Preparation Of Nano Ca（OH）₂ By Microemulsion-hydrothermal Method And Its Photocatalytic Degradation Of MB

In this paper,calcium hydroxide nanomaterials was successfully prepared by the combination of microemulsion and hydrothermal method.The photocatalytic degradation performance of the prepared material on methylene blue under visible light and its role in the degradation process were explored.Microemulsion is prepared by adding surfactant,co-surfactant（Cyclohexane）and cyclohexane as the oil phase,and the microemulsion was treated with hydrothermal method,and finally nano-scale Ca（OH）₂was successfully prepared.The morphological characteristics,chemical structure and photocatalytic performance of the materials were systematically analyzed through a series of characterization methods such as XRD,SEM,Raman,FTIR,XPS,EPR,UV-vis DRS,and PL.The experimantal results show that the prepared nano-calcium hydroxide has a particle size of 300～500 nm with high purity.The crystallinity is good and the corresponding morphology is hexagonal crystal.The band gap of the nano calcium hydroxide prepared by this work is reduced to 2.46 e V,which improves the light response range,enhances the light absorption performance of the material,and improves the utilization rate of solar energy.Under dark conditions,the adsorption equilibrium for MB can be reached in 30 minutes,the maximum adsorption efficiency can reach 11.7%,Adding the best solid-to-liquid ratio of 0.33 g/L nano-calcium hydroxide can achieve a total removal rate of 98.7%for methylene blue under visible light.The photocatalytic reaction kinetics follows the quasi-first order kinetic equation.The mechanism of photocatalytic degradation of methylene blue under visible light was explored by EPR detection and free radical trapping experiments and HPLC-MS.The hydroxide provided by the nano-calcium hydroxide and the oxygen molecules absorbed by the surface of the undissolved part capture the electrons generated by the photocatalytic,and the two active substances are converted to realize the degradation of methylene blue.For the active substance,the hydroxyl free radicals plays a major role,and the superoxide radical acts the secondary role.In summary,nano-calcium hydroxide prepared by microemulsion-hydrothermal method exhibits excellent performance in the process of photodegrading methylene blue.