Preparation and characterization of Scallop shell coated with Fe₃O₄ nanoparticles for the removal of azo dye: Kinetic, equilibrium and thermodynamic studies

Abstract

In this study, Scallop shell-Fe₃O₄ nanoparticles have been used as adsorbents for investigation of the adsorption kinetics, isotherms and thermodynamic parameters of the Acid Red 14 (AR14) from aqueous solutions at various <em>p</em>H, dye concentrations, adsorbent dosages, temperatures and ionic strength. Scallop shell-Fe₃O₄ nanoparticles are synthesized by co-precipitation method in vacuum condition. Efficient coating of Fe₃O₄ nanoparticles onto Scallop shell is identified by FT-IR, XRD, SEM, EDX and VSM analysis. Removal efficiency of AR14 by Scallop shell-Fe₃O₄ nanoparticles is greater than that by Scallop shell-alone and Fe₃O₄-alone. Maximum adsorption is observed at acidic condition. The removal efficiency of AR14 increased with increasing adsorbent dosage, but decreased with increasing initial AR14 concentration and temperature.The adsorption capacity of AR14 onto adsorbent is little affected by the type of ionic strength except carbonate ion. In kinetic studies, removal rate is better described by the pseudo-second order model than the pseudo-first order model and intra-particle diffusion model. Adsorption isotherm is analyzed by both Langmuir and Freundlich equation. Experimental results reveal that the adsorption reaction is exothermic process. Adsorption efficiency of AR14 by Scallop shell-Fe₃O₄ nanoparticles is maintained even after six successive cycles.