•Novel magnetic carbon nano-onions (MCNOs) were fabricated in gram scale.•The MCNOs showed high adsorption capacity toward bisphenol A (BPA).•The influences of initial concentration of BPA, solution pH, and adsorption time were investigated.•The adsorbents are easily regenerated and recycled by using an external magnet.In this work, a scalable and cost-effective approach was developed for the synthesis of magnetic carbon nano-onions (MCNOs) by using iron (III) acetylacetonate modified candle as the raw materials. The candle soot was collected from the burning candle and then subjected to calcination at 800 °C under N2 atmosphere. The obtained MCNOs were further applied as adsorbent for the removal of bisphenol A (BPA) from aqueous solutions. Adsorption of BPA onto the MCNOs was investigated with the influence of initial concentration of BPA, solution pH, and adsorption time. The results demonstrated the adsorption of BPA onto the MCNOs was almost not affected by pH in the range from 5–9. The adsorption isothermal and kinetic's data were better fitted by Langmuir isotherm and pseudo-second-order kinetic model, respectively. Moreover, the MCNOs are easily recycled by using and external magnet and regenerated by simply methanol washing. The results present here not only provide a novel synthetic approach toward low-cost nanocarbons but also revealed the great application potential of the MCNOs for the removal of endocrine disrupting compounds from aqueous solution.Download high-res image (212KB)Download full-size image

Graphene-based multifunctional composites were prepared by encapsulating of magnetic ZnFe2O4@chitosan (ZnFe2O4@CS) particles into graphene oxide (GO) layers. The obtained ZnFe2O4@CS/GO were characterized using scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Adsorption of basic fuchsin (BF) onto the ZnFe2O4@CS/GO was investigated using pH, adsorption time, initial BF concentration and temperature. Kinetic data and adsorption isotherms were better fitted by a pseudo-second-order kinetic model and Langmuir isotherm model, respectively. The values of activation parameters such as free energy (ΔG, −14.02 to −16.56 kJ mol−1), enthalpy (ΔH, 23.27 kJ mol−1) and entropy (ΔS, 127.75 J mol−1 K−1) were calculated, suggesting that the adsorption was a spontaneous, favorable and endothermic process in nature. The results demonstrated that the ZnFe2O4@CS/GO composites are potentially suitable materials for the removal of organic dyes from large volumes of wastewater.

•Zeta potential had minor effects on interactions between two planar surfaces.•Zeta potential greatly affected interactions between membrane and foulant particles.•There are an energy barrier and a critical zeta potential regarding its effects.•Rough surface membrane corresponded to a significantly low interaction strength.Effects of both membrane and sludge foulant surface zeta potentials on interfacial interactions between membrane and sludge foulant in different interaction scenarios were systematically investigated based on thermodynamic methods. Under conditions in this study, it was found that zeta potential had marginal effects on total interfacial interaction between two infinite planar surfaces, and the total interfacial interaction between foulant particles and membrane would be more repulsive with increase of absolute value of zeta potential. Adhesion of foulant particles on membrane surface should overcome an energy barrier. There exists a critical zeta potential below which energy barrier would disappear. Results also showed that rough surface membrane corresponded to significantly low strength of interfacial interactions. This study not only provided a series of methods to quantitatively assess the interfacial interactions between membrane and sludge foulants, but also reconciled the contradictory conclusions regarding effects of zeta potential in literature, giving important implications for membrane fouling mitigation.Graphical abstract

•A novel aptamer-based sensor using carbon nanoparticle combined with aptamer is constructed.•Carbon nanoparticles expand the range of variation in fluorescence anisotropy.•We explain the foundation of our sensor design for apyrase detection.•Signal-amplification and real-time detection of apyrase are realized.Carbon nanomaterial combined with aptamer has been developed as an efficient bioanalytical method in sensor design. Herein, depending on carbon nanoparticle (cCNP)-enhanced fluorescence anisotropy (FA), a novel aptamer-based sensor (aptasensor) enabling signal-amplification and real-time detection of apyrase is reported. The foundation of our sensor design based on ATP-aptamer(P) can be adsorbed on the surface of cCNPs, resulting in the increase of FA due to the mass of cCNPs, and P–ATP complex has weak binding ability to cCNPs with minimal change of FA. Apyrase, being an integral membrane protein, can hydrolyze ATP and make P–ATP complex disassemble, and thus lead to the increasing of FA. Therefore, this approach is demonstrated to be a novel candidate for the detection of apyrase, with high sensitivity and selectivity. The linear dynamic range for the concentrations of apyrase is between 0.1 and 0.5 U/μL along with a detection limit of 0.05 U/μL. Furthermore, these results indicated that our design is a flexible and sensitive method for biomolecule analysis, which makes it promising for practical biomolecule analyses.A novel aptamer-based sensor (aptasensor) enabling signal-amplification and real-time detection of apyrase is reported, based on the binding ability between ssDNA and ssDNA-target complex on the cCNP surface. The sensor has a liner response to apyrase in the range of 0.1 to 0.5 U/μL with a detection limit of 0.05 U/μL.

