Experimental Study On Leaching Of Witherite And Preparing For Barium Ferrite

Barium ferrite is widely used as main magnetic recording materials, permanentmagnetic materials and microwave absorbing materials due to its cheap and goodchemical stability. It has wide prospect and research value. In recent years, with therapid development of science and technology, industries of barium ferrite demand isincreasing, the study of high barium ferrite is put forward higher request.Ammonium chloride leaching of low-grade witherite from Chengkou Country inChongqing was investigated and the effect of leaching conditions was studied. Theexperiment deals with how to move the useless iron, aluminium, strontium and calciumfrom it so as to prepare the high-pure barium. This text puts forward a coprecipitationmethod of preparing barium ferrite.The leaching condition of witherite was studied by the method of ammoniumchloride leaching. Electric field intensification process was experimentally employed toleach witherite with NH4Cl. It showed that leaching rate of barium was91.17%underthe operation conditions the mass ratio of liquid to solid4, the anodic current density900A/m2, and mass ration of ore to NH4Cl1at90℃for3h. Compared leachingprocess without electric field intensification, the leaching rate of barium was improvedby10%. According to the analysis of the mechanism, it is concluded that the motion ofH₂O and H⁺is becoming stronger and the activity of ions is becoming higher in thesolution by electric field intensification. It makes H₂O and H⁺to go into the inside ofmineral and react with the ions which are hard to leaching. So the dissolution rate ofmineral was improved.The impurity removal in leaching solution of pyrolusie was discussed in this study.Hydrolyzation-precipiation method was chosen to remove Fe²⁺and Al³⁺. The pH valuewas adjiusted to9, Fe²⁺and Al³⁺were converted to Fe（OH）2and Al（OH）₃which couldbe removed as precipitant. Sr²⁺and Ca²⁺were converted to deposition adding NH4F at75℃. Finally, the expenditure of NH₄F is1.25times theoretical amount, the removalrate of Ca and Sr was100%and78.5%respectively. The pure solution of bariumchloridewas prepared. After refining the barium chloride by ethanol, Sr has beenremoved effectively.Finally, dropping a certain concentration of ferrous chloride, ferric chloride, sodiumhydroxide, sodium carbonate into the purified solution of barium chlorid, a black precipitation was obtained by the way of co-precipitation method. Then, through theprocesses of filtration, washing and drying, the barium ferrite precursor was gained.Barium ferrite was obtained by sinter barium ferrite precursor in different temperature.Factors associated with molar magnetic susceptibility were investigated. It showed thatthe optimal process were: adding temperature was35℃, the Fe/Ba ratio was13, thesintering temperature was950℃,the sintering time was3h.