The Preparation Of Fe₃O₄ Composite Materials And Adsorption Characteristics Of Heavy Metal Ions In Water

In recent years,many studies have been carried out on the removal of metal ions with the industrial,agricultural,human life discharge a large number of pollutants into the environment.Adsorption method is simple,relative low-cost,effective and flexible in design and operation.However,most of these adsorbents show unsatisfied adsorption capacity due to diffusion limitation or the lack of enough active surface sites,and some problems,including high cost,difficulties of separation and regeneration of adsorbents from wastewater,and secondary wastes,have to be faced.So,it is very important to develop novel adsorbents with large adsorptive surface area,low diffusion resistance,high adsorption capacity and fast separation for large volumes of solution.In this paper,two new adsorption materials-amphiprotic magnetic chitosan adsorbent and carboxylated magnetic cellulose microsphere were synthesized.The study of adsorption characteristics of two adsorbents for different metal ions were carried out.The research were as follows:DTCS-Fe₃O₄ was synthesized through a co-precipitation method that contained-NH₂,-C=S and-COOH groups.The adsorbent was suitable for simultaneously adsorbing a variety of metal ions with different physical and chemical properties and was less affected by p H in the solution,which expanded the application range of adsorbent.The adsorbent was characterized by SEM,XRD,FT-IR,VSM,XPS and TGA.The results showed that the saturation magnetization intensity of DTCS-Fe₃O₄was 38.48 emu·g^-1,which had a high saturation magnetization intensity.Therefore,solid liquid separation could be realized within 1 min after metal adsorption in the solution.Batch adsorption results showed that pseudo-second-order kinetics and Langmuir isotherm datas were well fitted,and the single-layer adsorption of Cr（Ⅵ）and Cd（Ⅱ）could reach 321.3 mg g^-1 and 367.9 mg·g^-1,respectively.Na OH and EDTA-2Na were used as desorption agents for Cr（Ⅵ）and Cd（Ⅱ）,respectively.After repeated desorption for five times,the desorption rate still reached 78.84%and70.59%,respectively,indicating that the desorption rate of Cd（Ⅱ）was lower than that of Cr（Ⅵ）,mainly because of the different adsorption mechanism of Cr（Ⅵ）and Cd（Ⅱ）.According to the mechanism study,the Cd（Ⅱ）ion adsorption was mainly a complexation reaction process,while the adsorption of Cr（Ⅵ）contained a variety of reaction processes.（2）DPMC was synthesized through a col-gel method,which was characterized by SEM,XRD,FT-IR,XPS and Zeta potential to look into its morphology,surface functional groups.Batch adsorption experiments showed that pseudo-second-order kinetics and Langmuir isotherm datas were well fitted,and the single-layer adsorption of Cu（Ⅱ）reached 298.62 mg·g^-1.The adsorbent could be effectively regenerated using1 mol·L^-1 HCl.After repeated adsorption-desorption for 5 cycles,the adsorption rate of Cu（Ⅱ）could still maintain more than 80%,indicating that the adsorption of Cu（Ⅱ）by DPMC had a good reusability.Mechanism studies showed that the adsorption of Cu（Ⅱ）was mainly the interaction between N,O and Cu（Ⅱ）,which binded to the surface of adsorbent in the form of complexation.These adsorbents prepared in this study had good reusability and high adsorption capacity,which had a good purification ability for wastewater contaminated by heavy metals.Meanswhile,these were easy to be separated and reused by magnetic separation technology.Therefore,these adsorbents had a good application prospect in purifying wastewater contaminated by heavy metals.