Removal of Chromate from Aqueous Solution by a Novel Clinoptilolite-Polyanillin Composite

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Unmodified zeolites show little affinity for anions due to the fact that their surfaces are negatively charged. However modification of zeolites with amines turns their negative surface charge to positive and creating higher adsorption capacity for anions. In this study, polyaniline-clinoptilolite composite was prepared by polymerization of anilinium on the surface of zeolite. The composite was characterized by elemental analysis and X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Fourier Transform InfraRed (FT-IR) techniques. The adsorption capacity of the composite for removal of CrO42- from aqueous solutions was studied under different experimental conditions including initial concentration, pH, temperature, and contact time. The maximum adsorption capacity of this adsorbent was higher than the values reported for similar adsorbents. The adsorption process was kinetically fast and the equilibration was attained after 30 minutes. The Langmuir and Freundlich isotherm models were applied to describe the equilibrium adsorption and the Freundlich model agreed well with the experimental data.