Adsorption Of Modified Magnetic Chitosan On Cr(VI)

With the frequent occurrence of heavy metal pollution incidents,chromium has become a hot topic as a toxic substance with strong oxidizing properties.The problem of chromium-containing wastewater treatment has also received increasing attention from researchers.Therefore,in this study,magnetic chitosan and thiosemicarbazide modified magnetic chitosan were prepared by modification of chitosan,and the preparation process of two kinds of adsorbent materials was optimized.The adsorption performance of adsorbent materials was explored by combining the characterization of two adsorbent materials,adsorption behavior analysis and single factor influence test.The effects of environmental factors on the adsorption of Cr（VI）on thiosemicarbazide-modified magnetic chitosan,the regeneration performance and adsorption mechanism of thiosemicarbazide-modified magnetic chitosan were finally investigated.In this study,the mass ratio of chitosan to Fe₃O₄ and the mass ratio of thiosemicarbazide to magnetic chitosan during the preparation were changed to investigate their effect on adsorption capacity.So that the optimal proportion was determined.The two adsorbent materials were characterized by scanning electron microscopy（SEM）,vibrating sample magnetometer（VSM）and Fourier transform infrared spectroscopy（FTIR）.The results show that both adsorbent materials have magnetic response,and the thiosemicarbazide modification can change the morphology of the adsorbents.The adsorption behavior analysis and single factor effect test showed that the magnetic chitosan and thiosemicarbazide modified magnetic chitosan were consistent with the pseudo second-order kinetic model and the Freundlich adsorption isotherm.There was intraparticle diffusion and chemical adsorption in the adsorption process.The acidic condition is more favorable for the adsorption of Cr（Ⅵ）by the two adsorbent materials.The increase of the ambient temperature and the increase of the initial concentration will increase the adsorption capacity of the two adsorbent materials.The reaction is an endothermic process,and the presence of P043-in the solution reduces the adsorption capacity of the magnetic chitosan and the thiosemicarbazide-modified magnetic chitosan by 71.56%and 60.00%respectively.The effect of environmental factors on the adsorption of Cr（Ⅵ）on thiosemicarbazide-modified magnetic chitosan was analyzed by response surface methodology and the interaction of influencing factors was analyzed.It is proved that the pH of the solution has the greatest influence on the adsorption capacity of Cr（Ⅵ）,and the interaction between the initial concentration and the pH of the solution is most obvious.In this study,the reutilization performance of thiosemicarbazide-modified magnetic chitosan was analyzed.The adsorption capacity recovery of adsorbent after treatment with 0.1M NaOH+0.1M HCl was the best.X-ray photoelectron spectroscopy analysis concluded that the adsorption of Cr（Ⅵ）by thiosemicarbazide-modified magnetic chitosan was related to redox,electron transfer,sharing electron and electrostatic adsorption.