Evaluating Thin-Film Nanocomposite Membranes to Treat Brackish Waters through Reverse Osmosis

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OVERVIEW The objective of the project is to identify whether a mixed-matrix nanocomposite membrane can be formulated that can treat real-world water, in an operating plant environment, for a representative length of time (e.g., a minimum of three months), because there are no reports in the scientific literature on this. While there are published studies on long-term performance of polyamide/zeolite reverse osmosis membranes on recovery of seawater, there are no published studies on these membranes’ performance on brackish waters (total dissolved solids < 3000 ppm). Work in 2007 identified a mixed-matrix membrane formula that produced brackish-water type performance, but there are no published reports on long-term (>48 hour) testing of these types of membranes. The project entails evaluating nanocomposite RO membranes with brackish water performance for potential scale-up and use for treating brackish waters via long-term (~3 months) tests on a small-scale test unit (swatch = 3 x 2 inch test coupons) in the Yuma Area Office Water Quality Improvement Center (WQIC). The recipient will perform tests on both controlled waters (RO permeate from the WQICs Pilot System 1) and real-world waters (pretreated agricultural drainage for RO feed). RECIPIENT INVOLVEMENT Membrane Casting and Membrane Characterization 1. Casting of membrane sheets from polyamide/zeolite nanocomposite membranes. ASU will cast materials to supply a minimum of 9 3x2 swatches from zeolite/polymer nanocomposite materials. 1 month duration --- 0-1 on timeline 2. Pre-test membrane characterization of test membranes. ASU will perform flux and rejection tests on swatches of the sheets to verify baseline performance in the laboratory at ASU under the expected operating conditions of longer-term tests. They will also characterize the physico-chemical nature and morphology of the as-cast membranes using Contact Angle, Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). 1 month duration --- 0-1 on timeline 3. Post-test membrane characterization of test membranes. ASU will perform post-characterization of the physico-chemical nature and morphology of the membranes tested in the WQIC for 3 months using Contact Angle, ATR-FTIR, AFM, SEM, and XPS. 1 month duration --- 5-6 on timeline Engineering Evaluate performance of test membranes. ASU will evaluate performance of membranes in terms of flux and rejection, using data generated during three months of testing at the WQIC. 3 months duration --- 2-5 on timeline RECLAMATION INVOLVEMENT Substantial involvement on the part Reclamation is anticipated for the successful completion of the objectives to be funded by this award. In particular, Reclamation will be responsible for the following: Membrane Testing – Reclamation staff will work closely with ASU in testing the experimental membranes. Reclamation’s role will include: 1. Provide infrastructure, water, power and test skid to evaluate the test membranes (9-cell, bench-scale test unit known as “Swatch Unit”). 2. Provide operations, maintenance and engineering support to operate the test unit, collect performance data and troubleshoot unit operating problems. 3. Provide typical RO lab analyses for swatch feed & product (per membrane type) water streams (2 dates per run).

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