Organic Dyes In Wastewater Research Articles

Treatment of Methylene Blue and Methyl Orange Dyes in Wastewater by Grafted Titania Pillared Clay Membranes.

Background: Amphoteric membranes such as Titania Pillared Clay (TiPILC) membranes exhibit different charges at different pH ranges, subsequently show efficient separation for cationic and anionic organic pollutants in wastewater based on solution pH. The structural properties of such membranes determine their permeability and selectivity to a large extent. The present work is initiated to explore the possibility of enhancing the surface area of TiPILC membranes by grafting with 3-aminopropyltriethoxysilane.Method: Grafted TiPILC membranes were fabricated by colloidal sol- gel route followed by dip coating, drying and sintering the membranes at 300oC. X-ray diffraction (XRD) spectra of the pillared photocatalyst membranes show the presence of only anatase phase, which exhibits better photocatalytic activity. Fourier Transform Infrared (FT-IR) spectra reveal the formation of delaminated TiPILC material. The specific surface area of TiPILC membrane obtained at pH3.5 is 183m2/g.Results: Literature survey of 47 papers was carried out for the work. 10 papers were based on patents being dealt on degradation of organic dyes in wastewater by conventional methods, though reports of membrane technology are limited in literature. The rest 37 papers outlined the importance of widespread use of titania photocatalyst powder for degradation studies.Conclusion: The membrane material thus developed is efficient in complete decolouration of both Methylene Blue and Methyl Orange dyes on account of the high surface charge and high surface area in just one cycle of filtration.

Synthesis of multifunctional photocatalyst vanadium oxide/activated carbon via in situ utilization of stone coal ore

In this work, activated carbon (AC), vanadium oxide (V2O5), and V2O5/AC photocatalyst were prepared by in situ utilization of stone coal ore for the first time. The synthesis conditions for activated carbon (AC) and V2O5/AC were thoroughly investigated via orthogonal experiments and single factor experiments, respectively. The obtained optimal parameters could be directly adopted in practical application about utilization of stone coal ore. The optimal deashing experimental parameters for stone coal ore were: HF concentration of 15%, H2SO4 concentration of 15%, acid leaching temperature of 85 °C, and acid leaching time of 2 h. The as-prepared activated carbon from stone coal ore could be applied to the removal of methylene blue. The as-prepared V2O5/AC photocatalyst possessed a highly visible-light-driven photocatalytic activity for the removal of Rhodamine B (RhB) dye. The RhB degradation ratio could reach to 90.0% after only 3 h photocatalytic reaction. This photocatalyst would be possibly applied to treatment other organic dye wastewater. Actually, this work would extend the application field of stone coal ore. Most importantly, we hope the proposed new concept that in situ utilization of ore can be widely spread and applied.

Sonophotocatalytic degradation mechanisms of Rhodamine B dye via radicals generation by micro- and nano-particles of ZnO

In this work, it is proposed an environmental friendly sonophotocatalytic approach to efficiently treat polluted waters from industrial dyes exploiting ZnO micro- and nano-materials. For the first time, we deeply investigated the generation of reactive oxygen species (ROS) under ultrasound stimulation of different ZnO structures by Electron Paramagnetic Resonance Spectroscopy (EPR). Indeed, five zinc oxide (ZnO) micro- and nano-structures, i.e. Desert Roses (DRs), Multipods (MPs), Microwires (MWs), Nanoparticles (NPs) and Nanowires (NWs), were studied for the Rhodamine B (RhB) sonodegradation under ultrasonic irradiation. The DRs microparticles demonstrated the best sonocatalytic performance (100% degradation of RhB in 180 min) and the highest OH radicals generation under ultrasonic irradiation. Strikingly, the coupling of ultrasound and sun-light irradiation in a sonophotodegradation approach led to 100% degradation efficiency, i.e. color reduction, of RhB in just 10 min, revealing a great positive synergy between the photocatalytic and sonocatalytic mechanisms. The RhB sonophotocatalytic degradation was also evaluated at different initial dye concentrations and with the presence of anions in solution. It was demonstrated a good stability over repeated cycles of dye treatment, which probe the applicability of this technique with industrial effluents. In conclusion, sonophotocatalytic degradation synergizing sunlight and ultrasound in the presence of DRs microparticles shows a great potential and a starting point to investigate further the efficient treatment of organic dyes in wastewater.

