Synthesis And Application Of The Lignin-based Declorizing Flocculant

Lignin is a kind of complicated polymer compounds that exists inmost land plants xylem, with cellulose and hemicellulose constitutedthe main components of the plant skeleton.Second to cellulose,lignin isone of the most abundant renewable resources produced by plants.Theapplication of this environmentally friendly biodegradable lignin resourceof being as substitutes of dwindling petroleum oil based materials is animportant aspect of sustainable development.Numerous reactive hydroxylgroups including both phenolic and aliphatic hydroxyl groups andcarboxyl groups exist in lignin molecular.These structural features makelignin a potential source of preparing network materials.Synthesis ofvarious functional derivatives from lignin has attracted increasedattentions from researchers in recent years.In this paper,first the solid base catalysts CaO/MgO to catalyzedegradation of alkaline lignin to improve its reactivity and purified it tocharacterization.Under different calcium magnesium oxide mass ratio（0.01,0.02,0.04,0.06,0.08,0.10）,the CaO/MgO solid compound alkaliwas compounded.It turns out that,with the increase of the alkalinity,thephenolic and aliphatic hydroxyl groups and carboxyl groupsincreased,and the molecular weight decreased.The molecular weight can decreased from thousands to less than1000. The phenolic groupsincreased from3.06%to3.53%and the aliphatic hydroxyl groupsincreased from44.7mgKOH/g to142.2mKOHg/g.After thepurification,the ash content decreased from18.54%to2.13%,and thewater content decreased from14.12%to5.68%.Secondly,Epoxy propyl trimethyl ammonium chloride were used tomodify the lignin, introduce the cationic groups.The product is known aslignin flocculant.In this process, we mainly discussed the effect ofreaction time（2、4、6h）, reaction temperature （50、60、70℃）、NaOH concentration（2、3、4mol/L）and the mole ratio（1:1、1:1.1、1:1.2）.The optimum synthetic process conditions are obtained byorthogonal experiment,different dye solutions need different flocculants.At last,the lignin base flocculating agent was applied to reactivedyes, acid dyes and direct dyes wastewater decolorizing.The resultsshowed that the flocculants has excellent decolorization,thedecolorization rates are all above99%,the best pH is2,the adding thequantity is between2~5g/L.