Anionic Orange Research Articles

Eco-Friendly g-C3N4/Carboxymethyl Cellulose/Alginate Composite Hydrogels for Simultaneous Photocatalytic Degradation of Organic Dye Pollutants.

The presented study was focused on the simple, eco-friendly synthesis of composite hydrogels of crosslinked carboxymethyl cellulose (CMC)/alginate (SA) with encapsulated g-C3N4 nanoparticles. The structural, textural, morphological, optical, and mechanical properties were determined using different methods. The encapsulation of g-C3N4 into CMC/SA copolymer resulted in the formation of composite hydrogels with a coherent structure, enhanced porosity, excellent photostability, and good adhesion. The ability of composite hydrogels to eliminate structurally different dyes with the same or opposite charge properties (cationic Methylene Blue and anionic Orange G and Remazol Brilliant Blue R) in both single- and binary-dye systems was examined through adsorption and photocatalytic reactions. The interactions between the dyes and g-C3N4 and the negatively charged CMC/SA copolymers had a notable influence on both the adsorption capacity and photodegradation efficiency of the prepared composites. Scavenger studies and leaching tests were conducted to gain insights into the primary reactive species and to assess the stability and long-term performance of the g-C3N4/CMC/SA beads. The commendable photocatalytic activity and excellent recyclability, coupled with the elimination of costly catalyst separation requirements, render the g-C3N4/CMC/SA composite hydrogels cost-effective and environmentally friendly materials, and strongly support their selection for tackling environmental pollution issues.

Investigation of Visible and UV Light‐Induced Photocatalysis Properties of Oleic Acid‐Ligated Cobalt‐Mixed Magnesium Ferrite Nanoparticles for Photodegradation of Cationic and Anionic Dyes

Owing to numerous potential applications in multiple fields, the study of nanosized magnetic spinel ferrites has been gaining significance. Synthesis and characterization of high‐quality magnetic nanocrystals with narrow size distribution, enhanced magnetic saturation, and outstanding properties for bioenvironmental applications are presented in the current study. Nanoparticles of oleic acid‐ligated Co0.5‐mixed Mg0.5Fe2O4 were prepared by a simple thermal decomposition method. The effect of cobalt (Co2+) content on the structural, optical, magnetic, and thermal properties of magnesium ferrite was assessed by powder X‐ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT‐IR), and vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). High‐resolution transmission electron microscopy (HR‐TEM) and energy dispersive X‐ray (EDX) spectroscopy were used to determine morphology and composition, respectively. Nanoparticles produced are highly crystalline and homogeneous, having an average size of 10 nm, with large saturation magnetization (61 emu/g) and high magnetic moment. Photocatalytic properties of prepared nanocrystals were studied by degradation of anionic Orange II and cationic methylene blue (MB) dyes under UV and visible light radiations for different time intervals. The anionic Orange II dye exhibited higher degradation, up to 97.2% and 92.2%, within a 90‐minute time period of ultraviolet and visible light irradiation, respectively. The cationic MB dye also displayed significant degradation, up to 91.9% and 93.8%, within 300 min under UV and visible light sources, respectively. The synthesized OA‐ligated nanoparticles degrade cationic and anionic dyes more effectively than previously reported in the literature and, thus, can be prime candidates for effective photo catalytic dye degradation and waste water cleaning applications, through the harvesting of ambient solar energy.

Highly efficient photocatalytic degradation of hazardous organic and inorganic contaminants by heterogeneous nZVI-doped Al2ZnTiO6 double perovskite/g-C3N4 photocatalyst under visible light irradiation

