Preparation of nano-spherical LaAlO3 and its fluoride removal performance under acidic environment
In order to solve the problem of synthesizing LaAlO3 crystalline phase with good surface properties by lowering the calcination temperature at lower pH for application in deep fluoride removal in wastewater(＜1.5mg/L),the nano-spherical perovskite LaAlO3 by co-precipitation hydrothermal method was prepared and the preparation factors affecting the surface properties of LaAlO3 was investigated.It was found by SEM,XRD,ICP-MS and BET that the formation of hydrothermal precursors of alkali carbonic acid precipitation can make Al3+and La3+precipitation more tightly bound and the optimal preparation conditions for LaAlO3 were obtained:co-precipitation pH=6,hydrothermal temperature=160℃and calcination temperature of 850℃.The behavior of F-adsorption by LaAlO3 was analyzed by static adsorption experiments and regeneration experiments systematically,and the results showed that LaAlO3 could achieve deep fluoride removal under acidic(pH＜3)conditions and the fluoride removal rate reached 93.22%at pH=2.The adsorption process conformed to the Langmuir adsorption isotherm model and pseudo-second-order kinetic model,which was a chemical monolayer adsorption with exothermic reaction.Under the condition of initial fluorine concentration of 200mg/L,the adsorption capacity of LaAlO3 adsorption reached 53.8mg/g in 8min and the equilibrium adsorption capacity reached 66.5mg/g in 4h.By using alum as desorbent,LaAlO3 can maintain more than 90%of the original fluoride removal rate after 4 cycles with excellent regeneration performance and high utilization value.
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