| With the in-depth study of the toxicity and pathogenicity of nitrite,the removal and detection of nitrite in water has attracted more and more attention.In the first part of this study,polyvinyl alcohol?PVA?was blended with chitosan?CS?to obtain a chitosan polyvinyl alcohol mixed gel.Quaternized chitosan polyvinyl alcohol cross-linked membrane?QCPC?was prepared by cross-linking hyperbranched jimicy quaternary ammonium salt with the mixed gel.The structure,morphology,mechanical properties and swelling properties of QCPC were investigated.The adsorption performance of QCPC on sodium nitrite?NaNO2?in the water environment was studied,and the adsorption kinetics and adsorption isotherm were studied in depth.Studies show that the adsorption of NaNO2 by QCPC conforms to the quasi-second-order kinetic equation and the isothermal adsorption process can be described by the Langmuir model.The maximum monolayer adsorption capacity is 200.00mg/g at 288K.The optimal removal conditions of NaNO2by orthogonal experiments were determined:the adsorption time was 15h,the dosage of the adsorbent was 0.8g/L,the pH was 8,and the temperature was25°C.The removal rate can still reach more than 70%after QCPC was reused3 times.In the second part of this study,QCPC was used as the binding phase of diffusive gradients in thin film?DGT?to construct a QCPC-DGT device for enrichment and detection of NO2-in water.At 25°C,the diffusion coefficient of NO2-is?2.94±0.32?×10-6cm2·s-1?n=3?.The elution efficiency reached78.53%using 0.05mol/L NaOH as the eluent for the adsorption of NO2-in the binding phase gel.The accumulation of NO2-by QCPC-DGT has no significant difference in the range of ionic strength?0.0010.1mol/L NaCl?and pH?411?.The effective adsorption capacity for NO2-by QCPC-DGT is72.18?g/cm2.The experimental results show that the in situ collection and measurement of NO2-in water environment can be carried out by the combination of QCPC-DGT sampling technology and UV spectrophotometry. |
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