Preparation Of Chitosan Antibacterial Composite Materials And Study On Their Adsorption Properties For U(?)

Chitosan is widely used as a preservative in food preservation because of its strong antibacterial properties.In addition,chitosan has been applied gradually in depth in other fields by developing its functions such as adsorption,film formation and biodegradability.In this study,aiming at the problem of abundant uranium resources in seawater but difficult extraction,based on the excellent physical and chemical properties of chitosan,a new type of chitosanbased composite material with high adsorption performance and strong antibacterial ability was prepared,in order to realize the realization of chitosan.At the same time,it provides a new idea for uranium extraction from seawater.In this paper,CS-BT composite aerogels and CS-BT-PG composite membranes were prepared by modification using two biological resources,chitosan and bayberry tannin.The adsorption properties of CS-BT composite aerogel and CS-BT-PG composite membrane in deionized water and seawater were investigated,respectively.The main findings are as follows:(1)The CS-BT composite aerogel with three-dimensional porous and high specific surface area(26.06 cm2/g)was prepared by mixing chitosan and bayberry tannin for modification at 45 °C and freeze-drying.Analysis of the leaching rate of bayberry tannin from the aerogel under different p H conditions showed that chitosan and bayberry tannin were successfully cross-linked and maintained good stability in the p H range of 3-9.The static adsorption of U(VI)by aerogel in deionized water was analyzed,and the results showed that when the initial concentration of uranium ions was 20 mg L-1,p H=5.0,the feeding amount was 0.02 g,and the temperature was 25 ?,CS-BT composite For the aerogel pair,the adsorption of U(VI)reached equilibrium within 15 h,and the maximum removal rate was as high as 99%.The changes before and after adsorption were analyzed by XPS,which showed that the adsorption of uranium by aerogel was mainly through the chelation of-OH and U(?).According to the analysis of the fitting results of the kinetic model and adsorption isotherm model,the adsorption process of CS-BT composite aerogel is more in line with the pseudosecond-order kinetic model and the Freundlich nonlinear model,and the adsorption process of CS-BT composite aerogel is a multilayer Adsorption-based chemical reaction.Further analysis of thermodynamic parameters indicates that the aerogel adsorption of U(VI)is a nonspontaneous,exothermic,disorder-increasing reaction.Finally,the effect of multiple coexisting ions on the adsorption of uranium was investigated,and the results showed that only Cr3+ had a small inhibitory effect on adsorption,and the material could largely avoid the interference of impurity ions such as Pb²⁺,VO^3-,Fe³⁺,Ni²⁺ and Cd²⁺.(2)The antibacterial properties of CS-BT composite aerogel in actual seawater system and its adsorption effect on U(VI)were further investigated.The results show that the aerogel has a significant inhibitory effect on B.aquimaris;when the amount of aerogel added is 0.03 g,B.aquimaris cannot multiply within 24 hours,and the material is not decomposed by B.aquimaris in large quantities.The results of uranium adsorption in seawater show that when the initial concentration of uranium ions is 8 mg L-1,p H=5.0,the feeding amount is 0.02 g,and the temperature is 25 ?,the aerogel adsorption can reach equilibrium within 400 min,and the removal rate is as high as 99%.The competitive effects of various ions on the adsorption of uranium were further investigated,and the results showed that the adsorption capacity of aerogels was in the order of UO₂²⁺ > VO₃^-> Mg²⁺ > Na⁺ > Ni²⁺ > Fe³⁺ > Pb²⁺;the adsorption capacity for uranium ions was the largest,reaching 1.5255 mg g-1,the selectivity reached 70%.(3)After modification of chitosan and bayberry tannin,adding a film-forming agent,and defoaming by ultrasonic,the CS-BT-PG composite membrane was prepared,and the adsorption of U(?)by the composite membrane in deionized water was investigated.Effect.The results show that under the conditions of initial uranium ion concentration of 20 mg L-1,p H=5.0,feeding amount of 0.02 g,and temperature of 25 ?,the removal rate of uranium by the composite membrane can be as high as 99%,and the adsorption capacity can reach 49.09 mg g-1.According to the fitting results of the kinetic model and adsorption isotherm model,the uranium adsorption process of the composite membrane is more in line with the pseudosecond-order linear kinetic model and the Freundlich adsorption isotherm model.The thermodynamic parameters of U(VI)absorption by the composite membrane were calculated and analyzed,indicating that the process of U(VI)absorption by the CS-BT-PG composite membrane was a non-spontaneous endothermic reaction with increasing disorder.Using the antibacterial property of chitosan,the prepared antibacterial composite material is used to adsorb U(?),which has the advantages of good antibacterial property and high adsorption performance of the material.This realizes the cross-domain application of food chitosan,and also provides a new idea for uranium extraction from seawater.