Rare Earth Gypsum Preparation Calcium Sulfate Crystal And Modified

Rare earth gypsum is an industrial by-product produced in the treatment of wastewater in rare earth metallurgy process.Its recycling is in line with the current strategic measures of green metallurgy and clean production,and is the primary task of realizing circular economy.It can be seen that the research of this paper has environmental value,economic value and social value for the recycling of waste residue.In this experiment,calcium sulfate whisker was prepared from rare earth gypsum.The purpose is to realize the recycling of resources and realize the clean production of rare earth metallurgy process,which is an important measure to solve the problem of economic growth and environmental coordinated development.In this paper,the influence of preparation methods and process conditions on the morphology of calcium sulfate whiskers was investigated,characterized and analyzed by SEM and XRD,and the growth process of calcium sulfate whiskers was explored.Calcium sulfate whisker was modified to increase its stability and hydrophobicity,so as to expand its application field as a hydrophobic material.XRD,SEM,FT-IR,TG and XPS were used to characterize and analyze the effect of modification conditions on the modification effect.The main research contents and conclusions are as follows:Study on Preparation of calcium sulfate whisker,In this experiment,rare earth gypsum was used as raw material to prepare calcium sulfate whiskers by atmospheric acidification,ultrasonic and microwave methods.The effects of three methods on the morphology of calcium sulfate whiskers were discussed.The results show that the morphology of calcium sulfate whisker prepared by microwave method is good,and the average length of calcium sulfate whisker is 190.41 when the addition of rare earth gypsum is 0.22 g/m L,microwave heating time is 30 min,hydrochloric acid concentration is 2.8 mol/L,reaction temperature is70℃,aging time is 1.5hμm.The average aspect ratio is 14.37,At the same time,a small amount of rare earth elements in gypsum can promote the growth of whiskers.The growth mode of whiskers was explored.During the aging time of 0.5 h～4 h,it was found that the whiskers mainly grew in layers.During the growth process,the whiskers grow longitudinally along the c-axis at first.When the whiskers grow completely,further prolonging the growth time will lead to the secondary nucleation on the surface of the whiskers,resulting in the surface roughness of the whiskers,and then the particle size of the whiskers becomes larger and larger.The effect of Ca²⁺content on the morphology of whiskers in the crystallization process was studied.The experimental results show that with the gradual decrease of Ca²⁺concentration in the solution,the aspect ratio of whiskers gradually increases,indicating that low concentration is conducive to the refinement of crystal form.At the same time,in order to ensure the integrity of whisker growth,the aging time should be appropriately extended to obtain whiskers with good crystallinity.The research on the modification of calcium sulfate whisker,using trisodium phosphate and stearic acid as inorganic organic modifier,the results show that the contact angle of the modified product can reach 96.50°when the dosage of calcium sulfate whisker is 2 g,the amount of stearic acid modifier is 0.12 g,the modification time is 15 min,the modification temperature is 80℃,and the concentration of trisodium phosphate is 0.02 mol/L,At the same time,the activation index of modified calcium sulfate whisker is 0.56.