Fabrication of carboxymethyl chitosan–hemicellulose resin for adsorptive removal of heavy metals from wastewater

Carboxymethyl chitosan–hemicellulose resin(CMCH) was synthesized by thermal cross-linking process and characterized by FTIR, TGA, and SEM. Subsequently, the adsorption properties of CMCH toward Ni(Ⅱ),Cd(Ⅱ), Cu(Ⅱ), Hg(Ⅱ), Mn(Ⅶ) and Cr(Ⅵ) were evaluated. Various factors affecting the uptake behavior such as pH, temperature, contact time and the initial concentration of the metal ions were investigated.The results showed that all adsorption processes fit the pseudo-second-order model and Langmuir isotherm equation. Significantly, the regeneration experiments showed CMCH can be used as a potentially recyclable and effective adsorbent for the removal and recovery of metal ions from wastewater.     

Prussian blue–gold nanoparticles-ionic liquid functionalized reduced graphene oxide nanocomposite as label for ultrasensitive electrochemical immunoassay of alpha-fetoprotein

In this work, poly(diallyldimethylammonium chloride) (PDDA) protected Prussian blue/gold nanoparticles/ionic liquid functionalized reduced graphene oxide (IL-rGO-Au-PDDA-PB) nanocomposite was fabricated. The resulting nanocomposite exhibited high biocompatibility, conductivity and catalytic activity. To assess the performance of the nanocomposite, a sensitive sandwich-type immunosensor was constructed for detecting alpha-fetoprotein (AFP). Greatly enhanced sensitivity for this immunosensor was based on triple signal amplification strategies. Firstly, IL-rGO modified electrode was used as biosensor platform to capture a large amount of antibody due to its increased surface area, thus amplifying the detection response. Secondly, a large number of Au-PDDA-PB was conjugated on the surface of IL-rGO, which meant the enrichment of the signal and the more immobilization of label antibody. Finally, the catalytic reaction between H₂O₂ and the IL-rGO-Au-PDDA-PB nanocomposite further enhanced the signal response. The signals increased linearly with AFP concentrations in the range of 0.01–100 ng mL⁻¹. The detection limit for AFP was 4.6 pg mL⁻¹. The immunosensor showed high sensitivity, excellent selectivity and good stability. Moreover, the immunosensor was applied to the analysis of AFP in serum sample with satisfactory result.     

Modified nanoporous magnetic cellulose–chitosan microspheres for efficient removal of Pb(II) and methylene blue from aqueous solution

Pyromellitic dianhydride-modified nanoporous magnetic cellulose–chitosan microspheres (PNMCMs) were designed and synthesized to introduce abundant carboxyl groups onto the basic microstructure. The novel microspheres were studied by scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Subsequently, a batch technique was applied to investigate various environmental parameters that could affect the adsorption behavior of the PNMCMs. Due to its nanoporous structure and large quantity of carboxyl groups, the cellulose/chitosan-based bioadsorbent exhibited excellent adsorption performance for removal of Pb(II) ions and methylene blue (MB) from aqueous solution, with maximum adsorption capacity of 384.6 and 833.3 mg/g, respectively. Furthermore, the adsorption kinetics and isotherms of Pb(II) ions and MB on PNMCMs obeyed the pseudo-second-order and Langmuir isotherm models, and the rate of adsorption was found to be controlled by film diffusion. Finally, the PNMCMs with adsorbed Pb(II) and MB could be easily regenerated using HCl, retaining removal capacity of almost 89% after six repeated uses.     

Fluorescent detection of cholesterol using β-cyclodextrin functionalized graphene

A fluorescence based cholesterol detection method has been developed using competitive host-guest interaction between graphene bound β-cyclodextrin (β-CD) with rhodamine 6G (R6G) and cholesterol. Fluorescence of β-CD incorporated R6G is quenched by graphene but is 'turned on' by cholesterol as it replaces R6G from the β-CD host.     

Gamma irradiation induced preparation of poly(acrylamide–itaconic acid)/zirconium hydrous oxide for removal of Cs-134 radionuclide and methylene blue

Adsorption experiments were carried out to investigate the removal of Cs-134 radionuclide and methylene blue (MB) from aqueous solution using poly(acrylamide–itaconic acid)/N,N′-methelyenediacrylamide/zirconium hydrous oxide composite [poly(AM–IA)/DAM/Zr(OH)₄] as an adsorbent. The effects of initial pH value, initial concentration of Cs or MB, adsorbent dose, contact time and temperature on adsorption were investigated. Characterization of the prepared composite was carried out using FT-IR, XRD, TGA, DTA, and SEM. The adsorption behaviors showed that the adsorption kinetics and isotherms were in good agreement with the pseudo-second-order and the Langmuir models indicating the chemosorption mechanism. Thermodynamic studies were carried out and it was found that the process was spontaneous exothermic in nature. Discussion of the results of the adsorption behavior showed that the prepared composite can be used as a promising adsorbent for removal of Cs-134 or MB.     

