Interaction profiles in poly (amidoamine) dendrimer/montmorillonite or rice straw ash hybrids-immobilized magnetite nanoparticles governing their removal efficiencies of various pollutants in wastewater

In this study, magnetite NPs (M) of 0.4 and 1.2 wt% were immobilized into polyamidoamine dendrimer (PAMAM)/montmorillonite (MMT) or rice-straw-ash (RSA) hybrids to improve the depolluting efficiency of magnetite phase. The operating interaction profiles in these nanocomposites were assessed via XRD, FTIR, DLS, N-2-physisorption, TEM and SEM techniques. The increase in magnetite loading encouraged the aggregation of incorporated dendrimer molecules, forming the so-called dendrimer colonies. Such colonies caused marked exfoliation of clay layers in PAMAM/MMT hybrid and considerable coalescence of silica particles in PAMAM/RSA hybrid. The as synthesized M@PAMAM/MMT nanocomposites exhibited pronounced sorption efficiencies for NI4+ (96%) and NO3- (83%), and a progressive degradation efficiency toward xylenol- orange (similar to 85% mineralization). Meanwhile, the M@PAMAM/RSA nanocomposites possessed distinguished sorption efficiencies of 92% for Hg2+ and 98% for Br-, and a significant degradation efficiency toward malachite-green (similar to 99% mineralization). Such depollution behaviours were governed by the interaction profiles involving the incorporated M NPs and dendrimer colonies. Both the mechanisms of sorption of ions and degradation of dyes obeyed the pseudo first-order kinetics, supporting the film-diffusion controlling model. The reuse of the synthesized nanocomposites for removal of various water-pollutants under study was successfully achieved in seven cycles with an average efficiency of 95%. (C) 2017 Elsevier B.V. All rights reserved.