Preparation And Adsorption Ability Of Surface Molecularly Imprinted Polymer On The Magnetic Carbon Nanospheres For Desulphurization

Surface molecular imprinting desulfurization technology, as one of the most promising deep desulfurization technologies, has many advantages, such as high removal efficiency, mild operation conditions, simple process, and environmental friendly. However, the effective recovery and utilization of the nanosized adsorbent is a technical challenge which is not easy to avoide by the surface molecular imprinting desulfurization technology. In the process of recycling, centrifugation and vacuum filtration are commonly used, not only causing energy and time consumption, but also lead to the loss of molecularly imprinted materials. Thus, the purpose of this paper is to solve the problem of difficult to recovery and utilization after application of surface molecularly imprinted desulfurization materials. Carbon encapsulated Fe₃O₄（Fe₃O₄@C） synthesized by solvothermal method and highly porous Fe₃O₄@C（p-Fe₃O₄@C） obtained through annealing were chosen as supports to prepare surface molecularly imprinted desulfurization materials（MIP/Fe₃O₄@C and MIP/p-Fe₃O₄@C）. Morphologies and microstructures of all the products were systematically characterized and adsorption properties were tested to obtain the surface molecularly imprinted desulfurization material which is easy to recycle and has excellent adsorption performance. The main results are listed as follows:1. Preparation and adsorption of MIP/Fe₃O₄@C: MIP/Fe₃O₄@C was synthesized by free radical polymerization with dibenzothiophene as template. The influence of the amount of cross-linker on the structure and morphology of MIP/Fe₃O₄@C was investigated. The characterization results show that imprinted polymer was grafted onto the surface of Fe₃O₄@C, and MIP/Fe₃O₄@C has a good morphology and dispersion when the molar ratio of the template molecule to the cross-linker is 1:5. Adsorption performance shows that MIP/Fe₃O₄@C had no adsorption ability to DBT, and the main reason is that the surface property of Fe₃O₄@C prevents the imprinting of DBT into the polymer layer.2. Effect of annealing treatment on the morphology and structure of Fe₃O₄@C: The surface properties of Fe₃O₄@C were improved by means of annealing treatment, and p-Fe₃O₄@C was thus prepared at the same time. The influence of annealing temperature and annealing time on the morphology and structure of Fe₃O₄@C was explored. When the temperature is lower than 500℃, Fe₃O₄@C maintains its original structure. As the temperature increases, the carbon layer becomes thinner, the pore size becomes smaller, and rich porous structures are formed on the surface of Fe₃O₄@C. When the annealing temperature is 600℃, the core–shell structured Fe₃O₄@C is transformed into the yolk–shell structure. When the temperature rises to 700 ℃, carbothermic reduction is induced drastically, the structure of Fe₃O₄@C is destroyed. At 500℃, Fe₃O₄@C has favorable thermostability, while annealing time has no significant effect on the morphology and structure of Fe₃O₄@C.3. Preparation and adsorption of MIP/p-Fe₃O₄@C: MIP/p-Fe₃O₄@C was prepared by using p-Fe₃O₄@C as support and DBT as template. Characterization results indicate that imprinted polymer was grafted onto the surface of p-Fe₃O₄@C. Adsorption experiments show that the saturated adsorption amount of MIP/p-Fe₃O₄@C towards DBT 15.20 mg g-1, the adsorption equilibrium time is 40 min at 298 K, and the imprinting factor is 1.62. Kinetic adsorption and isothermal adsorption fit better with the pseudo-second order model and Freundlich model, respectively. MIP/p-Fe₃O₄@C presents good recognition for DBT with selection factor of 2.09. The adsorption rate of MIP/p-Fe₃O₄@C towards DBT still mantain 81.5% after 5 times of recycle, indicating that MIP/p-Fe₃O₄@C has excellent regeneration ability.