Sea shell powder as a new adsorbent to remove Basic Green 4 (Malachite Green) from aqueous solutions: Equilibrium, kinetic and thermodynamic studies

In this work the feasibility of employing sea shell powder to remove Basic Green 4 (BG 4), a cationic dye from its aqueous solutions was investigated. Parameters that influence the adsorption process such as particle size, pH, adsorbent dose, initial dye concentration, contact time and temperature were studied in batch experiments. Optimum adsorption of Basic Green 4 took place at pH 8.0. Further, the adsorbent was characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). FTIR analysis revealed that –OH, –CO3, and –PO4 functional groups were mainly responsible for the adsorption process. The experimental equilibrium adsorption data fitted well to the Langmuir isotherm model. The maximum monolayer adsorption capacity was found to be 42.33 mg g−1 at 303 K. The kinetic data conformed to the pseudo-second-order kinetic model. Intraparticle diffusion was not the sole rate-controlling factor. The activation energy (Ea) of dye adsorption was determined at 15.71 kJ mol−1 according to Arrhenius equation which indicated that the adsorption process of Basic Green 4 onto sea shell powder may be physical adsorption. Thermodynamic parameters such as Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) were also calculated and it was found that the adsorption of dye by sea shell powder was a spontaneous process. It was concluded that sea shell powder has potential for application as adsorbent for removal of Basic Green 4 from aqueous solution.