One-pot amination and carboxylation functionalization of lignin for efficient adsorption of Cr(VI) and Cd(II): Influence of functional groups on adsorption equilibrium and mechanism

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Physicochemical and engineering aspects, 2024-11, Vol.703, p.135278, Article 135278
• Main Authors: Jia, Zuoyu, Liang, Fengkai, Xu, Xinze, Zhou, Haifeng, Zhang, Yaqing, Liang, Peng
• Format: Article
• Language: English
• Subjects: Adsorption; Amination; Carboxylation; Heavy metal; Lignin
• ISSN: 0927-7757
• DOI: 10.1016/j.colsurfa.2024.135278

The removal of multiple heavy metal pollutants remains a challenge. Amination and carboxylation modified lignins (NCLs) prepared by one-pot hydrothermal method were used as adsorbents for Cr(VI) and Cd(II) removal. The oxygenous groups content in adsorbents was quantitatively analyzed by Boehm titration in which NCL10 (the mass ratio of citric acid: triethylene diamine = 10) possessed a maximum carboxyl group content of 1.22 mmol/g. The Langmuir adsorption isotherm model was the most suitable, with the highest theoretical adsorption capacity of Cr(VI) and Cd(II) of 1298.6 and 103.1 mg/g, respectively. Meanwhile, FT-IR and XPS exhibited that NCL5 surface contained many functional groups beneficial to the removal of Cr(VI) and Cd(II). The contribution of carboxyl and hydroxyl groups to the removal of Cr(VI) and Cd(II) was quantitatively analyzed. After the blocking of carboxyl and hydroxyl groups, the adsorption rate of Cr(VI) and Cd(II) decreased by 26.4 %, 67.7 % and 7.2 %, 43.3 %, respectively. This study provides effective strategies to overcome the limitations of lignin adsorbents for wastewaters containing a wide range of heavy metal pollutants. [Display omitted] •The amino- and carboxylation-modified NCL5 surface facilitated the adsorption of Cr(VI) and Cd(II) from wastewater.•The content of oxygenous groups in adsorbents was quantitatively analyzed by Boehm titration.•The contribution of carboxyl and hydroxyl groups to the removal of Cr(VI) and Cd(II) was quantitatively analyzed.•The adsorption mechanism of NCL5 on Cr(VI) and Cd(II) was investigated in details.