Efficient Separation And Extraction Of Iodine In Wet-process Phosphoric Acid

Iodine resources Mainly extracted from oil-gas field water and extraction liquid of kelp in China.In recent years,the demand for iodine in China has far exceed the mining volume.In order to meet the demand,researchers begun to explore the extraction and extraction of trace iodine from phosphate rock.The associated iodine contained in phosphate rock was a potential resource but difficult to mine directly.The wet process phosphoric acid（WPA）process to decompose phosphate rock,it was found that iodine will enter the phosphate acid（PA）,and it was a important significance to efficiently separate and recover trace iodine in PA.Although the iodine extraction from WPA was industrialize,as the content of iodine in the phosphate rock decreases,the concentration of iodine in PA was reduced,making iodine enrichment and capture more difficult,and the cost was gradually rising.This paper proposes a new separation method-bubble membrane separation method,which its for separation of iodine in PA.The main results of the thesis research were as follows:（1）Research on leaching and oxidation of iodine in phosphate rock under different conditions was carried out.The effects of different ratios of phosphoric acid and sulfuric acid,liquid-solid ratio and temperature on the leaching rate of iodine in phosphate rock were studied through orthogonal experiments.When the temperature was 75℃and the liquid-solid ratio was 4:1,the ratio of phosphoric acid to sulfuric acid was 3:2 The leaching rate of iodine was 68.8%,the concentration of iodide ion in PA was 2.12 ppm,and iodine is mainly present in PA in the form of I^-.The effect of different oxidants on oxidizing I^-to I₂ was studied such as（NH₄）₂S₂O₈,H₂O₂,Fe（NO₃）₃.（NH₄）₂S₂O₈ was choosed the reason why was the best oxidation performance on I^-,and the residual rate of I^-was 1.91%in PA.（2）Research on the effects of different capture agents for the capture efficiency of iodine was carried out.On the basis of（NH₄）₂S₂O₈oxidation,using SO17,xylene,carbon tetrachloride,sulfonated kerosene and other different capture agents,the effect of different reaction temperature,reaction time,stirring rate,etc.on iodine capture efficiency.When the temperature was 45℃,the addition amount was 1:3 V/V%,the reaction time was 60 min,and the iodine capture efficiency can reach 99%without stirring.SO17 was choosed the reason why was the best capture efficiency for iodine,meanwhile the cycle performance of SO17 is studied.After 7 cycles of testing,the capture rate of iodine is still above 95%.By heating the temperature of the trapping agent to 185℃,the iodine in the trapping agent can be recycled.（3）Analysis and research of iodine capture mechanism was carried out.Based on the principle of bubble transport,Using the constant interface cell method,set the maximum contact area of the separation layer phase and the solution phase,research was conducted on the formation and rise of iodine-containing bubbles in PA and trapping phases at different temperatures.The different factors were used to study the bubble rising rate and bursting,such as the temperature,the viscosity of the PA,the viscosity of the trapping agent,the surface tension of the trapping agent,the viscosity of the iodine vapor,etc.The results of the experimental data were in good agreement,and the kinetic model can be used to guide the process of iodine capture and separation.