Study On Biomimetic Mineralization Of Calcium And Magnesium Carbonate

Calcium carbonate minerals are common in nature and organisms.However,the physical and chemical properties of calcium carbonate in organisms are superior to those in nature.In the same organism,calcium carbonate can also exist in the form of aragonite,calcite and other phases,this phenomenon is extremely rare in natural calcium carbonate minerals.Due to the extremely complex biomineralization process and the difficulty in replicating its biomineralization microenvironment,the current research on the biomineralization mechanism of calcium carbonate is relatively weak.In organisms,anhydrous magnesium carbonate crystals can be formed under normal temperature and pressure conditions,while anhydrous magnesium carbonate crystals in nature need high temperature and high pressure to form.Anhydrous magnesium carbonate and calcium carbonate have similar crystal structure and physical and chemical properties.Therefore,in this paper,calcium carbonate and anhydrous magnesium carbonate were selected for biomimetic mineralization experiments to study the biomineralization process and mechanism of calcium-magnesium carbonate crystals.In order to study the regulation mechanism of biomolecules on the growth of calcium carbonate crystals,the paper adopts biomimetic mineralization technology,using inorganic substances（magnesium ions,inorganic molecules of phosphoric acid and boric acid）and organic molecules（acetic acid,tartaric acid and L-aspartic acid）as crystal form inducers,to study the regulation of crystal form inducers with different properties on the phase and microscopic morphology of calcium carbonate crystals,to analyze the adsorption of crystal form inducers on the surface of crystal grains and their interface chemical behavior,to study the functional groups of crystal form inducers The relationship between exposed ions on the surface of crystal grains,the influence of crystal form inducers on the phase composition,crystal growth and crystal morphology of calcium carbonate crystals,and the induction of crystal form inducers on the controllable synthesis of calcium carbonate microcrystals mechanism.The research results show that inorganic substances with different properties have a great influence on the calcium carbonate phase and crystal growth:calcium carbonate crystals induced by magnesium ions are conducive to the formation of vaterite phase and aragonite phase;phosphoric acid molecules can delay the formation of calcium carbonate phase and crystal growth.The crystallization rate promotes the phase transformation of calcium carbonate to vaterite;boric acid molecules can promote the formation of rhombohedral calcite.Short-chain organic molecules such as acetic acid,tartaric acid,and L-aspartic acid can accelerate the dehydration phase transformation of hydrated calcium carbonate crystals into calcite;under the action of acetic acid molecules,it is beneficial to the formation of pine-cone vaterite;under the action of succinic acid molecules,it is conducive to the formation of radial morphology of aragonite crystals;under the induction of tartaric acid molecules,it is conducive to the formation of spiny calcite.On this basis,the paper uses long-chain organic molecules as calcium carbonate crystal form inducers to conduct experimental research on its biomimetic mineralization process.It is conducive to the formation of vaterite and amorphous calcium carbonate;under the action of citric acid molecules,calcium carbonate crystals grow rapidly perpendicular to the（001）crystal plane.Based on the biomimetic synthesis of calcium carbonate,the paper selected oxalic acid,succinic acid,L-aspartic acid,tartaric acid and citric acid as crystal form inducers,and studied the factors affecting the biomimetic synthesis of anhydrous magnesium carbonate.The research results show that under the induction of oxalic acid and succinic acid,anhydrous magnesium carbonate crystals with dodecahedral morphology were synthesized at a reaction temperature of 100℃;Anhydrous magnesium carbonate crystals with irregular dodecahedron and spindle shapes were synthesized at the reaction temperature.The molecular simulation method was used to study the crystallization process of anhydrous magnesium carbonate,and by comparing the movement differences of different inducers on water molecules and Mg²⁺in the magnesium carbonate model system,the mechanism of crystal form inducers promoting the crystallization of anhydrous magnesium carbonate and the reasons for different morphologies were explained reason.