Photocatalytic Degradation Of Congo Red Research Articles

Synthesis of (Zn/Co)-based zeolite imidazole frameworks and their applications in visible light-driven photocatalytic degradation of Congo red

Zinc/cobalt (Zn/Co)-based zeolite imidazole frameworks (ZIFs) with varying Zn/Co molar ratios from 0/10 to 10/0 were synthesized by a microwave-assisted method, and the resulting materials were characterized by x-ray diffraction (XRD), nitrogen adsorption–desorption isotherms, scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and atomic absorption spectroscopy (AAS). The microwave-assisted approach required a very short synthesis time as well as yielded (Zn/Co)ZIFs with high specific surface areas (1637.3 m2 g−1). It was found that the introduction of zinc into ZIF-67 enhanced catalytic activity in visible-light region. (Zn/Co)ZIF with a Zn/Co molar ratio of 2/8 manifested an excellent photocatalytic degradation of Congo red (CGR). The kinetic model of photocatalytic degradation was proposed based on adsorption isotherms (Langmuir model) and a unimolecular reaction for the heterogeneous catalysis. Further, the reusability was also addressed.

Ag–ZnO Submicrometer Rod Arrays for High-Efficiency Photocatalytic Degradation of Congo Red and Disinfection

Ordered nanostructures are drawing a tremendous amount of attention for their potential applications in many fields. Herein, Ag–ZnO submicrometer arrays (SRA) were synthesized by a new polycarbonat...

WO3 nanocrystal prepared by self-assembly of phosphotungstic acid and dopamine for photocatalytic degradation of Congo red

WO3 nanocrystal was prepared through a simple calcination treatment of hierarchical nanostructures self-assembled from phosphotungstic acid and dopamine. The morphology, composition, and formation process of WO3 nanoparticles were characterized in detail. The results showed that as-prepared WO3 nanoparticles were highly crystallized and 40–50 nm in size with quite smooth surface. Moreover, the photocatalytic property of WO3 nanocrystal was investigated by the decomposition of typical azo dye under UV light irradiation (254 nm). Pure WO3 nanocrystal showed a high photodegradation efficiency for Congo red even under quite low UV irradiation. In view of its simplicity and low-cost, the present work provides a new way for fabrication of WO3 nanoparticles in the photocatalysis field.

Oxygen enriched network-type carbon spheres for multipurpose water purification applications

Abstract Potassium hydroxide (KOH) modified network-type carbon spheres (CSs) with abundant oxygen-rich groups were synthesized using a simple hydrothermal carbonization (HTC) of glucose precursor and utilized for the adsorptive removal of cadmium(II) heavy metal and congo red (CR) dye as well as photocatalytic degradation of CR. Characterizations on the samples using SEM, FT-IR, TGA, XPS and BET surface area confirmed the presence of porous activated CSs with large surface area of 1125.91 m2. Adsorbent with KOH to CS ratio of 1:1 exhibited maximum adsorption capacities of 276.09 and 382.15 mg/g for Cd(II) and CR respectively. Adsorption data corroborated well with Freundlich isotherm revealing that the multi-layer sorption was predominant. Pseudo-second-order kinetics model described the adsorption process well implying chemisorption was the major contributor for the adsorption capacity. Photocatalytic degradation of CR was achieved with 95% removal efficiency within 90 min proving that adsorbent was a promising multipurpose water treatment material.

Carboxylate-Assisted Assembly of Zinc and Cadmium Coordination Complexes of 1,3,5-Tri-4-pyridyl-1,2-ethenylbenzene: Structures and Visible-Light-Induced Photocatalytic Degradation of Congo Red in Water

