Dissertation > Industrial Technology > Chemical Industry > Inorganic compounds, the chemical industry of the metal elements > Section II group metal elements of inorganic compounds > Inorganic compounds of elements of the alkaline earth metal (Ⅱ A family ) > Barium inorganic compound

Study on Preparation of High-purity Ultrafine BaCO3

Author YuJing
Tutor DuJun
School Chongqing University
Course Chemistry
Keywords Leaching Purification High-purity ultrafine BaCO3 Preparation
CLC TQ132.35
Type Master's thesis
Year 2010
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Barium carbonate, as a very important inorganic salt, which is used widely in the electric, building materials, pigment, ceramic, barium ferrite and chemical industry, and it is an important industrial material.In recent years, with the rapid development of science and technology, each profession requests it develop into the direction of high-purity and super-thin, the study of high barium carbonate is taking on board too.Hydrochloric leaching of low-grade witherite from Chengkou Country in Chongqing was investigated and the effect of leaching conditions was studied. The experiment deals with how to move the useless iron, aluminium, strontium and calcium from it so as to prepare the high-pure barium. This text puts forward a new way of preparing BaCO3 under the help of microwave-assisted ionic liquid.The leaching condition of witherite was studied by traditional method of acid leaching.The optimal leaching conditions in hydrochloric acid concentraction of 1.0 mol/L at the temperature of 55℃, pulp density of 50g/L, stirring rate of 50~120r/min and reaction time of 45 min~60min,the leaching ratio of witherite in ore was about 98.6%.The impurity removal in leaching solution of pyrolusie was discussed in this study.Hydrolyzation-precipiation method was chosen to remove Fe3+ and Al3+.The pH value was adjiusted to 5~6, Fe3+ and Al3+ were converted to Fe(OH)3 and Al(OH)3 which could be removed as precipitant.Within the stirring time of 100min at 75℃. Sr2+ and Ca2+ were converted to deposition adding NH4F during the pH value from 3 to 5 at 50℃. Finally, the expenditure of NH4F is 2.5 times theoretical amount, the removal rate of Ca and Sr were 100% and 97.87%, respectively. The pure solution of barium chloride was prepared.Dropping a certain concentration of ammonium carbonate solution into the purified solution of barium chlorid, a white precipitation of BaCO3 was obtained by the microwave-assisted ionic liquid method. Then, through the processes of filtration, washing and drying, the high purity BaCO3 powder was gained. The experiment will also focus on the how does the various factors effect the content of barium Carbonate .Finally the optimum preparation conditions with microwave heating were set: the reaction temperature should be 25℃, the reaction time should be 30min, the microwave power should be 800W, the volume of the[BMIm]BF4 should be1.0mL, the dropping speed of (NH4)2CO3 (0.5mol/L) should be 5mL·min-1 and the drying temperature should be 60℃, The product of purity can achieve above 99.5%. Then by using the Scherrer formula, the mean particle size is calculated between 60 and 280nm. According to the analysis of the mechanism, it is concluded that heating by microwave can accelerate the polarization of ions under the rapidly changing electric field of the microwave results in anisotropic growth of crystals, thus forming BaCO3 nano-rod. The kinetics of homogeneous precipitation was studied, the reaction order was 1.74, and the active denergy was about 79.15kJ/mol.

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