The Research On Preparation Of Heavy Metal Absorbent By Black Liquor Of Papermaking

Lignin was the by-product of papermaking industry. Because it had not be applicated effectively,it not only became one of pollution,but also wasted a lot of lignin resource.This thesis extracted lignin from black liquor by acid, then modificated it with formaldehyde,Finally, used it to adsorped heavy metal ions Cu2+,Ni2+,Zn2+,Pb2+ and Cd2+ for exploring the possibility to prepare heavy metal absorbent from lignin,the result showed that:1. Analysised influential factors on lignin extracted process,the result showed that pH is the most obvious influential factor on lignin obtained rate.The heating temperature and time, precipitation time were relatively less influential on it. The best acidification condition followed:the pH, heated temperature and time, precipitation time were respectively 3.0,50℃,45min and 60min.2. Analysised on influential factors on lignin modification, the result showed when lignin reacted with formaldehyde, temperature was the first important influential factor on lignin grafting, reaction time and pH was the second important influential factor, formaldehyde quantity was the third important influential factor, catalyst quantity had a little effect on lignin grafting rate. Through single factor which was effective on lignin grafted experiment,drawed out the best modification condition:the Heated temperature and time, pH, formaldehyde quantity and catalyst quantity were respectively 100℃,180min,7.0 and 1.0g.3. Research on the acid and alkaline resisting ability of lignin modification, the result showed that it was difficult to dissolve in acidic solution and easy to dissolve in alkalic solution.Compared between lignin and lignin modification by electron microscope scanning, the surface of lignin modification had more porous appearance. Based on caculated,surface area of modification was 56.11 m·g-1,31.61 m·g-1 bigger than the 24.50 m2·g-1 of unmodificated lignin.4. Compared between lignin and lignin modification on infrared spectrum found the speak of lignin's O-H group broadened obviously and C-O group near 1219 cm-1 disappeared. 5. Analysised on the factors on which effected lignin modification adsorped heavy metal, the result showed adsorption time was the first influential factor on adsorption process, pH was the second factor, original concentration of heavy metal was third factor and adsorption temperature had little influential.Analysised on single factor which influenced adsorption of lignin modification, the result showed the best adsorption condition were respectively 120min,7.0,25℃.6. By determination the adsorption capacity of lignin and its modification conduction, discovered the adsorption capacity of modification conduct was obviously enh-anced.The adsorping capacity for Pb2+ was maximum and reached 55.47m2·g-1,the adsorping capacity for Ni2+ was minimum and only was 25.14m2·g-1,and the adsorping capacity for Cu2+,Zn2+,Cd2+ wre respectively 35.41 m2·g-1,30.35m2·g-1 and 40.37 m2·g-17. Accorded to the result of desorption experiment that adsorping heavy metal with lignin modification, the desorption of heavy metal approached equilibrium when HCl concentration was 1.5mol·L-1. on the continuous four experiment that lignin modification adsorped heavy metal, result showed that the fourth capacity of five heavy metals only decreased respectively 3.71mg,3.34mg,5.35mg,4.81mg,5.35mg.It showed that lignin modificatial conduct had high stability on utilization and the heavy metal desorption rate of lignin modification were high, much than 90%.