Chitosan Modification And Its Adsorption Of Heavy Metals Cu、Cd In Water

In recent years, with the development of the industry in our country, various kinds of heavy metal sewage are discharged into water, which makes heavy metal pollution much worse. The heavy metals in water is of high toxicity and can not easily be degraded, they will enrich in organisms, and can cause various organs injury and pathological changes. Therefore, how to treat heavy metal wastewater with high efficiency is becoming a hot spot of water treatment research. Adsorption is a method of heavy metal treatment with advantages of simple operation, low cost and good effect. Chitosan contains rich amino and hydroxyl and has strong adsorption of heavy metal, but it can only dissolve in weak acid circumstance, and is weak in mechanical strength and chemical stability. Those disadvantages greatly limits its application.The chelation of chitosan with iron can enhance the mechanical strength of chitosan, thiol modification of chitosan can enhance its adsorption of cationic heavy metals. Forming core-shell structure with magnetic Fe3O4can make it easier for chitosan to separated from solution after the adsorption. So. this paper uses chitosan and magnetic Fe3O4to prepare core-shell material, and modify chitosan with methods of calcination, thiol modification.The prepared materials are used to remove heavy metals in water.This paper take advantage of the strong magnetic and chemical stability of magnetic Fe3O4. and coat chitosan to the outside of magnetic Fe3O4through water and oil emulsification. The core-shell structure of Fe3O4@chitosan is modified with14%(wt%)NaOH and CS2solution. The modified material is used to adsorb cadmium ions. The results are as follows:1) We study the adsorption kinetics and thermodynamics, the adsorption of Fe3O4@chitosan of Cd2+fits the pseudo-second order kinetic equation and Langmuir isotherm equation. Through the calculation of Langmuir isotherm equation, we get the maximum adsorption capacity of Fe3O4@chitosan to Cd2+is197.8mg/g.2) When pH=6, the adsorption capacity is95mg/g,which reaches its maximum.3) The coexistence ion in water will not affect the adsorption behavior.In this paper, we chelat chitosan with Fe+, which can strengthen its chemical stability; we modified chitosan with thiol. which can enhance its adsorption of cationi heavy metal; we calcine chitosan, which improve its mechanical strength. Chitosan is modified with three methods above, and get three different adsorbents, the adsorbents are designed for the removal of copper ions. The results are as follows:1) the adsorption of three adsorbents of Cu2+fits the pseudo-second order kinetic equation and Langmuir isotherm equation. Through the calculation of Langmuir isotherm equation, we get the maximum adsorption capacity of the three different adsorbents to Cu2+are412,293,267mg/g respectively.2) When the pH=6, adsorption removal rate reached its maximum; And with the loss of the pH value, adsorption removal rate is gradually reduced.3) through the comparison of modification conditions and adsorption capacity of three types of adsorbents, we can get the conclusion that three kinds of modified methods(chitosan and iron chelation, thiol modification, calcine) used in combination can greatly improve the adsorption of heavy metal of chitosan.