Solvothermal reactions of zinc and cadmium nitrates with 1,3,5-tri-4-pyridyl-1,2-ethenylbenzene (tpeb) in the presence of various carboxylic acids including 4-iodobenzoic acid (4-HIBA), benzene-1,4-dicarboxylic acid (1,4-H2BDC), 2,5-furandicarboxylic acid (2,5-H2FDC), 2,5-dibromoterephthalic acid (2,5-H2DBTPA), 1,2-cyclohexanedicarboxylic acid (1,2-H2CHDC), and 1,5-pentanedioic acid (1,5-H2PDC) gave rise to eight coordination complexes, viz, [Zn(tpeb)2(4-IBA)2]·2H2O (1), {[Cd(NO3)(tpeb)(4-IBA)]·H2O}n (2), {[Cd2(NO3)2(tpeb)2(1,4-BDC)]}n (3), {[Cd2(tpeb)2(2,5-FDC)2]·2H2O}n (4), [Cd(tpeb)(2,5-DBTPA)2]n (5), {[Cd2(H2O)2(tpeb)2(1,2-CHDC)2]·H2O}n (6), [Zn(tpeb)(1,2-CHDC)]n (7), and {[Zn(tpeb)(1,5-PDC)]·H2O}n (8). Compound 1 is a discrete mononuclear complex with its Zn(II) center coordinated by two pairs of tpeb and 4-IBA ligands. Compound 2 has a 2D waterfall-like network constructed from bridging [Cd(NO3)(4-IBA)] units with tpeb ligands. Compounds 3, 4, and 5 contain similar 1D [Cd(tpeb)]n chains, which are l...

Surface modified nanostructured-TiO2 thin films for removal of Congo red

We synthesized nanostructured TiO2 thin films by the modified sol-gel template method using the polyethylene glycol as filler media. The TiO2 surface modification for both the thin films, i.e., template and non-template, was done with the ascorbic acid. All the four thin film samples, S1 (TiO2 (non-template), TiO2 (template), S3 (S1 modified with ascorbic acid) and S4 (S2 modified with ascorbic acid), were characterized by various analytical methods. Phase evaluation was monitored by the X-Ray diffraction analysis. Moreover, the thin films particle sizes were obtained to be 22.32, 21.20, 14.52 and 16.77 nm, respectively for the samples S1, S2, S3 and S4. The changes in particle size and morphology due to the PEG and ascorbic acid were determined by scanning electron microscopy (SEM). Similarly, thermal gravimetric (TG) and differential scanning calorimetry (DSC) were performed to determine the decomposition behavior of organic compound present in the solid samples. The functional groups were determined by infrared (IR) analysis. The photocatalytic efficiency, as a reference of Congo red, was conducted using all the four samples of TiO2 thin films. Complete photocatalytic degradation of Congo red was achieved by these samples within 130, 80, 40 and 30 mins of UV illumination.

Temperature dependent photocatalysis of g-C3N4, TiO2 and ZnO: Differences in photoactive mechanism

Photocatalysis has been believed as one of the green and sustainable avenues to address energy and environmental crises by converting solar energy to chemical energy via reactions. Temperature is usually a vital factor controlling kinetics and thermodynamics of a reaction, but it has been less investigated in photocatalysis. In this work, the effect of reaction temperature on photocatalysis was investigated in a simple process, photocatalytic degradation of Congo Red (CR) on three typical catalysts, g-C3N4, TiO2 and ZnO, to differentiate the interfacial radical generation and reaction mechanism. The results showed that the temperature has a positive effect on the photocatalytic activity of the three catalysts. The scavenger experiments at various temperatures indicated that the generation of reactive species from the three photocatalysts is different and that the free radicals can be produced more quickly at higher temperatures, causing improved activities in photocatalysis. However, photocurrent analysis and EIS at various temperatures showed that the temperature had a different effect on recombination rate and transfer barriers of the charge carriers from each catalyst. Therefore, the dramatic enhancement in photodegradation activities probably originated from a novel mechanism of the photothermocatalytic oxidation. The interfacial reaction and mechanism from the influence of reaction temperature on the photocatalytic process was proposed.

