Study On The Adsorption Of Hexavalent Chromium And Divalent Nickel On Chitosan-loaded Nickel Ferrite Nanoparticles

At present,with the development of industry and human activities,heavy metal pollution in surface water and groundwater is becoming more and more serious.Chromium and nickel are two representative heavy metal pollutants.Due to its simple operation,adsorption method is widely used in the treatment of heavy metal wastewater,high adsorption efficiency and low operating cost.Adsorbent is the most important factor to determine the adsorption efficiency.Compared with other traditional adsorbent materials,magnetic nanomaterials have large specific surface area,convenient recovery and good adsorption effect on heavy metal ions.Chitosan,as a kind of absorbent with great potential and wide application,has been widely used in the field of environmental protection,especially in the treatment of wastewater containing heavy metals,due to its biocompatibility,environmental friendliness,antimicrobial inhibition,and in vivo degradation by humans and organisms.In this paper,synthesis of nickel ferrite nanoparticles（NF）,and its load chitosan,chitosan can be produced from load nickel ferrite nanoparticles（CNF）,compared the CNF and NF on Cr（Ⅵ）and Ni（Ⅱ）adsorption performance,in order to investigate the influence of different reaction conditions on the adsorption effect,through the analysis of the adsorption kinetics and adsorption isotherm further discusses the reaction mechanism.Specific research contents and relevant conclusions are as follows:（1）NF and CNF were prepared by hydrothermal method,and the surface properties of NF and CNF were analyzed by means of SEM,EDS,XRD and FTIR.The results showed that NF was smooth and globular,and the main elements were Fe,Ni and O.CNF has a rough surface and abundant pore structure,which is conducive to increasing its adsorption capacity.CNF well preserved the original structure of NF and chitosan,and the material was stable.In the FTIR spectrum of CNF,the characteristic peak stretching vibration of fe-o at 596 cm-1,C=H at 2865 cm-1 and n-h at 1080 and 710cm-1 appear,indicating that CNF has been synthesized,and the abundant organic functional groups on its surface are conducive to chelating reaction with heavy metals.（2）The adsorption of Cr（Ⅵ）by CNF and NF required 120 min and 240 min respectively to reach the adsorption equilibrium,and the adsorption of Ni（Ⅱ）required 180min and 240 min respectively to reach the equilibrium state.Compared with NF,under the same reaction conditions,the adsorption capacity of Cr（Ⅵ）and Ni（Ⅱ）by CNF was larger,indicating that the adsorption capacity of NF was effectively improved after the combination of NF and chitosan.When pH=2,the adsorption effect of Cr（Ⅵ）on NF and CNF was the best,with adsorption capacities of 6.08 and 15.21 mg/g,respectively.When pH=8,the adsorption effect of NF and CNF on Ni（Ⅱ）was the best,with adsorption capacities of 16.11 and 22.34 mg/g,respectively.The results of adsorption isotherm analysis showed that the Langmuir model could better fit the adsorption process of Cr（Ⅵ）by CNF（R²=0.9685）and the Freundlich model could better fit the adsorption process of Ni（Ⅱ）by CNF（R²=0.9878）.Adsorption kinetics showed that the quasi-second-order kinetic model could best fit the adsorption process of Cr（Ⅵ）and Ni（Ⅱ）by CNF,with R²of 0.9885 and 0.9902,respectively.（3）After the adsorption of Cr（Ⅵ）and Ni（Ⅱ） by CNF,SEM,EDS,XRD,FTIR and other characterization methods were further used to analyze the surface properties of the material.SEM analysis results show that the surface of CNF becomes rough after adsorption reaction.EDS analysis showed that Cr and Ni elements appeared on the surface of CNF,indicating that Cr（Ⅵ）and Ni（Ⅱ）had been adsorbed on the surface of the material.The FTIR analysis results showed that the Cr-O characteristic peak at 786cm^-1and the Ni-O characteristic peak at 2332cm^-1appeared in the CNF after Cr（Ⅵ）and Ni（Ⅱ）adsorption,indicating that some groups in CNF may have reacted with Cr（Ⅵ）and Ni（Ⅱ）,reflecting the adsorption and removal of Cr（Ⅵ）and Ni（Ⅱ）by CNF.（4）Desorption experiments showed that NaOH solution had the best desorption effect on CNF after Cr（Ⅵ）adsorption,and HCl solution had the best desorption effect on CNF after Ni（Ⅱ）adsorption.The removal rate of Cr（Ⅵ）and Ni（Ⅱ）of CNF can still be maintained above 80%after 5 times of desorption and recycling adsorption,indicating that CNF has good recycling property.