Biochar from Orange (citrus sinensis) Peels by Acid Activation for Methylene Blue Adsorption

Abstract

<em>In this work, orange (Citrus sinensis) peels biochar (OPBC) were prepared by one-step H₂SO₄ activation for Methylene Blue (MB) adsorption from aqueous solution. The physicochemical properties of OPBC were characterized using instrumental analyses such as CHNS-O analyzer, Fourier Transform InfraRed (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and point-of-zero charge (pH_pzc) analysis. Batch mode adsorption study was conducted by varying operational parameters such as adsorbent dosage (0.02 – 0.20 g), solution pH (3 – 11), initial MB concentrations (50 – 300 mg/L), and contact time (0 – 1440 min). The equilibrium data was found to better fit with Langmuir isotherm model compare to Freundlich and Temkin models. The maximum adsorption capacity, q_max of OPBC for MB adsorption was 208.3 mg/g at 303 K. The kinetic study revealed that the present system obeyed Pseudo-Second-Order (PSO), model. The thermodynamic adsorption parameters such as standard enthalpy (ΔH°), standard entropy (ΔS°), and standard free energy (ΔG°) showed that the adsorption of MB onto OPBC surface endothermic in nature and spontaneous under the experimental conditions. All above-mentioned results indicate that the OPBC can feasibly employ for the elimination of MB from aqueous solution</em>