Anionic Dye Methyl Orange Research Articles

Polyethyleneimine-grafted polyphosphazene microspheres for rapid and efficient capture of anionic dyes from wastewater

Developing novel adsorbent to capture organic contaminants from wastewater rapidly and efficiently is highly desirable for waste treatment and environmental restoration. Herein, we reported a new amino-rich spherical adsorbent (PZS-PEI) for highly-efficient uptake of anionic dyes from aqueous solution. The PZS-PEI adsorbent was fabricated through a two-step process including synthesis of PZS-Cl microspheres via room temperature polymerization of hexachlorocyclotriphosphazene with bis(4-hydroxyphenyl) sulfone and subsequent surface grafting reaction of PZS-Cl microspheres using branched polyethyleneimine (PEI). The microstructure of as-obtained PZS-PEI microspheres was fully characterized by scanning electron microscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, zeta potential, and N2 adsorption test. The adsorption performance of the PZS-PEI microspheres towards organic dyes was evaluated through carrying out a series of studies including various influence factor analysis, adsorption isotherm, kinetics, and thermodynamics. Results show that the PZS-PEI adsorbent owned good adsorption selectivity towards anionic dyes, and the maximum adsorption capacities for methyl orange (MO), acid chrome blue K, eosin-Y reached 190.29, 152.90, and 92.34 mg/g at 25 °C, respectively. In addition, the uptake behavior of organic dye by the PZS-PEI adsorbent conformed to Freundlich isotherm and pseudo-second order kinetic model, and the adsorption process followed a three-stage intraparticle diffusion mode with an endothermic and spontaneous characteristic. Electrostatic interaction and hydrogen bonding were responsible for the highly-efficient adsorption of the PZS-PEI adsorbent towards typical anionic dye MO.

Tunable amine-functionalized silsesquioxane-based hybrid networks for efficient removal of heavy metal ions and selective adsorption of anionic dyes

By changing the acid scavenger from NEt3 to NaHCO3, two novel kinds of amine-functionalized silsesquioxane (SQ)-based hybrid networks (PCS-N1, PCS-N2) with different molar ratios of –NH2/NH– and NH3+ were successfully prepared via nucleophilic substitution of octa(3-chloropropyl) silsesquioxane (SQ-Cl8) with triaminoethylamine, respectively. Both networks were fully characterized by FTIR, SEM, TEM, XPS, BET, TGA, WCA and solid-state 13C and 29Si NMR spectra. No porosity was observed for these two hybrid networks; however, they exhibited good thermal stability and hydrophilicity. To our surprise, they strongly adsorb heavy metal ions due to ion exchange and coordination. The adsorption capacities for Ag+ and Hg2+ are as high as 358 ± 6 and 721 ± 5 mg g−1, respectively. More interestingly, PCS-N1 can selectively adsorb the anionic dye methyl orange with a capacity as high as 731 ± 13 mg g−1. Furthermore, they regenerate easily and offer potential for water purification. This work provides a new approach to prepare and tune amine-functionalized SQ-based networks for multipurpose.

Aramid nanofibers/Bacterial cellulose nanocomposite aerogels for high-efficient cationic dye removal

Aramid nanofibers/Bacterial cellulose (ANFs/BC) nanocomposite aerogels have been successfully synthesized via a facile process. Benefiting from the hydrophilicity and negative charge on the surface, the aerogels could selectively adsorb cationic dye in effluent. Compared with slight adsorption of anionic dye methyl orange (MO), the aerogels exhibited high adsorption efficiency for cationic dye methylene blue (MB). The effect of aerogels synthesized by different mass ratios of BC and ANFs on the adsorption efficiency of MB were studied. The dyes removal efficiency (R%) towards MB was 98.8%, which was obviously higher than that of pristine BC aerogels (27.9%). The adsorption kinetic parameters suggested that it fitted the pseudo-second-order model (R2 > 0.99) well and the adsorption process followed the Langmuir model. Besides, the effect of diverse experimental conditions such as adsorption time and initial dyes concentration on the adsorption performance of aerogels was also investigated, the adsorption capacity of aerogels could reach 54.27 mg/g. Consequently, the excellent selective adsorption of ANFs/BC nanocomposite aerogels may exhibit a promising application in effluent treatment.

