Adsorptive Removal of Methylene Blue Dye Using Biodegradable Superabsorbent Hydrogel Polymer Composite Incorporated with Activated Charcoal

Hydrogels have attracted great attention as good adsorbents due to their extraordinary water retention capacity, unique hydrophilic nature, biocompatibility, and abundance in availability. In this work, a superabsorbent polymer (SAP) hydrogel and its composite were synthesized, with the introduction of activated charcoal (SAP-AC) for deep removal of the ecotoxic organic dye methylene blue (MB). The formation of the hydrogel was confirmed by FTIR analysis, and scanning electron microscopy (SEM) revealed the appearance of a porous microstructure due to the incorporation of AC. A continuous upflow column was set up, and the adsorption parameters were optimized using an experimental Doehlert uniform array design. The residual concentration of MB was analyzed by UV-Vis spectrophotometry at 665 nm (λmax). The experimental data were also discussed in terms of adsorption kinetics and adsorption isotherm models. Accordingly, MB adsorption followed pseudo second-order kinetics and better fits the Freundlich isotherm, suggesting a chemisorption mechanism and a multilayer MB adsorption system. The maximum adsorption capacity was 202.84 mg g−1 (96.96%) using the SAP and 213.2 mg g−1 (99.48%) using the SAP-AC. The present study proved that the synthesized composite hydrogel has good activity and selectivity for deep removal of the MB dye and can be effectively used in wastewater treatment.