Removal of Methylene Blue from Aqueous Media Using Coffee Inner Husks

Virgin coffee inner husk (VCIH) and VCIH calcined at 1000°C (CIH1000) were prepared in this study. These adsorbents were characterized by scanning electron microscopy imaging, thermal analysis, specific surface area measurements, surface functional groups, and point-of-zero charge (pHpzc). The adsorption capacity of methylene blue (MB) was greater for CIH1000 than for VCIH. In addition, the MB adsorption capacity was evaluated by demonstrating the effect of initial concentration, temperature, contact time, and pH on the adsorption. The results were fitted to both the Langmuir model (correlation coefficient: 0.915–0.997) and the pseudo-second-order model (correlation coefficient: 0.989–0.997). To elucidate the MB adsorption mechanism, elemental distributions and binding energies were characterized and the components of MB (carbon, sulfur, and nitrogen) were detected after adsorption. These findings provide useful information for the removal of MB from aqueous media.