Organic Dyes In Aqueous Solution Research Articles

Radiation-Assisted Assembly of a Highly Dispersed Nanomolybdenum-Functionalized Covalent Organic Framework.

Two-dimensional covalent organic frameworks (2D COFs), featuring a large surface area and 1D pore structure, serve as promising scaffolds for anchoring functional guest compounds, which can significantly enhance their performance and thus expand their potential applications. Postsynthetic strategy for COFs functionalization is versatile but challenging because of their tedious procedure with high time and energy consumption, generation of excess reaction waste, and damage to COF crystallinity. We report in this work a general strategy for the synthesis of inorganic nanocompound-functionalized COF composites in a one-pot way. Specifically, a high-crystallinity nanoscale molybdenum compound is successfully introduced into a COF skeleton with high dispersion in situ during the crystallization process of the COF induced by gamma ray radiation under ambient conditions. The obtained COF@Mo composites exhibit remarkable sorption performance for methylene blue and many other organic dyes in aqueous solution with the advantages of ultrarapid uptake dynamics and high removal efficiency.

Fabrication of activated carbon from polyethylene terephthalate plastic waste (PET) and their application for the removal of organic dyes in aqueous solution by chemical method

Synthetic plastics are found in all manufacturing industries and in daily life because plastic products bring convenience to life. Polyethylene terephthalate (PET) is one of the most popular synthetic plastics with increasing consumption. Every year, the huge amount of PET plastic waste is discharged into the environment. Therefore, it is necessary to have an effective solution for PET plastic waste. In this study, PET waste plastic was utilized to fabricate activated carbon using the chemical activating approach. H3PO4 acid was used as activating agent. The influence of impregnation rate of PET waste platic with H3PO4, activating temperature, activating time on the surface areas of activated carbon was investigated. The prepared activated carbon was well-characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), FTIR, and BET. The activated carbon prepared from the :PET plastic waste revealed high absorption toward methylene blue in aqueous solution in a wide range of pH solutions. The fabrication of activated carbon from the plastic waste not only address the environmental issues, but also produce high-value activated carbon for the environmental remediation.

A bifunctional imidazolium-based porous organic polymer for efficient detection of Cr2O72− and adsorptive separation of Cr2O72− and MO in water

The presence of heavy metal ions and organic dyes in aqueous solutions has a significant impact on the ecological environment and human health. Herein, a novel bifunctional imidazolium-based porous organic polymer (IMSPF-Br-C=C) was prepared successfully via quaternization reaction of spirobifluorene and 1,4-dibromo-2-butene. The synthesized material was characterized by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), Fourier transform infra-red spectra (FTIR), Thermogravimetric analysis (TGA), X-ray diffraction (XRD), N2 adsorption-desorption analysis and solid-state 13C CP/MAS NMR spectroscopy, confirming its structure and stability. Owing to the conjugated structure of spirobifluorene, IMSPF-Br-C=C showed excellent recognition performance for dichromate anion (Cr2O72−) with the limit of detection (LOD) of 1.58 μmol/L. In addition, IMSPF-Br-C=C with the abundant imidazolium cations showed the outstanding adsorption performance in the removal of Cr2O72− and methyl orange (MO). Removal efficiencies and adsorption capacities of IMSPF-Br-C=C were 98.3 % and 99.4 %, 452.8 and 1304.2 mg/g in 6 min, respectively. The results show that the electrostatic interactions and π-π stacking play crucial roles in the fluorescence detection of Cr2O72− and adsorptive separation of Cr2O72− and MO. Furthermore, physico-chemical techniques, density functional theory (DFT) calculation and frontier molecular orbital theory (FMO) were used to explain action mechanism. This work provides a cost-effective IMSPF-Br-C=C as a bifunctional platform for sensing Cr2O72− and adsorptive separation of Cr2O72− and MO in aqueous solution.

