Inhibition of biofouling by in-situ grown zwitterionic hydrogel nanolayer on membrane surface in ultralow-pressurized ultrafiltration process.

Ultralow-pressurized ultrafiltration membrane process with low energy consumption is promising in surface water purification. However, membrane fouling and low selectivity are significant barriers for the wide application of this process. Herein, an ultrathin zwitterionic hydrogel nanolayer was in-situ grown on polysulfone ultrafiltration membrane surface through interfacially-initiated free radical polymerization. The hydrogel-modified membrane possessed improved biological fouling resistance during the dynamic filtration process (bovine serum albumin, Escherichia coli and Staphylococcus aureus), comparing with commercial polysulfone membrane. The enhanced biofouling resistance ability of zwitterionic hydrogel nanolayer was derived from the foulant repulsion of hydration shell and the bactericidal effect of quaternary ammonium, according to the results of foulant-membrane interaction energy analyses and antibacterial performances. In surface water treatment, the zwitterionic hydrogel layer inhibited biofouling and resulted in the formation of a loose and thin biofilm. In addition, the hydrogel-modified membrane possessed 22% improvement in dissolved organic carbon (DOC) removal and 134% increasement in stable water flux, compared to commercial polysulfone membrane. The in-situ grown zwitterionic hydrogel nanolayer on membrane surface offers a prospectively alternative for biofouling control in ultralow-pressurized membrane process.

Red-emitting carbon dots aggregates-based fluorescent probe for monitoring Cu2.

R-CDAs have been synthesized in a one-pot solvothermal procedure starting from 3,4-diaminobenzoic acid in an acidic medium. Transmission electron microscopy (TEM) revealed that R-CDAs nanoparticles exhibited a much larger diameter of 7.2-28.8 nm than traditional monodisperse carbon dots. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) revealed the presence of polar functional groups (hydroxyl, amino, carboxyl) on the surface of R-CDAs. Upon excitation with visible light (550 nm), R-CDAs emit stable, red fluorescence with a maximum at 610 nm. Under the optimum conditions, Cu2+ ions quench the fluorescence of this probe, and the signal is linear in a concentration range of copper ions between 5 and 600 nM with the detection limit of only 0.4 nM. Recoveries from 98.0 to 105.0% and relative standard deviations (RSD) from 2.8 to 4.5% have been obtained for detection of Cu2+ in real water samples. Furthermore, the R-CDAs fluorescent probe showed negligible cytotoxicity toward HeLa cells and good bioimaging ability, suggesting its potential applicability as a diagnostic tool in biomedicine.

Microstructure Dependence of Effective Thermal Conductivity of EB-PVD TBCs.

Microstructure dependence of effective thermal conductivity of the coating was investigated to optimize the thermal insulation of columnar structure electron beam physical vapor deposition (EB-PVD coating), considering constraints by mechanical stress. First, a three-dimensional finite element model of multiple columnar structure was established to involve thermal contact resistance across the interfaces between the adjacent columnar structures. Then, the mathematical formula of each structural parameter was derived to demonstrate the numerical outcome and predict the effective thermal conductivity. After that, the heat conduction characteristics of the columnar structured coating was analyzed to reveal the dependence of the effective thermal conductivity of the thermal barrier coatings (TBCs) on its microstructure characteristics, including the column diameter, the thickness of coating, the ratio of the height of fine column to coarse column and the inclination angle of columns. Finally, the influence of each microstructural parameter on the mechanical stress of the TBCs was studied by a mathematic model, and the optimization of the inclination angle was proposed, considering the thermal insulation and mechanical stress of the coating.

Spectrophotometric determination of hydrogen peroxide in water with peroxidase-catalyzed oxidation of potassium iodide and its applications to hydroxylamine-involved Fenton and Fenton-like systems.

A spectrophotometric method for the rapid measurement of hydrogen peroxide (H2O2) in aqueous solutions was developed in this study. This method is based on a reaction catalyzed by peroxidase (POD) in which potassium iodide (KI) is oxidized to generate the stable yellow-colored I3- within 15 s. The absorbance of the generated I3- at both 350 nm and 400 nm had good linear relationships with H2O2 concentration in the range of 0-70 µM (R2 > 0.999) with sensitivities of 2.34 × 104 M-1 cm-1 and 5.30 × 103 M-1 cm-1 respectively. Meanwhile, through calculation, the detection limits of the proposed POD-KI method at 350 nm and 400 nm were 0.09 µM and 0.33 µM, respectively. Even when the concentration of H2O2 was up to 350 µM, the absorbance of the generated I3- at 350 nm did not decrease observably. The generated I3- was found to be stable enough in ultrapure water, underground water, reservoir water and samples containing the strong reducing agent hydroxylamine. Moreover, the proposed POD-KI method was successfully used to analyze trace H2O2 in rainwater, and to monitor the change of H2O2 concentration in the Fenton, hydroxylamine/Fenton and hydroxylamine/Cu(II)/H2O2 systems. Overall, the POD-KI method could be adopted as a candidate method to determine H2O2 in Fenton and Fenton-like systems, and especially in those involving hydroxylamine.

