Synthesis, characterizations, and RSM analysis of Citrus macroptera peel derived biochar for textile dye treatment

Abstract

Textile wastewater discharging to the surface water body is a great concern because it contains different pollutants such as dyes, organics, surfactants, inorganic salt and heavy metals. An effective low-cost treatment technology has not been developed yet. The objective of this study was to develop a low-cost biochar adsorbent from was from a novel Citrus macroptera peels (CMPs) using a conventional slow pyrolysis process and applied it for the treatment of methylene blue dye in an aqueous solution. The chemical functionalities, surface textures, and crystallinity of the synthesized biochar were characterized by Fourier Transform-Infrared (FTIR) spectroscopy, Field Emission Scanning Electron Microscope (FESEM) analysis, and X-ray powder Diffraction (XRD), respectively. Different functional groups such as -COOH, OH, and R-OH, randomized porous structures with tunnel-like cracks were confirmed from the FTIR and FESEM, respectively. Typical non-linear disordered 3D carbon structure was predicted from the XRD. Response surface methodology (RSM) was performed with the central composite design (CCD) technique, and analytical tuning of the process variables, e.g., pH, contact time, and methylene blue concentration, was also carried out to validate the RSM optimization. The adsorption isotherms and kinetics were investigated, where isotherm and kinetics followed Langmuir and pseudo 2nd order models. RSM results at pH 8 showed 85% of dye removal within 75 min of contact time. According to the Langmuir isotherm model, the maximum adsorption capacity, qm was 139.7 mg/g, which aligned with the experimental value. The present work shows that the low-cost CMPs-derived biochar has the potential for dye removal from industrial effluents.