Zinc oxide nano-particles – Sonochemical synthesis, characterization and application for photo-remediation of heavy metalUltrasonics Sonochemistry


Prantik Banerjee, Sampa Chakrabarti, Saikat Maitra, Binay K. Dutta
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l s h tra lkata irat

Sonochemical synthesis ave prop area s ob red  2011 Elsevier B.V. All rights reserved. ve wid trical iverse rimar aracte be controlled properly to achieve the morphology of the nanostructure.

Among the recent material synthesis techniques, ultrasound (20 kHz–1 MHz) based processes have been employed by many researchers to produce nanosized materials, alloys, composites and metal oxides. Intensive sonication of a liquid generates bubnanosized oxides of copper, iron, zinc and cobalt. The starting materials were the respective acetates in water–DMF solution.

Wei and Chang [6] synthesized zinc oxide nanoparticles from zinc chloride and potassium hydroxide in presence of CTAB (cetyl trimethyl ammonium bromide) surfactant. It was observed that sonication at 50 C yielded lower sized particles compared to that synthesized at room temperature. In all of these studies, an alkali was added for hydrolysis in order to introduce a salt in the medium that influenced the growth-kinetics of the nanostructures. It is, however, desirable to synthesize ZnO nanoparticles with minimum ⇑ Corresponding author.

E-mail addresses: prantik.banerjee85@gmail.com (P. Banerjee), sampac.2008@gmail.com (S. Chakrabarti), maitrasaikat@rediffmail.com (S. Maitra), bdutta@pi.ac.ae

Ultrasonics Sonochemistry 19 (2012) 85–93

Contents lists availab

Ultrasonics So els(B.K. Dutta).of nanosized ZnO have received significant attention in the recent years. It has been found that the morphology of the ZnO particles can be modified to serve specific requirements by employing suitable synthetic processes. High energetic synthesis of ZnO nanoparticles uses techniques such as thermal evaporation and decomposition, arc-plasma, sputtering and laser ablation, whereas relatively low energetic synthesis routes rely on hydrothermal and solvothermal, hydrolysis and sol–gel techniques [1]. Among the different low energetic methods of synthesis, solution-based approach is the simplest, but the solvent and the precursor as well as reaction conditions such as pH, temperature and time need to et al. [3] studied the effects of temperature and sonication power on the morphology of ZnO synthesized from ZnCl2 and KOH precursor. They observed that the spherical form predominated at an elevated temperature and high sonication power. Bhattacharya and Gedanken [4] prepared hexagonal ZnO nano disks using zinc acetate in dimethyl formamide medium under ultrasound irradiation. They observed that the product was more porous when synthesized under an argon atmosphere compared to that when exposed to air. Also, the micropores could not withstand high temperature whereas the mesopores were stable up to 550 C. Vijayakumar et al. [5] sonochemically synthesized and characterizedPhotoreduction

Hexavalent chromium 1. Introduction

Zinc oxide (ZnO) nanoparticles ha tions in catalytic, photocatalytic, elec cesses and systems [1]. For these d morphology of ZnO particles are of p quently, studies on the synthesis, ch1350-4177/$ - see front matter  2011 Elsevier B.V. A doi:10.1016/j.ultsonch.2011.05.007e technological applicaand optoelectronic proapplications, size and y consideration. Conserization and properties bles by cavitation which collapse and create a very high temperature (up to 5000 K) and pressure (up to 1800 atm) momentarily inside the collapsing cavity. This ‘hot spot’ is responsible for the homogeneous sonochemical reactions [1]. It will be pertinent at this point to review the more important recent literature in this regard. Jung et al. [2] reported sonochemical preparation of various forms of ZnO nanostructure such as cup, rod, flower etc. KandjaniKeywords:

Zinc oxide nanoparticles

It was observed that the initial reduction rates varied with the difference in morphology of ZnO crystallites.Zinc oxide nano-particles – Sonochemica and application for photo-remediation of

Prantik Banerjee a, Sampa Chakrabarti a,⇑, Saikat Mai aDepartment of Chemical Engineering, University of Calcutta, 92, Acharya P.C. Road, Ko bGovernment College of Engineering and Ceramic Technology, Kolkata, India cChemical Engineering Programme, The Petroleum Institute, Abu Dhabi, United Arab Em a r t i c l e i n f o

Article history:

Received 7 December 2010

Received in revised form 3 May 2011

Accepted 10 May 2011

Available online 18 May 2011 a b s t r a c t

Zinc oxide nanoparticles h methanol, ethanol and isoXRD, AFM and BET surface sized using isopropanol wa used for the photocatalytic journal homepage: www.ll rights reserved.ynthesis, characterization eavy metal b, Binay K. Dutta c 700 009, India es been synthesized sonochemically from zinc acetate solution in aqueous anol containing about 5 volume% of alcohol. Characterization with FESEM, shows that the synthesized particles differ in shape and size. ZnO syntheserved to be the most crystalline one. The synthesized nanoparticles were uction of hexavalent chromium in aqueous medium under solar radiation. le at ScienceDirect nochemistry evier .com/ locate /ul tsonch 1:1 methanol and ethanol, centrifuged using a REMI R-24 research

Sonforeign chemicals. Hosono et al. [7] reported synthesis of zinc oxide nanocrystals from alcoholic solution of zinc acetate at 60 C through chemical route without addition of a base. Zhang et al. [8] reported one-step synthesis of trigonal-shape particles of varying morphology from zinc acetate dihydrate in paraffin oil in presence of stearic acid at an elevated temperature of 220–280 C. The alcohols used were methanol, ethanol and 2-methoxy ethanol.

Methanolic solution was found to be the most suitable one for the synthesis of nano-sized zinc oxide particles.

Zinc oxide has a band gap energy of 3.2 eV and is very effective as a photocatalyst, sometimes more effective than TiO2 in the visible region [9,10] for photocatalytic treatment of wastewater containing either organic pollutants or heavy metals or both. Kabra et al. [11] presented a good review on the application of the photocatalytic technique for remediation of inorganic and organic pollutants in wastewater. Oxidation of organic pollutants has been widely studied in connection with the treatment of drinking water and industrial wastewater. However, the reducing capacity of the semiconductor photocatalyst, which can be profitably used for remediation of heavy metals, has been less explored.