Synthesis Of Plate-like Nano Calcium Carbonate And Research On Carbonization Crystallization Process

Calcium carbonate is a kind of important inorganic filler,widely used in papermaking,rubber,paint and other industries,and has broad market prospect in the world.With the development of science and technology,all walks of life puts forward higher requirements on the quality of calcium carbonate.Ultrafjne calcium carbonate with special features and specific morphology is more and more popular.Therefore,preparing nano calcium carbonate which has specific morphology and special features and exploring its carbonization crystallization mechanism have important practical significance.Synthesis of plate-like nano calcium carbonate by using intermittent bubbling carbonation method and an additive selected from various crystal orientation agents.This paper discussed the influence of technological parameters on the crystal phase,morphologies and particles size distribution of products,and explored the carbonization crystallization mechanism of plate like nano calcium carbonate by FE-SEM,XRD,FT-IR and TGA et al.Finally,the interaction of oxalate and calcium carbonate was investigated through molecular dynamics simulation calculation based on density functional theory(DFT).The main research contents and results are as follows:(1)Comparing the morphology,crystal phase and particle size distribution of calcium carbonate precipitated with different crystal orientation agents.The oxalic acid was selected as the optimal crystal orientation agent.(2)Optimizing the process conditions of preparation of calcium carbonate,and obtained optimum conditions of preparation products.Results indicated that dispersal and narrow particles size distribution calcite calcium carbonate with a mean size of 60.9 nm can be synthesized using 7.0wt%oxalic acid as crystal orientation agent at 20?,CO2 gas mixture content 0.2m3/h and Ca(OH)2 slurry concentration 0.6mol/L.(3)The samples taken from different phases of carbonization process had been analyzed by SEM,XRD,FT-IR and TGA.Furthermore,carbonization crystallization mechanism of plate-like nano calcium carbonate under acting of oxalic acid was mainly studied.Researches show that the combining of carboxyl of oxalic acid molecule and free Ca2+ ions in solution promoted nucleation.What's more,we believe that oxalic acids adsorbed on some certain faces of calcite calcium carbonate crystal inhibited these crystal faces grow.The particles can grow along other faces to form plate-like calcium carbonate.(4)Finally,the interaction of oxalate and calcium carbonate was investigated through simulation calculation based on density functional theory.The results show that,the single bond 0 atoms of carboxyl adsorbed on(104)crystal face of calcite stably,then oxalate inhibited this face grow.This conclusion coincides with the previous experiment results.