Degradation Of Organic Dye Pollutants Research Articles

A novel n-type CdS nanorods/p-type LaFeO3 heterojunction nanocomposite with enhanced visible-light photocatalytic performance

In this work, a novel n-type CdS nanorods/p-type LaFeO3 (CdS NRs/LFO) nanocomposite was prepared, for the first time, via a facile solvothermal method. The as-prepared n-CdS NRs/p-LFO nanocomposite was characterized by using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), UV-visible diffuse reflection spectroscopy (DRS), vibrating sample magnetometry (VSM), photoluminescence (PL) spectroscopy, and Brunauer–Emmett–Teller (BET) surface area analysis. All data revealed the attachment of the LFO nanoparticle on the surface of CdS NRs. This novel nanocomposite was applied as a novel visible light photocatalyst for the degradation of methylene blue (MB), rhodamine B (RhB) and methyl orange (MO) dyes under visible-light irradiation. Under optimized conditions, the degradation efficiency was 97.5% for MB, 80% for RhB and 85% for MO in the presence of H2O2 and over CdS NRs/LFO nanocomposite. The photocatalytic activity of CdS NRs/LFO was almost 16 and 8 times as high as those of the pristine CdS NRs and pure LFO, respectively. The photocatalytic activity was enhanced mainly due to the high efficiency in separation of electron–hole pairs induced by the remarkable synergistic effects of CdS and LFO semiconductors. After the photocatalytic reaction, the nanocomposite can be easily separated from the reaction solution and reused several times without loss of its photocatalytic activity. Trapping experiments indicated that ·OH radicals were the main reactive species for dye degradation in the present photocatalytic system. On the basis of the experimental results and estimated energy band positions, the mechanism for the enhanced photocatalytic activity was proposed.

PVP assisted synthesis of high efficient BiOI/Graphene oxide nanohybrid and its photocatalytic performance in degradation of organic dye pollutants

In this paper, highly visible-light active BiOI/Graphene oxide nanohybrids (BG) were synthesized by a simple solvothermal technique using polyvinylpyrrolidone (PVP). The as-synthesized photocatalysts were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transition electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) and UV–vis diffusive reflectance spectra (UV–vis DRS). The nanohybrid samples synthesized with PVP (BGP) showed extremely high efficiency in photodegradation of Reactive Blue 19 (RB19) under visible light. Specially, BGP-1 photocatalyst (1 wt% of graphene oxide (GO)) exhibited the highest RB19 degradation efficiency (about 100%) in 120 min, which was almost 60% and 65% higher than that achieved by using as-synthesized BG nanohybrids and pure BiOI particles, respectively. The results showed that PVP plays a crucial role as a template and strongly controls the growth of BiOI nanoparticles on the surface of graphene nanosheets. The enhanced photocatalytic performance of BGP-1 nanohybrids could be attributed to significant synergetic effects between graphene and BiOI nanoparticles, higher visible light absorption capacity and migration of photoexcited electrons on high conductive graphene nanosheets. This research suggests that BGP nanohybrid is a promising material for the photodegradation of organic dye pollutants under visible light irradiation and could be used commercially in wastewater treatment units.

Enhanced Pyroelectric Catalysis of BaTiO3 Nanowires for Utilizing Waste Heat in Pollution Treatment.

A novel catalytic effect of pyroelectric materials induced by a change in temperature, namely pyroelectric catalysis, was found to be attractive due to its ability to utilize waste heat in pollution treatment. In this work, the pyroelectric catalytic properties of BaTiO3 (BTO) nanowires synthesized by a template hydrothermal method have been thoroughly investigated. The nanowires with an elongated polar axis show a superior pyroelectric catalytic performance in comparison with the equiaxial nanoparticles. Our numerical simulation results with a finite element method indicate that the enhanced catalytic efficiency of BTO nanowires can be attributed to the higher pyroelectric potential. On the basis of the pyroelectric effect and our experimental results, a pyroelectric catalytic degradation mechanism has been proposed by taking into account the migration of charge carriers and the formation of reaction radicals. This study for enhancing the pyroelectric catalytic activity by using BTO nanowires may provide a facile, promising, and new reusable strategy for the catalytic degradation of organic dye pollutant by means of temperature variation. It is hoped that the present work gives a clear understanding of the mechanism of pyroelectric catalysis.

