Study On Preparation Process And Surface Modification Of Nanometer Calcium Carbonate From Oyster-shells

Resources and environmental issues have become one of the topics,which needs to be resolved by human on 21st century.As china's economic and social rapid development, valuable and non-renewable natural resources will be less and less.How to make use of existing non-renewable resources and research for renewable resources have become a research focus of experts and scholars both at home and abroad.As improvment of people's living standards and rapid development of aquaculture,in this background.With the development of oyster industry and processing industry,a large number of oyster shell become into scrap or low-value resources,occupy a number of beach and land,and bring much adverse impact on the environment because of corruption or stink.Therefore,There is great significance on comprehensive development and utilization of oyster-shells.So, research direction and purpose of the subject is how to comprehensive develope and use oyster-shells resource and make them from waste to treasure.To this end,the subject commence to study on the use of oyster-shell resources,which not only save resources but also protect the ecological environment.First of all,the first study of this topic takes the oyster-shells as raw materials,double decomposition method is used to synthesize nano-calcium carbonate under the condition of additives and nano-calcium carbonate is modified.It is a normal temperature and pressure process,the entire process carried out detailed studies to determine the test parameters in all processes.The process compared to other preparation techniques,is an environment-friendly and clean technology,the advantage is that oyster-shells are't calcined at high temperature, low energy is consumed,process is easy,operating conditions are moderate,the degree of pollution is small.The technology have good environmental benefits,social benefits and promotion prospects.Secondly,the first study of this topic use Control-step method and the amended Debye-H(u|¨)ckel activity coefficient model to research kinetic equation of double decomposition reaction synthesis of nano-calcium carbonate,at normal temperature and pressure conditions,through the kinetic analysis,reaction order:n=0.5,reaction rate constant:k=0.3974×10^-4;reaction rate equation as follow:r=0.3974×10^-4×(ω-1)^0.5.The reaction is mainly affected by precipitation of calcium carbonate crystals,and fit the experimental data for model validation,the dynamic equation is ideal.Finally,the first study of this topic make Response Surface Methodology(RSM) used in the preparation and the modification of nano-calcium carbonate to optimize experiments.At the basis of single factor experiment,through the RSM,the optimum theoretical conditions of Preparing nano-calcium carbonate:additives are A and E,Stirring speed is 900r/min,reaction temperature is 20.26℃,reaction time is 8.44min,concentration of CaCl₂ is 0.34mol/L, dosage of A and E is separately 0.22g[4.4%wt(CaCl₂)],the average size is 44.31nm.XRD, TEM are used for Analysis and characterization,product generated by the structure of Calcite-type and flake,the optimum theoretical modified conditions:modifier is Sodium stearate,Stirring speed is 1050r/min,Drying temperature is 100℃,Drying time is 2h,dosage of modifier is 7.56‰wt(CaCO₃),concentration of slurry is 3.22%,modified temperature is 73.09℃,modification time is 38.42min,activation degrees is 99.98%.