| Summary: | 碩士 === 國立宜蘭大學 === 環境工程學系碩士班 === 104 === Due to environmental concern and energy insecurity, there has been an intensive interest on developing renewable energy resources to replace fossil fuels in international level. Lignocellulosic biomass being abundantly available in nature is an attractive alternative as biofuel substrate. Lignocellulosic biomass is composed of cellulose, hemicellulose, and lignin. Because of its structural complexity, lignocellulosic biomass needs to be pretreated and saccharified for releasing fermentable sugars before converting to biofuels. Either the pretreatment or the hydrolysis usually accompanies with the generation of byproducts such as furan derivatives and phenolic compounds. These compounds will inhibit the activity of fermenting microbes and then hamper the biofuel productions. Therefore, the inhibitory compounds have to be removed in advance. This can be achieved by employing overliming, enzyme treatment, activated carbon adsorption, or ionic exchange. However, the drawbacks of these technologies are either the increase of conductivity in hydrolysate, expensive, not selective adsorption, or not reusable, and thus limiting their practical application. On the other hand, adsorption by magnetic particles is a promising technology to remove these inhibitory compounds. Under magnetic field, adsorbed compounds on the surface of magnetites will easily and efficiently be separated from the hydrolysate. The collected magnetic particles after desorption also can be repeated used for the next run. Additionally, this technique will not change the characteristics of hydrolysate, and will avoid the increase of conductivity due to pH adjustment.
This study used ferroferric oxide (Fe3O4) as magnetic adsorbent to adsorb the furfural, hydroxymethylfurfural (HMF), and vanillin, the byproducts producing from the pretreatment or hydrolysis of lignocellulosic biomass. Ferroferric oxide was modified with polystyrene to form P-St/Fe3O4 magnitite for furfural and HMF adsorptions, while the modification of ferroferric oxide with amine functional group produced NH2/SiO2/Fe3O4 magnitite for vanillin adsorption. Before adsorption experiments, the characteristics of the modified meganetites were determined via fourier transfer Infrared instruments (FTIR), thermogravimetric analyzer (TGA), bet surface area analyzer (BET), vibrating sample magnetometer (VSM), and x-ray diffractometer (XRD). A central composite design (CCD) was employed to evaluate the adsorption efficiency between furfural and HMF. Result indicates that P-St/Fe3O4 magnitite adsorbed furfural greater than HMF. However, the opposite result was obtained when the adsorption experiment was performed at higher temperature. For the study of vanillin adsorption, results show that the optimal pH for NH2/SiO2/Fe3O4 magnitite to adsorb vanillin was 4.5, and the optimal temperature was 40℃. Meanwhile, the maximum vanillin adsorption capacity was 35.4 mg/g. Langmuir isotherm was found to be the main mechanism to describe the vanillin adsorption. In addition, the results of gibbs free energy for vanillin adsorption under 40 and 50℃ were -8.8 and 9.32 kJ/mol, respectively. The kinetic analysis also indicates that the maximum activated energy was 17.95 kJ/mol. Based on the results, the removal of vanillin by NH2/SiO2/Fe3O4 magnitite was of physical adsorption. In sum, the use of modified ferroferric oxide as magnetic adsorbent efficiently removed the inhibitory compounds from ligocellulosic biomass hydrolysate.
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