Study On Adsorption Performance And Mechanism Of Peanut Husk Lignocellulose-based Hydrogel For Cadmium And Lead In Water

Due to their high biological toxicity,cadmium（Cd）and lead（Pb）can not only affect the growth and development of plants,but also endanger human health and life through the amplification of the food chain.Therefore,it is of great significance to effectively remove Cd and Pb in water.In recent years,the application of hydrogel adsorbents to treat heavy metal ion wastewater has gradually attracted attention.This method has the advantages of simple operation,low cost,and no secondary pollution.In this paper,lye was used to extract lignocellulose from peanut shells as monomer,and two peanut shell lignocellulose-based hydrogel materials(peanut shell lignocellulose-polyacrylic acid hydrogel（PS-PAA）and peanut shells lignocellulose/β-cyclodextrin/polyacrylic acid composite hydrogel（PS/β-CD/PAA）were prepared,and used them for the adsorption of Cd²⁺and Pb²⁺.The effects of various factors,such as the dosage of hydrogel adsorbent,the p H value of the solution,the adsorption time,the temperature and so on,had been studied.The process and the adsorption mechanism of adsorbing Cd²⁺and Pb²⁺by the hydrogel adsorbent were discussed to provide a certain theoretical reference for the resource utilization of peanut shells and the development of peanut shell lignocellulose-based hydrogel materials’design and application in the treatment of heavy metals in water.The two main research works were as follows:（1）Preparation,characterization of PS-PAA and study on its adsorption performance and mechanism for Cd²⁺and Pb²⁺The PS-PAA hydrogel adsorbent was prepared by a water bath heating polymerization method,and the hydrogel material was characterized by SEM,FT-IR,XRD,TG,compression and tension,indicating that the PS-PAA hydrogel adsorbent had a three-dimensional network structure,contained a large number of functional groups,certain mechanical properties and thermal stability.PS-PAA hydrogel adsorbent showed good adsorption performance for Cd²⁺and Pb²⁺,and had a good removal effect on Cd²⁺and Pb²⁺in a wide p H range(Pb²⁺（3.0-5.7）,Cd²⁺（4.0-8.4）).The adsorption equilibrium time of PS-PAA hydrogel to Cd²⁺and Pb²⁺was short,and the adsorption process conformed to the quasi-two-stage adsorption kinetic model,and was determined by both external diffusion and internal diffusion.Thermodynamic studies showed that the adsorption process was a spontaneous exothermic process,and the adsorption conformed to the Langmuir isotherm adsorption model.The analysis of FT-IR and XPS showed that the adsorption mechanism of Cd²⁺and Pb²⁺to PS-PAA hydrogel was the complexation or coordination of Cd²⁺and Pb²⁺with functional groups（groups containing O and N）interaction.（2）Preparation and characterization of PS/β-CD/PAA composite hydrogel and study on its adsorption performance and mechanism for Cd²⁺and Pb²⁺Usingβ-cyclodextrin as the reinforcing material,PS/β-CD/PAA composite hydrogel adsorbent was prepared by the heating polymerization method.Compared with PS-PAA,PS/β-CD/PAA had a more stable three-dimensional network,and its mechanical properties were better.The PS/β-CD/PAA could effectively remove Cd²⁺and Pb²⁺in a wide p H range of3-8.The adsorption could reach adsorption equilibrium within 60 minutes.And the adsorption process conformed to the quasi-second-order kinetic equation and Langmuir isotherm adsorption model.The analysis of FT-IR and XPS showed that the adsorption of composite hydrogel for Cd²⁺and Pb²⁺was carried out through ion exchange,complexation or coordination action.And when the 4 g L^-1composite hydrogel material was used to treat heavy metals in AMD,the removal efficiency of Pb²⁺,Cu²⁺and Cd²⁺were 76.4%,88.6%and72.9%,respectively.PS/β-CD/PAA can be adopted to treat actual wastewater containing Pb²⁺,Cu²⁺and Cd²⁺.The good adsorption performance of peanut shell lignocellulose-based hydrogel for Cd²⁺and Pb²⁺makes it can be used for the adsorption and remove of Cd²⁺and Pb²⁺in water.It provides a theoretical basis for the resource utilization of peanut shells and the application of peanut shell lignocellulose-based hydrogel materials in water heavy metal treatment.