Elsevier

Ultrasonics Sonochemistry

Volume 37, July 2017, Pages 298-309
Ultrasonics Sonochemistry

Ultrasound-assisted degradation of organic dyes over magnetic CoFe2O4@ZnS core-shell nanocomposite

https://doi.org/10.1016/j.ultsonch.2017.01.019Get rights and content

Highlights

  • Magnetic CoFe2O4@ZnS core/shell nanostructure was synthesized by a new method.

  • Hydrothermal degradation of DEDTC complex on the CoFe2O4 resulted in CoFe2O4@ZnS nanocomposite.

  • CoFe2O4@ZnS nanocomposite was used as an efficient sonocatalyst for the degradation of organic pollutant.

  • The sonocatalytic activity of CoFe2O4@ZnS nanocomposite was more than of pure ZnS and CoFe2O4.

  • CoFe2O4@ZnS nanocomposite can be magnetically recovered.

Abstract

Magnetic CoFe2O4@ZnS core-shell nanocomposite was successfully synthesized via one-step hydrothermal decomposition of zinc(II) diethanoldithiocarbamate complex over CoFe2O4 nanoparticles at low temperature of 200 °C. The obtained nanocomposite was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, UV–Vis spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, magnetic measurements, and Brunauere-Emmette-Teller. The results confirmed the formation of CoFe2O4@ZnS nanocomposite with the average crystallite size of 18 nm. The band gap of 3.4 eV was obtained using UV–vis absorption of CoFe2O4@ZnS nanocomposite, which made it a suitable candidate for sono-/photo catalytic processes. This nanocomposite was applied as a novel sonocatalyst for the degradation of organic pollutants under ultrasound irradiation. The results showed complete degradation of methylene blue (MB) (25 mg/L) within 70 min in the presence of CoFe2O4@ZnS nanocomposite and H2O2 (4 mM). The trapping experiments indicated that radical dotOH radicals are the main active species in dye degradation. In addition, sonocatalytic activity of the CoFe2O4@ZnS nanocomposite was higher than those of pure ZnS and CoFe2O4, showing that the combining ZnS with magnetic CoFe2O4 could be an excellent choice to improve its sonocatalytic activity. The nanocomposite could be magnetically separated and reused without any observable change in its structure and performance even after five consecutive runs.

Introduction

Hazardous colorful wastewater realized from industries, particularly textile industry, is one of the major causes of the pollution of the water resources [1], [2]. The release of the synthetic dyes into the aqueous environment causes serious problems because of their strong color and low biodegradability [3], [4]. The removal of these pollutants from the contaminated aqueous solutions is of great importance in the environmental processes [5]. Thus, there is currently a considerable interest in developing effective processes for degradation of these types of organic pollutants [6].

In recent years, sonochemical degradation has been introduced as a possible method for wastewater treatment, and its successful application has been reported for the degradation of halogenated hydrocarbons [7], pesticide components [8] and dyes[9]. During this process, ultrasound waves lead to a quick growth and collapse of bubbles within the solution, which results in an extremely high temperature and pressure in the bubbles. High temperature near the bubbles causes thermal dissociation of water and generates hydroxyl radicals (radical dotOH) as a strong oxidant for non-selective oxidation of organic pollutants [10]. However, ultrasound alone is not efficient for the degradation of the target organic pollutant because of the need for longer time and higher amount of energy for an effective degradation. To overcome to this problem, catalysts which are active under ultrasonic irradiation, namely sonocatalyst, can be used for degrading organic pollutants in the aqueous phase. The generation of radical dotOH will be accelerated during the ultrasonic irradiation in the presence of an insoluble sonocatalyst [11], [12]. In this context, some metal oxide nanostructures such as Fe3O4, ZnO, and MgO have been used as sonocatalysts for the degradation of organic dyes [13], [14], [15].