Among the hazardous organic and inorganic pollutants, organic dyes, nitrate (NO3-), carbon dioxide (CO2), and toxic heavy metals (THMs) are four types of hazardous contaminants that have become a serious global problem. Recently, perovskite photocatalysts have shown high efficiency in removing water and air contaminants. In this research, zero-valent iron nanoparticles (nZVI)- doped Al2ZnTiO6 (AZTO) double perovskite/graphitic carbon nitride (g-C3N4(gCN)) nanocomposite (NC) was firstly synthesized by the sol-gel method as a new high-efficiency perovskite photocatalyst. Also, the influence of the main factors such as solution pH, reaction time, photocatalyst dosage, and contaminants concentration on the photocatalytic performance of the nZVI-doped Al2ZnTiO9/g-C3N4 nanocomposite was evaluated. Due to the unique features of the nZVI-doped Al2ZnTiO6/g-C3N4 structure and suitable band gap position, which is suitable for the efficient migration e-/h+ charges dissociation and the enhancement of photocatalytic activity, this nanocomposite showed effective performance to the elimination of methyl orange (MO) anion, and methylene blue (MB) cation dye, NO3-, CO2, and THMs contaminants. The UV–visible spectra showed the elimination efficiency of 88%, 87%, 80%, 72%, and 90% for methyl orange anion dye, methylene blue cation dye, nitrate, carbon dioxide, and toxic heavy metals in optimal experiment conditions, respectively. Also, IEC and GC analysis showed an efficiency of 60% for the photoconversion of nitrate to harmless nitrogen gas (N2) and 42% for the photoconversion efficiency of CO2 to Methane (CH4) gas fuel. Eventually, the nZVI-doped Al2ZnTiO6/g-C3N4 nanocomposite displayed good recyclability and high photocatalytic activity compared to recently synthesized photocatalysts by testing its photocatalytic property after five repetitions.

A novel tetrafluoroterephthalonitrile-crosslinked quercetin/chitosan adsorbent and its adsorption properties for dyes

A new tetrafluoroterephthalonitrile crosslinked quercetin/chitosan (T-QT/CS) adsorbent was successfully synthesized for the adsorption of both cationic and anionic dyes in water. The structure of the resulting T-QT/CS was characterized by FTIR, 13CNMR, TGA, BET, SEM, and XPS, and the surface-charge property of the T-QT/CS at different pH values was determined by the zeta potential measurement. It was found that the adsorption behavior of the T-QT/CS for the cationic methylene blue (MB) dye and the anionic orange G (OG) dye conformed to the pseudo-second-order kinetic model and the linear Langmuir isotherm model. Furthermore, basing on the linear Langmuir isotherm model, the T-QT/CS possessed good dye-adsorption ability, and the maximum adsorption capacities of the T-QT/CS for the MB (at pH=9) and OG (at pH=2) at 303 K were 917.4 mg/g and 349.9 mg/g, respectively. The thermodynamic experimental results showed that the MB and OG adsorption processes of the T-QT/CS were endothermic and spontaneous. In addition, the T-QT/CS exhibited good reused ability for the adsorptions of MB and OG even after five adsorption-desorption experiments.

Thermodynamic analysis of methyl orange anion association with α-cyclodextrin using a conductometric approach

The electrical conductivities of aqueous solutions of the azo dye methyl orange (sodium salt) were measured at 25.0 °C in the concentration range between 2.103 × 10–4 and 9.255 × 10–4 mol L−1. Molar conductivity values fit the Debye–Hückel–Wager equation for a symmetric electrolyte. The estimated value of the molar conductivity of the sodium salt of methyl orange at infinite dilution is found to be 77.93 ± 0.38 S cm2 mol−1. The calculated ionic conductivity at infinite dilution of the anion of methyl orange is 27.82 S cm2 mol−1. Using the same methodology, a thermodynamic analysis of the association between methyl orange anion and α-cyclodextrin was conducted at 20.0, 25.0, 32.0, and 40.0 °C. The measured molar conductivities decreased as the mole ratio of α-cyclodextrin to methyl orange went below 3. The conductivity measurements were analysed using a model 1:1 stoichiometry at the four different temperatures. The values of the thermodynamic quantities ∆H° and ∆S° for the inclusion process were calculated by using Van’t Hoff plot, their values are − 27.35 kJ mol−1 and − 9.70 J K−1 mol−1 respectively. For this case of the studied inclusion process this inclusion was disfavored through entropy change and favored through enthalpy change.

