A Study Of Crystallization Of Calcium Carbonate By Eggshell Substrate

Eggs are one of the most common food in daily life,it is widely used in food production,feed processing and medical research.In this paper,analyzing the eggshell structure and component,exploring the effect of eggshell to crystallization of calcium carbonate and investigating the nucleation process of calcium carbonate are important to understand the growing process of calcium carbonate and scale control in the process of water system.In this paper,eggshell,egg white,inner and outer egg membrane were as experiment substrates,these structure and property were characterized and analyzed in detail.The experiment results found that eggshell is composed of five distinct layers.From the inside to the outside of the eggshell,there were inner and outer egg membranes,mammillary layer,palisade layer,verticle crystal layer and cuticle.The content of organic substance in eggshell powder was measured.These data indicated that organic component mainly exists in cuticle and egg membrane.The surface structure of eggshell and outer egg membrane both were network of organic fibers by SEM,moreover outer egg membrane had many tiny protein bulges along the fibers,the surface of the inner eggshell membrane showed a dense and rough structure.Egg substrates have important influence on the crystallization process of calcium carbonate.The structure and morphology of calcium carbonate could be changed in different solution condition and egg substrates.The results found that there were stable calcite formed on the egg substrate at low concentration of 0.01 and 0.2 mol/L Ca Cl2 and Na2CO3 solution,moreover the main product was vaterite at high concentration of 1.0 mol/L.At room temperature and 0.01 mol/L,raw egg substrates could induce to produce calcite particles,there were spherical vaterite formed on boiled egg substrates.At concentration of 0.2 mol/L,the product was calcite on all of egg substrates.At high concentration of 1.0 mol/L,raw egg substrates could change the morphology of vaterite,induced to produce bundle of vaterite.In the experiment of different experimental conditions effect on the crystallization process of calcium carbonate,raw eggshell and outer egg membrane were as substrates,the polymorph and morphology of calcium carbonate at different experiment temperature and reaction time were recorded.At concentration of 1.0 mol/L,the result were that the morphology of calcium carbonate was changed from spherical to spheroidicity,eventually grown to spindle structure with temperature increased.At concentration of 0.5 mol/L and 60?,calcium carbonate covered on the surface of raw eggshell substrates,which was similar to the growing process of eggshell in nature.This phenomenon was more obviously with p H value increased.When reaction solution was in electric field,there were rhombic-like calcite on raw eggshell,moreover calcium carbonate was more uniform and their size was smaller with voltage increased.