Multi-wavelength spectrophotometric determination of hydrogen peroxide in water by oxidative coloration of ABTS via Fenton reaction.

In this study, a sensitive and low-cost multi-wavelength spectrophotometric method for the determination of hydrogen peroxide (H2O2) in water was established. The method was based on the oxidative coloration of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) via Fenton reaction, which resulted in the formation of green radical (ABTS•+) with absorbance at four different wavelengths (i.e., 415 nm, 650 nm, 732 nm, and 820 nm). Under the optimized conditions (CABTS = 2.0 mM, CFe2+ = 1.0 mM, pH = 2.60 ± 0.02, and reaction time (t) = 1 min), the absorbance of the generated ABTS•+ at 415 nm, 650 nm, 732 nm, and 820 nm were well linear with H2O2 concentrations in the range of 0-40 µM (R2 > 0.999) and the sensitivities of the proposed Fenton-ABTS method were calculated as 4.19 × 104 M-1 cm-1,1.73 × 104 M-1 cm-1, 2.18 × 104 M-1 cm-1, and 1.96 × 104 M-1 cm-1, respectively. Meanwhile, the detection limits of the Fenton-ABTS method at 415 nm, 650 nm, 732 nm, and 820 nm were respectively calculated to be 0.18 µM, 0.12 µM, 0.10 µM, and 0.11 µM. The absorbance of the generated ABTS•+ in ultrapure water, underground water, and reservoir water was quite stable within 30 min. Moreover, the proposed Fenton-ABTS method could be used for monitoring the variations of H2O2 concentration during the oxidative decolorization of RhB in alkali-activated H2O2 system.

Spectrophotometric determination of hydrogen peroxide in water by oxidative decolorization of azo dyes using Fenton system.

In this study, based on the oxidative decolorization of three azo dyes (Orange G (OG), Acid Orange 7 (AO7) and Reactive Black 5 (RB5)) with hydroxyl radicals generated in Fenton system, we have successfully established three types of azo dyes spectrophotometric methods for measuring aqueous hydrogen peroxide (H2O2) concentration. The decolorization extent of OG, AO7 and RB5 at the corresponding characteristic wavelengths of 478 nm, 484 nm and 597 nm are proportion to the concentration of H2O2 in aqueous solutions. Under the selected reaction conditions, three well linear correlations between the depletion of azo dyes and the H2O2 concentration are established in the range of 0.45-175 µmol L-1 of OG, 0.36-120 µmol L-1 of AO7 and 0.44-175 µmol L-1 of RB5, respectively. These proposed spectrophotometric methods are enough accurate to measure low concentrations of H2O2 in practical water samples and monitor the variations of H2O2 concentration during the phenol degradation in the Cu(II)/HCO3-/H2O2 process.

Selective separation of structure-related alkaloids in Rhizoma coptidis with "click" binaphthyl stationary phase and their structural elucidation with liquid chromatography-mass spectrometry.

It is a new task to separate structure-related compounds into a fraction according to their structural characteristics in a complex traditional Chinese medicine (TCM). This method makes separation of the components of the sample simple and structural elucidation easy. In this study, selective separation of alkaloids in Rhizoma coptidis was realized on a "click" binaphthyl column possessing a planar conjugate structure. Three kinds of alkaloids, aporphine, tetrahydroprotoberberine and protoberberine in Rhizoma coptidis showed better retention than other compounds by virtue of π-π interactions with the stationary phase. Moreover, the "click" binaphthyl column could distinguish the aporphine and tetrahydroprotoberberine alkaloids possessing two benzene rings from the protoberberine alkaloids possessing three benzene rings. After separating on the "click" binaphthyl column, the fractions containing the alkaloids were collected and then analyzed with liquid chromatography-mass spectrometry (LC-MS). Totally, 23 alkaloids were identified, and among these alkaloids, three tetrahydroprotoberberine, two aporphine and seven protoberberine alkaloids were first found in Rhizoma coptidis. These newly found alkaloids are minor compounds, and they are always neglected without eliminating the interference of compounds in large amounts by pre-separation on the "click" binaphthyl column. The typical fragmentation pathways of each class of alkaloids were summarized to illustrate their structures. In the MS(2) spectrum, the loss of a molecule of dimethylamine ((CH(3))(2)NH) was observed as the characteristic loss of aporphine alkaloids. All the tetrahydroprotoberberine alkaloids would undergo the Retro-Diels-Alder (RDA) fragmentation reaction in the MS(2) fragmentation. For protoberberine alkaloids, different characteristic fragmentations were observed with different skeleton structures.