Ternary Metal-Alginate-Chitosan Composites for Controlled Uptake of Methyl Orange

Three ternary metal composites (TMCs) with iron nitrate, aluminum nitrate, and copper nitrate (Fe-TMC-N, Al-TMC-N, Cu-TMC-N) were synthesized and their physicochemical properties were investigated. Characterization of the TMCs was achieved by elemental analysis (XPS), infrared (IR) spectroscopy and thermogravimetric analysis (TGA). The surface charge of the TMCs was estimated from the point-of-zero-charge (PZC), which depended on the type of metal nitrate precursor. The adsorption properties of the TMCs showed the vital role of the metal center, where methylene blue (MB) is a cationic dye probe that confirmed the effects of surface charge for effective methyl orange (MO) anion dye uptake. MB uptake was negligible for Al-TMC-N and Cu-TMC-N, whereas moderate MB uptake occurs for Fe-TMC-N (26 mg/g) at equilibrium. The adsorption capacity of MO adopted the Langmuir isotherm model, as follows: Al-TMC-N (422 mg/g), Cu-TMC-N (467 mg/g) and Fe-TMC-N (42 mg/g). The kinetic adsorption profiles followed the pseudo-second order model. Generally, iron incorporation within the TMC structure is less suitable for MO anion removal, whereas Cu- or Al-based materials show greater (10-fold) MO uptake over Fe-based TMCs. The dye uptake results herein provide new insight on adsorbent design for controlled adsorption of oxyanion species from water.

Adsorption behaviors of modified clays prepared with structurally different surfactants for anionic dyes removal

In this study, the properties and adsorption behaviors of organoclays synthesized with two structurally different surfactants having the same carbon chain length (hexadecyltrimethylammonium bromide (HDTMAB) and benzyldimethylhexadecylammonium chloride (BDHAC)) were evaluated. The structural properties of the synthesized organoclays were examined using Fourier-transform infrared spectroscopy, zeta potential analysis, X-ray diffraction, and N2 adsorption-desorption test. The modified clays with increased surfactant loadings (from 0.5 CEC to 3 CEC) were prepared to find the optimal surfactant loading. As a result, 1.5 cation exchange capacity (CEC) was found to be the optimal surfactant loading. The organoclay prepared using HDTMAB (H-Bt) exhibited the maximum adsorption capacity of 114.3 mg/g for anionic Orange G dye, which was 1.74 times higher than that of the organoclay prepared using BDHAC (B-Bt). Furthermore, in the presence of a mixture of cationic and anionic dye molecules in water, H-Bt tended to remove more of the cationic target compound than B-Bt (i.e., methylene blue (MB)), suggesting that H-Bt can serve as a more efficient adsorbent for the uptake of environmental contaminants in practical scenarios. Moreover, this study examined the effects of surfactant molecules on the structural properties of organoclays and their adsorption behaviors in the uptake of dye molecules.

Flocculation inspired combination of layered double hydroxides and fulvic acid to form a novel composite adsorbent for the simultaneous adsorption of anionic dye and heavy metals

Currently, simultaneous removal of anionic and cationic pollutants from combined pollution wastewater is a challenging subject. Here, a novel composite adsorbent which can simultaneously adsorb anionic azo dye and heavy metal cations was developed by flocculation inspired assembly of Mg2Al layered double hydroxides (LDH) and fulvic acid (FA). The results show that the negatively charged macromolecule FA is firmly intertwined with the positively charged LDH through electrostatic attraction and adsorption bridging. This composite adsorbent (Mg2Al LDH-FA) can effectively capture anionic Orange II by anion exchange adsorption derived from LDH component with the maximum adsorption capacity of 604 mg/g. Mg2Al LDH-FA also exhibits good adsorption performance for heavy metals due to the complexation with FA and surface precipitation on LDH. The adsorption isotherms of heavy metals coincided with Langmuir model or Freundlich model, and the adsorption capacities for Pb2+, Cu2+, Ni2+, Cd2+ could reach up to 661.5 mg/g, 116.3 mg/g, 117.3 mg/g, 235.2 mg/g respectively. Particularly, Mg2Al LDH-FA can simultaneously uptake Orange II and heavy metals from the stimulated combined pollution wastewater, moreover it shows higher adsorption capacity for each pollutant than that in the single pollutant case as the result of the synergistic adsorption effect between LDH and FA.

Photocatalytic hydrogen evolution on CdS–based composites derived from in situ carbonization of a sulfonic azo dye complex

Engineered CdS@NC composites were fabricated via the carbonization of a crystalline complex comprised by cadmium cations and methyl orange anions, [Cd(H2O)6(C14H14N3SO3)2] 1, and were developed as viable photocatalysts for enhanced hydrogen (H2) production under visible irradiation with a H2 evolution rate of ca. 7428.0 μmol h−1 g−1, which was relatively high for CdS–based nanomaterials reported hitherto.

