pH graded lignin obtained from the by-product of extraction xylan as an adsorbent
2022
Fan, Huiming | Li, Fengyu | Huang, Hanyi | Yang, Jingkun | Zeng, Deli | Liu, Jianan | Mou, Hongyan
As an important agricultural residue, corn stalks have been continuously used in various industries. In this work, lignin, the by-product of xylan extraction from corn stalks, was used as a useful adsorbent for the removal of methylene blue from aqueous solutions. Lignins were precipitated from the hydrolysates of pH 3 (LG3) and 5 (LG5), hoping to explore the difference in adsorption performance between the two. Detailed discussions were performed to provide a firm evaluation of adsorption models followed by batch experiments to analyze the methylene blue adsorption performance. Results showed that the lignin obtained at pH 5 had a better adsorption capacity compared with pH 3, which was mainly caused by the difference in specific surface area. When the optimal adsorption conditions (pH: 10; temperature: 35 °C; adsorption time: 90 min) were achieved, the maximum adsorption capacity of LG5 can reach 134.3 mg/g, which was much higher than those of most unmodified lignins extracted from other biomass energy sources. Regarding the adsorption behavior, the adsorption data were fitted by pseudo-second-order kinetics model and the isotherm adsorption equilibrium followed the Langmuir model. Overall, these results indicate that lignin, the by-product of xylan extraction, offers a great potential for removing methylene blue from wastewater.
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