Decolorization Of Organic Dyes Research Articles

Use of lactic acid modified MoS2 nanopetals to improve photocatalytic degradation of organic pollutants

Transition metal dichalcogenide-based molybdenum disulfide (MoS2) are currently gaining considerable attention due to their prospective technological applications. Herein, we report a facile and simple one-step preparation of self-assembled two-dimensional MoS2 nanopetals modified with lactic acid (LA@MoS2). An investigation of the properties of the synthesized LA@MoS2 nanopetals under different conditions reveals that the weight percentage of lactic acid (LA) significantly influences the structural purity, crystalline quality, and morphology of the products, and the appropriate concentration of LA is the determining factor in the synthesis. Photocatalytic activity of LA@MoS2 nanopetals for organic dye decolorization is examined using crystal violet (CV) and methyl orange (MO). The results showed that LA molecules cover the MoS2 with C–S bonds, which significantly enhance photocatalytic decolorization of CV and MO pollutants under simulated solar light irradiation. The LA@MoS2 demonstrated excellent photocatalytic performance compared to bulk MoS2. Furthermore, electrochemical studies reveal fast electron and hole pathways for the reduction of pollutant molecules in aqueous solution. These results indicate that LA@MoS2 is a good photocatalyst because of the desirable active species in the modified catalyst.

Facile Water-Based Strategy for Synthesizing MoO3-x Nanosheets: Efficient Visible Light Photocatalysts for Dye Degradation.

Nanostructured molybdenum oxides are promising materials for energy storage, catalysis, and electronic-based applications. Herein, we report the synthesis of MoO3–x nanosheets (x stands for oxygen vacancy) via an environmentally friendly liquid exfoliation approach. The process involves the reflux of the bulk α-MoO3 precursor in water at 80 °C for 7 days. Electron microscopy and atomic force microscopy show that the MoO3–x nanosheets are a few nanometer thick. MoO3–x nanosheets exhibit near infrared plasmonic property that can be enhanced by visible light irradiation for a short time (10 min). Photocatalytic activity of MoO3–x nanosheets for organic dye decolorization is examined using two different dyes (rhodamine B and methylene blue). Under visible light irradiation, MoO3–x nanosheets make a rapid decolorization for the dye molecules in less than 10 min. The simple synthesis procedure of MoO3–x nanosheets combined with their remarkable photochemical properties reflect the high potential for using the nanosheets in a variety of applications.

Nanoporous cellulose membrane doped with silver for continuous catalytic decolorization of organic dyes

Despite the rapid progress in the development of catalysts for dye decolorization, the simultaneous catalyzing and product separation to achieve continuous processing remains a great challenge. Here, silver nanoparticle-doped bacterial cellulose (AgNP@BC) nanoporous membrane with AgNP diameter of ~ 8.1 nm is successfully fabricated without employing any other reductants, capping or dispersing agents. In the procedure, BC hydrogel with 3D network acts as not only a stable scaffold, but also a reductant for the synthesis of AgNPs. The as-prepared membrane exhibits high efficiency of continuous catalytic decolorization toward two typical organic dyes (rhodamine 6G and methyl orange) due to its distinct nanoporous structure. Furthermore, it shows excellent recyclability with a decolorization efficiency of ~ 99% even after ten times of reusing. Our strategy offers a novel, simple and eco-friendly route for the fabrication of nanoporous catalytic membrane and opens up new opportunities for the continuous catalytic decolorization of dyes in scalable application.

Assembly of TeO32- Ions Embedded in an Nb/O Cage with Selective Decolorization of Organic Dye.

A novel 24-niobic-2-tellurite, [H2Te2Nb24O72]14-, was isolated by incorporating tellurite anions into a polyoxoniobate cage. The synthesized cluster represents the first example of a sandwich-type polyoxoniobate with the largest telluroniobate aggregate. Furthermore, the hybrid material acts as an efficient catalyst for the decolorization of basic fuchsin.

Anatase TiO2 nanotube arrays and titania films on titanium mesh for photocatalytic NOX removal and water cleaning

An anodization method was developed for the preparation of highly photoactive titania nanotube arrays (TiNTs) on commercially available titanium mesh. The prepared material was characterized from the point of view of its structure and possible photocatalytic applications and was compared with titania films deposited on the Ti-mesh by liquid deposition (TiO2-LD) and sol-gel methods (TiO2-SG). The photoactivity was determined in gas phase using NOX decomposition according to the ISO standard no. 22 197-1 (2007) as well as in liquid phase by decolorization of organic dyes e.g. methylene blue (MB) and rhodamine B (RhB). The investigated anatase nanotube arrays on Ti mesh showed the highest photoactivity in both gaseous and liquid phases and are promising for applications in photocatalytic reactors for environmental purification.

