Zongxue Yu

Novel polyvinylidene fluoride nanofiltration membrane blended with functionalized halloysite nanotubes for dye and heavy metal ions removal.

Membrane separation is an effective method for the removal of hazardous materials from wastewater. Halloysite nanotubes (HNTs) were functionalized with 3-aminopropyltriethoxysilane (APTES), and novel polyvinylidene fluoride (PVDF) nanofiltration membranes were prepared by blending with various concentrations of APTES grafted HNTs (A-HNTs). The morphology structure of the membranes were characterized by scanning electron microscope (SEM) and atomic force microscopy (AFM). The contact angle (CA), pure water flux (PWF) and antifouling capacity of membranes were investigated in detail. In addition, the separation performance of membranes were reflected by the removal of dye and heavy metal ions in simulated wastewater. The results revealed that the hydrophilicity of A-HNTs blended PVDF membrane (A-HNTs@PVDF) was enhanced significantly. Owing to the electrostatic interaction between membrane surface and dye molecules, the dye rejection ratio of 3% A-HNTs@PVDF membrane reached 94.9%. The heavy metal ions rejection ratio and adsorption capacity of membrane were also improved with the addition of A-HNTs. More importantly, A-HNTs@PVDF membrane exhibited excellent rejection stability and reuse performances after several times fouling and washing tests. It can be expected that the present work will provide insight into a new method for membrane modification in the field of wastewater treatment.

Effect of functionalized multi-walled carbon nanotubes on the microstructure and performances of PVDF membranes

Functionalized multi-walled carbon nanotubes (f-MWCNTs) were synthesized by grafting carboxyl groups and 3-aminopropyltriethoxysilane (APTS) on the nanotube surface, respectively. A novel polyvinylidene fluoride (PVDF) membrane was prepared by incorporation of different dosages of APTS modified MWCNTs (A-MWCNTs) via the phase-inversion method. The dispersity of MWCNTs and compatibility between MWCNTs and the polymer matrix were enhanced after functional modification. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) testing showed that A-MWCNTs/PVDF blend membranes exhibited superior surface morphology and pore structure. Because of a strong interfacial interaction with the PVDF matrix, the mechanical strength of PVDF membranes was improved by adding A-MWCNTs and the optimum addition content was 2 wt%. More importantly, the bovine serum albumin (BSA) rejection of membranes increased significantly from 64.2% (nascent PVDF membranes) to 92.48% (A-MWCNTs/PVDF), which was attributed to the network structure of APTS. It can be expected that the blending modification of PVDF membranes by f-MWCNTs will have a bright and foreseeable application prospect.

Covalent modification of graphene oxide by metronidazole for reinforced anti-corrosion properties of epoxy coatings

Graphene can be used as an excellent protection material because of its barrier properties. This work reports a promising application of metronidazole (MET) modified graphene oxide (GO) composites (GME) for the corrosion protection of steel. The composites were synthesized using the carboxyl group of GO and hydroxyl group of MET with the help of maleic anhydride (MA), dispersing these sheets into epoxy resin at a low weight fraction of 0.2 wt%. A UV-vis absorption spectrum revealed that MET can be detected in NaCl (3.5 wt%) solution. An electrochemical impedance spectroscopy (EIS) test showed that the corrosion resistance performance is significantly enhanced by the addition of GME hybrids to epoxy compared to GO. A scratch test illustrated that fewer corrosion products formed in the scratch on the steel coated by GME. The strategy of using corrosion inhibitor modified graphene oxide can be extended to develop new graphene-based materials with other excellent materials for the protection of metal components.

Enhancing the photocatalytic and antibacterial property of polyvinylidene fluoride membrane by blending Ag–TiO2 nanocomposites

A novel polyvinylidene fluoride (PVDF) ultrafiltration membrane with photocatalytic and antibacterial properties was prepared by phase inversion. The in situ formed silver (Ag) nanoparticles were immobilized with titanium dioxide (TiO2) nanoparticles. And the modified PVDF membranes were fabricated by adding Ag–TiO2 into the casting solution. Results showed that the surface contamination of membrane can be degraded effectively by photocatalysis method. Compared with the pristine membrane, the hydrophilicity of modified membrane was improved. Besides, the modified membrane had an excellent antibacterial property. Therefore, the novel Ag–TiO2–PVDF membrane has a very promising application perspective.

