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Triclosan-immobilized polyamide thin film composite membranes with enhanced biofouling resistance
Park, Sang-Hee,Hwang, Seon Oh,Kim, Taek-Seung,Cho, Arah,Kwon, Soon Jin,Kim, Kyoung Taek,Park, Hee-Deung,Lee, Jung-Hyun Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.443 No.-
<P><B>Abstract</B></P> <P>We report on a strategy to improve biofouling resistance of a polyamide (PA) thin-film composite (TFC) reverse osmosis (RO) membrane <I>via</I> chemically immobilizing triclosan (TC), known as a common organic biocide, on its surface. To facilitate covalent attachment of TC on the membrane surface, TC was functionalized with amine moiety to prepare aminopropyl TC. Then, the TC-immobilized TFC (TFC-TC) membranes were fabricated through a one-step amide formation reaction between amine groups of aminopropyl TC and acyl chloride groups present on the PA membrane surface, which was confirmed by high-resolution XPS. Strong stability of the immobilized TC was also confirmed by a hydraulic washing test. Although the TFC-TC membrane showed slightly reduced separation performance compared to the pristine control, it still maintained a satisfactory RO performance level. Importantly, the TFC-TC membrane exhibited excellent antibacterial activity against both gram negative (<I>E. coli</I> and <I>P. aeruginosa</I>) and gram positive (<I>S. aureus</I>) bacteria along with greatly enhanced resistance to biofilm formation. Our immobilization approach offers a robust and relatively benign strategy to control biofouling of functional surfaces, films and membranes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Triclosan (TC), an organic biocide, is chemically immobilized onto TFC membranes. </LI> <LI> TC-immobilized membranes (TFC-TC) have high reverse osmosis separation performance. </LI> <LI> TFC-TC membranes exhibit strong and wide-spectrum antibacterial activity. </LI> <LI> TFC-TC membranes greatly enhance resistance to biofilm formation (biofouling). </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Park, Jong-Hun,Sim, Young-Bo,Kumar, Gopalakrishnan,Anburajan, Parthiban,Park, Jeong-Hoon,Park, Hee-Deung,Kim, Sang-Hyoun Elsevier 2018 Bioresource technology Vol.262 No.-
<P><B>Abstract</B></P> <P>This study investigated the kinetic parameters of high-rate continuous performance and biofilm layer formation in a H<SUB>2</SUB>-producing dynamic membrane bioreactor, composed of a continuously stirred tank reactor along with an external module containing polyester mesh with a pore size of 100 µm. A maximum H<SUB>2</SUB> production rate of 48.9 L/L-day and hydrogen yield of 2.8 mol/mol glucose<SUB>added</SUB> were attained at a hydraulic retention time of 3 h. The maximum specific growth rate and Monod constant were estimated as 14.92 d<SUP>−1</SUP> and 1.02 g COD/L, respectively. During the entire operation without backwashing, the transmembrane pressure remained below 1.7 kPa, while tightly bound extracellular polymeric substances increased as the dynamic membrane was developed. Fluorescent <I>in situ</I> hybridization and quantitative polymerase chain reaction assays revealed that <I>Clostridium butyricum</I> was dominant in all samples; however, the biofilm had a higher proportion of <I>Prevotella</I> spp. than the fermentation liquor.</P> <P><B>Highlights</B></P> <P> <UL> <LI> H<SUB>2</SUB>-producing dynamic membrane was rapidly formed on a mesh of 100 µm. </LI> <LI> Peak HPR of 48.9 L/L-day and HY of 2.8 mol/mol glucose<SUB>added</SUB> were achieved. </LI> <LI> Monod kinetic constants were estimated for high rate H<SUB>2</SUB> production. </LI> <LI> <I>Prevotella</I> spp. showed a higher fraction in the dynamic membrane. </LI> <LI> Without backwashing, transmembrane pressure remained below 1.7 kPa. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Antibacterial activity of the thin ZnO film formed by atomic layer deposition under UV-A light
Park, Kang-Hee,Han, Gwon Deok,Neoh, Ke Chean,Kim, Taek-Seung,Shim, Joon Hyung,Park, Hee-Deung Elsevier 2017 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.328 No.-
