Synthesis Of ZIFs/Hydrotalcite Composites And Their Adsorption Performances For Phthalic Acid Form Water

In this paper,hydrotalcite consisting of different metal elements was regared as a carrier for the in-situ growth of ZIFs on the surface of the hydrotalcite.The morphologies and structures of as-synthesized composites were characterized by XRD,SEM,CHN elemental analysis,XPS,TG,and N₂ adsorption-desorption methods.In addition,the adsorption properties for phthalic acid of the synthesized materials were tested under different conditions.The adsorption datas were fitted by the adsorption kinetic models and the adsorption isotherm models to further study the adsorption behavior.The main work included:?1?Zn-Al hydrotalcites?Zn-Al LDH?with different Zn/Al molar ratios were synthesized by co-precipitation method.Then,the hydrotalcite was used as a carrier and ZIF-8/LDH composites with different Zn/Al molar ratios were synthesized by in-situ growth method.The effect of Zn/Al molar ratios on the structure and morphology of the composites and the content of ZIF-8 was investigated.The composites were used as adsorbent to remove phthalic acid.The effect of the adsorbent adsorption time,initial concentration,adsorption temperature and pH on the adsorption performance were investigated,and the adsorption thermodynamics process were fitted by Langmuir,Frendlich and Langmuir-Frendlich adsorption isotherm model;the adsorption kinetics were fitted by pseudo-first order kinetic model,pseudo-second order kinetic model and intraparticle diffusion model.Finally,the regeneration of the adsorbent was tested.The results showed that the structure of ZIF-8 existed in the composites with different Zn/Al molar ratios after loading,and the content of ZIF-8 in the composites was higher at lower Zn/Al molar ratios.When Zn/Al molar ratios up to 4,the initial concentration of phthalic acid was 100 mg L^-1 and the temperature was 20 ^oC,the adsorption capacity reached the maximum,which was approximately 520 mg g^-1.The adsorption kinetics were well fitted the pseudo-second order kinetics model;the equilibrium adsorption isotherms could match well with Langmuir-Freundlich adsorption model.In addition,ZIF-8/LDH has excellent regeneration performance.?2?Co-precipitation method was used to synthesize Co-Al hydrotalcite.Then ZIF-67/LDH composite was synthesized by in-situ growth method.The composite was used as adsorbent to remove phthalic acid.The effect of the adsorbent adsorption time,initial concentration,adsorption temperature and pH on the adsorption performance were investigated,and the adsorption thermodynamics process were fitted by Langmuir,Frendlich and Langmuir-Frendlich adsorption isotherm model;the adsorption kinetics were fitted by pseudo-first order kinetic model,pseudo-second order kinetic model and intraparticle diffusion model.The results showed that there was a large number of ZIF-67 crystals on the hexagonal Co-Al LDH's surface after loading,indicating that ZIF-67was successfully synthesized in the composite.At 20 ^oC,C₀=100 mg L^-1,the adsorption capacity was about 530 mg g^-1.The adsorption kinetic datas were well fitted the pseudo-second order kinetic model;the equilibrium adsorption isotherms could match well with Langmuir-Freundlich adsorption model.