Enhanced electrocatalytic degradation of acid orange 7 by using double perovskite La2CoxNi1-xMnO6/nickel foam as the electro-Fenton cathodes

Adequate generation of hydrogen peroxide and its subsequent activation into reactive oxygen species (ROS) play a crucial role in the catalytic efficiency of heterogeneous electro-Fenton for the degradation of contaminants. Herein, a series of La2NiMnO6 double perovskite with Co doping (La2CoxNi1-xMnO6) were prepared by a facile sol-gel technique and applied as catalysts in heterogeneous electro-Fenton system to removal acid orange 7 (AO7). Nickel foam was chosen as the supporting substrate for the catalyst owing to its excellent physical properties to accelerate the conversion of O2 to H2O2. La2Co0.5Ni0.5MnO6 achieved 90.22 % of AO7 decomposition rate at 120 min via the heterogeneous electro-Fenton system, which was a significant improvement over the catalytic efficiency of both only NF and La2NiMnO6 electrodes. Further studies have shown that the introduction of Co could heighten the efficient redox recycling of Ni2+/Ni3+ and Mn3+/Mn4+ on the electrode surface, synergically facilitating the conversion of H2O2 to OH. Meanwhile, the three redox pairs (Ni2+/Ni3+, Mn3+/Mn4+ and Co2+/Co3+) also stimulated the production of superoxide radicals (O2−), which was also not negligible in enhancing degradation. Finally, the possible pathway and mechanism of the degradation of AO7 were proposed. This work demonstrates that La2CoxNi1-xMnO6/NF has the potential to be a satisfactory electrode for decomposition of organic dyes in aqueous solution.

Synthesis of CuO/g‐C3N4 Composite with High Anti‐Interference Ability for Enhanced Fenton‐Like Catalysis

AbstractThe combination of semiconductors and transition metal compounds for Fenton‐like application has been widely reported. However, there are still some problems that can be further studied such as the optimization of metal species and in‐depth research of mechanism. In this paper, using melamine and copper acetate as raw materials, a kind of composite of copper oxide and graphitic carbon nitride (CuO/g‐C3N4) is synthesized by a facile hydrothermal method. The synthetic conditions such as type of transition metal salt and ratio of raw material are further optimized. With the presence of H2O2, the CuO/g‐C3N4 composite shows exceptional broad‐spectrum Fenton‐like catalytic performance against the organic dyes in aqueous solution within a wide pH range, and the highest degradation rate of organic dyes can reach 99% within 10 min. After eight times of recycling, the catalytic activity of the composite can still remain more than 85%. More importantly, the CuO/g‐C3N4 composite presented excellent anti‐interference ability toward heavy metal ions and complex pollutants. Finally, the enhanced Fenton‐like catalytic mechanism is illustrated in detail.

Facile preparation of porphyrin@g-C3N4/Ag nanocomposite for improved photocatalytic degradation of organic dyes in aqueous solution

In the quest of improving the photocatalytic efficiency of photocatalysts, the combination of two and more semiconductors recently has garnered significant attention among scientists in the field. The doping of conductive metals is also an effective pathway to improve photocatalytic performance by avoiding electron/hole pair recombination and enhancing photon energy absorption. This work presented a design and fabrication of porphyrin@g-C3N4/Ag nanocomposite using acid-base neutralization-induced self-assembly approach from monomeric porphyrin and g-C3N4/Ag material. g-C3N4/Ag material was synthesized by a green reductant of Cleistocalyx operculatus leaf extract. Electron scanning microscopy (SEM), X-ray diffraction (XRD), FT-IR spectroscopy, and UV–vis spectrometer were utilized to analyse the properties of the prepared materials. The prepared porphyrin@g-C3N4/Ag nanocomposite showed well integration of porphyrin nanostructures on the g-C3N4/Ag's surface, in which porphyrin nanofiber was of the diameter in nanoscales and the length of several micrometers, and Ag NPs had an average particle size of less than 20 nm. The photocatalytic behavior of the resultant nanocomposite was tested for the degradation of Rhodamine B dye, which exhibited a remarkable RhB photodegrading percentage. The possible mechanism for photocatalysis of the porphyrin@g-C3N4/Ag nanocomposite toward Rhodamine B dye was also proposed and discussed.

