Study On The Vital Effect Of Algae On The Biomineralization Of Calcium And Strontium

Bio mineralization is a process that the cation was transformed into solid mineral by organism under selective adsorption conditions. It is a common phenomenon in the nature. Calcium carbonate is one of the main biominerals, which exists mainly in calcite, aragonite and vaterite and amorphous calcium carbonate in four ways. It is similar in size and chemical property between strontium and calcium. Strontium can enter into the crystal lattice of carbonate crystal by isomorphic replacement and shows the specific geochemical indicators. It has not been paid enough attention for the vital effects that organism activity influences the calcium and strontium mineralization as well as isomorphic replacement.In present research, the calcium and strontium were selected as the researching object. The effect of algae (Chlorella and Coccolith) on bio mineralization of calcium and strontium in the culture conditions were studied and the vital effect mechanism was discussed. The results as follows:(1) The sample was thin, loose, and easy to produce the vaterite structure without adding the Chlorella on calcium and strontium mineralization system. With the increase of strontium content, it was obviously weakened on the calcite surface characteristic peak (104) intensity of the crystal after adding Sr2+. The crystal converted to aragonite gradually.(2) It could cause CO32- antisymmetric telescopic peak V3 characteristic peak appeared splited peak phenomenon because of the cell walls of Chlorella and calcium ion coordination in the system of Chlorella. Most crystal form of the mineralization was calcite, and the degree of crystallinity was high. With the increasing of doped strontium ions content, Sr2+ adsorbed on the surface of the calcite and replaced Ca2+ entering into the lattice and impeded CaCO3 normal growth which would result in the calcite to aragonite conversion in the Chlorella system.(3) When the surface groups of ester of Chlorella were shielded, the formation of calcite was reduced. The ability of Ca2+ and Sr2+ concentration influence on the crystal form of calcite and aragonite was reduced and the control ability of Ca2+ and Sr2+ on crystal form was weakened. It could be seen that ester group had a great influence on the nucleation orientation of the crystal.(4) It was easy to produce vaterite structure on the calcium and strontium mineralization system under the coprecipitation system. After adding Coccolith, it inhibited the production of vaterite and form the stable structure of aragonite. It was mainly due to the Coccolith adsorption of Ca2+ in environment for its bio mineralization, resulting in reduction of Ca2+ concentration in the system. After adding a certain amount of strontium, the solution viscosity increased. The attraction of -OH group to Ca2+ would be affected by the polysaccharide of the metabolites, which could lead to the reduction of adsorption effect for Ca2+ Therefore it was not easy to generate vaterite structure. With the increasing of doped strontium ions content, the formation of crystal particles gradually became thin, calcite quantity decreased. It had obviously inhibitory effect on the formation of calcite. The crystal morphology changed gradually. Calcite(104) surface characteristic peak presented first to small angle then to big angle movement in the process of crystal growth. Thus crystal growth was a process of dissolution recrystallization.(5) The vital effect could be analysed through the bio mineralization on calcium and strontium by light and dark treatment. In the light conditions, it was easier to induce the formation of calcite, because the increasing of Chlorella cells and organic metabolites could enhance adsorption capacity of Ca2+ under the photosynthesis of Chlorella. When the Coccolith carryed on the photosynth, its own metabolism needed to consume a part of Ca2+ in the system, which leaded to the reduction of Ca2+ and the inhibition of the formation of calcite. When adding the Sr2+, it could weaken the adsorption quantity of Ca2+ and promote the formation of calcite. In terms of aragonite, light promoted its growth and dark reactions inhibited its growth.Based on the above results we could find that Chlorella and Coccolith had a certain regulation ability on bio mineralization of calcium strontium ions. Different algal species had different effects for the same system. The same algae species had different effects on the mineralization of different doped strontium content. It was closely related to the cell of Chlorella, Coccolith and the content of strontium ions. This provided a theoretical basis for new methods and techniques of analysis and regulation for biological mineralization.