The Influence Of Plasma Treatment On Surface Chemical Changes And Thermal Characteristic Of Enzymatic Hydrolysis Lignin

Increasing environmental and energy concerns have been the driving force of bio-ethanolresearch. Both cellulose and hemicelluloses in lignocellulosic biomass can be converted tosimple sugars that can be subsequently fermented to ethanol. The conversion of even a smallportion of this renewable resource into ethanol could substantially reduce gasoline consumptionand our dependence on petroleum. Therefore, related research and development has beenfocused on producing ethanol from wood and agricultural residues. However, lignin, which isone of the major three components of lignocellulosic biomass, is a barrier to enzymaticsaccharification of cellulose in wood and agricultural biomass. In cellulosic ethanol processes,lignin is considered as a waste product. For example, nearly one ton of residues are generatedfor every ton of bio-ethanol produced from corn stover;30-35%of these residues areEnzymatic hydrolysis lignin (EHL). Value-added utilization of EHL not only can help offset thecost of bio-ethanol production and boost the economic viability of the bio-ethanol industry butalso provide a source of renewable materials.The work described here explored the feasibility of using enzymatic hydrolysis lignin(EHL) as a natural binder for biocomposites manufacture and proposed an effective approach toactivating EHL. The effects of plasma treatment on the surface chemical changes and thermalcharacteristic of EHL were evaluated and the modification mechanism of the plasma wasinvestigated.The results are showed as following:1. With prolonging oxygen plasma treatment time, carboxyl content increasedsignificantly and a slight increase in carbonyl content. At the same time, carboncontent showed a gradual downward trend, hydrogen content also decreased with thetreatment time reduction. The oxygen content gradually increased with prolonging theprocessing time. The spin concentration of the enzymatic hydrolysis lignin (EHL)increased with prolonging the processing time.2. With increasing oxygen plasma treatment power, carboxyl content increasedsignificantly and a slight increase in carbonyl content. After oxygen plasma treatment,the carbon content in the enzymatic hydrolysis lignin (EHL) decreased gradually withthe increase of processing power but the range is not big. The hydrogen contentdecreased gradually with the increase of processing power, but it is not evident. Theoxygen content increased gradually with the increase of processing power. The spinconcentration of the enzymatic hydrolysis lignin (EHL) increased with the extension of the processing power, but the range is not big.3. After plasma treatment of different gases, carboxyl content increased significantly.Among these gases, the carboxyl content increased the most after the oxygentreatment, followed by air, nitrogen and argon. Carbonyl content all has slightlyincreased. After different plasma treatment, the carbon content of enzymatichydrolysis lignin (EHL) decreased. Among them, carbon content decreased the mostafter oxygen plasma treatment, followed by argon, nitrogen and air. Hydrogen contentalso decreased the most after oxygen plasma treatment, followed by nitrogen and air.The oxygen content is all increased and it increased the most after oxygen plasmatreatment, followed by air, nitrogen and argon. The spin concentration of theenzymatic hydrolysis lignin (EHL) increased the most after oxygen plasma treatment,followed by air,nitrogen and argon.4. The Tg value of enzymatic hydrolysis lignin (EHL) decreased after oxygen plasmatreatment under the same heating rate. Because the structure of lignin changed and thecontent of oxygen functional groups increased. The lignin contained a lot ofphenylpropanoid units and larger branched-chain after oxygen plasma treatment.These branched chains would generate many oxygen-containing functional groupssuch as hydroxyl, carbonyl, and carboxyl. The extension of the content of polarfunctional groups made the molecular motion of enzymatic hydrolysis lignin moreactive. May be it is because the ether bond of hydrolysis lignin macromoleculesruptured which reduced the molecular weight and made the glass transitiontemperature dropped.5. Adding EHL has a beneficial effect on the physicomechanical properties of thefiberboards. Oxidative activation of EHL with oxygen plasma treatment improves theproperties of the fiberboards significantly. The spectroscopic analyses indicate thatoxygen-related functional groups such as–OH, C–O,–C=O,–COO had beenimplanted efficiently onto the surface of EHL in the course of oxygen plasmatreatment. These groups and the free radicals generated have probably contributedsynergistically to the bonding improvement.