Efficient and Selective Removal of Organic Cationic Dyes by Peel of Brassica juncea Coss. var. gemmifera Lee et Lin-Based Biochar.

The design and preparation of cheaper, greener and more efficient adsorbents is essential for the removal of pollutants by adsorption. In this study, biochar was prepared from peel of Brassica juncea var. gemmifera Lee et Lin (PoBJ) using a facile, low-temperature and vacuum pyrolysis, and the adsorption mechanism toward organic dyes in aqueous solution was elucidated. The adsorbent was characterized by XPS, FT-IR and SEM, and zeta potential techniques. The adsorption ability of PoBJ biochar for cationic dyes (methylene blue, brilliant green, calcein-safranine, azure I, rhodamine B), anionic dyes (alizarin yellow R), and neutral dyes (neutral red) revealed that the biochar exhibited adsorption selectivity toward cationic dyes. The effects of different factors on the adsorption performance of PoBJ biochar, as well as the adsorption kinetics and thermodynamics, were further investigated by using methylene blue as the model adsorbate. These factors included temperature, pH, contact time and dye concentration. The experimental results showed that BJ280 and BJ160 (prepared at 280 °C and 160 °C, respectively) possessed relatively higher adsorption capacity of 192.8 and 167.40 mg g-1 for methylene blue (MB), respectively, demonstrating the possibility of utilization of PoBJ biochar as a superior bio-adsorbent. The experimental data of BJ160 toward MB were correlated with various kinetic and isothermal models. The results indicated that the adsorption process was consistent with the Langmuir isotherm model and nonlinear pseudo-second-order kinetic model. Thermodynamic parameters indicated that the adsorption of MB onto BJ160 was exothermic. Thus, the low-temperature prepared PoBJ biochar was an environmentally friendly, economic and efficient cationic dye adsorbent.

Efficient adsorption of methyl orange and methylene blue dyes by a novel carbazole-based hyper-crosslinked porous polymer

In this paper, a new type of carbazole-based hyper-crosslinked porous polymer (HCP-CP) was prepared through a very simple “knitted” method. The obtained novel polymer HCP-CP has a good adsorption property of methyl orange (MO) and methylene blue (MB) organic dyes in aqueous solution due to its high surface area and rich nitrogen atoms. The effect of pH, adsorption time, different initial concentration of dyes and adsorption reusability were investigated in detailed. The optimum pH is 8 for the adsorption of MB and 6 for the adsorption of MO, respectively. Under the best condition, the Langmuir model fitted the adsorption isotherm well and the adsorption behavior follow pseudo-second-order kinetics. The maximum adsorption capacity of HCP-CP for cationic dye MB (qmax=751.88 mg/g) is more than twice higher than that of anionic dye MO (qmax=274.73 mg/g). These capacity differences may be owing to the stronger electrostatic interaction between the negatively charged nitrogen atoms of HCP-CP with the cationic dye MB than that of MO. Moreover, the used polymer HCP-CP still retain a removal percentage above 92% after 5 times adsorption-desorption recycle. Therefore, this work provided a convenient synthetic route to develop a novel hyper-crosslinked polymer with high adsorption capacity for the entrapment of dyes from aqueous solution.

Synthesis of zinc-based metal–organic framework as highly efficient photocatalyst for decomposition of organic dyes in aqueous solution

Synthesis of zinc-based metal–organic framework as highly efficient photocatalyst for decomposition of organic dyes in aqueous solution

Degradation of Methylene Blue Using Fly Ash as a Heterogeneous Fenton Catalyst

Fly ash was used as a heterogeneous Fenton catalyst to degrade methylene blue in aqueous solution. The influence off key operating parameters on the degradation efficiency, including the concentrations of hydrogen peroxide and methylene blue, catalyst dosage, and the initial pH, were studied. The optimal degradation conditions were 2 mmol/L hydrogen peroxide, 4 mg/mL of fly ash, and pH 3. Under these conditions, the degradation efficiency was approximately 93% within 4 h. The degradation of methylene blue by heterogenous Fenton process followed the pseudo-first order kinetics and the activation energy shows that the reaction is thermodynamically feasible. Fly ash demonstrated acceptable reusability after 3 successive cycles. The results in the present study indicated that fly ash is a potent cost-effective catalyst for the degradation of organic dyes in aqueous solution by a heterogeneous Fenton process.

