Smart dual responsive alginate grafted copolymeric hydrogel for sorption of recalcitrant methylene green from water

ABSTRACT

The sorptive removal of recalcitrant dyes from aquatic media holds paramount significance in the contemporary research. The pressing problem has been addressed by facile fabrication and subsequent sorption studies on sodium alginate grafted poly (N-isopropyl acrylamide-co-acrylic acid) [Na-Alg-g-p(NIPAm-co-AAc)] hydrogel for sorption of methylene green (MG). The sorbent achieved equilibrium in 30 minutes, whereas highest sorption capacity was noted at optimum pH 5. At 25°C, the sorbed quantity of the adsorbate enhanced with the rise in initial concentration. The data of isothermal studies fitted well into the Langmuir isotherm as suggested by relatively higher R² of ≈ 0.98. The sorption obeyed pseudo-second-order kinetics as evidenced by exceptionally higher R² (0.999) and substantial agreement in experimentally obtained and theoretically calculated second-order rate constant. The validity of Langmuir isotherm and pseudo-second-order kinetic models imply the occurrence of chemisorption between anionic [Na-Alg-g-p(NIPAm-co-AAc)] sorbent and cationic MG. Moreover, the material exhibits dual (pH and temperature) responsive nature because the amount sorbed undergoes variation with change in temperature and pH. The results signify potential candidature of the fabricated sorbent for the reclamation of dye contaminated water and related applications.

KEYWORDS:

• Sorptive removal
• recalcitrant dyes
• facile fabrication
• polymeric hydrogel
• sorption experiments

Supplemental data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/01496395.2023.2279516

Disclosure statement

No potential conflict of interest was reported by the author(s).

Novelity statement

• Dual responsive sodium alginate grafted poly (N-Isopropyl acrylamide-co-acrylic acid) [Na-Alg-g-p(NIPAm-co-AAc)] hydrogel was fabricated by free radical polymerization method.

• Sorption behaviour of the graft co-polymeric material was explored in batch adsorption experiments by using methylene green (MG) as a probe dye.

• The sorption kinetics and isotherm were probed by applying different kinetic and isotherm models.

• The MG loaded sorbent was regenerated by adopting solvent extraction route using acetone

• The recycling behaviour of the spent sorbent was inspected for six successive sorption-desorption runs.

• The results signify potential candidature of the fabricated sorbent for the reclamation of dye contaminated water and related applications.