Photocatalytic Performance of SnO2:Mo Nanopowders Against the Degradation of Methyl Orange and Rhodamine B Dyes Under Visible Light Irradiation

Visible light-mediated photocatalytic performance of the Mo-doped SnO2 (SnO2:Mo) nanopowders synthesized via cost-effective chemical method against methyl orange (MO) and rhodamine B (RhB) dyes has been outlined in this paper. Mo concentration in SnO2 is varied as 0 wt.%, 5 wt.%, 10 wt.% and 15 wt.%. The nanopowders were characterized by x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy, diffuse reflectance spectra and photoluminescence. The (1 0 1) preferential growth observed for the undoped SnO2 is retained for all the doped samples. Uniform distribution of grains was observed from the SEM images of all the samples with grain size being reduced with Mo doping. XPS spectrum of the 10 wt.% Mo-doped sample confirmed that Sn and Mo exist in +4 and +6 oxidation states, respectively. The band gap of pure SnO2 decreased from 3.56 eV to 3.44 eV with Mo doping. Photocatalytic performance of pure SnO2 got enhanced with Mo doping and the 10 wt.% Mo-doped SnO2 sample exhibited maximum degradation efficiency of 90.23% against MO and 81.14% against RhB dyes. The results confirm that the SnO2:Mo nanopowders are well suited as an efficient catalyst for degrading organic dyes in waste water.

Preparation and characterization of 2D ZnO nanosheets/regenerated cellulose photocatalytic composite thin films by a two-step synthesis method

2D ZnO nanosheets-regenerated cellulose (ZNSRC) photocatalytic composite thin films were prepared from ZnCl2 by using a two–step synthesis method at room temperature. The results show that during the formation of ZNSRC composite thin film, ZnCl2 first reacted with NaOH to form Zn5(OH)8Cl2·H2O which was then converted to ZnO. The 2D ZnO nanosheets are 350–450 nm in transverse size and 80 nm in thickness, dispersed on both the surface and inside of the ZNSRC thin films. The ZNSRC prepared by 13 h of reaction time has a characteristic of nanoporous 2D ZnO nanosheets and exhibits the best photocatalytic activity, as 1.53 × 10−5 mol methyl orange was completely degraded in 50 min by using 1 g catalyst. Thus, we can conclude that the ZNSRC photocatalytic composite thin films can be very useful for degrading organic dye wastewater.

Facile synthesis of metal-doped magnesium ferrite from saprolite laterite as an effective heterogeneous Fenton-like catalyst

Metal-doped magnesium ferrite (MgFe2O4) with cubic spinel structure, large specific surface area and medium saturation magnetic strength was synthesized from saprolite laterite leaching solution through hydrothermal-calcination method and used as a heterogeneous Fenton-like catalyst. The influence of reaction temperature on the catalytic process was centrally discussed based on the hydroxyl radical theory. The as-prepared MgFe2O4 exhibited favorable catalytic activity for degradation of Rhodamine B (RhB), achieving 97.8% degradation efficiency of 10 mg·L−1 RhB within 300 min (90.0% degradation, 180 min) at the conditions of 45 °C, pH 6.44, 0.625 g·L−1 catalyst dosage and 1.00 vol% H2O2 concentration. And the TOC removal efficiency could reach 77.8%. After five consecutive degradation cycles, the reduction of degradation and TOC removal efficiencies were <3.0% and 8.0%, respectively, suggesting the metal-doped MgFe2O4 had high catalytic activity, good stability and excellent reusability. More importantly, the formed catalyst may broaden the application of saprolite laterite and provide a promising way for other natural minerals which contain transition metal elements in the treatment of organic dye wastewater.

