Facile synthesis of sulfur-doped chitosan/biochar derived from tapioca peel for the removal of organic dyes: Isotherm, kinetics and mechanisms

The carbon biomass has extensively been used for water/wastewater purification systems. However, pristine carbon matters have less efficiency in practical applications. Conversely, tuning of carbon with biomaterials has been widely employed. Herein, a sulfur tethered adsorbent of chitosan-tapioca peel biochar (S-CS@TB) composite was successfully fabricated. The peel of tapioca was used as a precursor for the fabrication of the biochar matrix. The organic dyes such as Malachite Green (MG) and Rhodamine B (RhB) were chosen as the adsorbates for this study, and the S-CS@TB composite shows the adsorption efficiency of 53.35 and 40.86 mg/g, respectively. The dye concentration used for this study was 50 mg/L, and the maximum dye molecules removal was observed at a pH range ~8, and the saturation observed within 120 min. The adsorption followed the pseudo-second-order kinetics and Langmuir isotherm model. The fabricated adsorbent was recovered and reclaimed in five successive cycles after the adsorption-desorption process. Electrostatic attractions, hydrogen bonding and π-π interactions were the essential mechanisms involved in the adsorption system. The fabricated adsorbent could be utilized as a capable adsorbent for the water/wastewater treatment process.