posted on 2020-02-06, 17:36authored byXianzhi Meng, Brent Scheidemantle, Mi Li, Yun-yan Wang, Xianhui Zhao, Miguel Toro-González, Priyanka Singh, Yunqiao Pu, Charles E. Wyman, Soydan Ozcan, Charles M. Cai, Arthur J. Ragauskas
How
to effectively remove toxic dyes from the industrial wastewater
using a green low-cost lignocellulose-based adsorbent, such as lignin,
has become a topic of great interest but remains quite challenging.
In this study, cosolvent-enhanced lignocellulosic fractionation (CELF)
pretreatment and Mannich reaction were combined to generate an aminated
CELF lignin which is subsequently applied for removal of methylene
blue and direct blue (DB) 1 dye from aqueous solution. 31P NMR was used to track the degree of amination, and an orthogonal
design was applied to determine the relationship between the extent
of amination and reaction parameters. The physicochemical, morphological,
and thermal properties of the aminated CELF lignin were characterized
to confirm the successful grafting of diethylenetriamine onto the
lignin. The aminated CELF lignin proved to be an effective azo dye-adsorbent,
demonstrating considerably enhanced dye decolorization, especially
toward DB 1 dye (>90%). It had a maximum adsorption capacity of
DB
1 dye of 502.7 mg/g, and the kinetic study suggested the adsorption
process conformed to a pseudo-second-order kinetic model. The isotherm
results also showed that the modified lignin-based adsorbent exhibited
monolayer adsorption. The adsorbent properties were mainly attributed
to the incorporated amine functionalities as well as the increased
specific surface area of the aminated CELF lignin.