<P><B>Abstract</B></P> <P>For the application of ZnO nanoparticles to water disinfection, immobilization of the ZnO nanoparticles on reactor surfaces is required; otherwise, the nanoparticles aggregate and leave the reactor over time. To overcome these limitations, we formed thin ZnO films on a glass substrate using atomic layer deposition (ALD) (n=400 at 140°C). An X-ray diffraction pattern and scanning electron microscope (SEM) images demonstrated that the thin ZnO film consisted of closely packed nano-sized grains. The grains had hexagonal wurtzite crystalline structures, which were mostly oriented vertically from the substrate. The thin ZnO film did not show a change in the optical properties of ZnO: absorbance at <380nm and band gap of 3.25eV. Furthermore, the thin ZnO films produced reactive oxygen species (ROS) such as superoxide anion, hydroxyl radical, and singlet oxygen, by irradiation with UV-A light (350–400nm), and the production of ROS was not diminished even after repeated use. Antibacterial activity against <I>Staphylococcus aureus</I> was observed when the ZnO films were placed under UV-A light. However, this was not evident when the ZnO films were in the dark or when the glass substrate without the ZnO film was exposed to UV-A light, suggesting that the antibacterial activity was due to ROS production by the ZnO film under UV-A light. Moreover, the bacterial cells exposed to the ZnO film under UV-A light showed a crushed morphology, indicating that the ROS facilitated the disruption of the bacterial cell membranes. Taken together, this study demonstrates that ALD firmly anchored the ZnO nanocrystalline structures on the substrate without hampering the ROS production or antibacterial activity for the purpose of water disinfection.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A thin ZnO film was fabricated on a glass substrate using atomic layer deposition. </LI> <LI> The thin ZnO film consisted of vertically-grown closely-packed nano-sized grains. </LI> <LI> The thin ZnO film generated ROS under UV-A light like ZnO nanoparticles. </LI> <LI> Antibacterial mechanism was due to cellular membrane damage by produced ROS. </LI> <LI> The thin ZnO film has practical importance for water disinfection. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Park, Jeong-Hoon,Kang, Hyun-Jin,Park, Kang-Hee,Park, Hee-Deung Elsevier 2018 Bioresource technology Vol.254 No.-
<P><B>Abstract</B></P> <P>Anaerobic digestion (AD) is a microbial process that produces renewable energy in the form of methane by treating organic waste and high-strength wastewater. Recent studies have demonstrated that conductive materials can promote direct interspecies electron transfer (DIET) between exoelectrogenic bacteria and methanogenic archaea. DIET via conductive materials is more effective for methane production than interspecies electron transfer using electron carriers such as hydrogen, a principal route of methane production in conventional AD. This critical review presents the current understanding of DIET via conductive materials for methane production, summarizes the relevant studies published to date, and analyzes these studies with regard to conductive materials, substrates, inocula, performance, and microorganisms. Based on this analysis, possible future directions are suggested for practical DIET applications via conductive materials in AD.</P> <P><B>Highlights</B></P> <P> <UL> <LI> DIET via conductive materials is a promising technology for anaerobic digestion. </LI> <LI> Critical reviews on current understanding of DIET were conducted. </LI> <LI> Relevant studies published to date were systematically analyzed. </LI> <LI> Future perspectives for practical applications are proposed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Park, Kang-Hee,Yu, Sang-Hyun,Kim, Han-Shin,Park, Hee-Deung IWA Publishing 2015 Water Science & Technology Vol.72 No.5
<P>In the operation of the forward osmosis (FO) process, biofouling of the membrane is a potentially serious problem. Development of an FO membrane with antibacterial properties could contribute to a reduction in biofouling. In this study, quaternary ammonium cation (QAC), a widely used biocidal material, was conjugated with a silane coupling agent (3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride) and used to modify an FO membrane to confer antibacterial properties. Fourier transform infrared spectroscopy (FT-IR) demonstrated that the conjugated QAC was successfully immobilized on the FO membrane via covalent bonding. Bacterial viability on the QAC-modified membrane was confirmed via colony count method and visualized via bacterial viability assay. The QAC membrane decreased the viability of <I>Escherichia coli</I> to 62% and <I>Staphylococcus aureus</I> to 77% versus the control membrane. Inhibition of biofilm formation on the QAC modified membrane was confirmed via anti-biofilm tests using the drip-flow reactor and FO unit, resulting in 64% and 68% inhibition in the QAC-modified membrane against the control membrane, respectively. The results demonstrate the effectiveness of the modified membrane in reducing bacterial viability and inhibiting biofilm formation, indicating the potential of QAC-modified membranes to decrease operation costs incurred by biofouling.</P>