Fabrication of Polyimide Membrane Incorporated with Functional Graphene Oxide for CO2 Separation: The Effects of GO Surface Modification on Membrane Performance.

Two kinds of isocyanate were used to modify graphene oxide (GO) samples. Then, polyimide (PI) hybrid membranes containing GO and modified GO were prepared by in situ polymerization. The permeation of CO2 and N2 was studied using these novel membranes. The morphology experiments showed that the isocyanate groups were successfully grafted on the surface of GO by replacement of the oxygen-containing functional groups. After modification, the surface polarity of the GO increased, and more defect structures were introduced into the GO surface. This resulted in a good distribution of more modified GO samples in the PI polymer matrix. Thus, the PI hybrid membranes incorporated by modified GO samples showed a high gas permeability and ideal selectivity of membranes. In addition, enhancement of the selectivity due to the solubility of CO2 played a major role in the increase in the separation performance of the hybrid membranes for CO2, although the diffusion coefficients for CO2 also increased. Both the higher condensability and the strong affinity between CO2 molecules and GO in the polymer matrix caused an enhancement of the solubility selectivity higher than the diffusion selectivity after GO surface modification.

Alcohol solvothermal reduction for commercial P25 to harvest weak visible light and fabrication of the resulting floating photocatalytic spheres.

In this study, to fabricate stable floating photocatalytic spheres, facile alcohol solvothermal reduction was first employed to modify commercial TiO2 (P25) photocatalysts to harvest visible light and improve their performances for photodegrading phenol in seawater exciting by visible light. Floating photocatalytic spheres were then prepared by loading reduced P25 photocatalysts on inner and outer surfaces of acrylic hollow spheres. The structural characterizations showed that reduction of P25 introduced disorder-crystalline shell-core structures with present Ti3+ in reduced P25 photocatalysts. These features facilitated visible light response and phenol degradation in seawater under visible light irradiation. As reduction time or temperature of alcohol solvothermal process rose, more Ti3+ and shell-core structures were introduced into reduced P25, resulting in higher performances towards phenol degradation in seawater. However, extended periods of time and elevated temperatures decreased disordered layer of reduced P25, deteriorating the photocatalytic performances. Thanks to good light transmission of the hollow spheres and the high performance of the reduced P25, the photocatalytic performances of spheres loaded with reduced P25 could effectively degrade phenol in seawater even at low concentrations. The removal rate of phenol by floating spheres reached more than 95% after 8 h. In addition, the floating spheres displayed good stability and convenient reusability after six repeated photocatalytic degradation for phenol in seawater, promising features for future treatment of organic pollutants in oceans.

Rapid decolorization of dye Orange G by microwave enhanced Fenton-like reaction with delafossite-type CuFeO2.

Bimetallic oxide CuFeO2 as a new heterogeneous catalyst has shown much higher catalytic ability for activating peroxide than single-metal oxides. The present work demonstrated a synergistic microwave (MW) enhanced Fenton-like process with CuFeO2 for rapid decolorization of azo dye Orange G (OG). The MW irradiation dramatically enhanced the OG degradation efficiency, achieving 99.9% decolorization within 15min at pH5. The XRD analysis of reused CuFeO2, together with metal leaching tests, indicated merits of recycling for CuFeO2. The subsequent surface element analysis by XPS for fresh and used CuFeO2 showed a complex network for reactions between copper-iron redox pairs and surface hydroxyl groups, leading to a synergistic Fenton-like system accelerated by MW irradiation. In the CuFeO2 initiated Fenton-like reactions, several oxidant species (i.e., OH, O2-, electron hole, and FeIVO) responsible to the OG oxidation were identified by quenching experiments, showing the MW generated high temperature and "hot spots" enhanced the yield of OH by generation of electron-hole pairs. Further, the 26 detected degradation products confirmed the OH dominant oxidation of OG. This study shows that the MW-enhanced Fenton-like reaction using CuFeO2 has potential applications for rapid decolorization of dye effluent.

Planar graphene oxide-based magnetic ionic liquid nanomaterial for extraction of chlorophenols from environmental water samples coupled with liquid chromatography-tandem mass spectrometry.

A planar graphene oxide-based magnetic ionic liquid nanomaterial (PGO-MILN) was synthesized. The prepared PGO-MILN was characterized by transmission electronmicroscopy (TEM) and Fourier-transform infrared spectrometry (FTIR). The results of adsorption experiments showed that the PGO-MILN had great adsorption capacity for 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and pentachlorophenol (PCP). Based on the adsorption experimental data, a sensitive magnetic method for determination of the five CPs in environmental water samples was developed by an effective magnetic solid-phase extraction (MSPE) procedure coupled with high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). The effects of main MSPE parameters including the solution pH, extraction time, desorption time, and volume of desorption solution on the extraction efficiencies had been investigated in detail. The recoveries ranged from 85.3 to 99.3% with correlation coefficients (r) higher than 0.9994 and the linear ranges were between 10 and 500ngL(-1). The limits of detection (LODs) and limits of quantification (LOQs) of the five CPs ranged from 0.2 to 2.6ngL(-1) and 0.6 to 8.7ngL(-1), respectively. The intra- and inter- day relative standard deviations (RSDs) were in the range from 0.6% to 7.4% and from 0.7% to 8.4%, respectively. It was confirmed that the PGO-MILN was a kind of highly effective MSPE materials used for enrichment of trace CPs in the environmental water.

[Study on seasonal characteristics of thermal stratification in lacustrine zone of Lake Qiandao].

Lake Qiandao is a typical subtropical man-made reservoir in China. The investigation on the seasonal and vertical dynamics of water temperature, dissolved oxygen (DO), pH value, turbidity, photosynthetic available radiation (PAR) and chlorophyll a was conducted in 2011 in order to find out the physical characteristics of Lake Qiandao. The average surface water temperature ranged from 10.4 to 32.7 degrees C. A monomictic thermal stratification was observed in Lake Qiandao, initiating in April and lasting until December. The results showed that thermal stratification had influences on vertical distribution of DO, pH value, turbidity, PAR and chlorophyll a. Very strong stratification of DO was found, inducing lower oxygen concentration in the thermocline layer and temporal hypoxia in the bottom water. The maximum turbidity was found in the thermocline layer and the precipitation affected the surface turbidity value. Moreover, the chlorophyll a concentration was higher in the surface water and lower in the bottom water as found in this study, implying that water quality was affected by stratification. Besides, the maximum photosynthesis rate and algal growth rate were found at the depth 5-10 m below the water surface. Therefore, the results can provide theoretical support for the sampling and analysis of algal blooms in Lake Qiandao.