Enhanced adsorption for malachite green by functionalized lignin magnetic composites: Optimization, performance and adsorption mechanism

Herein, a novel kind of magnetic amino-modified lignin (MAL) sorbents was designed through a facile strategy based on Mannich reaction, which was used for removing a typical aquatic pollutant malachite green (MG). During the synthesis procedure, the 3-amino-propyltriethoxysilane was used as the crosslinker between aminated lignin and magnetic nanoparticles. The physical and chemical structure of MAL were investigated through a series of characterization methods including FTIR, XRD, TGA, SEM, and XPS. The effect of pH shows that the adsorbent has excellent adsorption performance for MG at pH = 7. According to the adsorption data, the adsorption process was in line with the Langmuir model and the pseudosecond-order model, indicating that the adsorption was monolayer adsorption and chemisorption. MAL showed excellent sorption capacity of 456.62 mg/g and high adsorption speed within 35 min. Thermodynamic studies show that the adsorption is exothermic and spontaneous. Meanwhile, MAL shows good magnetic properties with the saturation magnetization intensities of 22.61 emu/g. In addition, the MAL could be easily recovered and reused at least five times, which performed good reusability. The mechanism of MG capture onto MAL can be mainly attributed to electrostatic attraction, hydrogen bonding, and pi- pi stacking. In a word, the as-prepared MAL showed great potential for wastewater treatment due to its excellent adsorption efficiency, environmental friendliness, and superparamagnetic behavior. (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

A novel magnetic amino-modified lignin (MAL) sorbent was designed through a facile Mannich reaction strategy for the removal of malachite green (MG) as a typical aquatic pollutant. The adsorbent exhibited excellent adsorption performance for MG at neutral pH, following the Langmuir and pseudosecond-order models. It showed high sorption capacity and speed, with exothermic and spontaneous adsorption thermodynamics. Additionally, MAL demonstrated good magnetic properties and reusability, making it a promising candidate for wastewater treatment due to its efficient adsorption, environmental friendliness, and superparamagnetic behavior.