Zn(II)/Cd(II)-Based Metal-Organic Frameworks as Bifunctional Materials for Dye Scavenging and Catalysis of Fructose/Glucose to 5-Hydroxymethylfurfural.

Functional neutral metal-organic frameworks (MOFs) {[M(5OH-IP)(L)]}n [M = Zn(II) for ADES-4; Cd(II) for ADES-5; 5OH-IP = 5-hydroxyisophthalate; L = (E)-N'-(pyridin-3-ylmethylene)nicotinohydrazide) have been synthesized by a diffusion/conventional reflux/mechanochemical method and characterized by various analytical techniques. Crystals were harvested by a diffusion method, and single-crystal X-ray diffraction (SXRD) analysis revealed that an adjacent [M2(COO)2]n ladder chain generates isostructural two-dimensional network motifs by doubly pillaring via L. The bulk-phase purity of ADES-4 and ADES-5 synthesized by a versatile synthetic approach has been recognized by the decent match of powder X-ray diffraction patterns with the simulated one. Both ADES-4 and ADES-5 showed selective adsorption of cationic dyes methylene blue (MB), methyl violet (MV), and rhodamine B (RhB) over anionic dye methyl orange (MO) from water with good uptake and rapid adsorption. Utilization of ADES-4 as a chromatographic column filler for adsorptive removal of individual cationic dyes as well as a mixture of dyes has been demonstrated from the aqueous phase. Interestingly, ADES-4 is reusable with good stability, and it showed a dye desorption phenomenon in methanol. The probable mechanism of cationic dye removal based on insight from structural information and plausible supramolecular interactions has also been explored. Both MOFs also showed efficient catalytic transformation of fructose and glucose into the high-value chemical intermediate 5-hydroxymethylfurfural of industrial significance.

β-Ni(OH)2/NiS/TiO2 3D flower-like p-n-p heterostructural photocatalysts for high-efficiency removal of soluble anionic dyes and hydrogen releasing

An ideal way to have the best of both worlds for environmental protection and energy conservation should be to juggle photocatalytic degrading pollutants and producing hydrogen from the pollutant solution synchronously. Herein, we have designed and synthesized a new 3D flower-like p-n-p heterostructure β-Ni(OH)2/NiS/TiO2 as a photocatalytic device, which is ideally suited for both removal of anionic dye methyl orange (MO), and release of hydrogen from the MO solution driven by photoelectric conversion without the need for using noble metals. The formation structure with optimal molar ratio 0.01-β-Ni(OH)2/0.001-NiS/TiO2 shows superior photocatalytic activity for removal of anionic dye MO and releasing hydrogen, its removal efficiency can reach as high as 98% in 15 min and the production of hydrogen is about 7.2 μmolh−1 from the MO solution. Results and analyses show that the outstanding performances of the sample should be attributed to the synergistic effects on two aspects. One is the high efficient charge separation and transfer driven by the internal electric field at the interfaces of NiS/TiO2 and the exposed high energy {001} facets of TiO2. The other is the modifier β-Ni(OH)2 as an assistant sacrificial agent can play an important role of the holes transfer for charge carriers transport balance in the oxidation-reduction process, and the generated active species NiOOH also has a beneficial effect on degrading MO and releasing hydrogen.

Nanoscale transformation in CuS Fenton-like catalyst for highly selective and enhanced dye degradation

Herein, we have synthesized covellite, copper sulfide nanoparticles (CuS NPs) as an excellent Fenton-like catalyst via facile precipitation method. We studied the structural and compositional changes of CuS Fenton-like catalyst before and after Fenton reaction, in dark and visible light conditions. CuS catalyst exhibited cationic dyes (methylene blue and rhodamine) degradation under dark conditions, whereas under visible light illumination both cationic dyes (methylene blue and rhodamine) and anionic dyes (methyl orange and bromophenol blue) were degraded. Moreover, the degradation rate of both cationic and anionic dyes were enhanced under visible light illumination. XRD, UV–Vis-NIR and XPS spectral studies shown that CuS catalyst through Fenton reaction transformed into Cu2-xS and Cu2S in dark and light conditions, respectively. Studies using reactive oxygen species (ROS) scavengers suggest that hydroxyl radicals are active species for degradation of cationic dyes in dark, whereas superoxide radicals were active species for degradation of anionic dyes in visible light. On one hand, the nanoscale transformation of catalyst facilitated the degradation activity for many cycles, on the other it offered the possibility for selective and enhanced round the clock degradation of dyes

