US 2014.0076728A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2014/0076728 A1 Prakash et al. (43) Pub. Date: Mar. 20, 2014 (54) CONCENTRATION POLARIZATION Publication Classification IDENTIFICATION AND MITIGATION FOR MEMBRANE TRANSPORT (51) Int. Cl. CO2F L/469 (2006.01) (71) Applicant: Ohio State Innovation Foundation, BOID 6/42 (2006.01) Columbus, OH (US) (52) U.S. Cl. CPC ............ C02F I/4693 (2013.01); B0ID 61/422 (72) Inventors: Shaurya Prakash, Columbus, OH (US); (2013.01) Karen Bellman, Columbus, OH (US) USPC .................................. 204/518; 204/627; 96/4 (73) Assignee: Ohio State Innovation Foundation, Columbus, OH (US) (57) ABSTRACT (21) Appl. No.: 14/032,164 Disclosed herein is a membrane separation apparatus with reduced concentration polarization and enhanced permeate (22) Filed: Sep.19, 2013 flux. Also disclosed is a method for separating permeate from retentate in a fluid using the disclosed membrane separation Related U.S. Application Data apparatus. Also disclosed is a method for inhibiting or pre (60) Provisional application No. 61/702.929, filed on Sep. venting concentration polarization of a permeable membrane 19, 2012. used in membrane separation. Patent Application Publication Mar. 20, 2014 Sheet 1 of 9 US 2014/0076728A1 FIG IA Patent Application Publication Mar. 20, 2014 Sheet 2 of 9 US 2014/0076728A1 FIG IB Patent Application Publication Mar. 20, 2014 Sheet 3 of 9 US 2014/0076728A1 FIG IC Patent Application Publication Mar. 20, 2014 Sheet 4 of 9 US 2014/0076728A1 FIG ID Patent Application Publication Mar. 20, 2014 Sheet 5 of 9 US 2014/0076728A1 FIG 2A Patent Application Publication Mar. 20, 2014 Sheet 6 of 9 US 2014/0076728A1 FIG 2B Patent Application Publication Mar. 20, 2014 Sheet 7 of 9 US 2014/0076728A1 e Ag/AgCl Goid Wire, Af Electrode Reference Electrodes Gold Wire, -- f Electrode Pereate Nanocapitary Array verbrane FIG 3 Patent Application Publication Mar. 20, 2014 Sheet 8 of 9 US 2014/0076728A1 FIG 5 ts 8: 8: : R: 3. & S: s: 88: Bias try FIG 6 Patent Application Publication Mar. 20, 2014 Sheet 9 of 9 US 2014/0076728A1 Concentration Polarization (N. KN y Á Concentration parizatio: iayer particle Suspension -arai e X The 8te areate fix FIG 7A, Cake Formation (N > N.) concentration polarization ayer Y. cake layer y particle 8 spesia -- XXXXXs X permeate fux FIG 7B US 2014/0076728 A1 Mar. 20, 2014 CONCENTRATION POLARIZATION slope than seen in the ohmic region (overlimiting region). IDENTIFICATION AND MITIGATION FOR This trend arises in electrokinetic flows. Furthermore, many MEMBRANE TRANSPORT systems work with pressure-driven flows and also exhibit a reduction in measurable flux due to concentration polariza CROSS-REFERENCE TO RELATED tion. This Voltage current behavior can be seen for any charge APPLICATIONS selective membrane or non-porous membrane that is being 0001. This application claims benefit of U.S. Provisional used to separate a purely electrolyte Solution. For membranes Application No. 61/702,929, filed Sep. 19, 2012, which is separating particles and molecules larger than ions, a cake hereby incorporated herein by reference in its entirety. layer can be formed, thus preventing the overlimiting region from forming and potentially causing an overall decline in STATEMENT REGARDING FEDERALLY flux as the cake formation progresses. SPONSORED RESEARCH ORDEVELOPMENT 0007 Current methods of polarization reduction can be classified into three broad categories, (i) mechanical, (ii) 0002 This invention was made with Government Support chemical, and (iii) electrical. Mechanical methods of polar under Grant No. 60024176 awarded by the Defense ization reduction include any method that can be achieved Advanced Research Projects Agency. The Government has with mechanical agitation to the fluid Surrounding the mem certain rights in the invention. brane, including but not limited to mixing, module vibration, TECHNICAL FIELD and flow pulsing. Chemical methods include chemical Sur face modification of the membrane or solution to be sepa 0003. This invention relates to methods and devices for rated. Electrical methods include applying an electrical, mag membrane separation, in particular for identifying and miti netic or a combination field on or near the membrane in order gating concentration polarization during membrane separa increase flux by mitigating concentration polarization. How tion. ever, current methods of polarization reduction are notable to achieve flux enhancement with low energy costs. BACKGROUND 0004 Membrane separation techniques involve the sepa SUMMARY ration, concentration, and/or purification of a raw material using a selective permeation membrane where components of 0008 Disclosed herein is a membrane separation appara the raw material