Research On The Preparation Of The Modified Materials Of Biological Carbon And The Adsorption Mechanism Of Six Chromium In Water

In this resarch, Eichhornia crassipes was used as raw material to prepare magnetic biochar(MB), and MB was modified by chitosan into magnetic biochar/chitosan(CMB). Moreover, we also studied the mechanism of CMB removing Cr(VI) from aqueous solution.The large specific surface area, porous structure, surface functional groups of biochars are the important features promising their high removal efficiencies of contaminants. However, the biochar powder particle is fine, so it is difficulte to separate biochar from aqueous solution. We embedded magnetic nanoparticles into the original biochar through pyrolysis method, and then the biochar was magnetic and easy to separate from aqueous solution. The Fe Cl3 treated biomass was pyrolyzed in a tube furnace at 600 °C in N2 environment. The product referred to as MB. For MB spectra, the peaks 576.8 cm-1 was found obviously. It indicated that γ-Fe2O3 particles were embedded in the pristine biochar. The magnetic hysteresis loop was S-like curve. The saturation magnetization(Ms) of the CMB composite was 11.60 emu/g, which was sufficient to be separated from aqueous solution by a permanent magnet. This method is simple and practicable, as well as environmentally friendly.(chapter 2)After that, we modified MB using chitosan, and acquired magnetic biochar/chitosan(CMB). Scanning electron microscopy(SEM), Fourier infrared spectrum(FTIR), X-ray photoelectron spectroscopy(XPS), magnet ic(VSM), aperture(BET), and surface Zeta potential were analyzed. The XPS before Cr(VI) adsorption proved the CMB surface functional groups were quite different from MB. The XPS after Cr(VI) adsorption showed that Cr(VI) was adsorbed onto CMB surface successfully. Analysis of saturation magnetization obtained CMB(Ms) was 11.60 emu/g, which was equal to magnetic biochar(MB) of saturation magnetization. This phenomenon showed the process of modification did not change the magnetic properties of magnetic biochar(MB). The Cr(VI) adsorption efficiency for CMB is remarkable, and the maximum adsorption capacity of Cr(VI) was up to 120 mg/g, which was four times the adsorption capacity of original biochar(B). Experimental data were well fitted with second-order kinetic model and the Langmuir isotherm model. Thermodynamics of adsorption experiments showed that the adsorption was an endothermic reaction spontaneous.(chapter 3)...