Facile synthesis and characterization of β-cobalt hydroxide/hydrohausmannite/ramsdellitee/spertiniite and tenorite/cobalt manganese oxide/manganese oxide as novel nanocomposites for efficient photocatalytic degradation of methylene blue dye

In this paper, our research team has synthesized new nanocomposites by simple precipitation/ignition method and using low-cost chemicals. Hence, β-cobalt hydroxide/hydrohausmannite/ramsdellitee/spertiniite and tenorite/cobalt manganese oxide/manganese oxide new nanocomposites were synthesized by precipitation of Mn(II)/Co(II)/Cu(II) solution using sodium hydroxide and ignition of precipitate at 700 °C for 3 hrs, respectively. The synthesized nanocomposites were characterized using different instruments such as energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), nitrogen gas sorption analyzer, and UV–vis spectrophotometer. Energy dispersive X-ray analysis revealed that the nanocomposite formed as a result of precipitation consists of copper, cobalt, manganese, and oxygen where the weight percentages are equal to 31.73, 27.01, 17.26, and 24 %, respectively. Also, the nanocomposite formed as a result of ignition consists of copper, cobalt, manganese, and oxygen where the weight percentages are equal to 31.26, 23.87, 14.56, and 30.31 %, respectively. Transmission electron microscope revealed that the nanocomposites formed as a result of precipitation and ignition consist of polyhedral and spherical shapes with an average diameter of 34.50 and 28.56 nm, respectively. The synthesized nanocomposites were used as new photocatalysts for the efficient degradation of methylene blue dye. 0.05 g of the synthesized nanocomposites degrade 100 % of 50 mL of 15 mg/L of methylene blue dye solution within 25 min in the presence of H₂O₂ under UV light.     

Carbon–silica composite bio-sorbents with a high density of oxygen-containing sites for efficient methylene blue adsorption

Research on Chemical Intermediates - There is a growing trend to employ agricultural waste/by-products (AWBs) as substrates for the development of dye bio-sorbents, and surface modification plays a...     

Facile synthesis of mesoporous magnesium oxide–graphene oxide composite for efficient and highly selective adsorption of hazardous anionic dyes

Mesoporous magnesium oxide–graphene oxide composite (MGC) has been synthesized using a facile post-immobilization method by mixing pre-synthesized magnesium oxide (MgO) with graphene oxide (GO). MgO used for fabrication of the composite has been synthesized using an environment-friendly method involving gelatin as a template. XRD, Raman and EDX analyses have confirmed the presence of MgO and GO in the composite. FTIR and SEM analyses of synthesized MGC have further elucidated the surface functionalities and morphology, respectively. Using N₂ adsorption–desorption isotherm, BET surface area of MGC has been calculated to be 55.9 m² g^?1 and BJH analysis confirmed the mesoporous nature of MGC. The application of synthesized MGC as a selective adsorbent for various toxic anionic dyes has been explored. Batch adsorption studies have been carried out to investigate the influence of different adsorption parameters on the adsorption of two anionic dyes: indigo carmine (IC) and orange G (OG). The maximum adsorption capacities exhibited by MGC for IC and OG are 252.4 and 24.5 mg g^?1, respectively. Plausible mechanism of dye adsorption has been explained in detail using FTIR analysis. In a mixture of cationic and anionic dyes, MGC selectively adsorbs anionic dyes with high separation factors, while in binary mixtures of anionic dyes, both dyes are adsorbed efficiently. Thus, MGC has been shown to be a potential adsorbent for the selective removal of anionic dyes from wastewater.

     

Kinetics of competitive adsorption of β-casein and methylene blue on hydrophilic glass

The competitive adsorption of methylene blue (MB) and β-casein on hydrophilic glass from an aqueous mixed solution was directly detected at the solution pH smaller than the protein isoelectric point (pI) by means of the waveguide-based broadband time-resolved evanescent wave absorption spectroscopy. The competitive adsorption causes the MB coverage to exponentially decrease with time from its peak value and prevents MB aggregation at the interface. The kinetic equation for the competitive adsorption of binary adsorbates was theoretically deduced based on the Langmuir model, and was used for creating the best fit to the experimental data. In the case of a fixed concentration of MB in the mixed solution, the best-fit parameter τ(-1) increases with the protein concentration at a specific pH and decreases with the solution pH at a given concentration of protein. The findings suggest that the β-casein concentration in sub-μM level can be rapidly determined by the time-resolved waveguide absorptiometry based on the competitive adsorption of MB and protein.     

