Fabrication of walnut shell cobalt ferrite green composite for the removal of cationic dyes in single and ternary dye systems: kinetic, isotherm and thermodynamic studies

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Water that is clean and safe is a vital requirement for society's ongoing economic development. As a result, treating contaminated water is important. In the present study, a magnetic composite i.e. Walnut shell cobalt ferrite (WSCoF) has been developed to effectively remove Crystal Violet (CV), Brilliant Green (BG) and Methylene Blue (MB) from aqueous solutions in single and ternary dye systems using the batch adsorption technique. Walnut shell cobalt ferrite has been characterised using FTIR (Fourier Transform Infrared Spectroscopy), FE-SEM (Field Emission Scanning Electron Microscopy), XRD (X-Ray Diffraction), TGA (Thermogravimetric Analysis), EDS (Energy Dispersive Spectroscopy), BET (Brunauer–Emmett–Teller) Analysis and pHzpc. Lagergren’s pseudo-second-order model of adsorption fitted best to kinetic studies indicating chemisorption. Among the different adsorption isotherms used, Langmuir isotherm fitted best with maximum adsorption capacity of 38.9, 70.4 and 78.1 mg/g in single dye systems and 23.8, 37.7 and 13.3 mg/g for dyes CV, BG and MB respectively, in ternary dye systems. The spontaneous character of the adsorption process was confirmed by thermodynamic studies. The composite's capacity for regeneration in both systems has been studied for six cycles. Thus, it is evident that the prepared WSCoF composite can be an effective alternative for removing cationic dyes from single and ternary systems of dyes.