WO3−x for rapid adsorption and full-spectrum-responsive photocatalytic activities

Dual-purpose method for efficient removal of harmful organic dyes has been successfully realized by W18O49 nanostructure via fast absorption and advanced full-spectrum-responsive photocatalytic degradation from UV to near infrared (NIR). The removal more than 99% of MB could be finished as short as 1–2 min. The strong electrostatic interaction between the negative charged W18O49 surface and the cationic MB species is major reason for such a fast adsorption response. In addition, W18O49 nanostructure also could behave as photocatalyst for further degradation of MB. Advantages of W18O49 nanostructure used in this purpose benefit from its high optical absorption covering ultraviolet, visible light and NIR, which has good mineralizing ability under each spectrum, thus taking full use of solar energy. What is noteworthy, the regeneration of W18O49 after the absorption of MB could be simply realized by photo-irradiation process. As a result, it will be promising to use this dual-function material for deeply removal of organic dyes in wastewater.

Optimized Fabrication of TiO2 Nanotubes Array/SnO2-Sb/Fe-Doped PbO2 Electrode and Application in Electrochemical Treatment of Dye Wastewater

A TiO2 nanotubes array/SnO2-Sb/Fe-doped PbO2 electrode with high oxygen evolution potential and enhanced electrochemical oxidation performance was successfully manufactured. The surface morphology and electrochemical performance of the electrode were characterized by a field emission scanning electron microscope, linear sweep voltammetry, and electrochemical impedance spectroscopy experiments. The effect of Fe doping concentration on the electrode performance was also investigated. This study shows the doping of Fe on a PbO2 electrode improved the micro-morphology and the conductivity of the electrode. The oxygen evolution potential was also increased to 1.95 V [versus a saturated calomel electrode (SCE)] via Fe doping. The optimal condition of Fe doping concentration was 0.02 M. The optimized electrode showed that the decoloration rate and total organic carbon removal ratio of methylene blue approached 98% and 96% after 30 min of electrochemical treatment, respectively. The accelerated lifetime of the optimized Fe-doped electrode was approximately 4.3 times larger than that of the undoped PbO2 electrode. A Ti/TiO2 nanotubes array/SnO2-Sb/Fe-doped PbO2 anode shows potential application in the electrochemical treatment of organic dye wastewater.

Optimal co-catalytic effect of NiFe2O4/ZnO nanocomposites toward enhanced photodegradation for dye MB

Abstract A series of magnetically recyclable NiFe2O4/ZnO nanocomposites have been successfully fabricated by a facile two-step route. The as-prepared NiFe2O4/ZnO nanocomposites were characterized by X-ray diffraction, field-emission scanning electron microscopy, vibrating sample magnetometer, ultraviolet-visible diffuse reflectance spectroscopy and photoluminescence spectroscopy. The results demonstrate that the NiFe2O4/ZnO nanocomposites are composed of ZnO particles (50–120 nm) integrated with NiFe2O4 particles (30–80 nm). Compared with bare ZnO, the NiFe2O4/ZnO nanocomposites exhibit evidently enhanced visible light absorption and decreased recombination of photo-generated electron-hole pairs. Moreover, the nanocomposites exhibit enhanced photocatalytic performance for the degradation of methylene blue under simulated solar light irradiation when compared with bare ZnO, and the 20%-NiFe2O4/ZnO nanocomposite is observed as the optimal composite. This is ascribed to the more efficient separation of photo-generated electron-hole pairs and generation of hydroxyl (˙OH) radicals in the 20%-NiFe2O4/ZnO nanocomposite. Furthermore, the NiFe2O4/ZnO nanocomposites have a high saturation magnetization, indicating that they can be magnetically separated and recycled from organic dye wastewater.