Glow-discharge plasma enhanced coating and functionalization of needle-punched nonwoven PET filter media for textile wastewater decolorization

This study reports the use of glow-discharge plasma coated and functionalized PET needle-punched nonwovens as filter media for decolorization of textile dye-containing effluent. The investigation had been aimed at proving the possibility of GDP enhanced coating and functionalization (GDP processing) to produce better results for successfully replace such thermochemical finishing of PEI coat onto the primary PET fibers. The fiber surfaces functionalization with branched polymers such PEI has aroused much interest recently due to their unique properties as dye-immobilization absorber. For this study, the effect of processing time on the dye retention capacity of the functionalized PET nonwovens was investigated. Comparison was made between the most influential parameters of the basic, chemically and GDP processed PET nonwovens, such as: material thickness, air permeability, and puncture strength. The dye-retention capacity of the basic and functionalized nonwovens was determined by two synthetic water effluent – the anionic Orange G and the cationic Methylene Blue test-dyes have been used. The normal glow-discharge plasma processing in air as residual gas at 80 Pa provide the best possible anionic dye retention capacity. Based on this study, it was confirmed that this PEI coated and functionalized PET nonwoven could be used for the immobilization of anionic dyes from colored textile wastewater: the retention capacity from 4.16 to 5.57 mg/g with is comparable to the other available products used as adsorbent in dye-immobilization wastewater treatment.

Insight into the removal process mechanism of pharmaceutical compounds and dyes on plasma-modified biomass: the key role of adsorbate specificity.

The reason that some molecules, but not others, are easily adsorbed was not fully understood. In order to spotlight the effect of morphological structure and surface functional composition of adsorbate rather than focusing only on the nature of adsorbent as in most of literature reports, this work reports the biosorption of two dyes (anionic Orange G and cationic malachite green) and two pharmaceuticals (Ibuprofen and ampicillin) as target representative contaminants onto plasma-modified cocoa shell (CPHP) used as alternative low-cost adsorbent. As results, when molecules were mixed in solution and then exposed to a substrate, the factors that affect adsorption include the relative solvation of the adsorbates, the ability of each molecule to adhere to the surface, and the degree of interaction between the molecules once they were adsorbed. The maximum adsorbed amounts at 298K of OG, MG, IBP, and AMP were 23.96, 14.65, 13.99, and 06.66mg/g, respectively. The most solvated molecules may not adsorb rapidly to the surface, while comparatively, the less soluble molecules will aggregate, so as to maximize self-interactions via Van der Waals, hydrogen bonds or other interactions. This work demonstrated that the adsorbate intrinsic properties could play a significant role in the adsorption process. Hence, properties such as functional active groups, dimensions, and hydrophobicity were the determining parameters in the adsorption process mechanism. Accordingly, the pharmaceuticals biosorption mechanism involved π-π bonding, hydrophobic effect, electrostatic interaction, and van der Waals forces whereas the dye biosorption mechanism was dominated as well known by electrostatic attraction and hydrogen bonding phenomenon. Experimental parameters such as initial pH of solution and contact time were optimized. The optimum pH values were 2.0 for ibuprofen (IBP) and 7.0 for ampicillin (AMP). The kinetics of adsorption and the experimental isotherms data were analyzed using non-linear models. Results indicated that Avrami fractional order was the most successfully fitted model for pharmaceutical biosorption and based on the statistical values of SD and R2adj parameters, Liu isotherm was the most successfully fitted model.

