this work,spent pickling liquors was used as raw material to prepare high quality Fe₃O₄ magnetic powder via an oxidation method.Being able to recover the dissolved iron from spent pickling solutions would not only dispose pickling solutions but it would also obtain higher-value Fe₃O₄ products.Therefore,the synthesis of Fe₃O₄ from spent pickling liquors which provides a theoretical basis can be used in industrialization when taking practical application into consideration.