Preparation of CuO/Water Nanofluids Using Polyvinylpyrolidone and a Survey on Its Stability and Thermal Conductivity

Abstract: In this article CuO/water nanofluid was synthesized by using polyvinylpyrolidone (PVP

Janus graphene oxide nanosheet: A promising additive for enhancement of polymeric membranes performance prepared via phase inversion

Although polymeric membranes find important role in water and waste water treatment in recent years, their fouling is still an important problem. Application of hydrophilic nanoparticles (NPs) is one of the proposed methods for reducing fouling of membranes but their dispersion and stability in hydrophobic polymer matrix is challenging. In this study Janus functionalization of the NPs was introduced as a promising technique toward achieving this goal. Polysulfone (PSf) membranes containing various concentrations of graphene oxide (GO) nanosheets and Janus graphene oxide (Janus GO) nanosheets (as additives) were fabricated via phase inversion. The synthesized nanosheets were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy and dynamic light scattering (DLS). The prepared membranes also were then characterized by scanning electron microscopy (SEM), contact angle (CA), water uptake, porosity, mean pore size and casting solution viscosity. The membrane performance was also tested by determining pure water flux (PWF), bovine serum albumin (BSA) separation, flux reduction by fouling and flux recovery. CA reduced from 85° to 68° and PWF increased from 23.15 L/m2 h to 230.61 L/m2 h for PSF and Janus GO nanosheets containing membrane, respectively. Also investigation of antifouling performance of membranes revealed that membrane with the 1 wt.% of Janus GO nanosheets had higher water flux recovery ratio (FRR) and lower irreversible fouling (Rir) of 84% and 16%, respectively. These improvements were attributed to the better dispersion and stability of Janus GO nanosheets in the prepared mixed matrix membranes

Effect of polymer concentration on the structure and performance of polyetherimide hollow fiber membranes

In this paper, polyetherimide (PEI) hollow fiber membranes were used in gas-liquid contacting process. Porous polyetherimide hollow fiber membranes were fabricated via wet phase inversion method. The polymer concentration in dope solution varied from 10 to 15. wt%. Water was used as internal and external coagulant. Gas permeation test using helium as test gas, liquid entry pressure of water (LEPw) test and scanning electron microscopy (SEM) were used for membrane characterization. The mean pore size, effective surface porosity and void fraction of membranes decreased as the polymer concentration increased, while LEPw and membrane density increased.CO2 absorption rate of fabricated membranes were measured in a gas-liquid hollow fiber membrane contactor system using distilled water as absorbent and the results showed that CO2 absorption rate of membranes increases as polymer concentration decreases. In addition, CO2 absorption rate of hollow fiber membranes in which polyetherimide concentration was between 10 and 12wt%, was higher than commercial PVDF hollow fiber membranes

Preparation and Characterization of Polyvinylidene Fluoride/Graphene Superhydrophobic Fibrous Films

A new strategy to induce superhydrophobicity via introducing hierarchical structure into the polyvinylidene fluoride (PVDF) film was explored in this study. For this purpose nanofibrous composite films were prepared by electrospinning of PVDF and PVDF/graphene blend solution as the main precursors to produce a net-like structure. Various spectroscopy and microscopy methods in combination with crystallographic and wettability tests were used to evaluate the characteristics of the synthesized films. Mechanical properties have been studied using a universal stress-strain test. The results show that the properties of the PVDF nanofibrous film are improved by compositing with graphene. The incorporation of graphene flakes into the fibrous polymer matrix changes the morphology, enhances the surface roughness, and improves the hydrophobicity by inducing a morphological hierarchy. Superhydrophobicity with the water contact angle of about 160° can be achieved for the PVDF/graphene electrospun nanocomposite film in comparison to PVDF pristine film

Preparation of chitosan/cellulose acetate composite nanofiltration membrane for wastewater treatment

Abstract: A chitosan/cellulose acetate (CA) composite membrane is prepared in this study. The effect of varying CA concentration on membrane morphology and performance is studied by using scanning electron microscopy and the composite membrane is characterized by differential scanning calorimetry and thermal gravimetric analysis. Molecular weight cut-off of the composite membrane is found to be 830 Da, which is in the range of nanofiltration. The rejection for copper from a common effluent treatment plant wastewater is observed to be 81.03% at 506.5 kPa applied pressure. The mean pore size is calculated to be 0.78 nm

Fabrication of magnetic nanocomposite membrane for separation of organic contaminant from water

In this work, separation of disperse dyes and polyethylene glycol (PEG) as organic contaminant by nanocomposite membrane was investigated. The main goal of this study is to achieve more efficient separation of contaminant from water at high fluxes. For this purpose, iron oxide nanoparticles (NP) were synthesized through co-precipitation, blended with polysulfone/N-methylpyrrolidone solution, and finally, dispersed in membrane structure after coagulation of casted polymeric solution. Effect of magnetic nanoparticle concentration on membrane structure and filtration performance was studied. According to filtration experiments, the increasing of nanoparticle concentration in membrane matrix cause permission flux to raise. On the other side, any increases in magnetic nanoparticle content improved disperse dyes and PEG rejection as organic contaminant. Iron oxide NP in polymeric solution act as an agent to increase viscosity and cause a delay in phase inversion, decrement in membrane pore size, and finally, solute rejection enhancement. The Fourier transform infrared spectroscopy confirmed nanoparticle existence in membrane matrix. Furthermore, the magnetic properties of nanocomposite membranes were measured by Vibrating Sample Magnetometer. Scanning electron microscopy images showed the effect of nanoparticle concentration on membrane porosity. The cross section of which confirmed the role of NP as a delay agent in membrane formatio