Preparation Of Chitosan/β-Cyclodextrin Composites And Comparative Study On Their Adsorption Capacity For Inorganic Substances

With the rapid development of urbanization and industrialization,some industries such as manufacturing and chemical industry will discharge a large amount of non-standard wastewater in the production process,and the wastewater contains a large amount of inorganic substances,including excessive chloride ion（Cl^-）wastewater,it will cause certain damage to vegetation,crops,human body,mechanical equipment and environment,and the same heavy metal ions such as zinc ions(Zn²⁺)will cause plant death in excess and pose a serious threat to human health.In recent years,because of its simple operation,low cost,reusable,environmental protection and other advantages,the adsorption method is often used in the treatment of various types of wastewater.In this study,β-cyclodextrin polymer（β-CDP）was synthesized by pretreatingβ-cyclodextrin（β-CD）with citric acid（CA）,then,chitosan（CTS）was crosslinked withβ-CDP using glutaraldehyde to prepare a chitosan/β-cyclodextrin（CTS/β-CDP）complex,for the adsorption of inorganic substances in wastewater.CTS/β-CDP complex before and after adsorption of Cl^-and Zn²⁺was characterized by Fourier-transform infrared（FT-IR）spectroscopy,scanning electron microscopy（SEM）,and X-ray diffraction（X-RD）.FT-IR and X-RD prove that CTS/β-CDP complex was synthesized,the absorption peaks after adsorption of Cl^-and Zn²⁺changed,but the diffraction peaks did not change much,indicating that the crystal structure of the sample was not changed.The SEM images showed that the surface of CTS/β-CDP complex was rough,the number of adsorption sites increased,and Cl^-and Zn²⁺were adsorbed.The effects of preparation conditions such as mass ratio of CTS toβ-CDP,reaction temperature,reaction time,25%glutaraldehyde addition on the adsorption rate of inorganic compounds Cl^-and Zn²⁺in wastewater were further investigated during the preparation of the composite.The optimum experimental conditions were as follows:a mass ratio of 1:5,a reaction temperature of 80℃,a reaction time of 90min,and 1.5 mL of glutaraldehyde,under these optimal conditions,the adsorption rates of Cl^-using CTS/β-CDP complex were 40.78%.The optimum experimental conditions were as follows:a mass ratio of 3:10,a reaction temperature of 80°C,a reaction time of 90min,and 2mL of glutaraldehyde,under these optimal conditions,the adsorption rates of Zn²⁺using CTS/β-CDP complex were 78.92%.Comparative studies on the adsorption of CTS,β-CD,β-CDP,and CTS/β-CDP complex showed that CTS/β-CDP complex had the highest adsorption efficiency.CTS andβ-CDP was cross-linked to prepare a CTS/β-CDP composite membrane was prepared by the casting method for the adsorption of inorganic substances in wastewater.CTS/β-CDP composite membrane before and after adsorption of Cl^-and Zn²⁺was characterized by FT-IR,SEM,and X-RD.FT-IR and X-RD prove that CTS/β-CDP composite membrane was synthesized,the absorption peaks after adsorption of Cl^-and Zn²⁺changed,but the diffraction peaks did not change much,indicating that the crystal structure of the sample was not changed.The SEM images showed that the surface of the composite membrane was rougher than the porous CTS membrane,which increased the number of adsorption sites and the adsorption efficiency,and Cl^-and Zn²⁺were adsorbed.The effects of the preparation conditions,such as the reaction temperature of CTS andβ-CDP,the concentration of acetic acid,the amount of water added when dissolvingβ-CDP,and the soaking time of sodium hydroxide（NaOH）,on the adsorption rates of Cl^-and Zn²⁺in wastewater were investigated.The results showed that the maximum adsorption rate 41.26%of Cl^-were obtained when the reaction temperature between CTS andβ-CDP was 50°C,the concentration of acetic acid was2.5%,the amount of water was 25 mL,and the soaking time in sodium hydroxide was 3h.The results showed that the maximum adsorption rate 94.14%of Zn²⁺were obtained when the reaction temperature between CTS andβ-CDP was 50°C,the concentration of acetic acid was 2%,the amount of water was 30 mL,and the soaking time in NaOH was1 h.Comparative studies on the adsorption of CTS membranes,CTS/β-CDP complex,and CTS/β-CDP composite membrane showed that CTS/β-CDP composite membrane had the highest adsorption efficiency.The swelling degree and transmittance of the CTS/β-CDP composite membrane were lower than the CTS membrane,which is more conducive to recycling after wastewater treatment.The experiment proves that the CTS/β-CDP composite material has higher adsorption efficiency on inorganic cations such as Zn²⁺than inorganic anions such as Cl^-and the CTS/β-CDP composite membrane can fully contact with inorganic substances from the time of adsorption,and can be easy to recycle,it can be known that the adsorption effect and practical application are stronger than CTS/β-CDP complex.