| With the pollution of heavy metal ions such as copper,mercury and chromium brought about by economic development,it poses a serious health threat to the growth of human beings,animals,plants and food crops,and will bring irreversible harm,at the same time,it will also cause huge economic losses.Therefore,it is of great theoretical and practical value to study a new,efficient,environmentally friendly,easily available,stable and inexpensive composite adsorbent for the adsorption of heavy metal ions in water,and to explore its adsorption characteristics and mechanism.In this study,waste Aspergillus niger mycelium and chitosan were used as raw materials to cross-link and solidify them to form a composite adsorbent.The adsorption kinetics of chitosan and Aspergillus niger mycelium-chitosan composite adsorbent was studied by Quasi-First-Order and quasi-second-order kinetic models,Langmuir and Freundlich isotherm models,and the adsorption model was established by using infrared and electron microscopy.The adsorption mechanism of the composite adsorbent was studied by technology.Finally,the analytical and regenerative abilities of the composite adsorbent were also studied.The results are as follows:1.Study on the Adsorption Mechanism of Chitosan to Cr(VI)In the static adsorption experiment,chitosan was used as raw material to investigate the adsorption effect of Chitosan on Cr(VI)under different temperatures,adsorption time,adsorbent volume and pH conditions.when the pH of the solution was 5,the dosage of adsorbent was 0.500 g,the adsorption temperature was 30?,the adsorption time was 120 min,and the concentration was 20 mg/L.The adsorption results showed that the optimum adsorption rate of chitosan for Cr(VI)was85.06%.2.Preparation of Aspergillus Niger mycelium-chitosan and its adsorption mechanism for Cr(VI)The composite adsorbent of Aspergillus Niger mycelium and chitosan was prepared by using waste Aspergillus Niger mycelium and chitosan as adsorbents,using epichlorohydrin as crosslinking agent and sodium tripolyphosphate as curing agent.In the static adsorption experiment,the effects of temperatures,time,pH value and the dosage of Aspergillus Niger mycelium-chitosan on the adsorption of chromium(VI)were investigated.The experimental results showed that when the pH of the solution of Cr(VI)is 6,the dosage of adsorbent is 0.400 g,the adsorption temperature is 50?,the adsorption time is 120 min,and the concentration was 20 mg/L,the maximum adsorption rate of Cr(VI)reaches 94.37%.Kinetic data analysis showed that the adsorption of chromium(VI)by Aspergillus Niger mycelium-chitosan biosorbent followed a quasi-second-order kinetic model(R~2=1).At the same time,the adsorption process conforms to Freundlich isotherm model,which indicates that the adsorption is a surface adsorption of heterogeneous system with uneven distribution.3.Structural Characterization of Aspergillus Niger Mycelium-Chitosan before and after AdsorptionThe structure of the composite adsorbent was characterized by scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FTIR)before and after the adsorption of Aspergillus Niger mycelium-chitosan.The results of characterization analysis showed that the rough surface and high specific surface area of the composite adsorbent were more conducive to the adsorption of heavy metal ions Cr(VI)by Aspergillus Niger mycelium-chitosan.FT-IR analysis showed that the composite adsorbent had ion exchange with oxygen-containing functional groups(—OH,—COOH).4.Analysis and Regeneration of Aspergillus Niger Mycelium-ChitosanDeionized 0.1 mol/L NaOH and used as analyzer to investigate the ability of the mycelium-chitosan of Aspergillus Niger to decompose and regenerate.Regeneration experiments showed that 0.1 mol/L NaOH had a good effect on the regeneration of Aspergillus Niger mycelium-chitosan,and the regeneration rate was still over 90%after four regenerations. |
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