Photoactive semiconductor based nanomaterials with high surface area and long life-span have been widely used for degradation of organic pollutants in water [16], [17]. Among them, ZnS (band gap energy: 3.6–3.8 eV) has served as one of the most efficient photocatalysts for the degradation of dyes, p-nitrophenol, halogenated benzene derivatives, reduction of heavy metals and water-splitting for H2 evolution [18], [19], [20], [21], [22], [23]. ZnS is a good photocatalyst due to the rapid generation of electron–hole (e/h+) pairs by photoexcitation and high negative reduction potentials of the excited electrons. However, it has a serious drawback of the easy recombination of e/h+ pairs, which in turn reduces the catalytic activity significantly [24], [25]. Moreover, the suspended ZnS photocatalyst suffers noticeable limitations such as the difficulty in separation, recovery, recycling and high cost in large scale production [26]. On the other hand, ZnS nanoparticles tend to agglomerate in aqueous solution and hinder the light penetration. For overcome to these drawbacks, ZnS was coupled with various magnetic semiconducting material. For example, Du et al. synthesized Fe3O4/ZnSe/ZnS magnetic fluorescent bifunctional nanocomposites by depositing heterogeneous semiconductor on magnetic nanoparticles [27]. Song et al. reported the MWNTs/ZnS/Fe3O4 nanocomposite with situ chemical precipitation method for the photocatalytic degradation of methylene blue solution with higher activity compared to pure ZnS nanoparticles [28]. Indeed, the sonocatalytic efficiency depends highly on the type of the catalyst. Then, the development of novel sonocatalysts is important to further understand the sonocatalytic mechanism and promote the sonocatalysis applications.

In this paper, we report the use of magnetic CoFe2O4@ZnS core-shell nanocomposite as a novel sonocatalyst for efficient H2O2-assisted sonodegradation of organic dyes in aqueous solutions. The sonocatalyst was prepared by a facile one-step hydrothermal decomposition of zinc(II) diethanoldithiocarbamate (Zn(DEDTC)2), as an air-stable, easily obtained single-source molecular precursor, over magnetic CoFe2O4 nanoparticles. Various spectroscopic techniques were used to characterize the CoFe2O4@ZnS nanocomposite. Thereafter, the sonocatalytic degradation of methylene blue (MB), Rhodamine B (RhB) and methyl orange (MO) organic dyes over the CoFe2O4@ZnS nanocomposite and effects of various operational parameters (e.g. H2O2 quantity, the catalyst amount, and initial dye concentration) on their degradation process were evaluated. Furthermore, the activity of CoFe2O4@ZnS nanocomposite was compared with those of pure ZnS and CoFe2O4 under similar conditions. To the best of our knowledge and based on the literature review, there is no report on the use of a magnetic core-shell nanocomposite such as CoFe2O4@ZnS for efficient and rapid sonodegradation of organic dyes, especially in the presence an environmental-friendly oxidizing agent (H2O2).

Section snippets

Materials

Zinc nitrate hexahydrate (Zn(NO3)2·6H2O, 99%), diethanolamine (C4H11NO2, 98%), carbon sulfide (CS2, 98%), iron(III) nitrate nonahydrate (Fe(NO3)3·9H2O, 99%), cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 99%), hydrogen peroxide (H2O2, 30%), methyl orange (MO, C14H14N3NaO3S), methylene blue (MB, C16H18ClN3S), and Rhodamine B (RhB, C28H31ClN2O3) were purchased from Merck chemical Company and used as received.

Characterization techniques

X-ray powder diffractometer (XRD, XPertPro Panalytical, Holland) with Cu kα radiation (40 kV,

Characterization of the CoFe2O4@ZnS nanocomposite

The Powder XRD measurement was done for ZnS, CoFe2O4 and CoFe2O4@ZnS nanostructures to characterize the phase and crystallization (Fig. 1). Fig. 1a illustrates a typical XRD pattern of CoFe2O4 nanoparticles and all diffraction peaks can be indexed to the spinel cubic structure of CoFe2O4 (JCPDS card: 01-1121). From Fig. 1b, it can be seen that cubic ZnS nanoparticles (JCPDS card: 77-2100) [30] have been prepared and the broadening of diffraction peaks is in accordance with their nanocrystalline

Conclusions

Magnetic CoFe2O4@ZnS nanocomposite, with average crystallite size of about 18 nm, was successfully synthesized by a simple hydrothermal reaction, and its sonocatalytic activity was evaluated through degradation of organic dyes in the presence of H2O2. Magnetic measurements revealed that CoFe2O4@ZnS nanocomposite showed a ferromagnetic behaviour that could be easily separated from the aqueous solutions. The effect of different operational parameters including the catalyst dosage, initial dye

Acknowledgement

The authors gratefully acknowledge the Lorestan University and Iran Nanotechnology Initiative Council (INIC) for their support.

References (71)

  • J. Wang et al.

    Sonocatalytic degradation of some dyestuffs and comparison of catalytic activities of nano-sized TiO2, nano-sized ZnO and composite TiO2/ZnO powders under ultrasonic irradiation

    Ultrason. Sonochem.

    (2009)
  • R. Hong et al.

    Synthesis, surface modification and photocatalytic property of ZnO nanoparticles

    Powder Technol.

    (2009)
  • I. Tsuji et al.