Decoloration of organic dyes in aqueous phase by catalytic hydrotreatment

The catalytic hydrotreatment of organic dyes has been carried out in aqueous solution under ambient-like conditions (25°C, 1atm) using a commercial Pd/γ-Al2O3 catalyst. The treatment leads to the total decoloration of the prepared aqueous solutions. The total decoloration of the resulting effluents was attributed to catalytic reaction with an important contribution of adsorption in some cases. The results obtained demonstrate that hydrotreatment could be potentially used to eliminate completely colour from industrial effluents that contain different type of organic dyes such as methine, anthraquinone, indigo, iminoquinone dyes and carotenes.

Chitosan–sodium alginate encapsulated Co-doped ZrO2–MWCNTs nanocomposites for photocatalytic decolorization of organic dyes

Photocatalytic decolorization properties of cobalt doped-ZrO2-multiwalled carbon nanotubes (Co–ZrO2–MWCNTs) and chitosan–sodium alginate encapsulated Co–ZrO2–MWCNTs (CS/Alg–Co–ZrO2–MWCNTs) with varying weight percentage of Co–ZrO2–MWCNTs are presented in this research paper. The Co–ZrO2–MWCNTs was first synthesized through homogenous co-precipitation method and introduced into the chitosan–sodium sodium alginate (CS/Alg) biopolymer matrix. The bio-nanocomposites were characterized using X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, (UV–Vis)-spectroscopy and energy dispersive spectroscopy to obtain information on their structure, formation, morphology, size and elemental analysis. The photodecolorization efficiency of the samples was determined through their decolorization of trypan blue dye aqueous solution in 180 min. Recyclability of the catalysts was also assessed. The bio-nanocomposites experienced reduced band gap values with subsequent improvement in visible light activity compared to the uncapped Co–ZrO2–MWCNTs. All the CS/Alg–Co–ZrO2–MWCNTs exhibited higher photodecolorization activities than the uncapped Co–ZrO2–MWCNTs. The most efficient catalyst (CS/Alg–40 % Co–ZrO2–MWCNTs) with a band gap of 2.56 eV displayed 94 % decolorization efficiency of the dye. Though reusability of the catalyst is significant, its efficiency diminished consistently after each cycle.

Preparation and catalytic properties of porous CoP nanoflakes via a low-temperature phosphidation route

In this paper, porous CoP nanoflakes were successfully synthesized through a two-step route. Porous Co3O4 nanoflakes were firstly prepared by pyrolyzing flake-like precursors. Then, porous CoP nanoflakes were produced through the low temperature phosphidation of porous Co3O4 nanoflakes. The phase and morphology of the as-prepared products were characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectrometry (EDS). Experiments showed that the as-prepared porous CoP nanoflakes presented outstanding catalytic activity in the reduction of some aromatic nitro compounds such as 4-nitrophenol (4-NP), 2-nitrophenol (2-NP) and 4-nitroaniline (4-NA), and organic dyes including Rhodamine B, pyronine B, methylene blue and safranine T, in excess NaBH4 solution, which provided a new catalyst option for the reduction of aromatic nitro compounds and the decoloration of organic dyes at room temperature. Interestingly, the preparation approach of the precursor could affect the morphology and the catalytic performance of the final CoP nanostructures.

Decolorization of organic dyes by gold nanoflowers prepared on reduced graphene oxide by tea polyphenols

The green approaches for chemical syntheses are becoming important in various fields comprising chemical synthesis.

Toward the design of Zn–Al and Zn–Cr LDH wrapped in activated carbon for the solar assisted de-coloration of organic dyes

Designing of materials for the extraction of organic toxins are the critical factors for environmental remediation.

Highly photocatalytic active thiomolybdate [Mo3S13]2− clusters/BiOBr nanocomposite with enhanced sulfur tolerance

The sulfur tolerant Mo3S132−/BiOBr nanocomposite photocatalysts were facilely fabricated by a hydrothermal method. The characterizations including X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), UV–vis diffuse reflection spectroscopy (DRS) and photoluminescence (PL) investigate the structures, elemental composition, morphologies and photocatalytic activities of Mo3S132−/BiOBr nanocomposite. The 5.0wt% Mo3S132−/BiOBr composite sample showed highest visible-light-driven photocatalytic activity for decolorization of organic dyes including Rhodamine B (RhB) and sulfure containing methylene blue (MB). The decolorization of RhB was dominated by the direct hole and the generated O2− radicals oxidation process. Our 5.0wt% Mo3S132−/BiOBr nanocomposite exhibited comparable photocatalytic activity as the state of art 1wt% BiOBr/Pt composite for photocatalytic decolorization of RhB. The 5.0wt% Mo3S132−/BiOBr composite possessed better sulfur resistance than 1.0wt% Pt/BiOBr composite.

