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유바라즈할도라이,Dian Kharismadewi,Dirk Tuma,심재진 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.8
Chitosan (CS)/iron oxide (Fe3O4) composites were prepared using a chemical precipitation method. The CS/Fe3O4 composite was characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and zeta-potential measurements. The composite was used to remove methyl orange (MO) dye from an aqueous solution. The factors affecting the adsorption capacity, such as adsorption time, absorbent dosage and solution pH were investigated. The results suggested that the composite was an effective adsorbent for the removal of MO dye from its aqueous solution. Kinetics studies showed that the adsorption process was consistent with a pseudo-second- order model. The adsorbent efficiency was unaltered, even after five cycles of reuse, and the adsorbent could be recollected easily using a magnet. In addition, the composite exhibited a superior antibacterial efficacy against Escherichia coli; 82% within 24 h, as measured by the colony forming units.
Quang Long Pham,심재진,유바라즈할도라이,웬방호아,ChanKyu Kang 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.11
Two highly supercritical CO2-soluble, poly(vinyl acetate) (PVAc)-based macro-reversible addition-frag-mentation chain transfer (RAFT) agents were synthesized. The RAFT agents were used for the first time in RAFT/macromolecular design via the interchange of xanthates (MADIX) and polymerization of vinyl acetate (VAc) and vinylpivalate (VPi) in supercritical carbon dioxide (scCO2). A homopolymer PVAc and a block copolymer PVAc-b-PVPimade by RAFT/MADIX polymerization were characterized, and the effects of time and RAFT agents on polymer-ization were examined. For the 8.4 wt% RAFT agent in VAc, the molecular mass (Mn) of homopolymer PVAc was26,000 g mol−1and PDI was 1.35. For the copolymerization of VPi using 9.8 wt% PVAc-RAFT agent in VPi for 24 h,the Mn and PDI of PVAc-b-PVPi reached 32,400 g mol−1and 1.42, respectively. These results suggest that the poly-dispersity can be controlled during the clean production of PVAc and PVPi by RAFT/MADIX polymerization in scCO2.
Mohammad Tariqul Islam,심재진,유바라즈할도라이,웬방호아,Muhammad Naoshad Islam,나춘섭 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.6
Poly(vinyl acetate) (PVAc) was synthesized by the atom transfer radical polymerization of vinyl acetate(VAc) in supercritical carbon dioxide using CuBr/2,2':6',2''-terpyridine complex as a catalyst and ethyl 2-bromoisobutyrateas an initiator. Polymerization proceeded in a controlled manner, and low to moderate conversion wasachieved within a reasonable time. The effects of the monomer amount, temperature, pressure, initiator, and ligandloading on monomer conversion, molecular weight and molecular weight distribution of the polymer were examined. The reaction kinetics was also investigated. The polymerization reaction was found to be first-order with respect to themonomer concentration. The molecular weights of the resulting PVAc increased linearly with increasing VAc conversion.
Quang Long Pham,Van Hoa Nguyen,유바라즈할도라이,심재진 한국화학공학회 2013 Korean Journal of Chemical Engineering Vol.30 No.5
This paper reports a successful free-radical dispersion polymerization of vinyl pivalate in supercritical carbon dioxide using poly(1H,1H-dihydroperfluorooctyl acrylate) and dimethylsiloxane-g-pyrrolidone carboxylic acid (Monasil PCA) as stabilizers. In both cases, no spherical polymer particles were obtained, which might be due to the high solubility of poly(vinyl pivalate) (PVPi) in supercritical carbon dioxide. The effects of the reaction time, pressure,temperature, monomer loading, stabilizer concentration and initiator concentration on the polymer yield and molecular weight of PVPi were also investigated. In addition, the formation of poly(vinyl alcohol) via saponification of the resulting PVPi is described.