Synthesis of ZnO@γ-Fe2O3 core–shell nanocomposites by a facile thermal decomposition approach and their application in photocatalytic degradation of congo red

ZnO@γ-Fe2O3 core–shell nanocomposites were synthesized by a facile thermal decomposition approach. ZnO nanorods were first synthesized by calcination of zinc acetate at 300 °C, in air. γ-Fe2O3 nanoparticles were then deposited on the surface of ZnO nanorods by the thermal decomposition of iron acetylacetonate at 200 °C in diphenyl ether. The structure, composition, optical and magnetic properties of the nanocomposites were studied using an array of techniques. XRD results suggest the presence of γ-Fe2O3 nanoparticles and ZnO, and FE-SEM images indicate formation of shell of iron oxide on the ZnO nanorods. Transmission electron microscopy studies clearly show that ZnO possesses rod morphology (length = 1.1 ± 0.1 μm, diameter = 40.1 ± 7 nm) and TEM images of the ZnO@γ-Fe2O3 nanocomposites show uniform shell of γ-Fe2O3 coated on the ZnO nanorods and thickness of the γ-Fe2O3 shell varies from 10 to 20 nm. Diffuse reflectance spectra of ZnO@γ-Fe2O3 nanocomposites reveal extended optical absorption in the visible range (400–600 nm) and photoluminescence spectra indicate that the ZnO@γ-Fe2O3 nanocomposites exhibit enhanced defect emission. The ZnO@γ-Fe2O3 core–shell nanocomposites show superparamagnetic behaviour at room temperature. The core–shell nanocomposites exhibit enhanced visible-light driven photocatalytic degradation of congo red in an aqueous solution as compared to pure ZnO nanorods and γ-Fe2O3 nanoparticles. The enhanced photocatalytic activity is attributed to good visible-light absorption and effective charge separation at the interface of ZnO@γ-Fe2O3 core–shell nanocomposites.

Photocatalytic Degradation of Congo Red and Crystal Violet Dyes on Cellulose/ PVC/ZnO Composites under UV Light Irradiation

UV light assisted photo degradation of congo red and crystal violet dyes over Cellulose/PVC/ZnO nano composites has been observed. Solution cast method was adopted for the synthesis of Cellulose/ PVC/ZnO thin film. UV-Vis diffused reflectance spectroscopy, powder X-ray diffraction, fourier transform infrared spectroscopy, scanning electron microscopy were employed to investigate the optical property and morphology of Cellulose/ PVC/ZnO composites. Congo red and crystal violet dyes were used as the model dyes in the degradation studies. Nearly 90% of the dyes were degraded after a very short irradiation time. The photocatalytic activity of the Cellulose/ PVC/ZnO composite was found to be better than that of the PVC/ZnO composite. The photocatalytic activity is found to be dependent on the concentration of the loaded photocatalyst.

Synthesis of novel Bi2O3–montmorillonite nanocomposite with enhanced photocatalytic performance in dye degradation

Novel Bi2O3–montmorillonite nanocomposite photocatalyst was synthesized and characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Effect of Bi2O3 intercalation with montmorillonite clay on photocatalytic performance of Bi2O3–montmorillonite under visible light irradiation was systematically investigated. The results indicate that Bi2O3–montmorillonite shows enhanced adsorption and photocatalytic performance for Congo red (CR) removal under visible light irradiation. Higher rate of light absorption and lower rate electron–hole pair recombination are responsible for the increase in photocatalytic efficiency. Adsorption of CR on Bi2O3–montmorillonite follows pseudo-second-order kinetics and the adsorption isotherm follows Freundlich isotherm. The monolayer capacity was observed to be 500mgg−1. The maximum percentage removal achieved upto 86.4% at pH 9 for 2gL−1 photocatalyst dose. Photocatalytic degradation of CR by Bi2O3–montmorillonite proceeds via advanced oxidative process.