Box–Behnken design for the optimization of methylene blue and methyl orange removal from aqueous solution by activated carbon

In this work, experimental design approach was adopted for the optimization of the removal of anionic and cationic model dyes (methylene blue and methyl orange) by activated carbon. A Box–Behnken surface statistical design with three factors and three-level combined with response surface modelling was employed to maximize dyes removal from aqueous solution. Three factors were used; solution pH, dyes concentration and activated carbon ratio to aqueous volume. Experimental results showed that solution pH has a positive effect on the adsorption of MB and a negative effect on the adsorption of MO. MO adsorption was more influenced by dye concentration in solution compared to MB adsorption. On the other side, MB adsorption was more influenced by the mass ratio of activated carbon compared to MO adsorption. The mass ration of activated carbon influence more MB adsorption at low dye concentration. In addition, at low solution pH, MO adsorption depends strongly on its concentration in solution

Eco-Friendly and Economic, Adsorptive Removal of Cationic and Anionic Dyes by Bio-Based Karaya Gum-Chitosan Sponge.

A novel, lightweight (8 mg/cm3), conjugate sponge of karaya gum (Kg) and chitosan (Ch) has been synthesized with very high porosity (~98%) and chemical stability, as a pH-responsive adsorbent material for the removal of anionic and cationic dyes from aqueous solutions. Experimental results showed that Kg-Ch conjugate sponge has good adsorption capacity for anionic dye methyl orange (MO: 32.81 mg/g) and cationic dye methylene blue (MB: 32.62 mg/g). The optimized Kg:Ch composition grants access to the free and pH-dependent ionizable functional groups on the surface of the sponge for the adsorption of dyes. The studies on the adsorption process as a function of pH, adsorbate concentration, adsorbent dose, and contact time indicated that the adsorption capacity of MB was decreased with increasing pH from 5 to 10 and external mass transfer together with intra-particle diffusion. The adsorption isotherm of the anionic dye MO was found to correlate with the Langmuir model (R2 = 0.99) while the adsorption of the cationic MB onto the sponge was better described by the Freundlich model (R2 = 0.99). Kinetic regression results specified that the adsorption kinetics were well represented by the pseudo-second-order model. The H-bonding, as well as electrostatic interaction between the polymers and the adsorption interactions of dyes onto Kg-Ch sponge from aqueous solutions, were investigated using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, and the highly wrinkled porous morphology was visualized in depth by field-emission scanning electron microscopy (FE-SEM) analysis. Moreover, the samples could be reused without loss of contaminant removal capacity over six successive adsorption-desorption cycles. The hierarchical three-dimensional sponge-like structure of Kg has not been reported yet and this novel Kg-Ch sponge functions as a promising candidate for the uninterrupted application of organic pollutant removal from water.

Green iron oxides/amino-functionalized MCM-41 composites as adsorbent for anionic azo dye: Kinetic and isotherm studies

In this work, green iron oxide nanoparticles (FeONPs) were prepared from Fe(III) precursor and Camellia sinensis (black tea) extract, and were anchored on amino-functionalized mesoporous silica MCM-41. The multicomponent composite named BTFe/MCM-41-NH2 was characterized and applied in the adsorption of the anionic azo dye methyl orange. The results indicated that BTFe/MCM-41-NH2 is 11 times more adsorbent than MCM-41 and 2.5 times more adsorbent than MCM-41-NH2, showing the improved adsorption property of the multifunctional material. Adsorption parameters such as adsorbent dosage, initial dye concentration, pH and time, were screened for BTFe/MCM-41-NH2, a provided an experimental adsorption capacity at equilibrium of qe,exp = 105.3 mg g−1 at 298 K. Zeta potential measurements showed the favored electrostatic interaction with the negatively charged dye at acid pH when BTFe/MCM-41-NH2 is positively charged. Kinetic studies revealed pseudo-first-order model characteristic of reaction-controlled adsorption. The experimental data at equilibrium was fit by several adsorption isotherms models. Freundlich and Temkin were the most suitable isotherms to describe the prepared material, suggesting an adsorption through a heterogeneous surface with multiple sites of adsorption, such as protonated amino groups, FeONPs, besides the tea polyphenols that provided extra sites of adsorption through π-π interactions with the aromatic rings of the dyes.

