The ability of CaCO3 to sequester methylene blue (MB) from water was assessed through spectrophotometric, kinetic, and isotherm studies. The adsorption process was greatly affected by pH, with the best results at pH 7.5. This is due to deprotonation of surface functional groups and stronger electrostatic attraction to positively charged dye molecules. An optimal amount of adsorbent at 1.500 g/L achieved about 83% removal, showing more active sites become available until saturation. Isotherm results indicated a strong affinity between MB and the adsorbent, with removal rates over 90% at low initial concentrations. At higher concentrations (40–100 mg/L), removal efficiency dropped as active sites became saturated. Nevertheless, the adsorbent still removed over 80% of the dye across the tested range, proving its durability and effectiveness. These findings suggest that modified CaCO3 is a promising, eco-friendly adsorbent for dye-laden wastewater treatment and offers a valuable use for periwinkle shells, which are usually waste.
Amakoromo et al. (Fri,) studied this question.