Eco-friendly porous carboxymethyl cellulose/dextran sulfate composite beads as reusable and efficient adsorbents of cationic dye methylene blue.

Eco-friendly hydrogel composite beads based on crosslinked-carboxymethyl cellulose (CMC) and dextran sulfate (DS) embedded within network were prepared using ionotropic gelation in presence of sodium n-dodecyl sulfate (SDS) as pore-forming template. The milligels composites C/Dx were characterized by FTIR, SEM/EDX and TGA analyses. The composites exhibited porous structure and enhance in swelling properties with enriching DS as well as pH-sensitivity. The effect of DS on adsorption of composites for cationic dye methylene blue (MB) was investigated by changing influencing factors: pH, adsorbent dosage, time contact, dye concentration, and temperature. The results revealed that adsorption performances were remarkably improved by increasing DS content into beads. Kinetics and isotherm adsorption studies revealed pseudo second-order and Langmuir isotherm as befitting models. The maximum Langmuir equilibrium adsorption capacity (qm) was found to increase from 82 mg g-1 for C/D0 to 526 mg g-1 for C/D1. Thermodynamic study revealed spontaneous and endothermic process nature. Furthermore, milligels displayed good reusability after five adsorption/desorption cycles and with an augment in their removal ability compared to starting ones, reaching 714 mg g-1 for R-C/D1. In view of easy preparation and recovery, effectiveness adsorption and good regeneration, the composites could be applied as low-cost adsorbents in wastewater treatment.