Comparative study on the removal of different-type organic pollutants on three-dimensional hexagonal-tungsten trioxide/reduced graphene oxide nanorod arrays: adsorption and visible light photodegradation

A series of self-supporting three-dimensional (3D) hexagonal-tungsten trioxide/reduced graphene oxide (h-WO3/rGO) nanorod arrays photocatalyst are synthesized by simple hydrothermal method without substrate. By selecting cationic dye methylene blue (MB), amphoteric dye rhodamine B (RhB) and anionic dye methyl orange (MO) as model organic pollutants, the experiments indicate that the 3D h-WO3/rGO photocatalyst shows a synergistic effect of adsorption and photocatalysis under visible light irradiation for the removal of MB and RhB. WrG1 which adding 1 wt% graphene oxide (GO) during synthesis demonstrates optimal adsorption and degradation activity and the bandgap energy (Eg) of WrG1 is 2.02 eV. Adsorption removal efficiency of MB, RhB and MO are 96.0%, 62.4% and 10.9% and the total removal efficiency of MB, RhB and MO are 99.3%, 84.8% and 18.3% by 0.3 g/L WrG1, respectively. Moreover, holes (h+) were the main active species for the photocatalytic degradation of organic pollutants. This work revealed the adsorption and photocatalysis activity of three different charge dyes on the h-WO3/rGO, which facilitates in understanding the removal mechanism in combination with other analytical methods and the impact of photocatalyst chargeability on degradation of organic pollutants. The visible light bifunctional catalyst h-WO3/rGO as adsorbent and photocatalyst presents a great potential in removal cationic and amphoteric organic pollutant from wastewater without additional treatment under ambient conditions.

Anionic Dye Removal by Polypyrrole-Modified Red Mud and Its Application to a Lab-Scale Column: Adsorption Performance and Phytotoxicity Assessment

In this study, polypyrrole-modified red mud (PRM) was prepared for the efficient removal of anionic dyes (methyl orange and Congo red) from aqueous solutions. The phytotoxicity (bean sprouts) of the dye solution before and after dye removal was investigated. Adsorption kinetics confirmed that the adsorption of methyl orange (MO) and Congo red (CR) on PRM was controlled by chemical reactions between the functional groups of polypyrrole and dyes. From Langmuir isotherm fitting, we found the theoretical adsorption capacities of MO and CR on PRM were 194.1 and 314.9 mg/g, respectively. The adsorption progress of MO and CR on PRM was found to be spontaneous and endothermic. The column studies demonstrated that, under dynamic flow, the PRM can efficiently remove MO and CR from aqueous solution, with adsorption capacities of 31.08 and 55.04 mg/g, respectively. In the toxicity test, the phytotoxicity of the column effluents (after dye removal) was significantly lowered compared to the initial dye influents. After the removal of MO and CR, the average root length of bean sprouts was increased from 3.30 cm to 5.18 cm and from 3.01 cm to 7.00 cm, respectively. These findings highlighted the efficient removal of dyes by PRM from aqueous solution, demonstrating the possible application of PRM for the removal of dye from dye-contaminated wastewaters.