Preparation of a novel anti-fouling β-cyclodextrin–PVDF membrane

As part of this work, polyvinylidene fluoride (PVDF) membranes were prepared via a phase inversion method. A novel β-cyclodextrin (β-CD)–PVDF membrane was prepared via an interfacial reaction, using Trimesoyl Chloride (TMC) and β-CD as cross-linking and modification agents, respectively. The membranes were modified by a simple dip-coating method. The results of comparison between the modified and unmodified membranes by attenuated total reflectance Fourier transform infrared spectroscopy (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS) methods confirmed successful grafting of β-CD on the membrane surfaces. The morphology of the membrane was investigated by scanning electron microscopy (SEM) and atomic-force microscopy (AFM). The roughness of PVDF membranes increased after their surfaces were grafted with β-CD. It was also found that β-CD–PVDF membranes had higher permeate flux and hydrophilicity than those of the pristine PVDF membranes. Furthermore, in protein fouling experiments, bovine serum albumin (BSA) was used as a protein model solution. Modified membranes exhibited a higher flux recovery ratio. The experiment showed that the anti-fouling performance of β-CD–PVDF membranes was more effective in reducing the irreversible membrane fouling. The results of this study hold promise for useful applications of β-CD–PVDF membranes in membrane separation areas.

Hydrothermal method synthesis CuS/Ag2S microspheres with reduced graphene oxide sheet degrade the organic dye under visible-light irradiation

ABSTRACT The CuS/Ag2S microspheres with reduced graphene oxide (CuS/Ag2S-rGO) composites have been successfully prepared via a hydrothermal method. The characteristic of CuS/Ag2S-rGO microspheres were characterized by the Scanning electron microscopy (SEM), the transmission electron (TEM), the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-Vis diffuse reflection spectroscopy (DRS). The photocatalytic experiments results shown that the CuS/Ag2S-rGO have high photodegradation rate about 98% for methylene blue (MB) under visible-light irradiation, and still retained 90% original catalytic activity after four cycles. The high visible photocatalytic degradation was attributed to the interfacial charge transfer in the Z-scheme photocatalytic systems of CuS/Ag2S and fast separation of photoelectric. This composition was expected to show considerable potential applications in water purification.

Attached β-cyclodextrin/γ-(2,3-epoxypropoxy) propyl trimethoxysilane to graphene oxide and its application in copper removal

The environmental applications of graphene oxide and β-cyclodextrin (β-CD) have attracted great attention since their first discovery. Novel nanocomposites were successfully prepared by using an esterification reaction between β-cyclodextrin/γ-(2,3-epoxypropoxy) propyl trimethoxysilane grafted graphene oxide (β-CD/GPTMS/GO). The β-CD/GPTMS/GO nanocomposites were used to remove the Cu2+ from aqueous solutions. The characteristics of β-CD/GPTMS/GO were detected by scanning electron microscopy (SEM), Fourier transform infrared, X-ray diffraction (XRD), thermogravimetric analysis (TG) and energy dispersive X-ray (EDX). The dispersibility of graphene oxide was excellent due to the addition of β-CD. The adsorption isotherms data obtained at the optimum pH 7 were fitted by Langmuir isotherm model. The excellent adsorption properties of β-CD/GPTMS/GO for Cu2+ ions could be attributed to the apolar cavity structure of β-CD, the high surface area and abundant functional groups on the surface of GO. The adsorption patterns of β-CD/GPTMS/GO were electrostatic attraction, formation of host-guest inclusion complexes and the ion exchange adsorption. The efficient adsorption of β-CD/GPTMS/GO for Cu2+ ions suggested that these novel nanocomposites may be ideal candidates for removing other cation pollutants from waste water.