biochar from orange (citrus sinensis) peels by acid activation for methylene blue adsorption

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 (phpzc) 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 the langmuir isotherm model compare to freundlich and temkin models. the maximum adsorption capacity, qmax 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.