Study On The Growth Mechanism Of Cerium Carbonate In The Special Morphology Of Sulfonic Acid Groups

The physical and chemical properties of cerium carbonate crystal,such as morphology,size and dispersion,determine its application in different production fields.Therefore,the research group took cerium carbonate crystal as the research object.In the previous experiments,it was found that the template can regulate the cerium carbonate crystal with special morphology,but the role of the template in regulating the growth of cerium carbonate is not clear.In this paper,Ce（NO₃）₃was used as cerium source,sodium dodecylbenzene sulfonate（SDBS）,sodium dodecyl sulfonate（SDS）as template,ammonium bicarbonate（NH₄HCO₃）as precipitant,and cerium carbonate crystals with hexagonal lamellar morphology were prepared by liquid phase precipitation method.The morphology,phase and crystal structure of the prepared cerium carbonate were characterized by SEM,XRD and FTIR.At the same time,molecular dynamics and density functional ab initio theory were used to study the growth mechanism of cerium carbonate crystal regulated by template by establishing a liquid phase system model and an adsorption model.Numerical simulation and experiment complement each other to better understand the growth mechanism of cerium carbonate crystal with special morphology regulated by template.The main results are as follows:The optimum preparation conditions of cerium carbonate crystal:SDBS concentration0.9g/L,aging time 4h,Ce³⁺concentration 0.05M,R value 3.3:1;SDS concentration 1.2g/L,aging time 4h,Ce³⁺concentration 0.05M,R value 3.3:1.The physical characterization of cerium carbonate crystal prepared by adding SDBS and SDS as templates by SEM,XRD and FTIR shows that SDBS and SDS have obvious regulation effect on cerium carbonate crystal,and each crystal surface has different degrees of regulation effect.SDBS and SDS mainly regulate the growth rate of crystal surface（010）,（111）and（101）,and the particle size of cerium carbonate crystal prepared by SDBS regulation is small and the crystallinity is better.In the induced nucleation stage,the optimal molecular structure of SDBS and SDS was found by optimizing the molecular structure.A liquid-phase reaction model was established.SO₃^2-in SDBS and SDS combined with Ce³⁺to form lanthanide sulfonate complex,which provided nucleation sites for cerium carbonate crystal growth.With the addition of precipitant NH₄HCO₃,the binding ability of CO₃^2-to Ce³⁺was greater than that of SO₃^2-to Ce³⁺,and cerium carbonate crystals began to nucleate and grow at the complex sites.At the growth stage,the adsorption of SDBS and SDS on each crystal surface of cerium carbonate crystal was compared through the analysis of crystal surface adsorption energy,COHP and ICOHP.The best adsorption crystal surface was found.SDBS and SDS had strong adsorption capacity on（010）crystal surface,that is,the growth of（010）crystal surface was hindered the most.In the equilibrium state,the（010）crystal plane has the highest probability of occurrence,and finally there will be a hexagonal sheet crystal structure growing around the（010）crystal plane.At the atomic scale,ab initio molecular dynamics simulation was used to simulate the effect of the addition of SDBS and SDS in cerium salt system on the growth of cerium carbonate crystals.It was found that the simulation result was irregular crystal morphology when SDBS and SDS were not added.After SDBS and SDS were added,the simulation result was hexagonal sheet crystal morphology due to the regulation of sulfonic acid groups in the template.However,SDS has one benzene ring less than SDBS,the polarity of benzene ring in SDBS,the adsorption energy of crystal surface,ICOHP and COHP values are more stable,the hydrophobic chain structure of SDS is shorter and the steric hindrance is smaller,which can not effectively prevent the agglomeration of cerium carbonate particles,and the formed products have obvious agglomeration.SDS is inferior to SDBS in controlling cerium carbonate crystal.