Enhanced adsorptive removal of toxic anionic dye by novel magnetic polymeric nanocomposite: optimization of process parameters

The novel magnetic manganese ferrite/polyaniline nanocomposite (MnFe2O4-PANI-NC) was prepared for eradication of toxic anionic methyl orange (MO) dye from wastewater at almost neutral pH condition by impregnating polyaniline onto manganese ferrite. The characterization properties of MnFe2O4-PANI-NC was found by XRD, FEGSEM, TEM, FTIR, VSM, and BET analysis to analyze the adsorption process. The MO dye removal efficiency by sono-assisted adsorption was found to be 90.03% at solution pH 6.0 and sonication time 15 min, whereas the batch stirring and shaking gives the MO dye removal of ∼65% to ∼74% at same experimental condition. The adsorption kinetics followed pseudo-second order kinetics model with additional effect of intra-particle diffusion. The linear fitting of isotherm model followed Langmuir isotherm with equilibrium adsorption capacity of 175.44 mg/g at room temperature. The MO dye adsorption mechanism onto MnFe2O4-PANI-NC can be described by the synergistic effect of electrostatic interaction and π–π dispersive bonding between anionic MO dye molecules and positively charged MnFe2O4-PANI-NC surface. The central composite design (CCD) predicts the maximum MO dye removal of 99.01% at optimum condition of sonication time 14 min, MnFe2O4-PANI-NC dose 0.5 g/L and initial methyl orange (MO) dye concentration 10.0 mg/L. The MnFe2O4-PANI-NC is found to be stable even after 5th consecutive cycle of adsorption-desorption without compromising its adsorptive potential. Thus the fabricated MnFe2O4-PANI-NC can be a potential adsorbent material for sono-assisted removal of MO dye for large scale application due to less dependency on solution pH, facile fabrication technique, and rapid as well as decent dye uptake capacity.

Mesoporous composite Ni-C-N/SA for selective adsorption of methylene blue from water

A mesoporous Ni-C-N/Silica aerogel (Ni-C-N/SA) was prepared by impregnation of the cationic [Ni(tepa)]2+ complex onto a negatively charged silica aerogel support followed by suitable thermal treatment. And Ni-C-N/SA was applied as an adsorbent for selective adsorption of methylene blue (MB). When [Ni(tepa)]2+ loading is 20% and thermal treatment temperature is 400 °C (denoted “NiT20-400/SA”), the adsorption of MB by NiT20-400/SA is 54 mg/g, which is three times that of raw silica aerogel (RSA). However, little adsorption was observed for the anionic dye methyl orange (MO) and large sized cationic dye rhodamine B (RhB), demonstrating that NiT20-400/SA showed selective adsorption for MB. The nitrogen adsorption/desorption results demonstrate that the total pore volume of NiT20-400/SA is about 1.27 cm3/g, which is 25.7% higher than that of the RSA. The pore size distribution also changed from a wide range pore size distribution (13–126 nm) in the RSA to a narrow range mesoporous distribution (mainly 5–15 nm) in NiT20-400/SA. All of these results are due to the “binder” effect of [Ni(tepa)]2+ on the RSA surface. XPS shows that multiple-doping with nickel, carbon and nitrogen (Ni-C-N) were successfully added to the RSA surface via the followed pyrolysis of [Ni(tepa)]2+. As temperature increases in the range 200–600 °C, Ni, C and N species undergo [Ni(tepa)]2+ → Ni-C-N → NiO changes process. The larger total pore volume, suitable pore size distribution, and the unique subject-object interaction between cationic dye and Ni-C-N components results in the increased adsorption capacity and selective adsorption of MB.

Preparation of MnO2 Loaded Hydrothermal Carbon-coated Electrospun PAN Fiber Membranes for Highly Efficient Adsorption and Separation of Cationic Dye

Hydrothermal carbonaceous materials and MnO2 have been proved to be promising adsorbents to remove organic dyes from wastewater. In this study, flexible MnO2 loaded hydrothermal carbon-coated electrospun polyacrylonitrile(AC/MnO2/PAN) fiber membranes were fabricated by a facile one-step hydrothermal method and activated by NaOH solution. The composite fibers exhibited large adsorption capacity toward cationic dyes and excellent mechanical properties. The adsorption performance can be fitted well with pseudo-second-order model and Langmuir isotherm model. The maximum adsorption for methylene blue(MB), methyl violet(MV) and malachite green(MG) are 1173.27, 1106.31 and 1129.89 mg/g, respectively, according to Langmuir fitting. The AC/MnO2/PAN fiber membrane also showed satisfactory performances for selective adsorption and recyclability. In addition, based on selective adsorption, the AC/MnO2/PAN fiber membranes that are repulsive to the anionic dye methyl orange(MO) can separate the MB/MO mixture solution by dynamic filtration. Thus, this work not only provides a facile strategy to fabricate large capacity adsorbents, but also demonstrates the potential applications in the dye wastewater treatment field.

