Room-temperature fabrication of core-shell nano-ZnO/pollen grain biocomposite for adsorptive removal of organic dye from water

A new core-shell nano-ZnO/pollen grain (n-ZnO/PG) biocomposite has been successfully synthesized via simple and low-temperature two-step liquid precipitation method. The synthetic strategy consists of grafting the surface of pine pollen grains (PG) with Zn2+-organic complexes followed by a treatment in Zn(CH3COO)(2)/NaOH solution, thus producing a closed n-ZnO shell around the organic core, with a thickness of similar to 450 nm. Scanning electron microscopy, X-ray diffraction, FTIR, XPS and UV-vis spectroscopy measurements along with N-2 adsorption/desorption were used to characterize the resulting n-ZnO/PG biocomposite. The as-prepared core-shell microparticles are meso-/macro-porous with BET surface area of 25 m(2) g(-1) and total pore volume of 0.26 cm(3) g(-1). The adsorption properties of n-ZnO/PG were evaluated through adsorption of Malachite Green (MG) from aqueous medium at room temperature (25 degrees C). For the sake of comparison, the physico-chemical and adsorptive properties of the raw PG and pure n-ZnO were also examined. Results indicate that n-ZnO/PG is the most favorable for the adsorption of MG under the conditions used in this study. The adsorption kinetic data for PG, n-ZnO and n-ZnO/PG follow the pseudo-second order equation and the maximum adsorption capacity follows an order of n-ZnO/PG > n-ZnO > PG. For n-ZnO/PG an adsorption uptake up to 145.9 mg g(-1) is observed. The as-prepared core-shell biocomposite material is a promising cost-effective and environmentally friendly adsorbent due to its textural properties, surface chemistry, adsorption capacity and recyclability. (C) 2016 Elsevier B.V. All rights reserved.