Selective nitrile oxide dipolar cycloaddition for the synthesis of highly functionalized β-aminocyclohexanecarboxylate stereoisomers

Highly functionalized β-aminocyclohexanecarboxylate regio- and stereoisomers were synthesized from a bicyclic β-lactam by successive regioselective iodolactonization, stereo- and regioselective nitrile oxide cycloaddition, lactone ring-opening and isoxazoline ring-opening.     

TiO2/polyaniline composites： An efficient photocatalyst for the degradation of methylene blue under natural light

Polyaniline (PAn) sensitized nanocrystalline TiO_2 composites (TiO_2/PAn) were successfully prepared and used as an efficient photocatalyst for the degradation of dye methylene blue (MB).The results showed that PAn was able to sensitize TiO_2 efficiently and the composite photocatalyst could be activated by absorbing both the ultraviolet and visible light (λ:190～800nm),whereas pure TiO_2 absorbed ultraviolet light only (λ<380nm).Under the irradiation of natural light,MB could be degraded more efficiently on the TiO_2/PAn composites than on the TiO_2.Furthermore,it could be easily separated from the solution by simple sedimentation.     

Fabrication of nitrogen-enriched graphene oxide/Cu NPs as a highly efficient and recyclable heterogeneous nanocatalyst for the Chan–Lam cross-coupling reaction

Herein, we demonstrate the direct polymerization of melamine and cyanuric chloride in the surface of graphene oxide (GO) (N-enriched GO) in order to develop a new nanocatalyst. The supramolecular polymerized GO acts not only as a spacer to prevent the restacking of graphene sheets but also as a nitrogen source to generate active centers for Cu NP attachments. Subsequently, the nitrogen on the surface of the GO sheets coordinates with copper ions to generate copper nanoparticles. The prepared nanocatalyst was characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and thermogravimetric analysis. This catalyst showed high efficiency and good activity in the Chan–Lam cross-coupling reaction of N-heterocycles and aniline derivatives with high yields in short reaction times. In addition, the nanocatalyst was easily recovered and reused for five consecutive runs without any noticeable loss of performance.     

Sonochemical synthesis of graphene oxide supported Pt–Pd alloy nanocrystals as efficient electrocatalysts for methanol oxidation

Pt–Pd bimetallic nanoparticles supported on graphene oxide (GO) nanosheets were prepared by a sonochemical reduction method in the presence of polyethylene glycol as a stabilizing agent. The synthetic method allowed for a fine tuning of the particle composition without significant changes in their size and degree of aggregation. Detailed characterization of GO-supported Pt–Pd catalysts was carried out by transmission electron microscopy (TEM), AFM, XPS, and electrochemical techniques. Uniform deposition of Pt–Pd nanoparticles with an average diameter of 3 nm was achieved on graphene nanosheets using a novel dual-frequency sonication approach. GO-supported bimetallic catalyst showed significant electrocatalytic activity for methanol oxidation. The influence of different molar compositions of Pt and Pd (1:1, 2:1, and 3:1) on the methanol oxidation efficiency was also evaluated. Among the different Pt/Pd ratios, the 1:1 ratio material showed the lowest onset potential and generated the highest peak current density. The effect of catalyst loading on carbon paper (working electrode) was also studied. Increasing the catalyst loading beyond a certain amount lowered the catalytic activity due to the aggregation of metal particle-loaded GO nanosheets.     

New functionalization of graphene oxide with N2O2 ligand for efficient loading of Cu nanostructures as a heterogeneous nanocatalyst for the synthesis of β-hydroxy-1,2,3-triazoles

A new and heterogeneous copper complex immobilized on graphene oxide (GO) was prepared. This was achieved through organic functionalization of GO using 1,8-diamino-3,6-dioxaoctane (DADO) and then inorganic coordination of copper on the edges and basal plane of the functionalized GO (GO-DADO-Cu), which was reduced to Cu(0). The chemical structure of the prepared nanocatalyst was analyzed using various techniques. Most of the analyses confirmed the successful anchoring of copper and organic ligand on the GO surface. Moreover, the synthesized nanocatalyst has shown high catalytic activity in the synthesis of β-hydroxy-1,2,3-triazole derivatives under mild reaction conditions (water and room temperature) resulting in good to excellent yields.     