Synthesis and characterization of CdS-based ternary composite for enhanced visible light–driven photocatalysis

Active ternary graphite and alumina-supported cadmium sulphide (CdS) composite was synthesized by impregnation method followed by high-temperature solid–gas reaction and characterized by X-ray diffraction (XRD), photoluminescence spectroscopy (PL), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) techniques. The ternary CdS–graphite–alumina composite exhibited superior catalytic activity compared with the binary CdS–alumina composite due to its better visible-light absorption and higher charge separation. The ternary composite has a bed-type structure. It permits a greater interaction at the interface due to intimate contact between CdS and graphite in the ternary composite. This composite has a highly efficient visible light–driven photocatalytic activity for sustainable hydrogen production. It is also capable of degrading organic dyes in wastewater.

Co-Mn layered double hydroxide as an effective heterogeneous catalyst for degradation of organic dyes by activation of peroxymonosulfate

In this study, Co-Mn layered double hydroxide (Co-Mn LDH) was synthesized, characterized, and tested as heterogeneous catalyst to activate peroxymonosulfate (PMS) for degradation of organic dyes. The results of characterization showed that Co-Mn LDH had high purity, uniform morphology and large specific surface area (49.9379 m2/g). The degradation experiments demonstrated that five different dyes with the concentration of 50 mg/L could be decomposed completely within 240 s using only 0.025 g/L of Co-Mn LDH and 0.1 g/L of PMS. Moreover, Co-Mn LDH/PMS system presented the highest decomposition efficiency for acid orange G (AOG) compared with other related materials under the same condition. Further investigation found that Co-Mn LDH/PMS system had an excellent adaptability in a wide pH range (from 3 to 10), and the best efficiency was achieved when the solution was natural (pH = 6.87). The mineralization of AOG was assessed by Total Organic Carbon (TOC), and 52.2% of TOC was removed. Meanwhile, the good reusability and high stability of Co-Mn LDH were demonstrated by recycle tests and ion-leaching tests. The catalytic mechanism was explored through quenching tests as well as X-ray photoelectron spectroscopy (XPS) analysis. Finally, all of the results suggested that Co-Mn LDH/PMS system with high stability and decomposition efficiency was suitable for the remediation of organic dyes in wastewater.

Self-template synthesis of nickel silicate and nickel silicate/nickel composite nanotubes and their applications in wastewater treatment

Hierarchical one-dimensional (1D) hollow nanostructures have attracted intense research attention due to their unique structures that may be capable of many promising applications. Here, we report a facile and effective strategy to prepare nickel silicate nanotubes (NiSNTs). Using this approach, mesoporous SiO2 nanorods served as sacrificial templates for a simple hydrothermal process to prepare NiSNTs via a self-template route. The obtained NiSNTs preserve the tubular hierarchical morphology and hollow interior structures, which confer the NiSNTs with high surface areas and large pore volumes. These features point to NiSNTs as superior candidates for efficiently adsorbing heavy metal ions and organic dyes in wastewater. Moreover, NiSNTs can also serve as both supports and nickel sources, forming nickel silicate/nickel nanocomposite tubes (NiSNTs/Ni) via in situ reduction of NiSNTs under hydrothermal conditions. The addition of nickel precursors and surface pre-activation are therefore unnecessary. The NiSNTs/Ni exhibit efficient and recyclable catalytic properties when used for the reduction of 4-nitrophenol (4-NP). With a rational adaption, we believe this synthetic strategy can be extended to fabricate multifunctional one-dimensional hollow nanostructures with diverse compositions and morphologies, which may be useful for environmental protection, catalysis, energy and many other important domains.

From Starch to Magnetic Porous Fe2O3@C: A Promising Peroxidase‐Mimicking Heterogeneous Biocatalyst for Degradation of Organic Dye

Researchers remain attracted to the development of more efficient and cost‐effective materials for the degradation of organic dyes in wastewater. Ultra‐small (sub‐5 nm) Fe2O3 nanocrystals embedding magnetic porous carbon, referred to as Fe2O3@C, in which starch is used as a carbon source, is demonstrated, and is synthesized by a facile microwave‐enhanced high‐temperature ionothermal method within 4 min. The Fe2O3@C obtained is used as a peroxidase‐mimicking catalyst in heterogeneous Fenton‐like reactions to degrade organic dyes (i.e., methylene blue) with aid from the green oxidant, hydrogen peroxide. Because of its unique structure and high specific surface area, Fe2O3@C displays enhanced treatment properties in the degradation of methylene blue. Moreover, Fe2O3@C demonstrates stability and resistance to a broad range of pH, recyclability, and convenient separation. This promising peroxidase‐mimicking composite material may have potential applications in degradation of organic pollutants in the environmental cleaning field.

