The Preparation Of Ion Modified Hydroxyapatite And Its Applications On Adsorption

With the increase of toxic and carcinogenic synthetic dyes discharged from industrial wastewater,they threaten the biodiversity of aquatic ecosystems and the quality of local water sources,which has increasingly become an environmental concern.However,the removal of non-biodegradable dyes in wastewater still requires huge costs and technologies that are affected by the environment.Among various removal strategies such as coagulation,photocatalytic degradation,membrane separation,and biological treatment,adsorption is a promising method.Due to its excellent biocompatibility,slow biodegradation,good mechanical stability,photocatalytic degradation activity,and excellent adsorption performance,hydroxyapatite(HA)has a lot of research in the environment.Especially the ion modification of HA has become a research hotspot in recent years.Therefore,it is of great significance to search for an adsorbent with a wide range of sources,excellent adsorption performance and recyclable use.The content and conclusions of this paper are as follows:(1)The preparation of carbonate doped hydroxyapatite and its applications on adsorption.The increasing content of harmful dyes in industrial wastewater has become a serious environmental problem worldwide.In this chapter,through the hydrothermal method,under the action of ethylenediaminetetraacetic acid(EDTA)and cetyltrimethylammonium bromide(CTAB),a high concentration of CO32-is added during the synthesis process to prepare a layered carbonate doped hydroxyapatite(LCHA).The morphological changes of HA were studied by SEM.The structure and crystal phase of LCHA were verified by XRD,FTIR,Raman and XPS.In addition,the adsorption performance of azo dye carmine and phenothiazine derivative methylene blue were also studied on the material.Carmine is an anionic dye,and methylene blue is a cationic dye.The kinetic and thermodynamic parameters are discussed in detail.The results show that the synthesized LCHA has better adsorption performance than ordinary hydroxyapatite,and the adsorption performance of carmine is better than the adsorption performance of methylene blue.It has a good adsorption effect on anionic dyes.Adsorption is dominated by chemical adsorption,which tends to be single-layer adsorption.Increasing the temperature is conducive to the progress of the reaction and improves the adsorption effect.It can maintain high adsorption performance under neutral and weak alkaline conditions.(2)Preparation of iron-doped carbonated hydroxyapatite and its applications on adsorption.On the basis of the previous chapter,this chapter adds Fe3+in the hydrothermal reaction process,and uses CHA as the matrix to modify HA through Fe3+and CO32-double doping.The Fe-doped carbonated hydroxyapatite is successfully synthesized.The synthesized sample is rod-shaped,so it is abbreviated as RCHA.The influence of doping with different Fe3+content on the morphology of CHA was studied,and the relationship between the aging time and the length of the rod was also explored.Commonly used physical characterization is also used to understand the chemical structure and crystal phase determination of RCHA.In the adsorption characteristic experiment,it is proved that the adsorption performance of RCHA is better than that of LCHA,and it can adsorb anionic dyes well.The BET test data also shows that RCHA has a larger specific surface area and has more adsorption active sites.In addition,the adsorption test results also show that RCHA conforms to the second-order kinetic equation and the Langmuir model.The adsorption method is single-layer adsorption,mainly chemical adsorption.High temperature also has a positive effect on the adsorption of dyes.A better adsorption effect can be obtained near a neutral environment.(3)Two-step hydrothermal method for preparing iron-doped carbonated hydroxyapatite and its applications on adsorption.In this chapter,the synthesis process of the previous part is improved.Fe-doped CHA is synthesized in two steps by hydrothermal method.The spherical calcium hydrogen phosphate is first hydrothermally synthesized,and then it is transformed into spherical Fe-CHA(SCHA).The process and mechanism of its morphology change are explored.The structure and crystal phase transition were also characterized.The results show that Fe doping has a certain effect on the spherical structure of SCHA,and the adsorption performance of SCHA obtained by the two-step method is better than that of RCHA.Adsorption is also mainly single-layer adsorption,chemical adsorption occupies the main part,and a proper increase in temperature can be beneficial to the adsorption and treatment of dyes.SCHA has higher adsorption capacity in neutral,weakly alkaline and weakly acidic applications.By improving the synthesis process,the specific surface area of the material is increased,and the adsorption performance is enhanced,so as to provide guidance for the treatment of dye wastewater in large-scale industrial applications.