Preparation And Crystal Morphology Of Optical/Nuclear Grade Boric Acid

Boric acid is an important inorganic chemistry raw material, which has a wide range of application in traditional industries and high-tech fields. Although China is a boron-rich country, by the constraints of quality of boron and preparation technology, the current domestic industrial boric acid is difficult to meet the requirements of optical materials, electronic materials, specialty glass, nuclear power industry and national defense in terms of the purity, particle size and crystallinity. So whether the perspective of creating economic value, or the perspective of development of the national industrial chain, the research of realizing high-purity boric acid preparation technology is of great significance. This paper focuses on preparation of optical grade and nuclear grade high purity boric acid of moderate particle size. Based on the traditional preparing process of domestic industries, this paper studied the preparation technology of boric acid by the method of crystallization, ion exchange, oxidation-complex crystallization and oxidation-ester crystallization, discussed effect of the process parameters and crystal morphology on the purity and crystal morphology of boric acid. The main contents are given as follows:1. Get the optical grade high purity boric acid by oxidation-complex crystallization. Study on the process conditions of ion exchange and recrystallization method. The method of oxidation-complex crystallization is proposed. This paper uses ICP, UV spectrophotometer to characterize the product. The results show that optical high purity boric acid which can be used in special optical glass industry is prepared by purification effect of both oxidant and complexone. The impurities of products are less than 10 ppm, content of Fe is less than 1 ppm.2. Get nuclear grade boric acid by using oxidation-ester crystallization method. The research studied on a new technology oxidation-ester crystallization process. The paper discussed the effect of process factors such as reactants ratio, purity of reactants, operating temperature and waste recycling, using ICP, ion chromatogram and TG to characterize the products. The results show that nuclear grade high purity boric acid could be prepared, and the content of impurities is less than 1 ppm.3. Study on crystal morphology control of boric acid. During the preparation of optical/nuclear grade boric acid, this paper discussed the effect of direct acidification, mixed solvents and alkalescence condition on the morphology of boric acid, using single crystal diffraction. XRD and fluorescence microscopy to characterize the product. The results show that different auxiliary agnet can control the crystal size. Acidic ammonium agent can make particle bigger. Different solution can control the crystal morphology. The solution of low ratio mix between alcohol and water can get acicular crystal, while the method of acidification by controlling crystal condition and in high ratio mix alcohol-water solvent can get granular-crystalline. Granular products are easy to separate and dissolve, carry lesser impurities.