Preparation Of Spherical Calcium Carbonate By Carbonation

Calcium carbonate is an important inorganic material.spherical calcium carbonate has a high specific surface area,high solubility and dispersion properties,and it can effectively improve the coating performance of paper and the filling performance of plastic,paint,ink,paper and so on.The preparation methods of spherical calcium carbonate are mainly manufaced by metathesis method and carbonization processes.At present,more research is the metathesis method.The metathesis method is focused on the preparation of spherical calcium carbonate by soluble calcium salt and carbonate reaction.However,The cost of this method is more expensive,it is not suitable for industrial production.In this paper,silk fibroin hydrolyzate was used as the inducing agent,and spherical calcium carbonate was synthesized by bubbling carbonization method,which provided a way for industrial production.The main results of this study are as follows:Firstly,we need to synthesis the crystal style controller.And we extract silk fibroin from industrial waste silk,The temperature is 60 ℃ and the pH is 8.5.And then we hydrolyze silk fibroin with alkaline protease for 2 hours,to prepare of hydrolyzate of silk fibroin,and the molecular weight of the hydrolyzate was 11808 Da～360 Da by gel chromatography.Secondly,We synthesize spherical calcium carbonate by using single variable method.In the experiment,we study the effects of factors such as calcium hydroxide concentration,reaction temperature,gas velocity,stirring speed,concentration of hydrolyzate of silk fibroin,aging time and pH value on the morphology and particle size of calcium carbonate.The optimum conditions for the preparation of spherical calcium carbonate were determined as follows:the mass concentration of calcium hydroxide suspension was 0.1%,the temperature of carbonation was 30 ℃,and the flow rate of carbon dioxide and nitrogen gas was 60 mL · min ’’ and 240 mL · min-1,and respectively,the total gas velocity was 300 mL · min-1,the rotation speed was 400 rpm,the concentration of silk fibroin hydrolyzate was 50%of the mass of calcium hydroxide,and the aging time was 30 min,in the carbonization pH = 9 to stop the reaction,and finally we synthesize spherical calcium carbonate products.And the average particle size is about 1 to 5 μm.In order to explore the interaction between the various factors in the preparation process,the L9(43)orthogonal test was designed to obtain the best conditions for the preparation of spherical calcium carbonate and it is same as the single factor optimal condition.Finally,We use calcium carbonate microspheres as template,and then cover dopamine to synthesis CaCO3 @ PDA microspheres.The mass ratio of dopamine and calcium carbonate is 1:1.The CaCO3 @ PDA were calcined at 750 ℃ for 1 h using a tubular furnace.The hollow CaO @ HPSC microspheres were obtained and then washed with deionized water,dilute hydrochloric acid and methanol,and then dry 120 ℃ for 10 h.The purpose is to activate,and finally we get the preparation of hollow porous spherical carbon material.The BET and Langmuir specific surface area of the samples were 187.03 and 274.10 m2·g-1,respectively,and the pore size is 4.27 nm.We use hollow porous spherical carbon material to adsorb hydrolyzate of casein and measure the adsorption effect by liquid chromatography,and then calculate the adsorption rate of hollow porous spherical carbon material by the standard curve.Compared with AC,OMC and P(GMA-DVB),the adsorption rate of hollow porous spherical carbon material composite microspheres was better.