    H 2 evolution from aqueous sulfite solutions under visible-light irradiation over Pb and halogen-codoped ZnS photocatalysts

    J. Photochem. Photobiol. A

    (2003)
  • C.L. Torres-Martínez et al.

    Efficient photocatalytic degradation of environmental pollutants with mass-produced ZnS nanocrystals

    J. Colloid Interface Sci.

    (2001)
  • J.-M. Herrmann et al.

    TiO2-based solar photocatalytic detoxification of water containing organic pollutants. Case studies of 2, 4-dichlorophenoxyaceticacid (2, 4-D) and of benzofuran

    Appl. Catal., B Environ.

    (1998)
  • C. Sceney et al.

    Thermal analysis of copper dithiocarbamates

    Thermochim. Acta

    (1975)
  • B. Senthilkumar et al.

    Structural, magnetic, electrical and electrochemical properties of NiFe2O4 synthesized by the molten salt technique

    Mater. Chem. Phys.

    (2011)
  • M. Salavati-Niasari et al.

    Synthesis and characterization of ZnS nanoclusters via hydrothermal processing from [bis (salicylidene) zinc (II)]

    J. Alloys Compd.

    (2009)
  • J.B. Silva et al.

    Influence of heat treatment on cobalt ferrite ceramic powders

    Mater. Sci. Eng. B

    (2004)
  • M.V. Bagal et al.

    Sonochemical degradation of alachlor in the presence of process intensifying additives

    Sep. Purif. Technol.

    (2012)
  • J. Zhang et al.

    Fabrication of Ag3PO4 − PANI − GO composites with high visible light photocatalytic performance and stability

    J. Environ. Chem. Eng.

    (2014)
  • A. Khataee et al.

    Sonochemical synthesis of Pr-doped ZnO nanoparticles for sonocatalytic degradation of Acid Red 17

    Ultrason. Sonochem.

    (2015)
  • L. Ai et al.

    Iron terephthalate metal–organic framework: Revealing the effective activation of hydrogen peroxide for the degradation of organic dye under visible light irradiation

    Appl. Catal. B: Environ.

    (2014)
  • R. Liang et al.

    A simple strategy for fabrication of Pd@ MIL-100 (Fe) nanocomposite as a visible-light-driven photocatalyst for the treatment of pharmaceuticals and personal care products (PPCPs)

    Appl. Catal. B: Environ.

    (2015)
  • N. Ertugay et al.

    The degradation of Direct Blue 71 by sono, photo and sonophotocatalytic oxidation in the presence of ZnO nanocatalyst

    Appl. Surf. Sci.

    (2014)
  • Y.L. Pang et al.

    Fe3+ doped TiO2 nanotubes for combined adsorption–sonocatalytic degradation of real textile wastewater

    Appl. Catal. B: Environ.

    (2013)
  • A. Khataee et al.

    Sonocatalytic degradation of Acid Blue 92 using sonochemically prepared samarium doped zinc oxide nanostructures

    Ultrason. Sonochem.

    (2016)
  • Y.L. Pang et al.

    Optimization of sonocatalytic degradation of Rhodamine B in aqueous solution in the presence of TiO2 nanotubes using response surface methodology

    Chem. Eng. J.

    (2011)
  • H. Zhang et al.

    Preparation of cube micrometer potassium niobate (KNbO3) by hydrothermal method and sonocatalytic degradation of organic dye

    Ultrason. Sonochem.

    (2016)
  • Y. Segura et al.

    Integrated heterogeneous sono–photo Fenton processes for the degradation of phenolic aqueous solutions

    Ultrason. Sonochem.

    (2009)
  • M. Entezari et al.

    Sono-sorption as a new method for the removal of methylene blue from aqueous solution

    Ultrason. Sonochem.

    (2007)
  • J. Saien et al.

    Sono-assisted photocatalytic degradation of styrene-acrylic acid copolymer in aqueous media with nano titania particles and kinetic studies

    J. Hazard. Mater.

    (2010)
  • X. Zhang et al.

    Preparation of photocatalytic TiO2 coatings of nanosized particles on activated carbon by AP-MOCVD

    Carbon

    (2005)
  • F. Soumia et al.

    Effect of potassium monopersulfate (oxone) and operating parameters on sonochemical degradation of cationic dye in an aqueous solution

    Ultrason. Sonochem.

    (2016)
  • Z.-D. Meng et al.

    Sonocatalytic degradation and catalytic activities for MB solution of Fe treated fullerene/TiO2 composite with different ultrasonic intensity

    Ultrason. Sonochem.

    (2011)
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