Development of novel surfactant functionalized porous graphitic carbon as an efficient adsorbent for the removal of methylene blue dye from aqueous solutions

In this work, an environmentally friendly and economically effective surfactant modified porous graphitic carbon (S-PGC) obtained from alginate biomass was successfully fabricated by functionalizing with anionic surfactants (sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS)) and used as an adsorbent for the removal of methylene blue cationic dye from aqueous solutions. The structural order and textural properties were examined using XRD, Raman spectroscopy and SEM-EDX. Batch adsorption experiments were conducted, where the influence of operating parameters such as solution pH, contact time, adsorbent dosage, initial MB concentration, and temperature on the sorption capacity were investigated. Compared with pristine PGC, the surfactant modified PGC (S-PGC) exhibited a much higher sorption capacity for MB due to the enhanced electrostatic interaction between the cationic dye and negatively charged S-PGC adsorbent. The adsorption isotherm and kinetics of adsorption were well fitted by the Freundlich isotherm and pseudo-second order model, respectively. The maximum adsorption capacity calculated from Langmuir isotherm was 714 and 769 mg/g for two adsorbents SDBS-PGC-3000 and SDS-PGC-3000, respectively at 25 °C, suggesting SDS-PGC has a comparatively higher sorption capacity. Further investigation confirmed that the adsorption of MB over S-PGC was spontaneous and endothermic in nature. Successful regeneration of the spent adsorbents with methanol along with its high dye adsorption performance strongly confirms the ability of utilizing S-PGC as a promising and reliable adsorbent for cationic dye removal.