Comparative studies of methyl orange adsorption in various metal-organic frameworks by nitrogen adsorption and positron annihilation lifetime spectroscopy

Abstract In this work, typical metal-organic frameworks (MOFs) MIL-101-Cr, MIL-53-Al and ZIF-8 with high specific surface areas were synthesized and applied in the removal of anionic dye methyl orange (MO) from water. Nitrogen adsorption and positron annihilation lifetime spectroscopy (PALS) were applied to study the pore characteristics of MOFs and their adsorption of MO, respectively. The specific surface areas of the synthesized MOFs are in the order MIL-101-Cr > ZIF-8>MIL-53-Al. The pore sizes of MOFs obtained from PALS are essentially the same as those from their crystal structure, suggesting that PALS is a useful probe to characterize the pore properties of MOFs. After MO adsorption in MOFs, the nominal mean pore sizes for MIL-101-Cr-MO and MIL-53-Al-MO from nitrogen adsorption are mainly attributed to the interspaces between grains because their inherent pores were occupied by MO molecules as revealed by PALS, while that of ZIF-8-MO represents the inherent pores and interspaces between grains. Langmuir adsorption of MO was found to occur in the MOFs, whereas the MO adsorption behaviors are different depending on the unique pore structures of specific MOFs. MIL-101-Cr and MIL-53-Al show the MO adsorption capacities of 196.08 and 100.0 mg/g due to their large specific surface areas and accessible pore windows, which can provide more accessible unsaturated metal sites. However, despite that the specific surface area of ZIF-8 is larger than that of MIL-53-Al, MO adsorption capacity in ZIF-8 is rather low because the size of its pore windows is smaller than MO dimension, which results in MO molecules inaccessible to the pores. Results showed that methyl orange anions (MO−) were electrostatically attracted by unsaturated metal sites in the cages/channel pores of MIL-101-Cr and MIL-53-Al in aqueous solutions, whereas MO was only adsorbed in the interspaces between grains in ZIF-8.

High-efficiency adsorption for both cationic and anionic dyes using graphene nanoribbons formed by atomic-hydrogen induced single-walled carbon nanotube carpets

Carbonaceous materials are considered as potential adsorbents for organic dyes due to their unique structures which provide high aspect ratios, hydrophobic property, large efficient surface area, and easy surface modification. In this work, graphene nanoribbons (GNRs) were prepared by atomic hydrogen-induced treatment of single-walled carbon nanotube (SWCNTs), which inspire the idea of cutting and unzipping the SWCNTs carpets with the modified in molecules prevent because of the unfolding of the side-walls. The unfolded spaces and uniform vertical arrangement not only enhance the active surface area, but also promote the electrostatic and π–π interactions between dyes and GNRs. The improved adsorption capacity of GNRs beyond original SWCNTs can be determined by the adsorption kinetics and isotherm, which are evaluated through adsorption batch experiments of the typical cationic methylene blue (MB) and anionic orange II (OII) dye, respectively. It is shown that the adsorption kinetics follow a pseudo second-order model while the adsorption isotherm could be determined by Langmuir model. The results reveal that the maximum adsorption capacities of GNRs for MB and OII are 280 and 265 mg/g, respectively. The GNRs present the highly efficient, cost effective, and environmental friendly properties for the commercial applications of wastewater treatment.

Synthesis and adsorption properties of amphoteric adsorbent HAx/CMC-yAl

Novel amphoteric microspheres adsorbents (HAx/CMC-yAl), based on carboxymethyl cellulose (CMC) modified with various amount of humic acid (HA) and cross-linker aluminum nitrate (Al(NO3)3), were synthesized facilely under mild conditions. Its adsorption properties toward representative cationic and anionic dyes were studied. The optimized adsorbent HA1.0/CMC-3Al was characterized and analyzed by fourier transform infrared spectroscopy, scanning electron microscopy, X-ray energy dispersive spectroscopy, thermogravimetric analysis and Zeta potentials. The effects of types of dye substrates, contact time, initial dye concentration, pH of the solution, and adsorbent dosage, on cationic methylene blue (MB) and anionic orange II (ORII) removal were systematically investigated. The HA1.0/CMC-3Al showed pH-sensitive and the maximum adsorption capacities toward MB and ORII were 76.92 and 71.43 mg g−1, respectively, within 300 min at pH 3 and 295 K. The swelling rate and the recylcing properties were also studied. The pseudo-second-order kinetic model and Langmuir isotherm provided better correlation with the experimental data for the adsorption of dyes onto HA1.0/CMC-3Al. The effects of coexistent NaCl and sodium dodecylbenzenesulfonate (SDBS) surfactant on a binary dye system (MB/ORII) were also investigated. The results indicated that the adsorption of dyes was inhibited by NaCl, while the adsorption of cationic dye was promoted by SDBS at given concentrations. In addition, the possible mechanism of adsorption process was proposed.

