Degradation Of Cationic Dyes Research Articles

Fabrication, activity and mechanism studies of transition metal molybdate/molybdenum trioxide hybrids as novel CWAO catalysts

Abstract We report for the first time the synthesis of a series of novel hybrid catalysts consisting α-MoO3 and MMoO4 (M = Cr, Mn, Fe, Co, Ni, Cu, or Zn) and their significantly enhanced catalytic activities for the degradation of cationic dyes at room temperature and atmosphere pressure. All obtained hybrid materials were thoroughly characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy-energy dispersive spectroscopy, and X-ray photoelectron spectroscopy, etc. The influence of divalent cations, calcination temperature, testing temperature, volume of dye and different kinds of cationic dyes were systematically investigated. Among all hybrid catalysts, MnMoO4/α-MoO3 and NiMoO4/α-MoO3 resulted in much better performance than all the others. We also demonstrated that such high activity can be not attained with either pure transition metal molybdates, pure α-MoO3 or the physical mixture of these two bulks. And only the hybrid catalysts prepared in this work containing both metal molybdates and α-MoO3 can deliver high catalytic activity for the CWAO of dye. The reaction kinetics and degradation mechanism were also explored. Electron spin resonance analysis suggests that the co-existence of transition metal molybdates and α-MoO3 promotes the formation of· OH radicals, which are crucial for their excellent catalytic activity. The intermediates produced during the catalytic degradation process was monitored using electrospray ionization-mass spectrometry analysis, based on which the degradation pathway was also proposed.

Composite Photocatalysts Containing BiVO4 for Degradation of Cationic Dyes

The creation of composite structures is a commonly employed approach towards enhanced photocatalytic performance, with one of the key rationales for doing this being to separate photoexcited charges, affording them longer lifetimes in which to react with adsorbed species. Here we examine three composite photocatalysts using either WO3, TiO2 or CeO2 with BiVO4 for the degradation of model dyes Methylene Blue and Rhodamine B. Each of these materials (WO3, TiO2 or CeO2) has a different band edge energy offset with respect to BiVO4, allowing for a systematic comparison of these different arrangements. It is seen that while these offsets can afford beneficial charge transfer (CT) processes, they can also result in the deactivation of certain reactions. We also observed the importance of localized dye concentrations, resulting from a strong affinity between it and the surface, in attaining high overall photocatalytic performance, a factor not often acknowledged. It is hoped in the future that these observations will assist in the judicious selection of semiconductors for use as composite photocatalysts.

Facile synthesis of Fe2O3/Cu2O nanocomposite and its visible light photocatalytic activity for the degradation of cationic dyes

Iron oxide-loaded Cu2O photocatalysts were prepared by a facile hydrothermal method. The binary mixed metal oxide photocatalyst was characterized by XRD, FE-SEM, FTIR, UV–Vis-DRS, particle size and zeta potential measurements. XRD analysis showed that Fe2O3/Cu2O catalysts were phase pure and highly crystalline in nature. FE-SEM images revealed the formation of nanospherical Fe2O3 over the Cu2O surface during hydrothermal reaction. From UV–Vis diffuse reflectance spectroscopy studies, the optical band gap of the Fe2O3/Cu2O photocatalyst was found to be slightly red-shifted to 1.85 eV, after loading of Fe2O3. The zeta potential analysis revealed that the surface of the Fe2O3/Cu2O photocatalyst was negatively charged in neutral solution. The loading of n-type Fe2O3 on p-type Cu2O augments the charge carrier separation at the interface, which was evident from the enhanced photodegradation of organic pollutants (Methylene blue and Rhodamine B dyes) under visible light irradiation.

Enhanced visible light responsive photocatalysis by ZnO:Mg/RGO nanocomposites

Mg and RGO activated ZnO nanocomposites were prepared using a low-cost soft chemical method. As per the structural studies the samples exhibit wurtzite structure of ZnO with hexagonal crystal system. No secondary phases were observed. The photocatalytic activity of the prepared samples were assessed through the degradation of cationic dyes, methylene blue (MB) and malachite green (MG) under visible light irradiation. The studies revealed that the ZnO:Mg/RGO nanocomposite exhibits enhanced photocatalytic as well as antibacterial behavior compared to bare ZnO. The optical, structural and surface morphological studies support the reports on the photocatalytic and antibacterial activities of the synthesized samples.

