Study On The Leaching Behavior Of Strontium In Strontium Slag And Preparation Of Strontium Barium Ferrite

Strontium slag is a kind of solid waste produced in the process of preparing strontium carbonate by carbonization of celestite,the main treatment method adopted by strontium salt enterprises is stacking at present,the stacked strontium slag will produce leachate containing more pollutants,which seriously threatens the local ecological environment.In addition,the content of strontium in strontium residue is similar to that of low grade lapis lazolite,which is close to 20%,if it is not recycled.In order to avoid the waste of strontium resources in strontium residue,it is necessary to recycle and utilize the strontium resources.Avoiding the pollution of strontium slag to the surrounding ecological environment and realizing the recycling and utilization of strontium slag have always been problems that the strontium salt industry wants to solve but has not solved.The research object of this paper is the strontium slag produced during the preparation of Sr CO₃ in a strontium salt enterprise in Dazu District,Chongqing.In order to realize the resource recovery and utilization of strontium slag,the basic characteristics of strontium slag before and after hydrochloric acid pretreatment,the ammonium carbonate/sodium carbonate conversion process,the barium chloride leaching process of strontium slag and the preparation of M-type strontium barium ferrite research were carried out,obtained the following conclusions:（1）The chemical composition of strontium slag before and after hydrochloric acid pretreatment was complex,and it contained many kinds of elements,mainly including metal elements such as Sr,Ca,Mg,Ba and non-metal elements such as Si,S.The surface morphology of strontium slag before and after hydrochloric acid pretreatment was irregular and agglomerated,the surface was covered with a layer of Si O₂,and Sr SO₄ was located in the interior of strontium residue,but the agglomeration of the strontium slag was improved after hydrochloric acid pretreatment;The main substances contained in the strontium slag before hydrochloric acid pretreatment were Sr SO₄,Si O₂,Ca（OH）₂,Ca（Fe,Mg）（CO₃）₂,Sr,Ca,Si,S,Mg content were 19.04%,13.56%,9.38%,6.61%,4.29%,the main substances contained in the strontium slag after hydrochloric acid pretreatment were Sr SO₄,Si O₂,the contents of Sr,Ca,Si,S,and Mg were respectively 17.88%,2.80%,17.30%,6.12%,1.43%;The content of strontium and barium in the strontium slag before hydrochloric acid pretreatment was determined by the national standard method-EDTA volumetric method,the content of strontium and barium was 18.95%and 0.38%respectively.Compared with the strontium content determined by XRF,the relative deviation was-0.47%;There are many forms of strontium in the strontium slag before treatment,including carbonate,sulfate,sulfide and residual strontium,the contents are 0.71%,17.72%,0.35%,and 0.17%,respectively.（2）The conversion process of ammonium carbonate/sodium carbonate was studied.It was found that the conversion rate of strontium reached 79.75%when the reaction temperature,reaction time,liquid-solid mass ratio and molar ratio of（NH₄）₂CO₃/Sr SO₄were 60℃,60 min,8 m L·g^-1 and 1.8,respectively.With sodium carbonate as the conversion agent,the conversion rate of strontium reached 86.66%when the reaction temperature,reaction time,mass ratio of liquid to solid and molar ratio of Na₂CO₃/Sr SO₄ were 100℃,30 min,8 m L·g^-1 and 1.8,respectively.（3）The process conditions of the Ba Cl₂ leaching process of Sr SO₄ in strontium slag were studied,and it was found that when the leaching temperature,leaching time,liquid-to-solid mass ratio and Ba Cl₂/Sr SO₄ molar ratio were 90℃,120 min,15 m L·g^-1,2.0,respectively,the leaching rate of strontium has reached 70.36%,and the factor that had a significant influence on the leaching rate of strontium was the leaching temperature;The Ba Cl₂ leaching process conformd to the surface diffusion control of the product layer,and its apparent activation energy was 38.75 k J/mol,the apparent rate of the leaching process can be expressed by the formula 1-2X/3–（1-X）^2/3=A·exp（38.75/RT）;During the leaching of barium chloride,Ba²⁺in the barium chloride solution first diffused into the strontium slag through the gaps of the Si O₂ layer on the surface of the strontium slag,and undergoed a metathesis reaction with the Sr SO₄inside the strontium slag,and the resulting Ba SO₄ product layer will cover the strontium slag.The surface of Sr SO₄ hindered the further reaction of Ba²⁺and Sr SO₄,and the generated Sr²⁺will diffuse from the inside of the strontium slag into the solution to form a Sr Cl₂ solution.（4）The prepared M-type strontium barium ferrite was a mixed ferrite of Sr Fe₁₂O₁₉,Ba Fe₁₂O₁₉ and Sr_0.5Ba_0.5Fe₁₂O₁₉,and had a hexagonal plate morphology and was a permanent ferrite material;The p H during the precipitation process had an effect on the phase composition,morphology and morphology of the strontium barium ferrite.The magnetic properties had the greatest impact;When the precipitation p H,calcination temperature,and calcination time were 12,900℃,and 2 h,respectively,the prepared strontium barium ferrite had high purity,and the apparent morphology was hexagonal or hexagonal flakes,and its saturation magnetization Ms was 60.29 emu/g,the coercive force Hc was 3870.40 Oe.In summary,it is an effective way to use barium chloride to extract the strontium slag pretreated by hydrochloric acid,and then use the barium chloride leaching solution to prepare the strontium barium ferrite material to realize the resource utilization of strontium slag.