The effect of titanium dioxide synthesis technique and its photocatalytic degradation of organic dye pollutants

Nanostructured mesoporous titanium dioxide (TiO2) particles with high specific surface area and average crystallite domain sizes within 2 nm and 30 nm have been prepared via the sol-gel and hydrothermal procedures. The characteristics of produced nanoparticles have been tested using X-Ray Diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, Scanning Electron Microscopy (SEM), Fourier Transform Infra-Red (FTIR), and Raman Spectroscopy as a function of temperature for their microstructural, porosity, morphological, structural and absorption properties. The as-synthesized TiO2 nanostructures were attempted as catalysts in Rhodamine B and Sudan III dyes' photocatalytic decomposition in a batch reactor with the assistance of Ultra Violet (UV) light. The results show that for catalysts calcined at 300 °C, ∼100 % decomposition of Sudan III dye was observed when Hydrothermal based catalyst was used whiles ∼94 % decomposition of Rhodamine B dye was observed using the sol-gel based catalysts. These synthesized TiO2 nanoparticles have promising potential applications in the light aided decomposition of a wide range of dye pollutants.

Reduced graphene oxide/strontium titanate heterostructured nanocomposite as sunlight driven photocatalyst for degradation of organic dye pollutants

Reduced graphene oxide/Strontium titanate (RGO/SrTiO3) heterostructured nanocomposite was synthesized by coupling Hummer's synthesized graphene oxide (GO) with hydrothermally synthesized SrTiO3 nanoparticles (SrTiO3) through a facile and unique high energy ultrasonication technique using triple solvents. XRD result confirmed the successful formation of pure, single phase and primitive cubic crystal structure RGO/SrTiO3 heterostructured nanocomposite. SEM result confirmed the successful intercalation of SrTiO3 nanoparticles over the two dimensional networks of RGO nanosheets. The synergistic and beneficial interactions between SrTiO3 and RGO resulted in smaller crystallite size (53 nm), reduced band gap (2.87 eV) and larger specific surface area (31 m2/g) than that of as prepared pure SrTiO3 nanoparticles. RGO strongly influenced the photocatalytic activity of SrTiO3 and hence RGO/SrTiO3 heterostructured nanocomposite exhibited greater efficiency in degrading Rhodamine B (RhB) and Rose Bengal (RB) organic dye pollutants under natural sunlight irradiation than that of pure SrTiO3 nanoparticles.

Controllable growth of MoS2 nanosheets on novel Cu2S snowflakes with high photocatalytic activity

Herein, we, for the first time, report the controllable syntheses of the snowflake-like Cu2S architectures by using a template free, facile hydrothermal route, in which thiourea as the precursor of sulfur and EDA as the solvent. It is surprising that the Cu2S snowflakes show a higher photocatalytic activity than the other samples (Cu2S dendrites and sheets), has been mainly ascribed to its high light absorbance and BET area. Then the MoS2 nanosheets (NSs) are uniformly distributed on the Cu2S snowflake (SF) substrate, the obtained MoS2 NS/Cu2S SF composite manifests high specific surface area (60.512 m2 g−1) and large pore volume (0.148 cm3 g−1), which are favorable for the efficient light capturing together with the rapid transfer of charge carriers. In comparison with the pure Cu2S, the MoS2 NS/Cu2S SF composite exhibits much enhanced activity and long-term stability towards the photocatalytic degradation of organic dye pollutants and hydrogen production. The improved photocatalytic activity could be owed to two aspects, namely the enhanced light trapping and scattering ability benefited from large specific area of unique snowflake-like structural features and improved charge separation activity of heterojunction between MoS2 and Cu2S.

Spinel NiFe2O4 nanoparticles decorated BiOBr nanosheets for improving the photocatalytic degradation of organic dye pollutants

Abstract The BiOBr nanosheets decorated by spinel NiFe2O4 nanoparticles were successfully prepared by a simple hydrothermal approach. The structure of as-synthesized magnetically recyclable BiOBr/NiFe2O4 (denoted as BOB/NFO) composite samples consisting of different BOB/NFO mass ratios was fully characterized and the photocatalytic performance was also detailedly evaluated through degrading rhodamine B (RhB) under visible light. BOB/NFO10 (10% NFO) composite photocatalyst represented the highest catalytic efficiency, degrading 99.8% of RhB after 30 min of irradiation. The rate constant of degradation was almost 1.72 and 60.3 times as high as those of the bare BiOBr and NiFe2O4, respectively, which should be ascribed to the efficient charge separation and transfer originating from heterostructure between BOB and NFO. Radical trapping experiments showed that h+ and •O2−played a crucial role in the photocatalytic system.

