Methylene Blue Adsorption Using the Metal-Organic Framework of Calcium Alginate (CaA)

Abstract

Methylene blue (MB) is one of the most commonly used dyes in the printing and textile industries. This research aimed to synthesize MOF CaA (Metal-Organic Framework Calcium Alginate) as an adsorbent for MB dye waste and investigate the effects of contact time and MB concentration on adsorption efficiency. MOF CaA was synthesized through ion exchange between sodium alginate (NaA) and calcium chloride (CaCl₂) solution to produce calcium alginate (CaA). The obtained CaA adsorbent was then calcined at 800 °C for two hours to produce MOF CaA. Characterization was carried out using FTIR and SEM-EDX. FTIR confirmed the presence of characteristic alginate functional groups. SEM-EDX showed C, O, Ca, Na, and Al in the CaA adsorbent. The results showed the highest MB reduction at 60 minutes of contact time, with MOF CaA concentrations of 0.02 g/L and MB concentrations of 0.005 g/L. The adsorption efficiency was 36.3549%. The adsorption kinetics of MB on CaA followed the intraparticle diffusion model, which showed the highest correlation coefficient (R²) of 0.9683 among the kinetic models evaluated. These findings demonstrate the potential of technical-grade CaA as an economical adsorbent for methylene blue removal from aqueous solutions.