Preparation And Application Of NIPAM Modified Chitosan Temperature-responsive Hydrogels

Heavy metal water pollution has always been a difficult problem in environmental pollution and control due to its characteristics of great harm,difficult management,high concealment,and great potential harm to human body.In this study,natural macromolecular chitosan?CTS?was used as the carrier,and N,N'-methylenebisacrylamide?MBAM?was used as the crosslinking agent.N-isopropylacrylamide?NIPAM?and maleic acid were successfully used?MA?modified onto chitosan to prepare chitosan-grafted poly-N-isopropylacrylamide and maleic acid hydrogels?CPNM?.The main research contents are:1.Scanning electron microscopy?SEM?,infrared spectroscopy?FT-IR?,X-ray photoelectron spectroscopy?XPS?,thermogravimetric analysis?TGA?,and elemental analysis were performed on the synthesized CPNM hydrogels to confirm Its structural characteristics and good adsorption performance for heavy metal ions.2.The swelling properties of CPNM hydrogels were studied,including:the influence of external conditions on the swelling properties of CPNM hydrogels;the structure-activity relationship of the swelling properties of CPNM hydrogels;the effects of different treatment methods on the swelling properties of CPNM hydrogels.3.The adsorption properties of CPNM hydrogels were studied,mainly including:?1?Comparison of adsorption performance between CPNM hydrogels and chitosan-grafted poly-N-isopropylacrylamide hydrogels?CPN?;?2?outside The influence of conditions on the adsorption performance of CPNM hydrogels;?3?the structure-activity relationship of CPNM hydrogels adsorption properties;?4?the effect of CPNM hydrogels adsorption properties on different treatment methods;?5?CPNM hydrogels Competitive adsorption of component heavy metal ions.4.The swelling process of CPNM hydrogels and the mechanism of adsorption of heavy metals were studied,including the mechanism of the swelling and adsorption process of CPNM hydrogels,adsorption kinetics,adsorption thermodynamics,and isothermal adsorption line.Research indicates:1.CPNM hydrogels has temperature response characteristics,its phase transition temperature is about 30?,and it has good swelling performance.Its saturated swelling rate is 20.4g·g^-1.Compared with CPN hydrogels,it is more effective for Cu²⁺,Ni²⁺,Cr³⁺adsorption performance has been greatly improved.2.At lower pH and higher temperature,CPNM hydrogels has higher adsorption performance for three kinds of heavy metal ions;the higher the initial concentration of heavy metal ions,the higher its adsorption capacity;two cations Na⁺and Ca²⁺are used as Interfering with ions,it was found that as the concentration of Na⁺and Ca²⁺increased,the adsorption amount gradually decreased;as the adsorption time increased,the adsorption amount of CPNM hydrogels to Cu²⁺,Cr³⁺,and Ni²⁺gradually increased.When the time exceeded 3 hours,adsorption The amount reached saturation.3.The higher the amount of cross-linking agent,the lower the solid content,and the lower the adsorption of three metal ions by CPNM hydrogels;using ultrasound or adding different concentrations of NaOH,HNO₃ and polyethylene glycol-4000?PEG-4000?has significantly improved Cu²⁺,Cr³⁺,Ni²⁺adsorption properties of CPNM hydrogels.4.CPNM hydrogels found that the binary competitive adsorption and ternary competitive adsorption of three heavy metal ions showed that CPNM has a higher selectivity for Cu²⁺,and its adsorption capacity is in the order of Cu²⁺>Ni²⁺>Cr³⁺;XPS energy spectrum results show that The three heavy metal ions have been successfully adsorbed,and the results of their valence band spectra show that they are mainly-COOH,-CO-NH-,-OH,-NH₂ coordination complexation;the adsorption kinetics is more in line with the quasi-second-order kinetic model,and the adsorption The isotherm is consistent with Langmuir adsorption,and the adsorption thermodynamics reflects that the adsorption process is a spontaneous endothermic process.