Continuous Flow Production Of Porous Calcium-magnesium Silicate And Its Bioactivity

Dolomite is an abundant natural carbonate mineral,and the composition ratio of Ca and Mg of ideal dolomite is 1:1,which provides raw materials for the calcium and magnesium-derived products.In addition,products from dolomite are mostly low-value-added products,such as adsorbents,fertilizer additives or flame retardants.The conventional conversion processes are energy-intensive and polluted,so it is expected to use dolomite as a raw material to prepare high value-added materials through a more environmentally friendly and energy-saving method.However,bioglasses are composed of a network of silica modified by the addition of certain network modifiers,such as Ca,Na,and P.Therefore,we selected the lightly burned dolomite as calcium and magnesium sources to synthesize calcium-magnesium silicate bioactive materials by a clean continuous flow method.Firstly,the composition of raw dolomite was analyzed and characterized.Then,the lightly-burned dolomite acid hydrolysis solution,Na₂Si O₃·9H₂O and template P123 were used to synthesize calcium and magnesium silicate materials respectively by sol-gel method and continuous flow method.In continuous flow process,the influence of the reactor inner diameter and feed flow rate on the structure of the material were investigated.Here,we demonstrated that lightly-burned dolomite was converted to porous calcium-magnesium silicate by a green and efficient continuous-flow synthesis method.Then,the in vitro biological properties of the materials were tested.Finally,the reaction mechanism of porous calcium magnesium silicate material was proposed.In this study,the porous calcium magnesium silicate material（p-CMS-C-2.5）was synthesized by continuous flow method.The samples were characterized by powder X-ray diffraction,Fourier transformed infrared spectroscopy,N₂ adsorption/desorption isotherms,thermogravimetric analysis,scanning electron microscopy and transmission electron microscopy.The results indicated that porous calcium magnesium silicate can be obtained by continuous flow synthesis with a 2 mm inner diameter reactor and an injection rate of 2.5 m L/min.The results suggested that the sample p-CMS-C-2.5possesses high specific surface area of about 443.13 m²/g and possesses mesoporous channels approximately 10 nm and some macropore structure.The maximum water absorption of p-CMS-C-2.5 reached 58%,and weight loss ratio reached 42%after immersing in Tris-HCl solution for 30 days,which indicated its good biodegradability.Besides,hydroxyapatite was formed on the surfaces after immersing in simulated body fluids（SBF）for 3d,which means the sample p-CMS-C-2.5 possessed good bioactivity.In summary,the porous calcium magnesium silicate material synthesized by continuous flow could be the base material of the potential bone repair biomaterial.In short,dolomite was converted into porous calcium magnesium silicate by green and efficient continuous flow synthesis method,achieving the green transformation of non-metallic minerals into biomaterial at a low cost.This reserch provided perspectives for the development and research of low-cost,high-value-added biomaterials.