Using Pressure-Driven Membrane Processes to Remove Emerging Pollutants from Aqueous Solutions

Abstract

Currently, there is great concern about global water pollution. Wastewater generally contains substances called emerging pollutants, and if the removal of these pollutants is not given sufficient attention, the pollutants can enter into the water cycle and reach the water supply for domestic use, causing adverse effects on the well-being of people. In order to avoid this menace, a multitude of techniques to reduce the high concentration levels of these substances dissolved in water are being researched and developed. One of the most-used techniques for this goal is the physical-chemical separation of contaminants in water through membrane technology. In this study, different membranes were tested with the objective of investigating the removal of three emerging pollutants: caffeine, metformin, and methyl-paraben. Initially, a nanofiltration (NF) membrane was selected, and the influence of pressure was evaluated in the rejection coefficients and permeate fluxes. Next, a screening of three new membranes to remove methyl paraben was completed. The influence of the operating variables, working pressure, and methyl paraben-feed concentration was checked. Finally, the solution-diffusion model was applied to predict the behavior of the different membranes in the removal of methyl paraben. A good correlation between experimental and calculated values of permeate flux and methyl paraben concentration was obtained.

Prediction of Flux and Rejection Coefficients in the Removal of Emerging Pollutants Using a Nanofiltration Membrane

“…It can be observed that the differences obtained are a consequence of the pressure and temperature range used in the tests, as well as the type of flow through the membrane, which can vary depending on the experimental equipment used. The highest permeability coefficients are obtained in tests conducted in other studies at pressures higher than 10 bar [21,23].…”

“…For each compound, four assays are conducted, where, in each one, the feeding concentration is kept constant at 5, 10, 15, and 25 ppm while the pressure varies from 5 to 20 bar. The experimental conditions tested-temperature 20 ± 1 • C; range of pressures; and concentrations-were selected taking into account other previous works [21]. (3) Experimental series for the final membrane characterization: This series includes the same assays as the first experimental series, but they are conducted after the experimentation with the emerging contaminants has been completed.…”

“…Overall, low determination coefficients are obtained, probably because this model works better to estimate the removal of inorganic salts in reverse osmosis membranes. However, the significance of applying this model lies in the fact that other authors [21,32,39] obtain high coefficients of determination and accurate estimations of the behaviour of nanofiltration membranes towards organic compounds. For example, this membrane has been used to eliminate methyl paraben, and the determination coefficients are higher [21].…”

“…tration membranes towards organic compounds. For example, this membrane has been used to eliminate methyl paraben, and the determination coefficients are higher [21].…”

“…Therefore, the simplified solution-diffusion model is considered valid for estimating the membrane behaviour towards carbamazepine but not capable of predicting its behaviour towards ketoprofen and bisphenol A. Other studies report a good fit between experimental values and values predicted using the Spiegler-Kedem-Katchalsky (SKK) model [21,32].…”