Study On The Synthesis Of Layered Double Hydroxides Using Dolomite As Calcium And Magnesium Source

As one of the geological minerals,dolomite is widely distributed in the world and used in iron and steel,rubber,glass.Development of calcium,magnesium of dolomite has been deeply focused,such as calcium carbonate,magnesium carbonate,magnesium hydroxide,magnesium and magnesium oxide.These products have been widely studied and industrialization.In addition,the transformation or synthesis of calcium and magnesium layered double hydroxide（Ca-Mg-Al LDH）using cheap dolomite mineral has become a hot topic in recent years.The layered Ca-Mg-Al LDH materials can be used as adsorbent,catalyst,flame retardant.The synthesis of Ca-Mg-Al LDH always using calcium salt and magnesium salt and alkaline by coprecipitation method.using dolomite as raw materials in laboratory.The existing methods for the synthesis of Ca-Mg-Al LDH is using calcined dolomite under high temperature calcined.The process consume much energy,is complex and the purity of the product is not high.The simple pretreatment of dolomite by acid or salt dissolving is the important part for making full use of the calcium and magnesium.Study on the effect of different pretreatment of raw dolomite and different mole ratio of(Ca²⁺+Mg²⁺)/Al³⁺for the synthesis of Ca-Mg-Al LDH.Different types of alkline affected the synthesis of Ca-Mg-Al LDH from dolomite,which has been dissoving acid.Effects of different hydrothermal temperature and time on the synthesis of Ca-Mg-LDH using dolomite dissolved by aluminum chloride solution.The samples were characterized by X-ray diffraction（XRD）,thermogravimetry-differential scanning calorimetry（TG-DSC）,Fourier transformed infrared（FT-IR）spectra,scanning electron microscopy（SEM）,energy dispersive spectrometer-mapping（EDS-Mapping）,transmission electron microscope（TEM）,atomic absorption spectroscopy spectrometre（AAS）,dynamic light scattering（particle analysis）and X-ray fluorescence（XRF）.The low energy consumption,environmental friendly and simple method has been investigated to prepare the LDH and make full use of dolomite.Different pre-treatment of dolomite,molar ratio of(Ca²⁺+Mg²⁺)/Al³⁺,hydrothermal temperature and time have been disscussed to study the synthesis of LDH.The best sample was synthesized using aqueous solution of dolomite and aluminium chloride hexahydrate as raw material.The best conditions were at(Ca²⁺+Mg²⁺)/Al³⁺mole ratio=1,hydrothemal temperature（T）=200?C,time（t）=24 h.The best utilization rate of Ca,Mg from dolomite to synthesize Ca-Mg-LDH reached36.3%and 95.5%respectively.The synthesis and its mechanism of Ca-Mg-LDH using dolomite and aluminum chloride as raw materials,which was prepared at the best conditions.At the same time,chlorine and carbonate of Ca,Mg salts were used to simulate the samples synthesized at optimum conditions using dolomite as raw material,to explore the structure of dolomite and how to prepare pure LDH material.The synthesis of the LDH layered material is a the breakthrough and important work.