Poly(aminohippuric acid)–sodium dodecyl sulfate/functionalized graphene oxide nanocomposite for amplified electrochemical sensing of gallic acid

Gallic acid (GA), as a main phenolic acid, has been considered the main player on the human health, including the effects of reduction of cholesterol, depression of hypertension, anti-oxidation, anti-microbial, protection against cardiovascular disease and cancer. This study describes the development, electrochemical characterization and utilization of a novel functionalized graphene oxide/poly(p-aminohippuric acid)–sodium dodecyl sulfate nanocomposite modified glassy carbon electrode (APTS@GO/PPAH-SDS/GCE) for the electrocatalytic determination of GA. The synthesized nanocomposite was characterized by different techniques such as Fourier-transform infrared spectroscopy, thermo-gravimetric analysis and transmission electron microscopy. The electrochemical oxidation of GA was investigated by cyclic voltammetry, differential pulse voltammetry and amperometry. The modified electrode showed a potent and persistent electron mediating behavior followed by well-defined oxidation peak of GA and the linear range of 0.006–2000 µmol L^?1 with a detection limit of 1.7 nmol L^?1 for GA (S/N?=?3) using amperometric method. Also, it was successfully used for the GA determination in the black tea and tab water as real samples. Additionally, this electrode exhibited good stability and reproducibility. The results imply that the APTS@GO/PPAH-SDS nanocomposite might be a promising candidate for practical applications in GA electrochemical detection.     

Preparation of graphene oxide–chitosan composite and adsorption performance for uranium

The composite adsorbent graphene oxide–chitosan was prepared using graphite and chitosan as the initial materials. The structures and morphology of the products were characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy. The products were used to remove uranium from aqueous solution by batch adsorption experiments. The effects of pH, adsorbent dosage, contact time, initial uranium concentration and temperature on the uranium removal were investigated, and the results were fitted by the adsorption isotherm models. The adsorption kinetic and thermodynamic were also studied in detail.     

Synthesis and characterization of <Emphasis Type="Italic">β</Emphasis>-cyclodextrin–carboxymethyl cellulose–graphene oxide composite materials and its application for removal of basic fuchsin

A novel β-cyclodextrin–carboxymethyl cellulose–graphene oxide composite material (β-CD–CMC–GO) was synthesized, and its application as excellent adsorbents was carried out for removal basic fuchsin (BF) in aqueous solution. The structure and morphology of β-CD–CMC–GO composite material were characterized by using FTIR, SEM, TEM, XRD, TG and DSC methods. The composites could remove basic fuchsin from aqueous solution efficiently. The adsorption experiment was carried out and the optimum experimental conditions were ascertained. The highest adsorption efficiency was obtained 97.3% at 0.015 g/mL dosage of β-CD–CMC–GO, the temperature of 25 °C and time of 2.5 h. Adsorption kinetics, adsorption isotherm and adsorption thermodynamic were used to analyze the adsorption system. The experimental data of adsorption kinetics of system were well followed by pseudo-second-order equation. The adsorption isotherm data were fitted using Langmuir isotherm model and Freundlich isotherm model. The maximum adsorption capacity of basic fuchsin reached 58.65 mg/g. The thermodynamic parameters indicated that the adsorption process was spontaneous and exothermic. The adsorbent has excellent regeneration ability and reproducibility. The proposed method shows that the β-CD–CMC–GO could be applied to removal of basic fuchsin in wastewater with satisfactory result.     

Three-dimensionally ordered macroporous metal oxide–silica composite for removal of mercaptan

A series of 3DOM and non-3DOM metal oxide–silica composites were prepared and tested dynamically in a packed-bed reactor at room temperature to remove ethanethiol from a gas stream containing ethyl mercaptan in moist N_2.The obtained sorbents were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption–desorption techniques. The experimental results showed that the adsorption ability of different kinds of metal oxide–silica composites with 3DOM structure decreased in the sequence: 3D-CuO/SiO₂ > 3D-NiO/SiO₂ > 3D-Co₃O₄/SiO₂ > 3D-ZnO/SiO₂. The best ratio of CuO to SiO₂ of 3DOM copper–silicon oxide sorbents for ethanethiol removal was found to be 1:2. The 3DOM structure could improve the removal activity of sorbents remarkably because of the high porosity with ordered interconnected macropores as well as the large surface area and high dispersion of CuO. It was also found that a moist atmosphere greatly benefited the adsorption of ethanethiol at ambient condition.     

Synthesis of π-conjugated, pyridine ring functionalized bis-terpyridines with efficient green, blue, and purple emission

A large variety of rigid, π-conjugated, pyridine ring functionalized bis-terpyridines are synthesized efficiently using tandem Miyaura/Suzuki-type cross-coupling reaction. Photophysical property study reveals that the absorption and luminescent properties of the obtained bis-terpyridines are profoundly affected by the nature of the functional groups at the peripheral pyridine and the spacers. Namely, by tailoring precisely the structures, the light-emitting efficiencies of bis-terpyridines can be enhanced significantly with quantum yields (Φ_f) of up to 0.62, and the emission colors can be tuned to display distinct colors including purple, bright blue, and bright green. Consequently, the novel bis-terpyridines are attractive ligands for the assembly of new metallo-supramolecule based functional materials.