Surface Modification Of Nano-calcium Carbonate And Preparation Of Hollow Rice-like Strontium Carbonate And Hollow Fiber Barium Carbonate

In the?A carbonates,calcium carbonate,strontium carbonate and barium carbonate are all basic inorganic chemical raw materials,which have extensive application.Among them,nanometer calcium carbonate?Nano-CaCO₃?as reinforcing material and filler has superior performance and wide applications in a variety of organic and inorganic compounds,but due to its hydrophilicity,limiting its scope of application.The preparation of active nano-CaCO₃ via surface modification is an important research topic,which has practical application value.In this paper,nano-CaCO₃ was treated by ball milling,and the high oleophilic active nano-CaCO₃was prepared,which expanded the use of nano-CaCO₃.In addition,calcium carbonate,strontium carbonate and barium carbonate with different morphologies have wide potential applications.Based on the technical requirements of inorganic materials in Guangdong Nanfang Soda Ash Industrial Company Limited,the preparations of hollow rice-like,fibrous calcium carbonate,strontium carbonate and barium carbonate were studied,and reactor design and pilot test process were explored,providing experimental basis for further development of new structural materials.The main contents and conclusions of this paper are as follows:?1?Using stearic acid as a modifier,the active nano-CaCO₃ coating stearic acid on the surface was prepared by the ball milling reaction successfully.The effects of the activation time,the amount of modifier and the rotational speed of ball milling on the reaction were studied and the best experimental conditions were obtained.The results show that the modification method of ball milling is simple,and the effect of coating is remarkable.When the activation time is too short,the calcium carbonate and the modifier cannot be fully contacted,and the good activation effect cannot be reached.While the long ball milling time may cause the coating agent to fall off,the activation degree is reduced,and the energy is wasted,the best activation time is 1h.When the amount of stearic acid is too little,the coating effect is not satisfied,because the amount is not enough to cover the calcium carbonate.When the amount reaches a certain value,the amount of stearic acid is increased,and the coating effect is basically the same.The optimum coating amount is 3%.The ball milling speed has little effect on the effect of stearic acid coated calcium carbonate.These results provide an important basis for the modification and utilization of nano-CaCO₃ in enterprises.?2?A stirred crystallization reactor with simple structure and continuous flow of carbon dioxide was designed.Through continuous monitoring of the condition parameters,rice-like hollow nano-CaCO₃ was prepared.This method has high productivity and short reaction time,and the hollow rice-like nano-CaCO₃ has great prospects for the application of biological medicine.?3?The hollow rice-like strontium carbonate was prepared by carbonation reaction of strontium hydroxide solution and carbon dioxide without any morphology control agent using a simple and convenient gas-liquid stirred reactor.The effects of temperature,carbon dioxide bubble rate and stirring speed on the morphology of strontium carbonate were investigated.It was found that when pH is between 7.5⁶.5 and conductivity is between 150?s/cm³00?s/cm,the hollow rice-like strontium carbonate can be obtained,with the length of 5?m²0?m and the maximum diameter of 0.5?m¹?m.With the increase of temperature,the hollow fibrous strontium carbonate length become longer,the diameter does not change;carbon dioxide bubble velocity doesn't change the basic morphology of hollow fibrous strontium carbonate,but it can shorten the reaction time.The stirring speed has no effect on the reaction with a suitable range.?4?Hollow fiber barium carbonate was prepared by directly using barium hydroxide solution and carbon dioxide to carbonate without using any morphological control agent on a simple and convenient continuous carbon dioxide flow reactor.The effects of the upper and lower reaction zoning,temperature and carbon dioxide bubble rate on the morphology of barium carbonate were investigated.It was found that under the experimental conditions of pH between 8.0⁷.0 and the conductivity of 300?s/cm⁴00?s/cm,the hollow fiber barium carbonate can be prepared.When the position of CO₂ bubbling device is below 2/10 of the reactor,and the position of the agitator blade is below 3/10 of the reactor level,the crystallization of barium carbonate is the best without agglomeration.When the reaction temperature is 50 centigrade,the average length of hollow fiber barium carbonate is about 20?m.When the reaction temperature is 60 centigrade,the average length is about 35?m,but the average diameter does not change basically.When the velocity of carbon dioxide bubbling is increased,the length and diameter are not changed,but the reaction rate is accelerated and the reaction time is shortened.The as-prepared hollow fiber barium carbonate has a good application prospect as an organic-inorganic structural material.