Adsorptive removal of cationic dyes using hybrid material-based polyelectrolyte modified laterite soil

Abstract

Strong polyanion, polystyrene sulfonate (PSS) on the laterite soil to form a new material has been investigated to remove cationic dyes from aqueous solution. The laterite soil after surface modification by PSS was characterized by Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and zeta potential measurements. The conditions for adsorption of PSS on laterite soil were selected as, contact time 150 min, 50 mM NaCl, pH 4, solid-liquid ratio 5 mg/mL. The laterite soil after PSS adsorption was called polymer modified laterite (PML). The PML was used for study on the removal of the molecular organic dyes, crystal violet (CV) and methylene blue (MB). The effective parameters for removal of both CV and MB using PML were adsorption time 75 min, while the optimum pH values were 8 and 9 for CV and MB, respectively. Using the optimum parameters, the removal efficiencies of CV and MB using PML achieved greater than 92% and 83%, respectively. The adsorption isotherms of CV and MB onto PML at different salt concentrations were in accordance with Langmuir model than Freundlich one. Thermodynamic study of CV and MB adsorption onto PML followed an exothermic process. Adsorption of cationic dyes onto PML was confirmed by electrostatic interactions based on adsorption isotherms, charging behavior by ζ potential and the change in the active groups by FT-IR. Our results indicate that PML is a high performance and novel adsorbent for removal of cationic dyes from water environment.