Modulation of valence band maximum edge and photocatalytic activity of BiOX by incorporation of halides

To better know the photocatalytic performance of bismuth oxyhalides (BiOX, X = Cl, Br, I) regulated by incorporation of halides within nanostructures, BiOX nanosheets were synthesized through morphology controllable solvothermal method and characterized systematically. The organic structural property greatly influences the photocatalytic activity of BiOX: 1) as for neutral molecular phenol, BiOX shows photocatalytic activity in the order of BiOCl > BiOBr > BiOI under simulated sun light irradiation, and the photo-oxidation kinetics follow Eley–Rideal mechanism; and 2) for adsorbed anionic orange II (OII) and cationic methylene blue (MB), BiOX shows photocatalytic activity in the order of BiOCl > BiOBr > BiOI, and the photo-oxidation kinetics follow Langmuir-Hinshelwood mechanism. The crystal structure of the catalyst also greatly influences the photocatalytic activity of BiOX: 1) The relative photo-oxidation power of O2•− radicals or HO radicals involved in this study were different which were quantitatively detected using typical radical trapping agent, separately; 2) The relative oxidation power of photogenerated holes (h+) in this study were in the order of BiOCl > BiOBr > BiOI, which may be ascribed to lowering the valence band maximum edge of BiOX through incorporation of halides as the atomic number of halides decreased. This study provides novel explanation for fabricating BiOX heterojunctions with tunable photocatalytic reactivity via regulating the halides ratio.

Highly Efficient Sorption of Methyl Orange by a Metal-Organic Resin-Alginic Acid Composite.

The composite anion-exchange material MOR-1-HA (metal-organic resin-1-alginic acid) was investigated as sorbent for the capture of the methyl orange anion (MO- ) from aqueous solutions. MOR-1-HA shows a remarkably high sorption capacity (up to 859 mg g-1 ) and rapid sorption kinetics, the fastest among the reported metal-organic sorbents. It is capable of absorbing MO- over a wide pH range (1-8) and, in addition, it exhibits significant MO- sorption affinity even in the presence of large excesses of competing anions (e.g., Cl- , NO3 - , SO4 2- ). The exceptional MO- -sorption properties of MOR-1-HA arise not only from its highly porous structure and easily exchangeable Cl- anions, but also from a multitude of interaction effects, such as electrostatic interactions between MO- and the NH3 + groups of the material, hydration/dehydration, hydrophobicity/hydrophilicity, size and capacity of generating lateral interactions, and intercalation as revealed by theoretical studies. An ion-exchange column with a stationary phase containing MOR-1-HA and silica sand showed high efficiency for the removal of MO- from various types of aqueous samples. The column can be readily regenerated and reused for many runs with minimal loss (2.3-9.3 %) of its exchange capacity. The simplicity of the MOR-1-HA/sand column and its high regeneration capability and reusability make it particularly attractive for application in the remediation of MO- -contaminated industrial wastewater.

BiOCl-montmorillonite as a photocatalyst for highly efficient removal of Rhodamine B and Orange G: Importance of the acidity and dissolved oxygen

A BiOCl-Mt material assembled from BiOCl and Na-montmorillonite (Na-Mt) was characterized by XRD, FT-IR, TEM, XPS and UV–vis DRS. Na-Mt was clearly demonstrated to be capable of improving BiOCl's photocatalytic performance. The focus was placed on the evaluation of BiOCl-Mt in the terms of photocatalytic activity for cationic Rhodamine B (RhB) and anionic Orange G (OG). Both can be removed more efficiently using BiOCl-Mt compared with pure BiOCl under ultraviolet light irradiation. Although hvb+ and O2− are the two primary reactive species, the improved photocatalytic degradation performance is primarily attributed to the enhanced separation of photogenerated charge carriers in the catalyst. The Bronsted acidity derived from montmorillonite acid sites and the dissolved oxygen in the solution are capable of promoting dye photocatalysis because they effectively capture the photogenerated electrons. Under optimized conditions, TOC mineralization with rates of 82.3% for RhB and 85.9% for OG was obtained in a BiOCl-Mt catalysed photocatalysis process. The mechanism responsible for the oxidative decomposition of the two different dyes is primarily hole-driven. BiOCl-Mt was stable during the process, with its structures remaining almost unchanged after it was recycled three times. Therefore, BiOCl-Mt will have a promising worldwide application in dye-containing wastewater treatment.

