Construction Of Three-dimensional Flower-spherical CuFe-LDHs/FeOOH Composites And Their Application In The Removal Of Congo Red And Orange Ⅱ

In recent years,with the continuous development of textile,leather,paper making,printing and other industries,more and more anionic dyes have entered the water body.These anionic dyes have deep chromaticity,high toxicity,and are difficult to degrade,which will threaten the health of human,animals and plants when they flow into the ecosystem.Therefore,the removal of anionic dyes in water has great significance.The adsorption method is widely concerned because of its advantages such as high removal efficiency,convenient operation and low cost and the key of the adsorption lies in the selecting of adsorbents.However,the traditional adsorbents have some disadvantages such as small adsorption capacity and non-reusability,which limit the wide application of adsorption methods.Therefore,this paper aims to prepare a new type of layered double hydroxides composites with low cost,simple synthesis route,reusability,large adsorption capacity and environment friendly,and apply them for the removal of anionic dyes in water.On account of the above research status and theoretical basis,the specific work of this dissertation mainly included the following:1.CuFe-LDHs/FeOOH was synthesized by urea hydrothermal method using urea as alkali source and Cu²⁺and Fe³⁺as lamellar ions.Then,the morphology and structure of as-synthesized materials were characterized by SEM,FT-IR,XRD,XPS and BET.According to SEM,Cu Fe-LDHs/Fe OOH presented a three-dimensional flower spherical structure.By FT-IR characterization,the interlaminar anion of the prepared Cu Fe-LDHs/Fe OOH wasCO₃^2-.According to XRD characterization,Cu Fe-LDHs/Fe OOH was indeed composed of Cu Fe-LDHs and Fe OOH.According to XPS characterization,Fe,C,O and Cu were the main constituent elements of Cu Fe-LDHs/Fe OOH.According to BET characterization,the prepared Cu Fe-LDHs/Fe OOH had a single point surface area of26.4872 m²·g^-1,pore volume of 0.09740 cm³·g^-1and average pore diameter of 14.2850 nm,and belonged to the mesoporous material.According to the Zata potentiometer,the isoelectric point of Cu Fe-LDHs/Fe OOH was p H=3.0,the material was negatively charged when p H>3.0 and was positively charged when p H<3.0.2.Using the prepared CuFe-LDHs/FeOOH as adsorbents,the application of Cu Fe-LDHs/Fe OOH in the removal of Congo red and orange II was studied by static adsorption method.The effects of p H value,initial concentration of Congo red and OrangeⅡ,reaction time and reaction temperature on the adsorption of Congo red and OrangeⅡby Cu Fe-LDHs/Fe OOH were investigated.And we also studied the kinetics,thermodynamics and thermodynamic behavior of Cu Fe-LDHs/Fe OOH on the adsorption process of Congo red and OrangeⅡ,and speculated the possible adsorption mechanism.The experimental results showed that at 45℃,when Congo red solution p H value was 11.5,the initial concentration was 1000 mg·L^-1,the ultrasonic time was 9 h,the adsorption of Congo red by Cu Fe-LDHs/Fe OOH reached equilibrium and the maximum adsorption capacity was8449.28 mg·g^-1.At 45℃,when OrangeⅡsolution p H value was 11,the initial concentration was 500 mg·L^-1,the ultrasonic time was 2.5 h,the adsorption of OrangeⅡby Cu Fe-LDHs/Fe OOH reached equilibrium and the maximum adsorption capacity was819.67 mg·g^-1.The adsorption process of Congo red by Cu Fe-LDHs/Fe OOH was accorded with Freundlich isotherm adsorption model（R²>0.99）and the quasi-first order dynamics mode（R²>0.99）.The experimental results showed that the adsorption of OrangeⅡby Cu Fe-LDHs/Fe OOH was accorded with Freundlich isotherm adsorption model（R²>0.99）and the quasi-second order dynamics model（R²>0.99）,and the adsorption was controlled by the rate limiting step.The recycling of Cu Fe-LDHs/Fe OOH was investigated by means of thermal desorption.After repeated use for 3 times,the adsorption capacity of Congo red by Cu Fe-LDHs/Fe OOH still maintained at a high level;after repeated use for 2 times,the adsorption capacity of OrangeⅡby Cu Fe-LDHs/Fe OOH still maintained at a high level.Finally,Cu Fe-LDHs/Fe OOH was applied for the removal of Congo red and OrangeⅡfrom river water,lake water and Yangtze River water.The results showed that Cu Fe-LDHs/Fe OOH could effectively remove Congo red and OrangeⅡfrom the actual water.