Amino-functionalized MCM-48 (NH2-MCM-48) modified with 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (DTES) was synthesized by a co-condensation method and was characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectrum, and thermogravimetric analysis techniques. Batch adsorption studies of Zn(II) on NH2-MCM-48 were investigated. The effect of experimental parameters including pH, adsorbent dose, Zn(II) concentration, and adsorption time was studied, and the research results indicated NH2-MCM-48 has a higher adsorption capacity for Zn(II) than other adsorbents. The experimental data were fitted to Langmuir and Freundlich isotherm models, and the Langmuir equation showed better correlation with the experimental data than the Freundlich. According to the parameters of the Langmuir equation, the maximum adsorption capacities of Zn(II) onto NH2-MCM-48 were (83.33, 90.91, and 100.00) mg·g–1 at (303, 313, and 323) K, respectively. The adsorption kinetics data were found to follow the pseudosecond-order kinetic model. The thermodynamic parameters (ΔG0, ΔH0, and ΔS0) were measured, and the negative value of Gibbs energy indicated the adsorption process was spontaneous in nature. Moreover, the adsorbent was applied in environmental samples, and the removal rate and recovery of Zn(II) from water were high. These results indicate that NH2-MCM-48 is an efficient adsorbent to remove Zn(II) from polluted water.

A novel and simple method to prepare well dispersed single-walled carbon nanotubes with strong visible fluorescence in water is reported. The visible fluorescence was found to be responsive to pH value and metal ions, and tunable emission ability of oxidized SWCNTs depending on the excitation wavelength and a novel self-excitation and emission process were found.

The limiting dissociative (D) and interchange dissociative (Id) water exchange pathways on Al(III) inside and outside single-walled carbon nanotubes (SWCNTs) were modelled using ONIOM calculations with density functional theory, and the influence of SWCNTs on both D and Id pathways was examined. The interchange dissociative water exchange pathway was revealed, in which the zigzag SWCNTs (13,0), (14,0) and (15,0) with the same length were modelled for interaction. The results indicate that the confinement effect of SWCNTs on the energy barriers is strong when the reaction takes place inside SWCNTs with small diameter relative to reaction complexes, and varies heavily along with the change of diameters of SWCNTs. The results also indicate that SWCNTs act as trans-activating ligand to effectively lower the energy barriers of both D and Id pathways outside SWCNTs. The interaction between aluminium-water complexes and SWCNTs can effectively lower the energy barriers in general and may accelerate the reaction rates, which has great importance for the influence of carbon nanotubes on dissolution and transformation rates of minerals such as aluminium (hydr)oxide.

As a first attempt, cloud point extraction (CPE) was developed to preconcentrate bisphenol A (BPA), α-naphthol and β-naphthol prior to performing capillary zone electrophoresis (CZE) analysis. The parameters influencing the CPE efficiency, such as Triton X-114 concentrations, pH value, extraction time and temperature were systematically evaluated.After diluting with acetonitrile, the surfactant-rich phase of CPE can be injected directly into the CE instrument. The CZE baseline separation was achieved with running buffer (pH 9.5) composed of 50 mM sodium tetraborate in 30% (v/v) methanol, and an applied voltage of 25 kV. Under the optimized CPE and CZE conditions, an preconcentration factor of 50 times could be obtained and the limit of quantification for the three analytes were found to be 1.67 μg L−1, 0.80 μg L−1 and 0.67 μg L−1 for BPA, α-naphthol and β-naphthol, respectively. The proposed methods have shown to be a green, rapid and effective approach for determination of three analytes present in river water samples.

A dissociative (D) and a solvent-assisted dissociative interchange (Id) water-exchange pathways for magnesium(II) in aqueous solution were simulated with density functional theory calculations. The D   mechanism of Mg(H2O)62+ includes a five-coordinated intermediate, while the Id   water-exchange pathway of Mg(H2O)62+ proceeds with the assistance of a solvent water molecule, which supports the experimental assignment of the reaction mechanism. The intrinsic activation volume was used to differentiate between Id and Ia mechanisms despite of the exclusion of the contribution of transmission coefficient. The calculated intrinsic activation volume for the Id mechanism is consistent with the experimental data, and is closer to the experimental data than that for D mechanism. The Id   mechanism is suggested as the dominate water-exchange pathway of Mg(H2O)62+ depending on the intrinsic activation volume with the assistance of the activation entropy. The calculations also showed that the influences of the explicit and bulk waters on energy barriers for D and Id mechanisms are obviously different.A dissociative (D) and a solvent-assisted dissociative interchange (Id) water-exchange pathways for magnesium(II) in aqueous solution were simulated with density functional calculations. The Id mechanism was identified depending on the calculated intrinsic activation volume, which supports the experimental assignment.