TiO2-modified g-C3N4 nanocomposite for photocatalytic degradation of organic dyes in aqueous solution

In the current study, a direct S-scheme titanium dioxide/graphitic carbon nitride (TiO2/g-C3N4) heterojunction structure was fabricated via simultaneous calcination of TiO2 precursors and g-C3N4. Guava leaf extract was utilized as a reductant for TiO2 production through a green synthetic method, and g-C3N4 was prepared by thermal decomposition of melamine. The pristine and nanocomposite photocatalysts were characterized by XRD, FTIR, BET, TGA, HRTEM, UV–vis DRS, and PL to elucidate their physicochemical properties. The photocatalytic activity of synthesized photocatalysts was examined through the degradation of rhodamine B (RhB) and methylene blue (MB) dyes under simulated solar light irradiation. The nanocomposite exhibited commendable photocatalytic performances with 96% degradation efficiency of RhB attained in 120 min and 95% degradation efficiency of MB achieved in 150 min. The enhanced photocatalytic activities were attributable to visible light-harvesting characteristics and the formation of an S-scheme heterojunction system between two catalysts which promotes interfacial charge separation efficiency and longer charge carrier lifespan. After 4 consecutive cycles, the degradation efficiencies of both RhB and MB remained above 85%. According to the trapping experiments, OH• and O2•− radicals were critical in the degradation of RhB, while h+ and O2•− radicals were dominant in the degradation of MB. The nanocomposite was also tested for elution of actual water pollutants by combining two dyes, and above 90% degradation efficiencies were achieved for both dyes after 240 min.

Effects of pH, Metal Powder and Their Magnetic Properties on the Removal Efficiency of Organic Dyes in Aqueous Solution

Organic dyes in wastewater pose serious threats to public health and ecological systems and, therefore, it is critical to search for a strategy to handle them. In this study, we investigated systematically the effects of acidity and magnetic metal powders on the removal of organic dyes in aqueous solution. The results demonstrate that the pH is a determining factor for the removal of organic dyes in addition to the coordination interaction between organic dyes and metal ions dissolved from magnetic metal powders.

Fabrication of activated carbon from polyethylene terephthalate plastic waste (PET) and their application for the removal of organic dyes in aqueous solution

Synthetic plastics have been considered as non-biodegradable materials. Polyethylene terephthlate (PET), one types of synthetic plastics, is commonly employed in many daily products. However, the end-use of the PET-based products is usually discarded to the environment, which causes serious problems to the ecosystem and human health. In this work, PET plastic waste was utilized to fabricate the activated carbon using the physical activating approach. The CO2 gas was used as activating agent. The effects of activating temperature, carbonizing and activating time on the surface areas of activated carbon were investigated. The prepared activated carbon was well-characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), FTIR, and BET. The resultant activated carbon prepared from the FET plastic waste revealed high absorption toward methylene blue in aqueous solution in a wide range of pH solutions. The fabrication of activated carbon from the plastic waste not only address the environmental issues, but also produce high-value activated carbon for the environmental remediation.

BODIPY-linked conjugated porous polymers for dye wastewater treatment

As a new family of functional porous materials, conjugated porous polymers (CPPs) with tuneable porosities and molecular architectures show great potentials in adsorption, light harvesting, and catalysis applications. This paper describes the incorporation of strong visible-light absorbing BODIPY molecules into the skeleton of CPPs via Sonogashira coupling reactions. The obtained CPPs displayed integrated properties of high surface area, hierarchical porous structures and strong visible-light absorption. As a result, the CPPs showed relatively high adsorption capacity and high photocatalytic degradation efficiency towards organic dyes. Mechanism studies revealed that the CPPs enabled the generation of singlet oxygen species under light irradiation, accounting for the main driving force for the dye degradation. This study provides a new route for the development of organic adsorbents and photocatalysts for water treatment and purification. • Conjugated porous polymers consisting of BODIPY skeletons were synthesized. • The CPPs demonstrated hierarchical porosity and strong visible light absorption. • The CPPs showed high adsorption capacity towards organic dyes in aqueous solution. • The CPPs can be used as photosensitizers for photodegradation of organic dyes.