Preparation of Ru Nanocatalysts Supported on SBA-15 and Their Excellent Catalytic Activity Towards Decolorization of Various Dyes.

In this paper, we report a simple aqueous solution based chemical method for preparation Ru nanocatalysts supported on mesoporous silica SBA-15 (Ru@SBA-15) catalysts. Synthesized catalysts were characterized by powder X-ray diffraction (XRD), Optical emission spectroscopy (ICP-OES), Fourier transform infrared spectroscopy (FTIR), high resolution transmission electron microscope (HRTEM) and N2 adsorption-desorption surface area and pore size analyzer, and particle size analyzer. Catalytic activity of the synthesized catalysts towards decolorization of various dyes, such as 4-nitrophenol, Methyl Orange, Congo Red, Rhodamine B, Methylene Blue and mixture of dyes was investigated in presence of excess NaBH4. Catalysis reactions were monitored by employing UV-vis spectroscopy. Catalysis reactions followed pseudo-first order rate equation. The catalyst with 2.5 wt% Ru nanoparticle exhibited excellent catalytic activity and convenient recycling. The high catalytic activity and simple preparation methodology make 2.5Ru@SBA-15 an attractive catalyst for decolorization of organic dyes.

Transition Metal (Ni, Cr)-Doped ZnO Assisted CTAB Performance on Decolorization of Organic Dyes

A series of semiconductor nanophotocatalyst based on transition metal (Ni and Cr) doped ZnO nanoparticles have been synthesized in the presence of cetril methyl ammonium bromide (CTAB) by co-precipitation method. Samples were characterized by X-Ray Diffraction (XRD), Energy Dispersive X-Ray (EDX), Field Emission Scanning Electron Microscope (FESEM), and Brunauer-Emmet-Teller (BET) method. The resulting materials were explored for the decolorization of 4 different organic dyes (methyl orange, methylene blue, malachite green, and congo red) under UV light irradiation. The resulting materials exhibited relatively higher photocatalytic decolorization than bare Ni- and Cr-doped ZnO nanoparticles with similar doping concentration

Mild fabrication of silica-silver nanocomposites as active platforms for environmental remediation

A new, simple and convenient approach to prepare silver nanoparticles supported on SiO2–PEI composites for the decoloration of organic dyes.

Preparation of Cu nanoparticle loaded SBA-15 and their excellent catalytic activity in reduction of variety of dyes

In this paper, we report a simple aqueous solution based chemical method for preparation of Cu nanoparticle loaded mesoporous silica SBA-15 (Cu@SBA-15) catalysts. Synthesized catalysts were characterized by powder X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), Fourier transform infrared spectroscopy (FTIR), high resolution transmission electron microscope (HRTEM), N2 adsorption–desorption surface area and pore size analyzer, and particle size analyzer. Catalytic activity of Cu nanoparticle loaded SBA-15 towards reduction of various dyes, such as 4-nitrophenol, Methyl Orange, Congo Red, Rhodamine B, Methylene Blue and mixture of dyes were investigated in the presence of excess NaBH4. Catalysis reactions were monitored by employing UV–vis spectroscopy. Catalysis reactions followed pseudo-first order rate equation. These catalysts exhibited excellent catalytic activity and convenient recycling. The high catalytic activity, cost effectiveness and simple preparation methodology make 12.5Cu@SBA-15 an attractive catalyst for decolorization of organic dyes.

Influence of Ultrasonic Time on the Preparation and Properties of LaCoO<sub>3</sub> Nanoparticles

Ultrasonic assisted citrate sol-gel is used to synthesis LaCoO3(LCO) ultrafine particles. The influence of ultrasonic time on the properties of the samples was investigated. TG-DSC is applied to determine the phase transition of LCO gel precursor. XRD, FESEM and H2-TPR were applied to characteristic crystalline phase structure, morphology, thermal stability of LCO samples. The results indicated that LCO particles exhibit a well-formed polycrystalline rhombohedral distorted perovskite structure, and their particles are well-decentralized, in a smaller size and better dispersivity as the increasing of ultrasonic time ranged from 0min to 60min. H2-TPR implied that ultrasonic assistance can lower the reduction temperature of the product in the zone of low temperature and raise the temperature in the zone of high temperature. Ultrasonic assistance is not conductive to increase organic dye decolorization efficiency of LCO powders in darkroom when taking methyl orange and gold orange II as targeted dye.