Electrocatalytic activity of a mononuclear yttrium(III)–methyl orange complex and Y2O2SO4 nanoparticles for adsorption/desorption of hydrogen

A new mononuclear yttrium(III) complex, [Y(MO)3(DMF)3(H2O)2] (where MO– is methyl orange anion (4-[(4-dimethylamino)phenyldiazenyl]benzenesulfonate)), was synthesized in an aqueous solution. The complex was characterized by elemental analysis, UV/Vis, FT-IR, and single-crystal X-ray crystallography. The yttrium oxysulfate nanoparticles (Y2O2SO4) were then prepared by calcination of [Y(MO)3(DMF)3(H2O)2]. The obtained nanoparticles were characterized by FT-IR, X-ray diffraction analysis (XRD), and field-emission scanning electron microscopy (FE-SEM). The hydrogen adsorption/desorption (Hads/Hdes) behavior of the Y(III) complex and Y2O2SO4 nanoparticles was studied at a carbon paste electrode (CPE) in H2SO4 by cyclic voltammetry (CV). The recorded voltammograms exhibited a pair of peaks corresponding to the adsorption/desorption of hydrogen for the Y(III) complex and Y2O2SO4 nanoparticles. The results show a reversible hydrogen adsorption/desorption reaction for both compounds. The voltammograms of the nanoparticles indicate an excellent cycling stability for the adsorption/desorption of hydrogen. In addition, the linear sweep voltammetry (LSV) technique was used to investigate the electrocatalytic activity of both compounds for the hydrogen adsorption reaction. The linear voltammograms of both compounds demonstrate the excellent electrocatalytic activity for the hydrogen adsorption reaction.

Biomass derived palygorskite–carbon nanocomposites: Synthesis, characterisation and affinity to dye compounds

Clay minerals can act as a uniform dispersion medium for nano-sized carbon particles. However, literature on the preparation and characteristics of palygorskite–carbon nanocomposites is scant. Using a hydrothermal carbonisation technique this study developed two nanocomposites on fibrous palygorskite from starch: the first without a post-synthesis treatment (Composite 1); and the second with an activation at 550°C for 3h (ramp at 10°Cmin−1) under CO2 environment (200mLmin−1) (Composite 2). A uniform dispersion of nano-scale carbon spheres was formed on partially destroyed palygorskite structures. Composite 2, which indicated the formation of graphitised carbon nanoparticles, generated a 17-fold greater specific surface area than Composite 1 and also created micro- and mesopores in its structure. The nanocomposites, especially in Composite 1, contained organic surface functional groups (CH, CC, CO) and indicated variable affinity to cationic and anionic dye compounds. While Composite 2 adsorbed a larger amount of anionic orange II dye (23mgg−1), Composite 1 adsorbed more cationic methylene blue (46.3mgg−1). Isothermal and kinetic modelling of the adsorption data indicated that in addition to electrostatic attraction for methylene blue adsorption on both nanocomposites, a pore diffusion mechanism was involved and the boundary resistance was greater for orange II than methylene blue adsorption. Being a material developed from green biomass (starch) and an abundant natural resource (palygorskite), these nanocomposites have immense potential for application in environmental remediation including in situ immobilisation of contaminants in soil.

Synthesis of P(NIPAM-co-Am)/Mesoporous Silica Composites and Their Temperature- Responsive Anion Exchange

The purpose of this study is to examine the structure and the temperature-responsive anion exchange property of amino-functionalized mesoporous silica coated with temperature-responsive copolymer, poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAM-co-Am)). For this purpose, the composites which contained 0, 10, or 20 wt% of Am were synthesized. From the TG results, it was found that the amounts of copolymer immobilized on the mesoporous silica were 1.6 - 2.6 wt%. XRD patterns revealed that the structures of composites were hexagonal and almost the same as that of original mesoporous silica without polymer. At low temperature the methyl orange (MO) anions adsorbed and desorbed reversibly with changing pH of the solution, while at high temperature the MO anions did not. This temperature, at which the amount of adsorbed MO anions changed considerably, shifted to the higher temperature side with increasing the amount of added Am.