Pd-ZnO nanoparticles decorated acid activated montmorillonite for the efficient removal of cationic dyes from water

Abstract

Efficient adsorbent being the need of the hour for the effective removal of dye stuff from textile effluents, we herein report the synthesis of palladium intercalated zinc oxide nanoparticles decorated acid activated montmorillonite (Pd-ZnO@H+-Mt)nanocomposite using ion-exchange process followed by wet impregnation technique with Citrus limon leaf extract as reducing agent and its application as an efficient adsorbent for methylene blue (MB) and malachite green (MG) removal from water. The successful intercalation of Pd into the ZnO lattice was identified by band gap value calculated using UV-DR spectra. ATR FT-IR, XRD, SEM, TEM, TGA, BET, and XPS techniques confirmed the successful preparation of Pd-ZnO@H+-Mt nanocomposite. The synthesized Pd-ZnO@H+-Mt nanocomposite was then evaluated for efficient uptake of cationic dyes through batch adsorption experiments and thereby various parameters that influenced adsorption process were found. The experimental maximum adsorption capacity, qm of Pd-ZnO@H+-Mt for MB and MG dyes were 205 and 167 mg/g. The main driving force for the adsorption of MB and MG was identified to be the presence of mesopores, high specific area of Pd-ZnO@H+-Mt on acid activation, total pore volume and the presence of Pd-ZnO NPs on the surface which enhanced the negative charges of Mt surface thus facilitated better loading of dye molecules. Multilayer coverage of MB/MG molecules on Pd-ZnO@H+-Mt were evidenced through Freundlich isotherm model and experimental data of both MB and MG were described well by pseudo second-order kinetic model. The adsorption phenomenon was identified as feasible, spontaneous, and endothermic for MB adsorption while exothermic for MG adsorption. Moreover, the adsorbent could be recycled thrice. Thus, the synthesized Pd-ZnO@H+-Mt nanocomposite could be utilized effectively in industrial water treatment for the removal of dye stuff as adsorbent.