Investigation of concentration polarization in a cross-flow nanofiltration membrane: Experiment and CFD modelling

Numerous researches have been investigated on the mass transfer phenomena and hydrodynamics for the fluid in the vicinity of the membrane surface by the mathematical modelling and simulation. Due to complexities involved in solving transport phenomena within membranes, the application of CFD simulation study for determining the concentration polarization (CP) profile in the membrane channel is limited. In this study, a 2D CFD modelling and simulation of CP phenomena in nanofiltration of an aqueous solution of MgSO47H2O in a vertical spacer-filled flat sheet membrane module was presented. A response surface methodology (RSM) statistical analysis has been designed in order to fully capture effects of variations of the feed liquid flow and the transmembrane pressure (TMP) on the permeate flux and concentration. It was also shown that increasing TMP or the liquid flow rate led to enhancing the permeate flux while increasing the feed concentration decreased it. The simulated results were validated and compared with the available experimental data, showing a satisfactory agreement. Eventually, the mass transfer coefficient derived from CFD simulations and calculated from Sherwood empirical relationships were compared which showed 10% and 33% difference in lower and higher liquid flow rates, respectively

Experimental investigation and mathematical modeling of nano-composite membrane fabrication process: focus on the role of solvent type

In this study, the effect of fabrication parameters on the performance of nano-SiO2-embedded membranes fabricated by three prevalent solvents was investigated. Genetic programming was applied for modeling and estimating the best preparation conditions to obtain a proper membrane for oily wastewater microfiltration. Membranes were prepared via a combination of vapor-induced phase separation and nonsolvent-induced phase separation methods. Different types of solvents such as N-methyl-2-pyrrolidone, N,N-dimethyl formamide, and dimethyl sulfoxide were used in cooperating with SiO2 nanoparticles to improve hydrophilicity properties of polyethersulfone. Thermodynamic behavior of solvents and their interaction with polymer and nonsolvent were considered as criteria for forming a suitable membrane with the maximum effectiveness of nanoparticles. The results showed that nanoparticles are more influential along with a solvent that has a weak affinity with a polymer, which subsequently can produce efficient membranes under conditions with a balance between exposure time and relative humidity. The optimum amounts of parameters were estimated by genetic algorithm to introduce a condition for having a membrane with the maximum permeate flux. Membranes fabricated with dimethyl sulfoxide represented the highest pore size and the most hydrophilic surface, which, in turn, led to the desired membrane (permeate flux 300L/m(2)hr and oil rejection 97%)

A novel approach to fabricate high performance nano-SiO2 embedded PES membranes for microfiltration of oil-in-water emulsion

The goal of this study was to determine the desired preparation conditions of polyethersulfone (PES) membrane for the microfiltration of oil-in-water emulsion. Membranes were fabricated via combination of vapor induced phase separation (VIPS) and non-solvent induced phase separation (NIPS) methods. SiO2 nanoparticle were used as the hydrophilicity modification agent in the casting solutions which led to a negative impacts on the permeate flux in high concentrations due to aggregation. The effects of nanoparticle concentration, exposure time and relative humidity on the permeate flux, and their interactions were determined. The morphology of the prepared membranes were studied using FESEM, pore size distribution, contact angle, porosity, and water uptake measurement. Besides, response surface methodology (RSM) and central composite design (CCD) were applied for modeling, statistical analysis and optimization of oil-in-water emulsion microfiltration. The most significant interactions were observed for the exposure time and relative humidity, and a contradictory trend was found for flux variation. The optimum preparation conditions for nanoparticle concentration, exposure time, and humidity were found to be 1%, 33s, and 80%, respectively, where the oil rejection was higher than 98% for all runs. (C) 2015 Elsevier B.V. All rights reserved