Study On Extraction, Characterization And Application Of Lignin From Corn Stover

In recent years, the world is facing an energy crisis, which has a significant relationship on irreversible depletion of fossil fuels. Thus increasing depletion of fossil fuels will severely hampering the sustainable development. How to reduce the consumption of fossil fuels and seeking renewable energy is becoming extremely urgent. People are concerned about the use of lignocellulosic materials(LCMs). After cellulose and hemicelluloses, lignin is the third most abundant constituent of LCMs, which widely exist in plant cell walls. Lignin is a natural polyphenolic polymer with characteristics of a high yield, renewability and degradability. And that could expand the application of lignin in the synthesis and modification of polymer materials such as efficient adsorbent, dye dispersant, and water reducer of concrete. Corn stover is agriculruural waste, containing abundent lignin in its cell wall. In order to fully utilize the resources of corn stover, this paper carried out the work of the extraction, characterization and application of lignin from corn stover.In this work, we demonstrated a method to extract lignin from corn stover by means of alkali-dissolving, alcohol-precipitating and acid-separating. Central composite design (CCD) was applied to optimize the extraction processes. The highest lignin yield achieved was 69.71% under the condition of 2.40 mol/L NaOH at 74 ℃ for 3.10 hours. The resulting lignin was analyzed using TG, FT-IR and UV-Vis. This lignin decomposes mainly between 130 and 500 ℃. Certain functional groups in this lignin form complex cross-linked thermal stable structures. The maximum UV absorption happens at the wavelength of 282 nm. This lignin is very reactive. It is suitable for polymer synthesis and modification.A large number of black liquor is produced as by-products in process of corn stover sugar alcohol production. Lignin is the main component of black liquor. By means of sulfonation and sulfomethylation, functional groups such as sulfonic acid group, sulfo-methyl group can be added into lignin molecule. Thus, hydrophily of macromolecules could be increased, and carbon chains extended in the same time. In this way, a water-reducing agent of cement (LSP) was prepared by molecular modification. Then the effect of LSP on water-reducing rate, setting time and compressive strength of cement hydration products were investigated, and further combined X-ray diffraction intensity (XRD) analysis with scanning electron microscope (SEM) to explain hydration process and regulation mechanism. The results indicated that LSP slowed down the early stage of hydration but promoted the late stage of hydration process efficiently, and it expressed good dispersion ability to the cement. When the water-cement ratio was 0.35 and dosage of LSP was 1.2%, water-reducing rate was 17.5%, LSP achieved the standard of superplasticizer. In addition, the initial setting time and final setting time of cement paste admixed with LSP were significantly prolonged, and compressive strength of hardened cement product were remarkable improved.In this work, as a raw material, corn stover was used to extract the lignin. We yearned for a high yield of lignin from corn stover. Central composite design (CCD) was applied to optimize the extraction processes. The resulting lignin was analyzed using different ways. black liquor of sugar alcohol from corn stover was used to prepare a water-reducing agent of cement successfully. The product reached the superplasticizer standards, and it had good performance in application. A new way of utilizing corn stover was provided.