Synthesis and functionalization of MnFe2O4 nano−hollow spheres for novel optical and catalytic properties

Herein, we synthesize MnFe2O4 nano−hollow spheres (NHSs) of average diameter 100nm through a facile template free solvothermal process and carry out a time dependent morphological study to investigate their process of core excavation. Further, a surface engineering of as−synthesized MnFe2O4 NHSs has been executed with organic disodium tartrate dihydrate ligand and interestingly, the surface modified MnFe2O4 NHSs are found to capable of emerging multicolor fluorescence starting from blue, green to red. The magnetic measurements through vibrating sample magnetometer demonstrate that room temperature superparamagnetic nature of MnFe2O4 NHSs remains unaltered after surface modification. Moreover, functionalized MnFe2O4 NHSs are found to exhibit excellent reusable photocatalytic efficiency in the degradation of cationic dye, methylene blue with rate constant of 2.64×10−2min.

Efficient removal of organic pollutants from aqueous media using newly synthesized polypyrrole/CNTs-CoFe2O4 magnetic nanocomposites

In this study, the polypyrrole/CNTs-CoFe2O4 magnetic nanohybrid (CNTs-CoFe2O4@PPy) was prepared and then used as adsorbent and catalyst to remove anionic and cationic dyes. The hybrid material was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), elemental analysis, BET surface area, Fourier transform infrared (FTIR) spectroscopy and vibrating sample magnetometer (VSM). Adsorption behaviors of the as-prepared composites for anionic dyes such as Methyl Blue (MB), Methyl Orange (MO) and Acid Fuchsin (AF) were conducted where the effects of solution pH, initial dye concentration, contact time and ionic strength were systematically studied. The equilibrium adsorption data of MB, MO and AF were well fitted to the Langmuir isotherm model, yielding the maximum monolayer adsorption capacity of 137.00, 116.06 and 132.15mg/g, respectively. Adsorption kinetics was best described by the pseudo-second order model. The introduction of CoFe2O4 into CNTs-CoFe2O4@PPy hybrid could not only provide an effective magnetic separation performance, but also act as catalyst to activate peroxymonosulfate (PMS) for the degradation of cationic dye, Methylene Blue (MEB), from aqueous solution. The results showed that CNTs-CoFe2O4@PPy presented higher catalytic activity, better stability and reusability for the decolorization of MEB, resulting in an almost complete removal of 50mg/L MEB after 30min with 1.0g/L catalyst and 4mmol/L PMS. The characteristics of high adsorption capacity, effective separation, excellent catalytic activity and good reusability would make CNTs-CoFe2O4@PPy a promising candidate for wastewater treatment.

Cationic Dye Degradation by means of an Efficient Photocatalyst promoted by Aluminum Oxide

Cationic Dye Degradation by means of an Efficient Photocatalyst promoted by Aluminum Oxide

Self-assembly of biosurfactant–inorganic hybrid nanoflowers as efficient catalysts for degradation of cationic dyes

The scheme of recycling of nanoflowers as an efficient catalyst for degradation of MB.

A new inorganic–organic nanohybrid based on a copper(II) semicarbazone complex and the PMo12O403− polyanion: Synthesis, characterization, crystal structure and photocatalytic activity for degradation of cationic dyes

A new inorganic–organic nanohybrid based on a Keggin-type polyoxomolybdate and a copper(II) semicarbazone complex, namely [Cu2(HL)2(PMo12O40)(OCH3)2(Cl)(H2O)]·8CH3OH·4H2O [HL=pyridine-2-carbaldehyde semicarbazone] (1) was synthesized by a sonochemical method. Single crystals of 1 were synthesized with the branched tube method. The nanohybrid 1 was characterized using FT-IR, PXRD, FESEM, TEM, EDX, UV–Vis, TG-DTA analysis and single-crystal X-ray diffraction. Single-crystal X-ray diffraction reveals that the PMo12O403− cluster acts as a bidentate inorganic ligand and coordinates two symmetrically equivalent [Cu(Cl)0.5(HL)(OCH3)(H2O)0.5] complexes. SEM and TEM images confirmed a highly porous plate-like morphology of the nanohybrid sample. To the best of our knowledge, 1 represents the first example of a hybrid based on POMs and semicarbazone Schiff base complexes. The photocatalytic properties of the nanohybrid 1 were investigated in detail and the results of the photocatalytic experiments show it can be used as an efficient and recoverable photocatalyst for the complete degradation of the cationic dyes methylene blue (MB) and rhodamin B (RhB).

