Kinetic and isotherm evaluation of xanthene triphenylmethane dye mixture adsorption on cobalt doped coconut husk encapsulated biochar

Water is an essential resource, but its quality is increasingly threatened by industrial activities. Textile industries are major contributors to water pollution due to the discharge of untreated synthetic dye effluents into water bodies. In this study, cobalt-doped coconut husk biochar (Co@CHBc) was synthesized by pyrolysis method at 600 °C. The manufactured material was characterized by FESEM, Mapping, EDX, FTIR, BET and XRD. The maximum removal of mixture of cationic dyes such as Rhodamine-B (Rh-B) and Malachite Green (MG) is observed at pH 8, contact time of 60 min, 20 mg/L of mixture of dye concentration, 600 mg of Co@CHBc dosage and at room temperature. The Kinetics data is best fitted with the Pseudo Second Order (PSO) having regression coefficients (R 2 ) of 0.996. The isotherm data is perfectly match with Langmuir Isotherm having R 2 of 0.9989. The adsorption capacity of the Co@CHBc was determined to be 31.74 mg/g. Thermodynamics study studies shows that the adsorption is exothermic for the mixture of cationic dyes. The reusability and regeneration studies were performed to check the capability of the Co@CHBc. A comparison studies of Co@CHBc is performed with different dyes such as Erichrome Black T (EBT), Methylene Blue (MB), Congo Red (CR), Methyl Orange (MO) and Crystal Violet (CV). Based on the models a purposed mechanism is designed between mixture of cationic dyes and Co@CHBc. The results indicate that cobalt-doped biochar is a low-cost and sustainable material with strong potential for wastewater treatment applications.