Efficient removal of Cr (VI) from aqueous solution by halloysite/poly (amidoamine) dendritic nano-hybrid materials: kinetic, isotherm and thermodynamic studies

This paper demonstrates functionalization of a new hybrid nanoclay for effective adsorption of chromium(VI) ions from wastewater. Halloysite nanotubes (HNTs) were functionalized by poly(amidoamine) dendritic polymers (HNTs-(DEN-NH2)) via a convergent synthetic route by carboxylic acid as a linkage. Various characterization methods confirm that poly(amidoamine) dendritic groups were effectively grafted onto the surface of HNTs that found a high specific surface area of 75 m(2)/g, as measured by micrometric BET analyzer. Moreover, the adsorption activity of HNTs-(DEN-NH2) for Cr (VI) was systematically investigated using a batch solution that reveals the removal efficiency of 98% for HNTs-(DEN-NH2) comparing to 23% for pristine HNTs, at optimum conditions. The enhancement of Cr(VI) removal for HNTs-(DEN-NH2) comparing to HNTs was mainly ascribed to be due to the electrostatic interaction, that was confirmed by the results of Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). Moreover, regeneration studies display that HNTs-(DEN-NH2) can maintain removal Cr(VI) with high efficiency after four consecutive cycles. (C) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.