Enhanced photocatalytic degradation of organic dyes by ultrasonic-assisted electrospray TiO2/graphene oxide on polyacrylonitrile/β-cyclodextrin nanofibrous membranes

Polyacrylonitrile (PAN)/β-cyclodextrin (β-CD) composite nanofibrous membranes immobilized with nano-titanium dioxide (TiO2) and graphene oxide (GO) were prepared by electrospinning and ultrasonic-assisted electrospinning. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD) confirmed that TiO2 and GO were more evenly dispersed on the surface and inside of the nanofibers after 45 min of ultrasonic treatment. Adding TiO2 and GO reduced the fiber diameter; the minimum fiber diameter was 84.66 ± 40.58 nm when the mass ratio of TiO2-to-GO was 8:2 (PAN/β-CD nanofibrous membranes was 191.10 ± 45.66 nm). Using the anionic dye methyl orange (MO) and the cationic dye methylene blue (MB) as pollutant models, the photocatalytic activity of the nanofibrous membrane under natural sunlight was evaluated. It was found that PAN/β-CD/TiO2/GO composite nanofibrous membrane with an 8:2 mass ratio of TiO2-to-GO exhibited the best degradation efficiency for the dyes. The degradation efficiency for MB and MO were 93.52 ± 1.83% and 90.92 ± 1.52%, respectively. Meanwhile, the PAN/β-CD/TiO2/GO composite nanofibrous membrane also displayed good antibacterial properties and the degradation efficiency for MB and MO remained above 80% after 3 cycles. In general, the PAN/β-CD/TiO2/GO nanofibrous membrane is eco-friendly, reusable, and has great potential for the removal of dyes from industrial wastewaters.

Microwave assisted green synthesis of p-type Co3O4@Mesoporous carbon spheres for simultaneous degradation of dyes and photocatalytic hydrogen evolution reaction

Carbon spheres decorated with cobalt oxide nanoparticles, which can interact with the visible light were prepared by facile microwave assisted green chemical protocol. The combination of cobalt and carbon spheres results in the formation of p-n heterojunction. Also, this combination was effective in the separation of photogenerated electron-hole pairs. The photocatalytic property of the material was evaluated by employing it for the degradation of both anionic dye methyl orange and cationic dye malachite green in water and it is also used for the hydrogen evolution reaction. Different mass ratios such as 2, 4, 6 and 8 wt% of Co-carbon spheres were employed in the degradation process. However, Co-carbon spheres with mass ratio 6% displayed the best photocatalytic performance. The decoloration and mineralization efficiencies were 89.4% ± 2.8 and 88.6% ± 3.2 after 40 min of treatment respectively for methyl orange and malachite green. Scavenger studies further revealed the photo generated holes as the main oxidant and the synergistic effect of cobalt and carbon for excellent photocatalytic efficiency of the material.

Selective removal of dual dyes from aqueous solutions using a metal organic framework (MIL-53(Al))

The adsorption process of the cationic dye Malachite Green (MG) and the anionic dye Methyl Orange (MO) onto an MOF, namely MIL-53(Al), was studied using several experimental parameters. Batch experiments were performed to investigate the feasibility of this MOF as a possible adsorbent for the removal of MG and MO from both single and binary-dye aqueous solutions. The experimental results revealed that MIL-53(Al) can quickly bind to both types of dyes with high removal efficiencies of more than 95%. The effects of different parameters, such as adsorbent dosage, initial concentration of the dye solution, pH of the solution and temperature for the adsorption process, were examined. Adsorption kinetic data were then fitted using pseudo first-order, pseudo second-order, and Eelovich models, with the results showing that the pseudo second-order model had the best fit for both dyes amongst all the models used in both single and binary-dye systems(R2 > 0.996). Moreover, adsorption isotherm models of Langmuir and Freundlich were studied and the isotherm data was found to be in good agreement with the Freundlich isotherm for both dyes. Thermodynamic studies on the change in Gibbs free energy, enthalpy and entropy were carried out and showed that the adsorption of both dyes was endothermic and spontaneous. The selectivity test for an equimolar binary-dye solution containing both MG and MO suggested the higher affinity of MIL-53(Al) towards MO over MG, as it reached a value of 13.58 under the optimum conditions. Finally, excellent reusability of MIL-53(Al) was shown by utilizing it for 4 cycles of adsorption–desorption with almost no reduction in the adsorption capacity, bringing about an additional examination of its applicability.

