Glycidyl and Methyl Methacrylate UV-Grafted PDMS Membrane Modification toward Tramadol Membrane Selectivity

Pharmaceutical wastewater pollution has reached an alarming stage, as many studies have reported. Membrane separation has shown great performance in wastewater treatment, but there are some drawbacks and undesired byproducts of this process. Selective membranes could be used for pollutant investigation sensors or even for pollutant recovery. The polydimethylsiloxane (PDMS) membrane was first tested on separated and mixed antibiotic (ATB) water solutions containing sulfamethoxazole (SM), trimethoprim (TMP), and tetracycline (TET). Then, the bare and ultra-violet grafted (UV-grafted) PDMS membranes (MMA-DMAEMA 10, GMA-DMAEMA 5, and GMA-DMAEMA 10) were tested in tramadol (TRA) separation, where the diffusion coefficient was evaluated. Finally, the membranes were tested in pertraction with a mixture of SM, TMP, TET, and TRA. The membranes were characterized using the following methods: contact angle measurement, FTIR, SEM/EDX, and surface and pore analysis. The main findings were that TET was co-eluted during mixed ATB pertraction, and GMA-DMAEMA 5 was found to selectively permeate TRA over the present ATBs.

Synthesizing Various Organic Polyacid Compounds for Modifying Forward Osmosis Membranes to Enhance Separation Performance

In order to overcome the challenges of low permeate flux (Jp) and the accompanying reverse solute flux (JS) during the forward osmosis (FO) membrane separation process, we synthesized four hybrid materials of polyacid-based organic compounds and incorporated them into the selective polyamide (PA) layer to make novel thin-film nanocomposite (TFN) FO membranes. The Jp and JS of each membrane were evaluated and used along with membrane selectivity (Jp/JS) as indicators of membrane separation performance. The fabricated and modified membranes were also characterized for ridge and valley surface morphologies with increasing hydrophilicity and finger-shaped parallel channels in the PSf substrate. Moreover, two highly hydrophilic nanoparticles of graphene oxide (GO) and titanium oxide (TiO2) were introduced with the hybrid materials for PA modification, which can further enhance the Jp of the TFN membranes. The highest Jp of the TFN membranes achieved 12.1 L/m2-h using 0.1% curcumin-acetoguanamine @ cerium polyacid (CATCP) and 0.0175% GO. The characteristic peaks of the hybrid materials were detected on the membrane surface using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, evidencing successful incorporation of the hybrid materials during membrane modification. Here, we present the novel TFN membranes using hybrid materials for separation applications. The reactions for synthesizing the hybrid materials and for incorporating them with PA layer are proposed.

Acid-Resistance Enhancement of Thin-Film Composite Membrane Using Barrier Effect of Graphene Oxide Nanosheets

In this study, the effect of graphene oxide nanosheets (GONs) embedded in a thin-film composite (TFC) polyamide (PA) membrane on the acid resistance of the membrane was investigated by comparison with the effect of oxidized single-walled carbon nanotubes (o-SWNTs). Both GONs and o-SWNTs increased the hydrophilicity of the membranes and caused the formation of ridges and clustered bumps on the surfaces, resulting in slightly improved water permeability. However, the o-SWNTs-embedded membrane did not show a difference in acid resistance depending on the concentration of embedded material, but the acid resistance of the GONs-embedded membrane increased with increasing concentration. The acid resistance of the GONs-embedded membranes appears to be mainly due to the barrier effect caused by the nanosheet shape of the GONs along with a sacrificial role of the PA layer protruded by the addition of GONs and the decrease of acid reaction sites by the hydrogen bonding between GONs and PA. When the TFC PA membrane was prepared with a high amount (300 ppm) of the GONs without considering aggregation of GONs, membrane selectivity exceeding 95% was maintained 4.7 times longer than the control TFC membrane. This study shows that the acid resistance can be enhanced by the use of GONs, which give a barrier effect to the membrane.