Liquefaction And Biosorption Properties Of Lignocellulose

With the depletion of oil resources and increasing environmental pollutions, the development of renewable biomass resources has become a hot topic in recent years. In this thesis, two kinds of biomass waste, hardwood powder and corn-cob residues, were used to prepare biosorbents and liquefied polyols, respectively. Then, the biosorbents were used to remove copper ions and methylene blue from aqueous solution, and the liquefied polyols were used to replace part of the industrial polyether polyol to prepare modified polyurethane foams.Firstly, citric acid modified hardwoods powder (CMH) and corn-cob residues (CCW) were prepared as biosorbents to remove copper ions and methylene blue (MB) from aqueous solution by batch techniques. SEM, XRD and FT-IR were used to characterize the two biosorbents. The effects of initial pH value, biosorption temperature, contact time, and initial adsorbate concentration on the biosorption capacities and adsorptivity of Cu2+ and MB onto CMH and CCW were investigated, and the biosorption mechanisms were discussed. The results showed that CMH and CCW exhibited better biosorption properties for MB than Cu2+. As for Cu2+, CMH showed better biosorption capacities and adsorptivity than CCW. pH values had a great influence on the biosorption properties. When the pH value was higher than 4.0, the initial MB concentration was 200 mg/L and biosorbents concentration was 2 g/L, the adsorptivity of MB onto CMH and CCW were above 99%; When the pH value was between 4.4 and 5.0, CMH and CCW exhibited optimum biosorption for Cu2+. The biosorption kinetics studies indicated that Cu2+ and MB biosorption onto CMH and CCW followed the pseudo-second-order model. The two biosorption-equilibriums can be well described by Langmuir isotherm model. Monolayer adsorption capacities of MB onto CMH and CCW were 237.2 mg/g and 211.4 mg/g, whereas the adsorption capacities of Cu2+ onto CMH and CCW were 165 mg/g and 28.3 mg/g, respectively.Secondly, hardwoods powder and corn-cob residues were liquefied by using polyethylene glycol 400 (PEG 400) and ethylene carbonate (EC) as a mixed liquefaction solvent, and concentrated sulfuric acid as a.catalyst. The effects of liquefaction temperature, liquefaction time, and mass ratio of PEG400/EC on the structures and properties of liquefied products were investigated. After that, liquefied polyols obtained from the two raw materials were used to replace part of industrial polyether polyols to prepare modified polyurethane foams, respectively. Structures and properties of the modified polyurethane foams were characterized and investigated. Results showed that hardwoods powder and corn-cob residues can be liquefied quickly in the mixed solvents of PEG400 and EC, and both of the liquefaction products of hardwoods powder and corn-cob residues were the mixture of polyester and polyether polyols. The study showed that when liquefaction time was 1 h, mass ratio of PEG400/EC was 8:2, mass ratio of liquid-solid was 5:1, liquefaction temperature was 160℃, the hydroxyl value and residue content of hardwoods powder were 324 mgKOH/g and 5.10%, whereas the hydroxyl value and residue content of corn-cob residues were 353.2 mgKOH/g and 1.1% at the liquefaction temperature of 130℃. In the process of liquefaction, there was the competitive reaction between cracking and condensation, and there are also the interaction between the lignocellulose and PEG400. With the increase in the feed content of liquefaction products in modified polyurethane foams, apparent density and compressive strength of the modified polyurethane foams increased firstly, and then decreased.In addition, compared with unmodified polyurethane foams, the thermal stabilities of the modified polyurethane foams raised slightly.