| In this dissertation,in the view of the main deficiencies in the production of nano CaCO3,such as agglomeration,larger particle size,worse size distribution and the hydrophily and hydrophobicity of unmodified nano CaCO3,based on a large amount of literature and the previous research results,nano CaCO3 was prepared via carbonization method using CO2 and carbide slag as raw materials.The work focused on the optimization of the preparation and modification conditions of nano CaCO3 from Ca2+ solution with higher concentration under Ca2+-H2O-CO32-reaction system and the action mechanism of the additives was preliminarily studied.The main work and obtained results include:(1)STP and PEG was selected as the more appropriate compound additive.The preparation conditions of nano CaCO3 were investigated and optimized as follows:addition of additive 3%STP and 1.5%PEG,reaction temperature 25?,CO2 flow rate 400mLˇmin-1,initial concentration of Ca2+ lmolˇL-1,stirring rate 600rpm and aging time Omin.The nano CaCO3 obtained performed preferable dispersity with a diameter of about 45nm.(2)From the analysis,the action mechanism of the additives might be:a certain kind of synergistic effect between STP and PEG reduces the surface energy of CaCO3 particles,restraining the growth of CaCO3 particles,inhibiting its aggregation,and thus reducing the average grain size of CaCO3 samples.(3)Sodium oleate was selected as the more suitable modifier of CaCO3 and the modification conditions of nano CaCO3 were optimized as follows:addition of sodium oleate 2.5%,the mass ratio of solid to liquid 8.5:100,modification time 120 min,modification temperature 45? and stirring rate 300rpm.The main technical indexes of the modified nano CaCO3 was as follows:the content of CaCO3 96.2%,Mg content 0.3%,water content 0.3%,pH 8.5,whiteness 95%and BET specific surface area 19.1,which could meet the national standard requirements of nano CaCO3 for the use in rubber and plastics(GB/T 19590-2011). |
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