selectively permeate the membrane when tus with reduced concentration polarization and enhanced there is a driving force (e.g., pressure difference, concentra permeate flux. The apparatus comprises a feed chamber and a tion difference, potential difference, or temperature differ permeation chamber separated by a fluid permeable mem ence). Different membranes and driving forces are employed brane. The permeable membrane comprises a separation side in different membrane separation processes. Examples of in contact with the feed chamber and a permeation side in membrane separation processes that have been industrially contact with the permeation chamber. The apparatus also used include microfiltration, ultrafiltration, reverse osmosis, comprises a primary electrode positioned at the fluid bound dialysis, electrodialysis, gas separation, pervaporation, and ary layer of the permeable membrane. The apparatus can also emulsion liquid membrane. In addition, there are many mem comprise an AC Voltage source configured to supply a Voltage brane separation processes under development, Such as mem less than 25 V, including between 0.5 and 10 V, to the primary brane extraction, membrane distillation, bipolar membrane electrode. electrodialysis, membrane split phase, membrane absorption, 0009. The fluid boundary layer can be determined by one membrane reaction, membrane control release, and mem of ordinary skill in the art. However, in some embodiments, brane biosensor. Membrane separation techniques are widely the primary electrode is positioned at a location within 10, 20, applied in petrochemical industry, biological pharmaceutical 30, 40, 50, 60, 70, 80, 90, or 100 um from the permeable industry, medical and sanitation fields, metallurgy industry, membrane. In some embodiments, the electrode is positioned electronics, energy field, light industry, textile industry, food on the separation side of the permeable membrane; however industry, environmental protection industry, aerospace indus a reverse orientation is also contemplated. try, maritime transport industry, and daily life field. 0005. However, concentration polarization during mem 0010. In some embodiments, the primary electrode com brane separation processes affects membrane flux and causes prises a conductive mesh positioned adjacent to the mem membrane fouling. Concentration polarization arises in brane. In other embodiments, the permeable membrane is membranes when rejected Solutes accumulate at the mem plated with a conductive material on the separation side that brane Surface. The rejected Solutes can cause apparent fouling acts as the primary electrode. and significantly impede solvent flux through the membrane. 0011. The apparatus also comprises a counter electrode, The impediment to flux is due to the rise in local osmotic e.g., positioned on the permeation side of the permeable pressure at the membrane Surface, which causes a decrease in membrane. For example, the counter electrode can be posi the effective driving pressure. tioned within the permeation chamber or at a location within 0006. In membranes and micro/nanoscale fluidic devices, 10, 20, 30, 40, 50, 60, 70, 80,90, or 100 um from the perme concentration polarization can obstruct the flow, causing a ation side of the permeable membrane. As with the primary shift from a linear relationship between applied voltage and electrode, the counter electrode can comprise a conductive current density (ohmic region) to an Voltage independent mesh, or the permeable membrane can be plated with a con current flow region (limiting region), where current density is ductive material on the permeation side that acts as the used to monitor the amount of flow through the membrane. counter electrode. Other configurations are contemplated so Eventually the relationship between applied voltage and cur long as at least one electrode is positioned at the fluid bound rent density returns to a linear relationship with a smaller ary layer of the permeable membrane. US 2014/0076728 A1 Mar. 20, 2014 0012. The AC voltage source can be configured to apply 0023 FIG. 5 is an image of an embodiment of a partition the voltage at an oscillation frequency between 1 kHz and 10 disk for use in a low energy pressure driven reverse osmosis MHz. For example, the AC voltage source can be a waveform system that was gold plated in order to render it conductive. generator. 0024 FIG. 6 is a graph showing concentration flux (nM/ 0013 The apparatus can further comprise a fluid having minim) as a function of bias (mV) for potassium phosphate retention components and permeation components in the feed buffer (pH 7+0.2) at 1 mM (square) and 0.2 mM (diamond) channel. In particular, the fluid can have one or more charged with 10 nm membranes. At