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Chu, Kyoung Hoon,Fathizadeh, Mahdi,Yu, Miao,Flora, Joseph R. V.,Jang, Am,Jang, Min,Park, Chang Min,Yoo, Sung Soo,Her, Namguk,Yoon, Yeomin American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.46
<P>Functionalized graphene oxide (GO), derived from pure graphite via the modified Hummer method, was used to modify commercially available ceramic ultrafiltration membranes using the vacuum method. The modified ceramic membrane functionalized with GO (ceramic(GO)) was characterized using a variety of analysis techniques and exhibited higher hydrophilicity and increased negative charge compared with the pristine ceramic membrane. Although the pure water permeability of the ceramic(GO) membrane (14.4-58.6 L/m(2) h/bar) was slightly lower than that of the pristine membrane (25.1-62.7 L/m(2) h/bar), the removal efficiencies associated with hydrophobic attraction and charge effects were improved significantly after GO coating. Additionally, solute transport in the GO nanosheets of the ceramic(GO) membrane played a vital role in the retention of target compounds: natural organic matter (NOM; humic acid and tannic acid), pharmaceuticals (ibuprofen and sulfamethoxazole), and inorganic salts (NaCl, Na2SO4, CaCl2, and CaSO4). While the retention efficiencies of NOM, pharmaceuticals, and inorganic salts in the pristine membrane were 74.6%, 15.3%, and 2.9%, respectively, these increased to 93.5%, 51.0%, and 31.4% for the ceramic(GO) membrane. Consequently, the improved removal mechanisms of the membrane modified with functionalized GO nanosheets can provide efficient retention for water treatment under suboptimal environmental conditions of pH and ionic strength.</P>
Evaluation of Humic Acid and Tannic Acid Fouling in Graphene Oxide-Coated Ultrafiltration Membranes
Chu, Kyoung Hoon,Huang, Yi,Yu, Miao,Her, Namguk,Flora, Joseph R.V.,Park, Chang Min,Kim, Suhan,Cho, Jaeweon,Yoon, Yeomin American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.34
<P>Three commercially available ultrafiltration (UF) membranes (poly(ether sulfone), PES) that have nominal molecular weight cut-offs (5, 10, and 30 kDa) were coated with graphene oxide (GO) nanosheets. Field-emission scanning electron microscopy, Fourier-transform infrared spectroscopy, confocal laser scanning microscopy, water contact angle measurements, and X-ray photoelectron spectroscopy were employed to determine the changed physicochemical properties of the membranes after GO coating. The water permeability and single-solute rejection of GO-coated (GO(c)) membranes for humic acid (HA) molecules were significantly higher by approximately 15% and S5%, respectively, compared to those of pristine UF membranes. However, the GOc membranes for single-solute tannic acid (TA) rejection showed similar trends of higher flux decline versus pristine PES membranes, because the relatively smaller TA molecules were readily adsorbed onto the membrane pores. When the mixed-solute of HA and TA rejection tests were performed, in particular, the adsorbed small TA molecules resulted in irreversible membrane fouling due to cake formation and membrane pore blocking on the membrane surface for the HA molecules. Although both membranes showed significantly higher flux declines for small molecules rejection, the GOc membranes showed better performance than the pristine UF membranes in terms of the rejection of various mixed-solute molecules, due to higher membrane recovery and antifouling capabilities.</P>
Im, Jong-Kwon,Heo, Jiyong,Boateng, Linkel K.,Her, Namguk,Flora, Joseph R.V.,Yoon, Jaekyung,Zoh, Kyung-Duk,Yoon, Yeomin Elsevier 2013 Journal of hazardous materials Vol.254 No.-
<P><B>Abstract</B></P> <P>Ultrasonic (US) and single-walled carbon nanotube (SWNT)-catalyzed ultrasonic (US/SWNT) degradation of a pharmaceutical (PhAC) mixture of acetaminophen (AAP) and naproxen (NPX) used as analgesics was carried out in water. In the absence of SWNTs, maximum degradations of AAP and NPX occurred at a high frequency (1000kHz) and under acidic conditions (pH 3) and different solution temperatures (25°C at 28kHz and 35°C at 1000kHz) during US reactions. Rapid degradation of PhACs occurred within 10min at 28kHz (44.5% for AAP; 90.3% for NPX) and 1000kHz (39.2% for AAP; 74.8% for NPX) at a SWNT concentration of 45mgL<SUP>−1</SUP> under US/SWNT process, compared with 28kHz (5.2% for AAP; 10.6% for NPX) and 1000kHz (29.1% for AAP; 46.2% for NPX) under US process. Degradation was associated with the dispersion of SWNTs; small particles acted as nuclei during US reactions, enhancing the H<SUB>2</SUB>O<SUB>2</SUB> production yield. NPX removal was greater than AAP removal under all US-induced reaction and SWNT adsorption conditions, which is governed by the chemical properties of PhACs. Based on the results, the optimal treatment performance was observed at 28kHz with 45mgL<SUP>−1</SUP> SWNTs (US/SWNT) within 10min.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Sonodegradation of acetaminophen and naproxen was performed. </LI> <LI> Degradation was enhanced with the dispersion of SWNTs under US irradiation. </LI> <LI> Synergistic effect on the degradation PhACs was observed in US/SWNT process. </LI> <LI> Significant removal of dissolved organic carbon was achieved. </LI> </UL> </P>