Cloud point extraction (CPE) has been used for the pre-concentration of lead, after the formation of a complex with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP), and later analysis by graphite furnace atomic absorption spectrometry (GFAAS) using octylphenoxypolyethoxyethanol (TritonX-114) as surfactant. The chemical variables affecting the separation phase were optimized. Separation of the two phases was accomplished by centrifugation for 15 min at 4000 rpm. Under the optimum conditions i.e., pH 8.0, cloud point temperature 40 °C, [5-Br-PADAP] = 2.5 × 10−5 mol l−1, [Triton X-114] = 0.05%, added methanol volume = 0.15 ml, pre-concentration of only 10 ml sample permitted an enhancement factor of 50-fold. The lower limit of detection (LOD) obtained under the optimal conditions was 0.08 μg l−1. The precision for 10 replicate determinations at 5 μg l−1 Pb was 2.8% relative standard deviation (R.S.D.). The calibration graph using the pre-concentration system for lead was linear with a correlation coefficient of 0.9984 at levels near the detection limits up to at least 30 μg l−1. The method was successfully applied to the determination of lead in water samples.

In the last years, anaerobic membrane bioreactor (AnMBR) technology is being considered as a very appealing alternative for wastewater treatment due to the significant advantages over conventional anaerobic treatment and aerobic membrane bioreactor (MBR) technology. Many articles have touted the diverse potential applications of AnMBR in various stream treatment, and membrane fouling issues. In current review, the fundamentals of AnMBR (including advantages and configurations, membrane materials and modules, and history development), application development in various stream treatment, and membrane fouling researches are summarized and critically assessed. The characteristics of AnMBR and aerobic MBR for wastewater treatment are also compared. AnMBR technology appears to be suitable for treatment of various streams, especially for food industrial wastewater and municipal wastewater. AnMBR treatment usually encounters more serious membrane fouling problem. This, however, can be remedied through various conventional and novel membrane fouling control or cleaning measures. Based on the review, future research perspectives relating to its application and membrane fouling research are proposed.Highlights► Recent progress in AnMBRs treating various wastewaters is summarized. ► Advances in membrane fouling control strategies in AnMBRs are addressed. ► Research directions regarding AnMBR technology are identified. ► AnMBR is a promising technology for wastewater treatment and reuse.

In this study, polyvinylidene fluoride (PVDF) microfiltration membrane was coated by dipping the membrane alternatingly in solutions of the polyelectrolytes (poly-diallyldimethylammonium chloride (PDADMAC) and polystyrenesulfonate (PSS)) via layer-by-layer (LBL) self-assembly technique to improve the membrane antifouling ability. Filtration experiments showed that, sludge cake layer on the coated membrane could be more easily washed off, and moreover, the remained flux ratio (RFR) of the coated membrane was obviously improved as compared with the control membrane. Characterization of the membranes showed that a polyelectrolyte layer was successfully coated on the membrane surfaces, and the hydrophilicity, surface charge and surface morphology of the coated membrane were changed. Based on the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) approaches, quantification of interfacial interactions between foulants and membranes in three different scenarios was achieved. It was revealed that there existed a repulsive energy barrier when a particle foulant adhered to membrane surface, and the enhanced electrostatic double layer (EL) interaction and energy barrier should be responsible for the improved antifouling ability of the coated membrane. This study provided a combined solution to membrane modification and interaction energy evaluation related with membrane fouling simultaneously.Figure optionsDownload full-size imageDownload high-quality image (378 K)Download as PowerPoint slide

A novel and simple method to prepare well dispersed single-walled carbon nanotubes with strong visible fluorescence in water is reported. The visible fluorescence was found to be responsive to pH value and metal ions, and tunable emission ability of oxidized SWCNTs depending on the excitation wavelength and a novel self-excitation and emission process were found.

The limiting dissociative (D) and interchange dissociative (Id) water exchange pathways on Al(III) inside and outside single-walled carbon nanotubes (SWCNTs) were modelled using ONIOM calculations with density functional theory, and the influence of SWCNTs on both D and Id pathways was examined. The interchange dissociative water exchange pathway was revealed, in which the zigzag SWCNTs (13,0), (14,0) and (15,0) with the same length were modelled for interaction. The results indicate that the confinement effect of SWCNTs on the energy barriers is strong when the reaction takes place inside SWCNTs with small diameter relative to reaction complexes, and varies heavily along with the change of diameters of SWCNTs. The results also indicate that SWCNTs act as trans-activating ligand to effectively lower the energy barriers of both D and Id pathways outside SWCNTs. The interaction between aluminium-water complexes and SWCNTs can effectively lower the energy barriers in general and may accelerate the reaction rates, which has great importance for the influence of carbon nanotubes on dissolution and transformation rates of minerals such as aluminium (hydr)oxide.