Dynamics of diffusion-limited photocatalytic degradation of dye by polymeric hydrogel with embedded TiO2 nanoparticles

Theoretical model has been developed for the diffusion-limited photocatalytic degradation of organic dye in aqueous solution by composite hydrogel filament with embedded photocatalyst nanoparticles. The model included transition of dye molecules from the supernatant solution into the composite hydrogel, diffusion of the dye inside and pseudo first-order reaction of dye photocatalytic degradation. Theoretical model was verified by the experimental studies of the methyl orange dye photocatalytic degradation in aqueous solution by composite polyacrylamide hydrogel different degrees of crosslinking with embedded commercial TiO2 nanoparticles Degussa/Evonik P25. The integral rate of the dye concentration diminishing of the supernatant solution can be nicely fitted by a single exponential decay function with an apparent kinetic constant of dye photocatalytic degradation reaction. The dependence of the apparent kinetic reaction constant, the diffusion coefficient of dye through hydrogel and the value of the “true” kinetic reaction constant has been discussed.

A multifunctional and environmentally safe superhydrophobic membrane with superior oil/water separation, photocatalytic degradation and anti-biofouling performance

Wastewater is typically complicated with spilled oil, water soluble toxic dyes and microorganisms, making it hard to be processed and causing a significant threat to the environmental safety and human health. In this paper, we demonstrate a simple solution immersion method to obtain a multifunctional cellulose-based membrane (CBM) that possesses both superhydrophobicity with a water contact angle of 163° and superior functionalities including self-cleaning, oil–water separation, anti-biofouling, and photocatalytic degradation capabilities. The achievement of separation efficiency (96%), comparatively high flux (141 L·m−2·h−1) and recyclable (7 times) oil/water separation performance is attributed to the robust superhydrophobicity enabled by the synergy of metal oxide (i.e., CuO) nanostructure coating and stearic acid (SA) modification. The superhydrophobic CBM also preferentially adsorbs organic dyes in aqueous solution, e.g., methylene blue (MB), promoting their efficient decomposition (about 70.3% of MB decomposed in 3 h) with high recyclability under UV irradiation. Most remarkably, the CBM exhibits superior anti-biofouling capability and persistently resists the algae adhesion in long duration (over 20 days), as a result of the self-cleaning ability as well as the antimicrobial property of CuO nanoparticles. Our finding here paves the way to use simple, cost-effective, environmentally safe, and reliable method to fabricate multifunctional materials for wastewater treatment in complex environments.

Hybrid Amino Acid‐TiO2 Materials with Tuneable Crystalline Structure and Morphology for Photocatalytic Applications

AbstractA method to produce hybrid organotitanias, both as thin films and suspensions, showing excellent photocatalyic activity in the degradation of organic dyes in aqueous solutions under visible light irradiation is disclosed. This method is based on the in situ incorporation of an amino acid, l‐tyrosine, during the synthesis of the titanias owing to its coordination and co‐condensation with the titania precursor under acidic conditions. This methodology allows the fine ‐tuning of their crystalline structure, size, and shape by simply varying the pH of the synthesis gel, leading to anatase nanoparticles of ≈5 nm and surface areas of ≈200 m2 g−1 at pH = 2.2, while highly crystalline rutile nanorods are formed at pH = 0. The incorporation of l‐tyrosine to both anatase nanoparticles and rutile nanorods enables these materials to absorb light in the visible range due to both the decrease in their band gap, as compared to the reference materials, and the presence of additional absorption edges at wavelengths higher than 400 nm. Consequently, the photocatalytic activity of both hybrid anatase nanoparticles and rutile nanorods exhibits a 120% enhanced photocatalytic efficiency, as compared to that of l‐Tyr‐free titanias and the commercial P25, which confirms their potential application in water remediation.

