Extraction And Application Of Lignin From Pulping Black Liquor

As energy crisis and environmental pollution are becoming more serious problem,increasing global pressure to recycle and reuse waste has become necessitated. Notonly can make full use of resources, economize energy, but also can effectively reduceenvironmental pollution and improve environmental quality.Pulping black liquor is one of the main by-products of the paper industry, and isconsidered a pollutant because it is a kind of black and viscous liquid with specialodor, and contains20%-30%of lignin. The complex structure of lignin is verydifficult for biodegradation, so it is one of the world’s major sources of pollution.Lignin is the second most abundant natural and renewable raw material aftercellulose, and is a mixture of polyphenolic compounds with a rather complexchemical structure. Due to the large amount of carbon content of lignin and a varietyof functional groups on the lignin surface, especially hydroxyl groups, it can beapplied in the preparation of activated carbon and partial substitute for bisphenol Atype epoxy resin.The significance of this thesis is:1. It expands the source of the raw materials forpreparation of activated carbon, reduces the cost and economizes the energy.2. Thenatural non-toxic polymer material of lignin partly insteads of the toxic substances ofbisphenol A in the preparation epoxy resin, and it can improve the safety of the epoxyproducts.3. Making full use of pulping black liquor to reduce pollution emissions,and making efficient use of natural resources have played a positive role inenvironmental protection.This thesis supplies a method of extraction and two aspects of application of thelignin from pulping black liquor. The lignin was extracted by acid precipitation,activated carbon was prepared by phosphoric acid activation method, and epoxy resinwas synthesized by hydrothemal method. Spherical lignin with highest extraction yield, better purity, good dispersivity,particle size of about100nm was produced under mild reaction conditions, that is, thereaction was at90oC with pH=2for8h, and surface functional groups were notdestroyed seriously. The key features of this methodology are its operationalsimplicity and low cost.The spheroidal microporous/mesoporous activated carbon was activated spheroidallignin by H3PO4at700oC with impregnation ratio of1:7and reaction time of1h. TheBET surface area was1797m2g1, and the high carbon content was68.0wt.%.Furthermore, the ash content was very low.Replacing bisphenol A by the lignin partly to prepare epoxy resin, the effects of thelignin content and reaction temperature on the epoxy resin property were discussed inthis thesis. The results showed that the epoxy value range was0.0548～0.0976mol/100g, the largest viscosity was408mPa·s, polymerization was higher, and themolecular weight was larger.