Preparation Of Modified Chitosan Membrane And Its Adsorption Properties For Cr???and Cu²⁺

Water is an indispensable material resource for human survival and development.With the development of global urbanization and industrialization,serious water pollution has become one of the major challenges facing humanity.The adsorption method is widely used in the treatment of drinking water,industrial wastewater and other wastewater due to its advantages of simple operation,low cost and environmental protection.The membrane adsorbent prepared or modified by chitosan has the advantages of simple preparation method,antibacterial property,non-toxicity,easy separation after adsorption and so on,which has attracted attention in the field of wastewater treatment.However,in practice,it still has the disadvantages of being easily soluble in acid,low adsorption efficiency,and long adsorption equilibrium time.In this paper,combined with the water treatment mechanism of chitosan membrane,the chitosan membrane was modified to improve its adsorption performance while improving its solubility.In view of the shortcomings of chitosan film being soluble in acid,a crosslinking agent was added to the film matrix to modify it.The chitosan was used as raw material,PEG-6000was used as plasticizer,glutaraldehyde was used as cross-linking agent,the chitosan film was prepared by solvent evaporation method.The surface morphology and structure were characterized by SEM and FT-IR.And the potassium dichromate solution was used as a simulated pollutant to study the adsorption performance of chitosan membrane on Cr???.The influence of various factors on the adsorption effect was discussed,the results showed that the addition of glutaraldehyde had little effect on the adsorption performance of chitosan membrane.When the initial concentration of Cr???was 100mg/L,the amount of adsorbent was 0.01 g,the HAc concentration was 1%?v/v?,the NaOH concentration was 0.2 mol/L,the NaOH soaking time was 4 h,the pH of potassium dichromate solution was 3,the chitosan film had the largest adsorption amount of Cr???,which was 163.1 mg/g.The adsorption reached equilibrium within 100 min.After three cycles,the adsorption capacity was 63.2mg/g.When the amount of glutaraldehyde added was 0.1 mL,the prepared chitosan membrane was immersed in HCl solution with pH of 1-5 for 30 days.Compared with the chitosan film to which no crosslinking agent wss added,the acid resistance was greatly improved.Based on the chelation mechanism of chitosan on metal ions and electrostatic adsorption mechanism,the adsorption efficiency was improved by layer-by-layer adsorption.Chitosan was used as raw material,PEG-6000 was used as plasticizer,glutaraldehyde was used as cross-linking agent,the chitosan film?CS?was prepared by solvent evaporation method.The prepared CS was immersed in ferric chloride solution and subjected to shaking adsorption Fe³⁺to obtain CS-Fe.It was characterized by SEM and FT-IR.The adsorption performance of CS-Fe on Cr???was studied by using potassium dichromate solution as simulated pollutants.The influence of various factors on the adsorption effect was discussed,the results showed that when the initial concentration of Cr???was 100 mg/L,the concentration of Fe³⁺was 250mg/L,the concentration of HAc was 1.5%?v/v?,the concentration of NaOH was 0.2 mol/L,and the soaking time of NaOH was 3 h.the amount of adsorbent was 0.01 g,and the pH was 3,the maximum adsorption capacity was 252.6 mg/g,which was 2 times of the adsorption amount of the chitosan membrane under the same conditions.The adsorption reached equilibrium within 60 min.The adsorption isotherm conformed to both the Langmuir model and the Freundlich model.The adsorption kinetics conformed to pseudo second-order kinetic model.After three cycles,the adsorption capacity still reached 113 mg/g.The chitosan was used as raw material,PEG-6000 was used as plasticizer,glutaraldehyde was used as cross-linking agent,PVA with high flexibility,good film forming performance and active site was added,chitosan/polyvinyl alcohol membranes containing Cu²⁺template(CS(Cu²⁺))/PVA)were prepared by blending and ion-imprinting.The surface morphology and structure were characterized by SEM and FT-IR.The copper sulfate solution was used as a simulated pollutant to study its adsorption performance on Cu²⁺.The influence of various factors on the adsorption effect was discussed,the results showed that when the PVA content was 7.5%,the initial concentration of Cu²⁺was 100 mg/L,the HAc concentration was 1.5%?v/v?,the NaOH concentration is 0.2 mol/L,the NaOH soaking time is 2 h,the amount of adsorbent was 0.01 g,and the pH was 5,CS(Cu²⁺)/PVA had the maximum adsorption capacity of Cu²⁺,and the largest adsorption amount was 182.1 mg/g,which was 1.9 times of the adsorption amount of chitosan membrane under the same conditions.The adsorption reached equilibrium within 90 min.The adsorption isotherm conformed to both the Langmuir model and the Freundlich model.The adsorption kinetics conformed to the pseudo second-order kinetic model.After three cycles,the adsorption capacity still reached 102.7 mg/g.In the mixed solution containing Pb²⁺,the adsorption capacity of CS(Cu²⁺)/PVA for Cu²⁺was 150.39 mg/g,which was 7 times higher than that of Pb²⁺,having excellent adsorption selectivity.