Nanofiltration separation of polyvalent and monovalent anions in desalination brines

This work, as part of a global membrane process for the recovery of alkali and acids from reverse osmosis (RO) desalination brines, focuses on the nanofiltration (NF) separation of polyvalent and monovalent anions, more specifically sulfate and chloride. This pretreatment stage plays a key role in the whole recovery process. Working with model brines simulating the concentration of RO concentrates, 0.2–1.2 M chloride concentration and 0.1 M sulfate concentration, the experimental performance and modeling of the NF separation is reported. The study has been carried out with the NF270 (Dow Filmtec) membrane. The effect of operating pressure (500–2000 kPa), ionic strength (0.4–1.3 M) and chloride initial concentration (0.2–1.2 M) on the membrane separation capacity has been investigated. Finally, the Donnan Steric Pore Model (DSPM) together with experimentally determined parameters, effective pore radius (rp), thickness of the membrane effective layer (d) and effective membrane charge density (Xd), was proved accurate enough to satisfactorily describe the experimental results. In this work we provide for the first time the analysis of partitioning effects and transport mechanism in the NF separation of sulfate and chloride anions in concentrations that simulate those found in RO desalination brines.This work has been financially supported by projects CTQ2008-0690, ENE2010-15585 and CTM2011-23912 (co-financed by ERDF Funds).The authors would like to acknowledge SADYT, S.A. for providing assistance for this work

Modelling the separation by nanofiltration of a multi-ionic solution relevant to an industrial process

International audienc

Mechanisms governing the selectivity of NF membranes during the concentration of clavulanic acid

International audienc

Nanofiltration of multi-ionic solutions: prediction of ions transport using the SEDE model

International audienceThis work focuses on the application of nanofiltration (NF) to the concentration of a pharmaceutical product, Clavulanate (), from clarified fermentation broths, which show a complex composition with six main identified ions (, , , , and ), glucose and glycerol. The solutes transport through the NF membrane pores was investigated using the SEDE (Steric, Electric and Dielectric Exclusion) model. This model was applied to predict the rejection rates of the initial feed solution and the final concentrated solution (10-fold concentrated solution). The best results were achieved with a single fitted parameter, (the dielectric constant of the solution inside pores) and considering that the membrane selectivity is governed by steric, electric (Donnan) and Born dielectric exclusion mechanisms. While the predicted intrinsic rejections of solutions comprising up to six ions and uncharged solutes were in good agreement with the experimental values, the deviations were much larger for the 10-fold concentrated solution

The two-dimensional Pore and Polarization Transport Model to describe mixtures separation by nanofiltration: Model validation

International audienc

DSP&DE Model Applications

International audienc