Preparation Of Chitosan Modified Carbon Felt Material For The Removal Of Lead Ions In Wastewater

In recent years,China’s economy has been on the fast track,and various industries have been developing vigorously.Meanwhile,the development of industry has also been accompanied by environmental problems that cannot be underestimated.Among them,when China is faced with the contradiction between supply and demand of water resources,water pollution has become a major stumbling block,especially the pollution of heavy metal wastewater,especially lead（Pb）.How to deal with the pollution of water resources has become the top priority at present,and how to efficiently purify the heavy metal pollutants is the top priority.In the current mainstream heavy metal wastewater treatment technology,adsorption method is a particularly mature one.However,no matter physical adsorption or chemical adsorption,there are still challenges:the selectivity of adsorbents to target ions remains to be further studied;And the adsorption capacity of the adsorbent is also a hot spot in the current research.Chitosan（CS）,as a kind of natural polymer material which can be obtained by deacetylation of chitin,has been widely paid attention in recent years.Because it contains-NH₂,-OH and other functional groups,it can coordinate with many heavy metal ions and has a very high application prospect.At the same time,it is easy to prepare,non-toxic,no secondary pollution,has been widely used in wastewater treatment.However,because CS is a natural compound,it still has inherent limitations,such as poor strength and stability,and difficult to recover in a low pH environment.In view of these problems,this paper tried to explore a more effective removal method for Pb²⁺through two approaches:ion imprinting technology and capacitive deionization technology.In this paper,two kinds of fiber carbon felt modified with CS were prepared by the dispersion polymerization method,and the exploration process of how to deal with Pb²⁺polluted water by these two different ways was presented respectively.The main research contents and conclusions are summarized as follows:（1）Based on the ion imprinting technology,the use of dispersion polymerization was prepared by Pb（Ⅱ）,molecularly imprinted chitosan modified carbon felt（Pb（Ⅱ）-IIP CS@CF）adsorption material.The materials were analyzed by X-ray photoelectron spectroscopy（XPS）,specific surface area measurement（BET）,scanning electron microscopy（SEM）,and Fourier infrared spectroscopy（FT-IR）.The characterization results show that the Pb（Ⅱ）-IIP CS@CF successfully grafted on the surface of carbon fiber layer of chitosan,and chitosan itself has can be combined with a bivalent lead ion specificity of special hole surface structure,more conducive to the combination of bivalent lead ion and adsorption.Then,the related adsorption efficiencies of 5 groups of adsorption experiments were discussed when the pH value was between 3 and 7.The results also showed that with the increasing of pH value,that is,the decrease of acidity,the adsorbent also showed a better adsorption efficiency for divalent lead ions.The experiment shows that the adsorption efficiency of the best pH value is 5,when the pH value increases to more than 5,the adsorption rate will show a slightly downward trend.（2）The preparation of carbon felt electrode modified with chitosan（CS@CFE）and its electrochemical properties were studied.CS@CFE was prepared by solution blending,and various characterization tests showed that the material had-NH₂,-N-H,-N=,-COOH and other groups,and had a strong removal effect on Pb²⁺.Because of the special three-dimensional porous structure of fiber carbon felt,it is more convenient to form the electric layer on the double surface of the electrode.At the same time,after the impedance spectroscopy（EIS）and cyclic voltammetry（CV）tests,it was further confirmed that the chitosan retained the electrochemical activity of Pb²⁺,but also found that the reaction on the electrode surface is actually oxidation-reduction reactions（ORR）.（3）The operation Settings of the electric repair process were explored.Using the pH control system,the voltage of 0.5 V,1.0 V and 1.5 V were set under the condition of maintaining pH=5.The results showed that the removal rate was the fastest when the voltage was 1.5 V,and the maximum adsorption rate was shown at about 1h.The electrode was characterized after electrokinetic remediation.The SEM image showed that the Pb deposited on the surface of the carbon felt fiber was in the shape of scales,which could be attributed to the directional production of electric field.XRD results show that the sediment is amorphous phase.The XPS test results showed that the carbon felt electrode showed the characteristics of Pb and Pb²⁺,respectively after electrokinetic remediation,which indicated that the Pb deposited on the carbon felt electrode was a mixture of various Pb and Pb²⁺,with the ratios of 42.31%and 57.69%,respectively.At the same time,the carbon-containing functional groups play an important role in the removal process.At the same time,the carbon-containing functional groups played an important role in the removal process.