Decolorization of organic dyes by zero-valent iron in the presence of oxalic acid and influence of photoirradiation and hexavalent chromium

In the present study, zero-valent iron (Fe0) film coated on indium tin oxide (ITO)-coated glass substrate was prepared with electrodeposion. Decolorization of methylene blue (MB) and orange II (OII) by the Fe0 film in the presence of oxalic acid (OA) and dissolved oxygen (DO) and the influence of photoirradiation and hexavalent chromium (Cr(VI)) has been investigated. The newly developed Fe0/OA/DO system is more effective in decolorization of MB than its EDTA counterpart, and is of a strong stability in prolonged use. Operating parameters such as pH and OA concentration have significant influence on the decolorization rate for MB in this system, and lower pH value and higher OA concentration are favorable. The low decolorization rate for OII can be dramatically enhanced by introduction of photoirradiation into the system. Coexistence of Cr(VI) has an opposite influence on decolorization of MB and OII in the photo-assisted Fe0/OA/DO system. In the latter case, Cr(VI) promotes the decolorization of OII, and itself can also be reduced, which allows effective simultaneous removal of OII and Cr(VI) from a mixed solution. Several mechanisms involved in decolorization of MB and OII have also been discussed.

Fast Degradation and Biodegradability Improvement of Reactive Brilliant Red X-3B by the Cobalt(II)/Bicarbonate/Hydrogen Peroxide System

The cobalt(II)-bicarbonate (HCO3–) complex is a very efficient catalyst for organic dye decolorization with H2O2 as an oxidant, but its mineralization degree is very low. One interesting alternative is the combination of the system with a subsequent biological step. With the aim of employing the Co2+-HCO3– system as a pretreatment method to dye wastewater, a typical azo dye, reactive brilliant red X-3B (X-3B), was selected as the model compound, and the biodegradability enhancement of the dye was investigated. The results showed that X-3B was effectively degraded by the Co2+-HCO3– system under various mild conditions, and the BOD5/COD ratio of the dye solution could markedly increase from 0.046 to higher than 0.46. The effluent treatment by the system was efficiently post-treated in a batch biological reactor with the COD removal around 44% after 8 h aeration, while a little decrease of the COD value of the raw solution was observed.

Kinetics and mechanism of organic pollutants degradation with cobalt–bicarbonate–hydrogen peroxide system: Investigation of the role of substrates

The kinetics and mechanism of a simple system, Co 2+–HCO 3 −–H 2O 2 for degrading highly stable organic pollutants have been reported. Fast and versatile decolorization of organic dyes was observed in an aqueous solution containing 10 mM NaHCO 3, 10 μM Co 2+ ions and 10 mM H 2O 2, while the degradation rate of p-nitrophenol and 2,4-dinitrophenol was very slow. From cyclic voltammetry and UV–vis spectra, it was found that different complexes between Co 2+ ions and methylene blue (MB) were formed in HCO 3 − solution, and being confirmed by photoluminescence probing and electron spin resonance spin-trapping technologies, the 1:1 complex [Co II(HCO 3 −)(MB)] + was more efficient in catalyzing decomposition of H 2O 2 into OH radicals. The other tested pollutants also played an important role in the rate of OH radicals production in the system. Based on the kinetic observations of MB decolorization, a possible mechanism was proposed.

Shape evolution of Cu-doped Mn3O4 spinel microcrystals: influence of copper content

Spinel-type Cu-doped Mn3O4 microcrystals with various shapes were synthesized by hydrothermal method. The interrelation between the preparative conditions and the composition, structure, and morphology of the products were investigated using various analytical techniques, such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermal gravimetric analysis. Results revealed that the introduction of Cu2+ ions into the reaction system promoted the formation of single phase Cu-doped Mn3O4. A gradual shape evolution from polyhedron to octahedron occurred upon increasing the additive copper content. Complete decolorization of organic dye (methylene blue) aqueous solution was achieved by treating the dye with Cu-doped Mn3O4 in acidic media, which shows the possible application of doped Mn3O4 as effective reagents for the degradation of organic contaminants in water.