Adsorption Isotherms, Thermodynamics, and Kinetic Modeling of Methylene Blue onto Novel Carbonaceous Adsorbent Derived from Bitter Orange Peels.

This work reports the production of activated carbons (AC) from bitter orange peel by using ZnCl₂ or H₃PO₄ as activating agent at two different carbonization temperatures (450 °C and 550 °C). Surface morphology analyses of produced bitter orange activated carbons (BOACs) were done by SEM. The surface areas of the produced BOACs, functional groups on the AC surfaces and compositions, were determined by using BET, FT-IR, and TGA analyses. Furthermore, their application for the removal of methylene blue (MB) was studied. The parameters affecting adsorption, such as pH and temperature, were evaluated. BOAC produced with ZnCl₂ at 550 °C, exhibits the highest surface area (1450.6 m² g⁻¹), whereas BOAC produced with ZnCl₂ at 450 °C yielded with the highest adsorption capacity (108.9 m² g⁻¹). Langmuir isotherm shows a good fit for the BOACs. Adsorption kinetics were studied and follows pseudo-second-kinetic model. The thermodynamic parameter studies indicate that the adsorption process is endothermic and spontaneous. [ABSTRACT FROM AUTHOR]