Fluid eddy induced piezo-promoted photodegradation of organic dye pollutants in wastewater on ZnO nanorod arrays/3D Ni foam

A novel nanocomposite with ZnO nanorod arrays vertically growing on the three-dimensional (3D) Ni foam has been synthesized under hydrothermal conditions, which displays both the piezoelectric and photocatalytic functions. When the solution is stirred by magnetic rotation, fluid eddies are produced within the unique macroporous structure in 3D network, causing deformation of ZnO nanorod to generate piezoelectric field. Meanwhile, UV light irradiation on ZnO semiconductor generates photoelectrons and holes, followed by starting photocatalytic degradation of organic dye pollutants in wastewater. The piezo-induced bias voltage promotes the separation of photoelectrons and holes and thus can inhibit their recombination, leading to the enhanced quantum efficiency (more than 5 times). The photocatalytic activity increased by increasing the stirring rate owing to the enhanced piezoelectric field.

Ag3PO4/CoFe2O4 magnetic nanocomposite: synthesis, characterization and applications in catalytic reduction of nitrophenols and sunlight-assisted photocatalytic degradation of organic dye pollutants

A novel magnetically recyclable Ag3PO4/CoFe2O4 nanocomposite was synthesized by a facile hydrothermal method and its photocatalytic/catalytic performance for the degradation of organic dyes or reduction of nitro compounds was investigated.

Leaf-like hybrid of bismuth subcarbonate nanotubes/graphene sheet with highly efficient photocatalytic activities

In this work, leaf-like hybrid with Bi2O2CO3 nanotubes as the “veins” and graphene sheet as the “laminae” is fabricated via a facile one-pot reaction of bismuth nitrate and graphene oxide in alkaline aqueous solution. With the uniform distribution of Bi2O2CO3 nanotubes on the graphene substrate, the obtained Bi2O2CO3-NT/G manifests high specific surface area (90.4m2g−1) and large pore volume (0.197cm3g−1), which are favorable for the efficient light capturing together with the rapid transfer of mass and charge carriers. In comparison with the pure Bi2O2CO3 nanotubes and commercial Bi2O2CO3, Bi2O2CO3-NT/G exhibits much enhanced activity and long-term stability towards the photocatalytic degradation of organic dye pollutant, which is owing to its unique leaf-like structural features.

CoFe2O4/CdS nanocomposite: Preparation, characterisation, and application in sonocatalytic degradation of organic dye pollutants

A magnetic CoFe2O4/CdS nanocomposite was prepared via one-step hydrothermal decomposition of cadmium diethanoldithiocarbamate complex on the surface of CoFe2O4 nanoparticles at a low temperature of 200 °C. The nanocomposite was characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), UV-visible spectroscopy, transmission electron microscopy (TEM), N2 gas sorption analysis, X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry. The FT-IR, XRD, EDX and XPS results confirmed the formation of the CoFe2O4/CdS nanocomposite. Based on the TEM analysis, the CoFe2O4/CdS nanocomposite constituted nearly uniform, sphere-like nanoparticles of ∼20 nm in size. The optical absorption spectrum of the CoFe2O4/CdS nanocomposite displayed a band gap of 2.21 eV, which made it a suitable candidate for application in sono/photocatalytic degradation of organic pollutants. Accordingly, the sonocatalytic activity of the CoFe2O4/CdS nanocomposite was evaluated towards the H2O2-assisted degradation of methylene blue, rhodamine B, and methyl orange under ultrasonic irradiation. The nanocomposite displayed excellent sonocatalytic activity towards the degradation of all dyes examined—the dyes were completely decomposed within 5–9 min. Furthermore, a comparison study revealed that the CoFe2O4/CdS nanocomposite is a more efficient sonocatalyst than pure CdS; thus, adopting the nanocomposite approach is an excellent means to improve the sonoactivity of CdS. Moreover, the magnetic properties displayed by the CoFe2O4/CdS nanocomposite allow easy retrieval of the catalyst from the reaction mixture for subsequent uses.

