Abstract
Lignin isolated from enzymatic hydrolyzed cornstalks (EH-lignin) is a renewable natural polymer noted for its versatility and applicability in a variety of uses. Graft copolymerization of EH-lignin with acrylamide (AM) and the application of this copolymer as a flocculant in dye wastewater treatment were studied in this article. The influences of some factors on yield of copolymer and the grafting ratio were investigated and the structure of EH-lignin/AM graft copolymer was characterized by FT-IR. According to the yield and the grafting ratio, the optimum conditions for graft copolymerization were as follows: initiator K2S2O8-Na2S2O3 with a quantity 3 wt% of EH-lignin, mass ratio of AM to EH-lignin was 2~3, reaction time 4h and temperature at 50℃. It was found that the absorption capacity of graft copolymer to two azo-dyes was enhanced with the increase of grafting ratio. Furthermore, the residue concentration of EH-lignin/AM graft copolymer remained in the supernatant after flocculation was much lower than that of pure EH-lignin.
Highlights
At present, the fossil resources are rapidly running out and the environmental pollutions are getting even more serious throughout the world
The effects of various factors on the yield of copolymer and the grafting ratio were investigated to determine the optimum conditions for graft copolymerization
total organic carbon (TOC) removal rate of the dye wastewater treated by EH-lignin/AM graft copolymer is much higher than that of pure EH-lignin, which means the graft copolymerization of EH-lignin with AM will help to minimize the residue amount of this copolymer in wastewater and diminish the potential secondary pollution
Summary
The fossil resources are rapidly running out and the environmental pollutions are getting even more serious throughout the world. Lignin is a renewable and biodegradable resource and noted for its versatility and applicability in a variety of uses. Making use of these biomaterials will enhance the economic benefit of bioengineering and diminish environmental pollutions [5,6]. Since the enzymatic hydrolysis process of the cornstalks is carried out under relatively mild conditions, many functional groups such as phenolic hydroxyl, alcoholic hydroxyl and methoxyl are well preserved in EH-lignin [8,9,10]. The concentration of residue lignin remains in supernatant after flocculation is very high, which may leads to a secondary pollution. The residue concentration of this flocculant remains in the supernatant after flocculation was measured
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