Resin modified MIL-53 (Fe) MOF for improvement of photocatalytic performance

Metal organic frameworks (MOFs) are fascinating materials for diverse applications due to their adjustability of aperture and structure. Herein, a three-dimensional iron-based MOF with BDC linker (BDC=1,4-benzenedicarboxylate), commonly known as MIL-53(Fe), has been synthesized and successfully composited with anionic resin (Amberlite IRA 200) and cationic resin (Amberlite IRA 900) resulting solid composite photocatalysts, AMIL-53 (Fe) and DMIL-53(Fe), respectively. In the novel composite photocatalysts, bulky MIL-53(Fe) MOF solids are used as both a support to anchor the finely ground Amberlite IRA resin powders and as a visible light active component for the degradation of organic pollutants in water. In addition to being a traditional support, the resins here were used as a co-catalyst (with loading ration of the resin to MIL-53(Fe) is controlled around 20wt%) to capture and transfer pollutant molecule from bulk solution into the active centers of the composited catalysts. Such an immobilization of the resins significantly alters MIL-53 (Fe) activity and degradation selectivity of dye pollutants; after 120min of visible light illumination (λ≥420nm) removal yield of SRB (24%) by the bare MIL-53 (Fe) was apparently improved to 96% after MIL-53 (Fe) was modified by Amberlite IRA 900, DMIL-53(Fe). The tunable degradation order was demonstrated by employing AMIL-53 (Fe) for the selective degradation of cationic dyes while DMIL-53 (Fe) for the degradation of anionic dyes. Furthermore, the composites activity was optimized by controlling resin to MOF ratio during immobilization. Immobilization also improves ease of separation and recyclability of the original MOF. Especially, AMIL-53 significantly reduces iron ion leaching resulting in an enhanced stability. The photocatalytic mechanism under visible-light irradiation is also discussed.

Facile decoration of TiO2 nanoparticles on graphene for solar degradation of organic dye

The reduced graphene oxide is interesting material for the synthesis of TiO2-based photocatalyst. In the present investigation, blackberry fruit, which contains high levels of anthocyanins and other phenolic compounds, was employed as a reducing agent mainly due to its high antioxidant capacity. The nano-crystalline TiO2 was decorated on different amounts of graphene oxide with sol–gel method and then the photocatalytic activity for degradation of cationic dye was evaluated by UV spectroscopy to achieve the optimum content of graphene oxide. The decoration of anatase nanoparticles on prepared reduced graphene oxide was investigated by X-ray diffraction, scanning and transmission electron microscopy techniques. The new composite gives significantly higher activity when is compared to the compositions fabricated by graphene oxide. The compact layer provides a large TiO2-graphene contact area and reduces the electron recombination. The decoration of TiO2 nanoparticles, 5–10 nm, on the graphene oxide reduced by blackberry juice further improves the dye removal. The results imply that the nanoparticle decoration is the key strategy to increase the degradation capacity.

Photocatalysis of Coomassie Brilliant Blue Using Clay Mineral

The presence of organic pollutants, which cannot be eliminated by conventional processes of primary and secondary treatment, can be problematic. Photocatalytic processes offer an efficient breakdown of organic pollutants into non-toxic compounds such as CO2 and H2O. This paper proposes the use of the titanium dioxide embedded in palygorskite as a photoactive material in the degradation of cationic dye, Coomassie Brilliant Blue. The system was irradiated using UV light for a maximum time of 120 minutes. The concentration of the dye used was 1.0x10-4 mol L-1 in 0.5 g L-1 of the photoactive material. The kinetics of the system was monitored by UV-Vis spectrophotometry. In 120 minutes of radiation, the process of photocatalysis reduced the initial concentration of the Coomassie Brilliant Blue dye in half.

Synergistic effects in N-K2Ti4O9/UiO-66-NH2 composites and their photocatalysis degradation of cationic dyes

AbstractN-K2Ti4O9/UiO-66-NH2 composites synthesized by a facile solvothermal method have a core-shell structure with UiO-66-NH2 forming the shell around a N-K2Ti4O9 core. Their photocatalytic activities in the degradation of dyes under visible light irradiation were investigated. The N-K2Ti4O9/ UiO-66-NH2 composites exhibited higher photocatalytic activity than the pure components. This synergistic effect was due to the high adsorption capacity of UiO-66-NH2 and that the two components together induced an enhanced separation efficiency of photogenerated electron-hole pairs. The mass ratio of N-K2Ti4O9 to ZrCl4 of 3:7 in the composite exhibited the highest photocatalytic activity. Due to the electrostatic attraction between the negatively charged backbone of UiO-66-NH2 with the positively charged groups of cationic dyes, the composites were more photocatalytically active for cationic dyes than for anionic dyes.

Synthesis and characterization of alkali metal molybdates with high catalytic activity for dye degradation

In this contribution, the synthesis and catalytic activity of alkali metal molybdates for the degradation of cationic dyes under ambient conditions were systematically studied.