Copper(I) sulfide (Cu2S) nanoparticles from Cu(II) diethyldithiocarbamate: Synthesis, characterization and its application in ultrasound-assisted catalytic degradation of organic dye pollutants

In this study, copper(I) sulfide (Cu2S) nanoparticles were easily synthesized via thermal decomposition of Cu(II) diethyldithiocarbamate complex at 220°C. Characterization by a variety of spectroscopic and physical techniques confirmed that the obtained product was pure Cu2S composed of about 50nm nanoparticles. An ultrasound-assisted advanced oxidation process (AOP) was developed for the degradation of methylene blue (MB) over the Cu2S nanoparticles. The ultrasound-assisted H2O2/Cu2S catalysis removed 100% MB (25mgL⿿1) in 12min with an apparent rate constant of 0.268min⿿1, which is 193 and 27.5 folds of that in the simple catalytic H2O2/Cu2S and US/H2O2 systems, respectively. The synergistic behavior between Cu2S catalysis and ultrasound waves was demonstrated to be dependent on Cu2S dosage and H2O2 concentration. Trapping experiments indicated that OH radicals were the main reactive species for MB degradation in the present sonocatalytic system. Furthermore, the cycling experiments revealed the good stability of Cu2S nanoparticles.

An efficient CeGeO4 catalyst for degradation of organic dyes without light irradiation at room temperature

In comparison with photocatalytic process, the catalytic degradation of organic dye pollutants in no need of light irradiation is highly interesting from the energy-saving point of view. In this paper, we developed a new CeGeO4 catalyst that can satisfy the energy-saving requirements in this regard. During the synthesis of CeGeO4, the influence of synthetic medium pH, the kind of precursor, etc., on the formation of crystalline CeGeO4 was investigated in detail. Importantly, the CeGeO4 catalyst exhibited significantly higher performance than that of CeGeO4/CeO2 or CeO2 in degradation of rhodamine B (RhB) or methylene blue (MB) in the dark at room temperature.

Nanosized zirconium phosphate/AgCl composite materials: a new synergy for efficient photocatalytic degradation of organic dye pollutants

Silver exchanged nanosized zirconium phosphate is used as a source of Ag+ions in the preparation of AgCl. The zirconium phosphate/AgCl composites work better than pure AgCl in the photoassisted degradation of Rhodamine B.

Template-free synthesis of Fe3O4 nanorod bundles and their highly efficient peroxidase mimetic activity for the degradation of organic dye pollutants with H2O2

The high surface to volume ratio of Fe3O4 nanorods facilitates the excellent activation of H2O2 for the photo-Fenton-like degradation of crystal violet dye under solar light.

Visible-light-driven photocatalytic degradation of microcystin-LR by Bi-doped TiO2

Bi-doped nano-crystalline TiO2 (Bi–TiO2) has been synthesized by sonocrystallization at low temperature. The Bi–TiO2 materials have narrower bandgaps than pristine TiO2, which endow them with significant visible light absorption. Accordingly, these materials had enhanced photocatalytic activity in the degradation of organic dye pollutants and the cyanotoxin microcystin-LR (MC-LR) under visible irradiation. It was found that degradation of MC-LR is rather efficient. After irradiation with visible light for 12 h the original MC-LR was removed completely, and 78% of the organic carbon was mineralized into CO2 after irradiation for 20 h. The hydroxyl radical (·OH) is the major active species responsible for the degradation reaction. Identified intermediates primarily originate from attack of ·OH radicals on the double bonds between C4 and C5 (C6 and C7) of Adda and the ethylenic bond of Mdha in MC-LR. Some peptide bonds are also broken with longer irradiation time.

Heterogeneous Fenton type processes for the degradation of organic dye pollutant in water — The application of zeolite assisted AOPs

Heterogeneous Fenton type processes using Fe-exchanged zeolite of ZSM5 type were investigated for the degradation of model organic pollutant, reactive azo dye C.I. Reactive Blue 137, in water. Research work was directed to compare process efficiency and to establish their advantages over corresponding homogenous Fenton type processes. The influence of UV irradiation on both heterogeneous and homogeneous processes was also studied. On the basis of decolorization and mineralization degree of dye aqueous solution the overall process efficiency was estimated. Homogeneous and heterogeneous Fenton processes yielded similar decolorization and mineralization, but the concentration of Fe ions in the bulk after the treatment was significantly lower in the latter case. Moreover, the usage of heterogeneous catalyst allows process to be operated at milder pH conditions minimizing the addition of counter ions (both anions and cations) for strong pH conditioning like in homogeneous Fenton processes. Besides that, another advantage of heterogeneous over homogeneous process is the avoidance of unnecessary additional loading of wastewater by counter ions that originated from iron salts. UV irradiation positively affected both decolorization and mineralization degree in all applied homogeneous and heterogeneous Fenton type processes.