Solvothermal synthesis of porous conjugated polymer with high surface area for efficient adsorption of organic and biomolecules

Aimed to prepare high efficient dye sorbent and control water pollution, herein we utilized solvothermal method to synthesize porous polyimide (PI) polymer with a large surface area using DMSO as solvent. Unlike the solid-state thermal polymerized PI with low surface area of 5 m2g−1, this PI material prepared in DMSO solvent possessed a large surface area of 430 m2g−1, which was beneficial for adsorption of organic dye in waste water, achieving a max MO adsorption of 200 mg g−1 three times higher than that of multiwalled carbon nanotube. The adsorption kinetics of dye molecules on PI was investigated in detail and the R2 value of 0.99071 for pseudo-second-order model confirms the adsorption was fitted best with Langmuir isotherm.

Role of europium on WO3 performance under visible-light for photocatalytic activity

Photocatalytic degradation of organic dyes in wastewater using visible light illumination is a green technology which requires efficient visible-light driven active catalytic material. For this, we have reported a novel visible light active Eu/WO3system with variation in europium contents (0, 2%, 4% and 6% Eu), which demonstrated enhanced photocatalytic activity for the degradation of various organic dyes including methylene blue (MB), methyl orange ((MO) and rhodamine B (RhB). Scanning electron microscopy (SEM), X-ray diffractometer (XRD), energy dispersive X-ray (EDX), UV–visible spectroscopy and photoluminescence (PL) spectroscopy were used for the characterization of nanostructures. The results showed that Eu has effective role in modifying the structural, morphological and optical properties of WO3 photocatalyst. Moreover, the photocatalytic performance of WO3 was improved due to incorporation of Eu. From results, it was seen that photocatalytic activity increases with increasing Eu concentration upto 4%, however, further increase in Eu concentration (6%) has decreased the performance under these condition for all dyes. The enhanced photocatalytic efficiency could be attributed to suppressed recombination of charge carriers and enhanced visible light absorption and increased BET surface area due to Eu doping into WO3 photocatalyst. The as-synthesized nanostructures will be considered as a promising photocatalytic materials for the future research in this field.

Novel magnetically separable Ag3PO4@CuFe2O4 micro-nanocomposite with highly enhanced visible-light-driven photocatalytic activity

An effective visible-light-driven Ag3PO4@CuFe2O4 Z-scheme magnetic micro-nanocomposite was successfully fabricated by a simple ion-exchange deposition method. The Ag3PO4@CuFe2O4 photocatalyst exhibited remarkably enhanced photocatalytic activity (degradation efficiency was ∼99% within 30min and kinetic constant reached 0.1423min−1) as compared to Ag3PO4 and CuFe2O4 for the degradation of Rhodamine B (RhB). Comparing the activity results dependence with the characterization results, which indicated that the dependence of the photocatalytic activity on the efficient separation of photogenerated h+-e− pairs. This study might provide a promising visible light responsive photocatalyst for the photocatalytic degradation of organic dyes in waste water.