A novel meso-tetrakis(2,4,6-trimethylphenyl) porphyrinato ([Zn(TMP)(4,4′-bpy)]) complex: Synthesis, characterization, and application

A new metalloporphyrin (4,4′-bipyridine)meso-tetrakis(2,4,6-trimethylphenyl) porphyrinato) zinc(II) ([Zn(TMP)(4,4′-bpy)]) (3) was obtained by reacting meso-tetrakis(2,4,6-trimethylphenyl)porphyrinato) zinc(II) [Zn(TMP)] (2) and 4,4′-bipyridine (4,4′-bpy). The starting material meso-tetrakis(2,4,6-trimethylphenyl)porphyrine (H2TMP, 1) as well as complexes (2 and 3) were characterized by the means of microanalysis, 1H NMR, and ESI-MS techniques. The molecular structure of the final complex (3) was also confirmed by single crystal X-ray crystallography. Detailed photo-physical and electrochemical properties of the complexes were also determined. The oxidative degradation ability of complexes (2 and 3) was evaluated and compared against an organic dye (calmagite). When used as catalyst, complex (2) showed better efficiency ~ 48% than the complex (3) (41%). Overall, this work not only explores the ability of metalloporphyrin to degrade organic dyes in aqueous solution, but also showed that the degradation ability of a metalloporphyrin complex can be fine-tuned by varying axial ligand.

Low-cost and facile fabrication of recyclable and reusable waste-based geopolymer for visible-light photocatalysis degradation

The development of a cost-effective and highly reusable visible-light responsive photocatalyst is necessary for reducing the costs of contaminant photodegradation. In this study, a novel visible-light driven waste-based loaded-geopolymer photocatalyst was prepared by a facile method. CdS nanoparticles were successfully loaded in the geopolymer slice by geopolymerization, and the optimal proportions of raw materials (CdS, Fe2O3, drinking water treatment residual, granulated blast furnace slag) were determined. The results indicated that the waste-based geopolymer loaded with 4 wt% CdS achieved the best photocatalytic performance of organic dye in aqueous solution. Geopolymer slice provided an easily recyclable and reusable carrier for CdS nanoparticles in the photocatalytic process that efficiently separated the photogenerated charges. In this sample, the recombination of photogenerated electron-hole pairs and photocorrosion of CdS were reduced, which effectively enhanced the reusability of loaded geopolymer. Overall, this work presents an effective and facile method for the rapid fabrication of visible-light driven loaded photocatalyst and provides a strategy by which the recyclability of photocatalyst could be enhanced.

Role of pH on Nanostructured SERS Active Substrates for Detection of Organic Dyes.

Surface Enhanced Raman Spectroscopy is commonly used as analytical improvement to conventional Raman spectroscopy, able to respond to qualitative diagnostic enquiries, which involve low-concentrated molecular species in complex matrix. In this paper, we described fabrication, characterization and testing of a type of SERS-active substrates realized specifically to detect pigments in work of art. In particular, we detailed the SERS activity of nanostructured noble metal films deposited by pulsed laser ablation onto glass and polishing sheets substrates. The SERS response of the substrates was tested against the presence of some organic dyes in aqueous solutions. Measurements were performed at different pH values, in acidic or basic range, in order to investigate its role in the adsorption mechanism, thus fostering the SERS amplification. In addition, we checked the possible deterioration of the structural properties of the substrates that could occur in presence of alkaline or acidic environment. SERS activity of the substrates was tested against a commonly dye used as a SERS standard (Blue Methylene). Thereafter, substrates have been tested on two organic dyes (Alizarine red-S and Brazilwood), which had proven to be Raman active but present also either a weak Raman scattering cross section and/or a high fluorescence emission. The substrates have proven effective in amplifying Raman scattering of all dyes, quenching troubling fluorescence effects. Furthermore, they have proven to be stable in the pH range between 3 and 11. Furthermore, we carry out of vibrational DFT-calculation of dyes that provide a complete description of the observed SERS spectra.