Synthesis, characterization, and selective dye adsorption by pH- and ion-sensitive polyelectrolyte galactomannan-based hydrogels

• Published in: Carbohydrate polymers 2021-07, Vol.264, p.118009-118009, Article 118009
• Main Authors: Li, Pengfei, Wang, Ting, He, Jing, Jiang, Jianxin, Lei, Fuhou
• Format: Article
• Language: English
• Subjects: Adsorption mechanism; Carboxymethyl guar gum; Dye; Polyelectrolyte hydrogel; Quaternary ammonium guar gum
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2021.118009

[Display omitted] •Two oppositely charged guar gums to make polyelectrolyte galactomannan hydrogels.•They showed highly tunable swelling behavior as response to pH/salt ions.•Polyelectrolyte galactomannan hydrogels with chemical and physical crosslinking.•Exhibited excellent adsorption capacities (1454 mg /g for CR) and high selectively.•Exhibited good anti-interference capability and regeneration efficiency. Three novel polyelectrolyte galactomannan hydrogels (PGHs) were fabricated by chemically crosslinking quaternary ammonium galactomannan (QAG) and carboxymethyl galactomannan (CMG), and employed for the removal of Congo Red (CR) and Methylene Blue (MB). Physicochemical characterization revealed that the PGHs are chemically and physically crosslinked. The PGHs are pH- and ion-sensitive, and their physical crosslinking can be destroyed by artificial urine; water swelling capacity (100.6–321.9 g/g dry gel) and artificial urine swelling capacity (35.9–80.5 g/g dry gel). The adsorption of CR and MB was studied and found to be pH-dependent and selective. The maximum adsorption capacities of CR and MB on the QAG and CMG gels are 1441 and 94.52 mg/g, respectively, and their adsorption kinetics and isotherm behavior obey the pseudo-second-order kinetics model and Langmuir isotherm model, respectively. The adsorption mechanism is dominated by electrostatic interactions and hydrogen bonding. Further, the PGHs have excellent salt resistance and are reusable.