Removal of methyl orange dye using activated biochar derived from pomelo peel wastes: performance, isotherm, and kinetic studies

The activated biochar derived from pomelo peel waste (PPAB) was prepared using pomelo peel (PP) wastes as the raw materials via chemical activation with phosphoric acid (H3PO4) for the removal of methyl orange (MO) dye in wastewater. The materials were characterized by various analytic methods including scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), N2 adsorption-desorption analysis, X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectrum (FTIR) and zeta potential analysis. The adsorption performance of PPAB was investigated and optimized with MO dye as target adsorbate under various operation parameters (contact time, pH, adsorbent dosage and initial dye concentration). The optimum dosage of PPAB was obtained 1 g/L, and the maximum adsorption took place at pH 3.0. Additionally, the results of equilibrium isotherms indicate the good fit of the adsorption data by Freundlich isotherm model, and the adsorption process belonged to the multilayer adsorption. The theoretical maximum adsorption capacity of PPAB calculated with Langmuir model reached to 163.105 mg/g at 25 °C. The kinetic results revealed that the adsorption fitted well with pseudo-second order kinetic model, and that the intraparticle diffusion was not the only rate-controlling step. Moreover, the possible mechanisms of modification and adsorption could be suggested through the results of SEM, EDS and FTIR. This study revealed that PPAB is a promising and efficient adsorbent for MO dyes, and the synthesis of PPAB provided a deep understanding about recycling and utilizing wastes in wastewater treatment.