Optimization of Methylene Blue Adsorption Using Hydrothermal Carbonization Chamaerops humilis-Derived Activated Carbon: A Response Surface Methodology Approach

Chamaerops humilis fruit pulp was employed in this work to prepare hydrochar-activated carbon (CHHAC), and the material was tested for the removal of Methylene Blue (MB) from aqueous solutions. The hydrothermal carbonization of pulp performed the preparation of CHHAC followed by phosphoric acid activation. Next, we optimized the MB solution preparation and adsorption process conditions (adsorbent mass, pH, contact time, and stirring speed). Based on these findings, response surface methodology (RSM) was used to optimize these conditions, which provided the optimal conditions as well as an understanding of the adsorption mechanism. The Brunauer-Emmett-Teller (BET) surface area of the CHHAC significantly increased from 0.1613 to 1,421.6891 m2 g-1 upon activation, with a slight decrease post-adsorption due to MB adsorption. Scanning electron microscopy (SEM) images showed the development of a porous structure, while energy-dispersive spectroscopy (EDX) analysis identified differences in elemental composition after adsorption. Fourier transform infrared (FTIR) spectra revealed the presence of new functional groups, indicating effective interaction among the dye molecules and the adsorbent. The adsorption desorption experiments revealed increased efficacy in the first and second cycles (99.66 and 99.56%) and good reusability, with a progressive decrease in effectiveness with continued use.