Study On Adsorption Of As(?) And Cr(?) By Chitosan Microspheres Or Capsules

In this paper,chitosan was used as raw material,chitosan microspheres and chitosan capsules were prepared by cross-linking reaction of chitosan with glutaraldehyde or sodium tripolyphosphate by embedding method.As???and Cr???were selected as target pollutants respectively.The effects of active substance content,solution pH,adsorption time,rotational speed,solution concentration,temperature,and coexisting ions were studied.The main research contents and results are summarized as follows:?1?The results of iron-doped chitosan microspheres to remove As???showed that the adsorption capacity benefited from the increase of iron content and the maximum adsorption capacity was obtained at pH=8.According to the study of adsorption kinetics,adsorption rate was controlled by liquid film diffusion at a lower rotational speed while it was controlled by chemical reaction rate at a higher rotational speed.The adsorption of As???on iron-doped chitosan microsphere was chemisorption and the active sites of adsorbents were non-uniform distributed.And the adsorption of As???onto iron-doped chitosan microsphere was a spontaneous adsorption process and the spontaneous process was driven by the energy of the reaction system decreases.The coexisting anions(NO₃^-,SO₄^2-or PO₄^3-)inhibited the As???removal at different level.The experiment results show that for As???adsorption,the competing anions effect were basically in the order of PO₄^3->SO₄^2->NO₃^-.Iron-doped chitosan microsphere could be efficiently regenerated by NaOH solution as a kind of promising adsorbent for As???.The results of XPS,FT-IR showed that the adsorption was mainly achieved by the coordination interaction between As???and doped Fe in adsorbent.?2?The adsorption data of chitosan capsules?ALCC?to remove Cr???ions in aqueous solution showed that with the increasing of Aliquat-336,the adsorption efficiency of Cr???ions was increased too.The adsorption capacity is declined with the increase of pH and the maximum adsorption capacity is realized at pH=2.The adsorption kinetics evidence the rate-limiting step change from the liquid film diffusion to the chemical sorption with increase of the rotational speed.Adsorption isotherm model suggesting that Cr???adsorbed onto ALCC mostly via monolayer chemical adsorption.And maximum adsorption capacity of 110.38,107.30,105.04and 101.83 mg·g^-1 for Cr???at 293,303,313 and 323 K,respectively.Adsorption thermodynamics experiment indicated the adsorption of Cr???onto ALCC was a spontaneous adsorption process and the spontaneous process was driven by the energy of the reaction system decreases.The result of coexisting ion interference experiment show that the coexisting anions inhibition was in the order of SO₄^2->NO₃^->PO₄^3-.The results of digital cameral and XPS showed that Cr???in solution was adsorbed in ALCC firstly which was reduced to Cr???slowly and gradually released into the chitosan-TPP shell and solution?3?In this chapter,the conclusions of chitosan capsules?CYCC?to remove Cr???ions are basically consistent with the conclusion that ALCC adsorbs Cr???ions.The results showed that CYPH@IL101 in CYCC played an important role in the adsorption process and the maximum adsorption capacity was achieved at pH=2.According to the study of adsorption kinetics,adsorption rate was controlled by liquid film diffusion at a lower rotational speed,while it was controlled by chemical reaction rate at a higher rotational speed.The results of isothermal adsorption experiments showed that the adsorption of Cr???ions by CYCC in solution is dominated by single-layer chemical adsorption.And maximum adsorption capacity of 113.77,110.50,106.50,103.52 mg·g^-1 for Cr???at 293,303,313 and 323 K,respectively.the adsorption process of Cr???on CYCC was spontaneous and the spontaneous process of CYCC for Cr???adsorption was driven by the energy of the reaction system decreases.The results of coexisting anion effect showed that the existence of NO₃^-,SO₄^2-and PO₄^3-had a certain inhibitory effect on the adsorption of Cr???by CYCC,and the order of inbibition was SO₄^2->NO₃^->PO₄^3-.The results of XPS showed that Cr???was adsorbed and then reduced to Cr???...