Synthesis, characterization, and selective dye adsorption by pH- and ion-sensitive polyelectrolyte...

Area of Science:

• Materials Science
• Polymer Chemistry
• Environmental Science

Background:

• Wastewater contamination by dyes like Congo Red (CR) and Methylene Blue (MB) is a significant environmental concern.
• Development of efficient and reusable adsorbent materials is crucial for dye removal.
• Galactomannan-based hydrogels offer potential due to their tunable properties.

Purpose of the Study:

• To fabricate novel polyelectrolyte galactomannan hydrogels (PGHs) for dye removal.
• To investigate the physicochemical properties and adsorption performance of PGHs for CR and MB.
• To explore the adsorption mechanisms and reusability of the developed hydrogels.

Main Methods:

• Chemical crosslinking of quaternary ammonium galactomannan (QAG) and carboxymethyl galactomannan (CMG) to form PGHs.
• Physicochemical characterization including swelling studies in water and artificial urine.
• Adsorption experiments to determine capacity, kinetics, and isotherm behavior for CR and MB.

Main Results:

• PGHs exhibited chemical and physical crosslinking, with pH and ion sensitivity.
• Swelling capacities ranged from 100.6-321.9 g/g (water) and 35.9-80.5 g/g (artificial urine).
• Maximum adsorption capacities reached 1441 mg/g for CR and 94.52 mg/g for MB, following pseudo-second-order kinetics and Langmuir isotherms.

Conclusions:

• The novel PGHs demonstrate high efficiency and selectivity for removing CR and MB dyes.
• Electrostatic interactions and hydrogen bonding are key adsorption mechanisms.
• PGHs possess excellent salt resistance and reusability, indicating their potential for practical wastewater treatment applications.