Synthesis of a nanocomposite adsorbent with high adsorptive potential and its application for abatement of chromium(VI) from aqueous stream

Abstract

Hydrated zirconium(IV) incorporated cerium(IV) oxide (HZICO) nano composites, a novel and efficient adsorbent of Cr(VI) have been synthesized and characterized to determine surface morphology, crystalline nature and particle size distribution by various tools including SEM, TEM, XRD, AFM, and FTIR spectroscopy. Removal of Cr(VI) from aqueous solution has been investigated by batch studies and the adsorption was dependent on numerous factors including solution pH, adsorbent dosage, temperature, initial loading of contaminant and contact time. The adsorption was highly dependent on pH providing maximum adsorption at pH 2 and equilibrium was achieved in 3h. The pseudo-second order equation describes the reaction kinetics better than the pseudo-first order equation. Freundlich isotherm model was recognized to be the best fit model indicating multilayered adsorption on heterogeneous adsorption sites of the adsorbent with maximum adsorption capacity achieved as 97.04mgg−1 for initial concentration ranging from 10 to 100mgL−1 at 303K. Thermodynamic parameters indicated that Cr(VI) adsorption was spontaneous and endothermic in nature. The spent adsorbent was regenerated effectively up to 85% by 2.0M NaOH in the first cycle and the adsorption efficiency of HZICO was retained around 60% even after fifth cycle of regeneration. A batch adsorber model has been designed with a view to pilot scale application for removal of Cr(VI) from aqueous stream effectively and thus, HZICO could be used as an efficient scavenger because of its relatively high adsorption capacity, regeneration efficiency and reusability.