One-pot synthesis of multifunctional magnetic N-doped graphene composite for SERS detection, adsorption separation and photocatalytic degradation of Rhodamine 6G

This work reports a one-pot solvothermal synthesis approach of magnetic γ-Fe2O3/N-rGO composite and its multifunctional application for detection, adsorption removal and degradation of organic pollutants. The uniform dispersed γ-Fe2O3 nanoparticles (NPs) are in situ grown on the surface of nitrogen doped reduced graphene oxide (N-rGO) sheets, thus forming a three-dimensional (3D) γ-Fe2O3/N-rGO composite with high specific surface area (146.2m2·g−1). The morphology and textural properties of the samples were characterized by scanning and transmission electron microscopies, X-ray diffraction, Raman and X-ray photoelectron spectroscopies. The γ-Fe2O3/N-rGO composite with 3D interconnected porous structure possesses multifunctional performance for dye removal with convenient magnetic separation operation. It exhibits good removal ability for Rhodamine 6G (R6G) with an adsorption capacity of 44.0mg·g−1. Meanwhile, the γ-Fe2O3/N-rGO composite shows a high sensitive surface-enhanced Raman spectroscopy (SERS) response toward R6G molecules where the detection limit is as low as to 5×10−7mol·L−1. Besides, it also serves as a photocatalyst to degrade the adsorbed R6G molecules under in situ SERS monitoring. Thus, the multifunctional γ-Fe2O3/N-rGO composite can present a promising potential for organic dye wastewater treatment and other applications.

RGO-stabilized MnO/N-doped carbon nanofibers for efficient removal of Pb(II) ion and catalytic degradation of methylene blue

rGO-MnO/NC nanocomposites with porous structure were prepared by one-pot solvothermal method combining with heat treatment. rGO nanosheets can serve as a substrate to prevent the irreversible fusion and aggregation during the high-temperature pyrolysis of Mn-precursor; meanwhile, the organic ligands in the precursor can provide N and C source, resulting in rGO-stabilized MnO/N-doped carbon nanofibers (rGO-MnO/NC). This study investigated the adsorption behaviors of Pb(II) ions onto rGO-MnO/NC under different rGO loading in composites, pH value and temperature of solution. The rGO-MnO/NC nanocomposites exhibited an enhanced performance for removal of Pb(II) ions as compared with pure MnO/NC. The adsorption isotherm of Pb(II) ions onto pure MnO/NC and rGO-MnO/NC were well fitted by Langmuir model, and the adsorption kinetics of Pb(II) ions onto rGO-MnO/NC was well described by pseudo-second-order model. The theoretical maximum adsorption capacity of Pb(II) onto rGO-MnO/NC-2 with 5 wt% rGO loading was 222.2 mg g−1 at 25 °C without adjusting solutions pH value. Furthermore, the rGO-MnO/NC-2 showed higher catalytic activity in Fenton-like oxidation of methylene blue than bare MnO/NC. The rGO-MnO/NC-2 catalyst achieved high removal of methylene blue (100% removal within 30 min) at the selected operating conditions (0.4 g catalyst L−1, [H2O2]:[MB] of 31.2 (mol/mol), 25 °C). The results suggest that the rGO-MnO/NC with suitable rGO loading could provide a promising option for effective decontamination and detoxification of heavy metal and organic dye wastewater.

Ag2O/sodium alginate supramolecular hydrogel as a film photocatalyst for removal of organic dyes in wastewater

As a film photocatalyst, a Ag2O/sodium alginate supramolecular hydrogel exhibited excellent photocatalytic degradability, great adsorptivity, highly efficient charge separation and reusability.

Anatase TiO2/cellulose hybrid paper: Synthesis, characterizations, and photocatalytic activity for degradation of indigo carmine dye

We report a facile easy method to deposit anatase titania (TiO[Formula: see text] on cellulose paper. The anatase TiO2/cellulose paper (ATCP) was characterized by scanning electron microscopy, transmission electron microscope, energy dispersive X-ray spectrometer, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. This hybrid paper with the anatase TiO2 content of around 13.86[Formula: see text]wt.% can serve as an eco-friendly flexible photocatalyst, which can rapidly degrade blue indigo carmine dye into a colorless solution within 30[Formula: see text]min under UV radiation. Moreover, compared to commercially available TiO2 P25 and anatase TiO2 powder, a faster decomposition rate of indigo carmine dye was acquired when using ATCP. These results suggest that this hybrid paper might be useful in the treatment of organic dye wastewater.