Hollow SnO2/Zn2SnO4 cubes with porous shells towards n-butylamine sensing and photocatalytic applications

The cube-shaped SnO2/Zn2SnO4 composites with hollow structure were synthesized using a facile solvothermal method followed by calcinations and applied as hazardous gas sensors and photocatalysts for the degradation of three different types of dyes. As-synthesized SnO2/Zn2SnO4 hollow cubes with a wall thickness of about 80 nm possessed plenty of pores, and average pore size was about 3.0 nm. The sensor based on SnO2/Zn2SnO4 hollow cubes displayed the response of 77.2 towards 100 ppm n-butylamine at the optimal operating temperature of 300 °C, which was 1.43-times larger than that of SnO2/Zn2SnO4 solid cubes and improved in comparison with previously reported values. Additionally, it exhibited great selectivity and long-term stability. For the photocatalytic performance, SnO2/Zn2SnO4 hollow cubes showed faster photocatalytic degradation efficiency towards the common cationic dye methylene blue, the anionic dye methyl orange and the neutral dye eriochrome black T than SnO2/Zn2SnO4 solid cubes under simulated sunlight. These excellent properties were originated from the porous surface, cube/cube junction and the hollow interior structure, which was highly advantageous to the mass transportation and reagent diffusion. It's worth mentioning that great reproducibility highlight the potential applications of the SnO2/Zn2SnO4 hollow cubes in monitoring inflammable and toxic gases, and photocatalytic degradation of pollution.

Kinetics and thermodynamic studies of Methyl Orange removal by polyvinylidene fluoride-PEDOT mats

We report the preparation of poly(3,4-ethylene dioxythiophene) (PEDOT)-modified polyvinylidene fluoride electrospun fibers and their use as a novel adsorbent material for the removal of the anionic dye Methyl Orange (MO) from aqueous media. This novel adsorbent material can be used to selectively remove MO on a wide pH range (3.0–10.0), with a maximum capacity of 143.8 mg/g at pH 3.0. When used in a recirculating filtration system, the maximum absorption capacity was reached in a shorter time (20 min) than that observed for batch mode experiments (360 min). Based on the analyses of the kinetics and adsorption isotherm data, one can conclude that the predominant mechanism of interaction between the membrane and the dissolved dye molecules is electrostatic. Besides, considering the estimated values for the Gibbs energy, and entropy and enthalpy changes, it was established that the adsorption process is spontaneous and occurs in an endothermic manner. The good mechanical and environmental stability of these membranes allowed their use in at least 20 consecutive adsorption/desorption cycles, without significant loss of their characteristics. We suggest that the physical-chemical characteristics of PEDOT make these hybrid mats a promising adsorbent material for use in water remediation protocols and effluent treatment systems.

Preparation of nanofiber aerogels by electrospinning and studying of its adsorption properties for heavy-metal and dyes

Developing novel and efficient adsorption materials to solve water pollution is a very challenging task for the sake of environmental protection and human health. Herein, an ultra-light and porous 3D nanofiber aerogels (NFA) has been prepared by freezing casting technology and cross-linking with epichlorohydrin(ECH) via short polyacrylonitrile (PAN)/polyetherimide (PEI) nanofibers, which features high mechanical stability and good mass transfer performance. Moreover, experiments show that the adsorption capacities of 3D nanofiber aerogels (NFA) for Cu(II), Cr(VI), As(V) and anionic dye methyl orange (MO) reach 242.71 mg/g, 214.14 mg/g, 258.36 mg/g and 183.06 mg/g, respectively. Importantly, the adsorbent still maintains considerable adsorption efficiency after seven adsorption-regeneration cycles.