Photobiological synthesis of noble metal nanoparticles using Hydrocotyle asiatica and application as catalyst for the photodegradation of cationic dyes

Solar light induced photo catalysis by plasmonic nanoparticles such as Au and Ag is an important field in green chemistry. In this study an environmental benign method was investigated for the rapid synthesis of colloidal Ag and AuNPs using the extract of Hydrocotyle asiatica, as a reducing and stabilizing agent under sunlight irradiation. The nanoparticles were formed in few seconds and were characterized by UV–Vis., FT-IR, TEM, EDAX, XRD, DLS and Zetasizer. The nanoparticles were stable in aqueous solution for more than 6 months. TEM analysis established that the Ag and AuNPs were predominantly spherical with average size of 21 and 8 nm, respectively. The flavonoids and glycosides from the extract of H. asiatica were proved to be responsible for the reduction and capping through FT-IR analysis. The antimicrobial studies of AgNPs showed effective inhibitory activity against the clinical strains of gram-negative and positive bacteria. The localized surface plasmon resonance of AgNPs was used for the photo-driven degradation of cationic dyes (malachite green and methylene blue). Thus, this green technique can be used for bulk production of AgNPs, and thus prepared nanoparticles may be used for removal of dyes from effluent.

Graphene quantum dots as novel and green nano-materials for the visible-light-driven photocatalytic degradation of cationic dye

In this paper, we have introduced a novel property of graphene quantum dots (GQDs) as efficient nano-materials for degradation of organic pollutant dyes based on the photocatalytic behavior of GQDs under visible light irradiation. GQD samples were synthesized directly through pyrolyzing citric acid method. The synthesized GQDs were characterized by various techniques including colorimetry, transmission electron microscopy (TEM), and UV–vis absorption, Raman spectroscopy, fluorescence spectroscopy, and zeta potential measurements. In this study, a cationic dye (i.e., New Fuchsin) was chosen as a model molecule to investigate catalytic behavior of the prepared GQDs as green nanomaterials. The influence of experimental parameters such as pH of the dye solution, contacting time, dosage of GQDs, and initial concentration of NF dye on the degradation efficiency of GQD were studied. The possible mechanisms of degradation of NF based on GQDs under visible light were discussed, too.

Study of photocatalytic activity of TiO2 fluorinated by thermal shock method for the degradation of different dyes

TiO2 P25 was fluorinated by thermal shock method in order to study the influence of thermal shock fluorination on the surface properties and the photocatalytic activity for the degradation of cationic and anionic organic dyes at different pH values. The surface charge of catalysts was characterized by the pHPZC measurement. The photocatalytic activity of catalysts was evaluated via the degradation of methylene blue (cationic dye) and methyl orange (anionic dye). The results showed that the thermal shock fluorination and the rise of solution pH can increase the surface negative charge of TiO2, which enhanced the adsorption of methylene blue and then improved the photocatalytic degradation of this cationic dye under UV and visible light. On the other hand, after the fluorination, the adsorption of methyl orange on TiO2 was strongly reduced, which limited the photocatalytic oxidation of this anion dye.

Comparative Studies of Mesoporous Ti-SBA-15 and Ti-KIT-6 for the Degradation of Cationic Dyes Under Sunlight

Comparative Studies of Mesoporous Ti-SBA-15 and Ti-KIT-6 for the Degradation of Cationic Dyes Under Sunlight

Selective sorption and subsequent photocatalytic degradation of cationic dyes by sonochemically synthesized nano CuWO4and Cu3Mo2O9

Sonochemically synthesized nano CuWO4and Cu3Mo2O9exhibit superior sorption affinity for cationic dyes and also display photocatalytic activity on exposure to visible light.

Fabrication of TiO2 hollow microspheres by ammonia-induced self-transformation

TiO2 hollow microspheres (TiO2–HMSs) have attracted great interest in recent years due to their unique physical and chemical properties such as low density, high surface area and effective light-harvesting property. In this paper, anatase TiO2–HMSs were synthesized by hydrothermal treatment of amorphous TiO2 microspheres precursor in the presence of ammonia solution at 180°C. The prepared TiO2–HMSs were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscopy (SEM). It was found that the presence of ammonia accelerates the hollowing process of TiO2 microspheres, and the phase transformation from amorphous TiO2 to metastable ammonium titanate occurs firstly and then to anatase TiO2 phase, forming fluffy core/shell and yolk/shell structured microspheres. The photocatalytic activity of the photocatalyst was evaluated both by photocatalytic degradation of cationic dye (Rhodamine B) and anionic dye (Brilliant Red X-3B) under UV irradiation. The calcined fluffy core/shell structured TiO2 microspheres with a hydrothermal reaction time of 18h showed the highest photocatalytic activity. Ammonia-induced self-transformation mechanism was also proposed for the formation of TiO2–HMSs.