The effect of operational parameters on the photocatalytic degradation of Congo red organic dye using ZnO–CdS core–shell nano-structure coated on glass by Doctor Blade method

Photocatalytic degradation of Congo red was investigated using ZnO–CdS core–shell nano-structure coated on glass by Doctor Blade method in aqueous solution under irradiation. Field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) techniques were used for the morphological and structural characterization of ZnO–CdS core–shell nanostructures. XRD results showed diffractions of wurtzite zinc oxide core and wurtzite cadmium sulfide shell. FESEM results showed that nanoparticles are nearly hexagonal with an average diameter of about 50nm. The effect of catalyst loading, UV-light irradiation time and solution pH on photocatalytic degradation of Congo red was studied and optimized values were obtained. Results showed that the employment of efficient photocatalyst and selection of optimal operational parameters may lead to complete decolorization of dye solutions. It was found that ZnO–CdS core–shell nano-structure is more favorable for the degradation of Congo red compare to pure ZnO or pure CdS due to lower electron hole recombination. The results showed that the photocatalytic degradation rate of Congo red is enhanced with increasing the content of ZnO up to ZnO(0.2M)/CdS(0.075M) which is reached 88.0% within 100min irradiation.

A facile and low-cost synthesis of granulated blast furnace slag-based cementitious material coupled with Fe2O3 catalyst for treatment of dye wastewater

A facile and low-cost route was used to synthesize a novel catalyst of alkali-activated granulated blast furnace slag-based cementitious material (ASCM) coupled with Fe2O3 by a three-step reaction of polymerization, ion exchange and impregnation. The FESEM and XRD results revealed that a high compressive strength ASCM with mean particle size about 50nm was synthesized and Fe2O3 covered on ASCM surface in the form of clusters. The photoluminescence peak sharply decreases with increase of Fe2O3 content due to the recombination probabilities of photogenerated electron–hole pairs to be inhibited. The photocatalytic activities for degradation of Congo red (CR) dye were evaluated and the sample of ASCM loaded about 5wt% Fe2O3 showed the highest degradation efficiency under UV irradiation. The photocatalytic degradation of CR in solution obeys second order reaction kinetics and a possible reaction mechanism is proposed.

Visible Light Photocatalysis with Rare Earth Ion-Doped Nanocomposites

Rare earth (R) ion-doped TiO2 nanocomposites (NCs) with general composition (R: Y, Yb, Gd; , 0.2) were synthesized through co-precipitation/hydrolysis (CPH). NC particles with average size of approximately a few tens of nm were obtained. Similar compositions of polycrystalline (PC) samples with larger particle size were also prepared employing solid state reaction (SSR) method. Visible light photocatalytic activity of all samples was investigated for degradation of Congo red (CR) dye. Both in terms of apparent rate constant () and percent degradation after 180 min (), all NCs produced significantly enhanced degradation as compared to pure TiO2 and PC samples. Best degradation of 95% ( value) resulted with composition of Y3+ doped NC with min−1. This was followed by of 85 and 80%, produced with Yb3+ and Gd3+ doped, NCs, at around and min−1, respectively. The observations clearly suggest that enhanced photocatalytic degradation of CR is directly related to smaller particle size of the catalysts. Moreover, the presence of rare earth ions in the composites facilitates further improvement of degradation efficiency through effective suppression of recombination.

Photocatalytic performance of silver TiO 2: Role of electronic energy levels

Nano-sized silver deposits on the surface of Degussa P25 TiO 2 (Ag-DP25) particles act as sites of electron accumulation where the reduction of adsorbed species takes place. Electrons can be transferred from Degussa P25 TiO 2 (DP25) to Ag particles because of the difference in the work functions of the two materials. The efficiency of the electron transfer depends on the size and the distribution of metal deposits. A significant photocatalytic oxidation enhancement by metal deposit will only be observed if the metal deposits play a more dominant role than just increasing the life time of charge carriers. The properties of metal deposits like, loaded amount, oxidation state of the deposit and its size will influence the performance. Further, a decrease in band-gap in DP25 and Ag-DP25 was observed due to the carbide ion substitution for the oxide ion in TiO 2. Such unintentional carbon incorporation is expected mostly in combustion synthesized materials. Silver metal deposits and unintentional incorporation of the carbon shows the beneficial effect by specific mechanism in the photocatalytic degradation of Congo Red (CR).

ZnO-Assisted Photocatalytic Degradation of Congo Red and Benzopurpurine 4B in Aqueous Solution

The photocatalytic degradation of two commercial azo dyes Congo red (CR) and Benzopurpurine 4B (BP4B) in aqueous solution was investigated under UV-A light at different operating conditions, including irradiation time, pH solution, initial dye concentration, amount of catalyst, light intensity as well as band gap of other semiconductor groups by UV-spectrophotometric monitoring. The highest decomposition were obtained at pH 8 as a result of 95.02 and 97.24 % degradation efficiencies of CR and BP4B for 60 and 80min of irradiation time respectively. Photodecomposition reactions of both dyes were correlated with pseudo-first-order kinetic model. For BP4B, the degradation data were satisfactory described by Langmuir–Hinshelwood (L-H) mechanism, whereas those of CR were not sufficient to conclude that the L-H mechanism is the most suitable one to describe the photocatalytic process of CR. These findings can support the design of remediation processes and also assist in predict their fate in the environment.

Iron (Fe3+) loaded TiO2 nanocatalysts: characterization and photoreactivity

Iron (Fe3+) loaded TiO2 nanocatalysts were prepared by the photochemical reduction process. These supported nanocatalysts were characterized by X-ray diffraction (XRD), surface area (BET) measurements, scanning electron microscopy SEM with energy dispersive X-ray (EDX-elemental mapping) analysis and atomic force microscopy (AFM) with adhesion force measurements. XRD and BET results showed adsorption of iron species on the surface of the TiO2 support. AFM and SEM images revealed obvious variations in the surface morphology of the support after loaded with Fe3+ ions. Photocatalytic activities of the supported nanocatalysts were examined for decolorization and degradation processes of Congo red (CR) under UV irradiation. Fe3+ ions improved the performances of the supported nanocatalysts by suppressing the electron–hole recombination reactions. Effects of Fe3+ ion content and initial CR concentration were investigated. A tentative model was proposed for the photocatalytic degradation of CR.

Optimisation of an annular photoreactor process for degradation of Congo Red using a newly synthesized titania impregnated kaolinite nano-photocatalyst

In this study, an annular photocatalytic reactor (APR) system was designed and operated to optimise the photocatalytic degradation of Congo Red (CR) using a newly synthesized titania impregnated kaolinite photocatalyst (TiO 2/K). The design parameters of the APR: reactor configuration, mass transfer, mixing and hydrodynamics were discussed. The influences of the operation parameters: pH, critical TiO 2/K loading, aeration rate and initial CR concentration on the photocatalytic performances were studied in a batch operation mode. Results showed that the initial pH was the most crucial operation parameter that significantly affected both the adsorption and photocatalytic reactions in the APR–TiO 2/K system. The point of zero charge for TiO 2/K was found to shift towards pH 9.5. The complete degradation of 40 ppm CR was attained in 4 h. Possible intermediates and by-products during the CR degradation were identified using the LC/MS technique. The TiO 2/K reactivation study showed that the TiO 2/K particles are highly stable and have a modest improvement in photoactivity for every recycle trial up to at least five cycles. The overall results revealed that the APR–TiO 2/K system has promising application for the development of a technically feasible and cost-effective industrial water and wastewater treatment process.

Photocatalytic degradation of Congo Red by hydrothermally synthesized nanocrystalline TiO 2 and identification of degradation products by LC–MS

Degradation of Congo Red (CR) dye in aqueous solutions was investigated by means of photocatalysis of TiO 2 which was hydrothermally synthesized at 200 °C in 2 h, in anatase phase with 8 nm crystallite size. Efficiency of TiO 2 in photocatalytic degradation under visible irradiation was studied by investigating the effects of amount of TiO 2, irradiation time, initial CR concentration and pH. It was found that complete decolorization is achieved within 30 min of irradiation. Effects of nitrate and sulphate ions and humic acid on the degradation were also tested. The results were compared with Degussa P-25 TiO 2 at the same degradation conditions. Degradation products were detected using LC–MS technique. The probable pathways for the formation of degradation products were proposed.