TY - JOUR A1 - Pham, Q.L. A1 - Haldorai, Y. A1 - Nguyen, V.H. A1 - Tuma, Dirk A1 - Shim, J.-J. T1 - Facile synthesis of poly(p-phenylenediamine)/MWCNT nanocomposites and characterization for investigation of structural effects of carbon nanotubes JF - Bulletin of materials science N2 - Poly(p-phenylenediamine) (PpPD)/carboxylic acid-functionalized multiwalled carbon nanotubes (c-MWCNTs) nanocomposites were prepared by chemical oxidative polymerization using potassium persulfate (K2S2O8) as an oxidant. Field-emission scanning electron microscopy (FE–SEM) and field-emission Transmission electron microscopy (FE–TEM) showed that a tubular layer of PpPD was coated on the surface of carbon nanotubes with a thickness of 10–20 nm. FT–IR analysis provided an evidence for the formation of nanocomposites. The thermal stability of nanocomposites was improved by addition of c-MWCNTs as confirmed by thermogravimetric analysis (TGA). XRD spectra showed that the crystalline nature of PpPD was not affected much by the addition of c-MWCNTs. As the content of c-MWCNTs was increased, the electrical conductivity of the nanocomposites increased due to the interaction between polymer and nanotubes that enhances electron delocalization. KW - p-Phenylenediamine KW - Multi-walled carbon nanotube KW - Nanocomposite KW - Oxidative polymerization PY - 2011 SN - 0250-4707 SN - 0973-7669 VL - 34 IS - 1 SP - 37 EP - 43 PB - Indian Academy of Sciences CY - Bangalore AN - OPUS4-24339 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tuma, Dirk A1 - Kharismadevi, D. A1 - Haldorai, Y. A1 - Nguyen, V. H. A1 - Shim, J.-J. T1 - Synthesis of graphene oxide-poly(2-hydroxyethylmethacrylate) composite by dispersion polymerization in supercritical CO2: adsorption behavior for the removal of organic dye JF - Composite Interfaces N2 - The use of a biocompatible and thermoresponsive polymer, poly (2-hydroxyethyl methacrylate) (PHEMA) grafted onto the surface of graphene oxide (GO) as an adsorbent for the removal of a cationic dye (methylene blue [MB]) from an aqueous solution is examined in this work. GO–PHEMA forms a hydrogel in water thus overcoming the problem faced by carbon-based adsorbent materials during post-treatment (i.e., separation of adsorbent from the aqueous phase). The GO–PHEMA composite was synthesized using a green approach through dispersion polymerization in supercritical CO2. The successful preparation of this composite was confirmed by a series of characterization techniques. The adsorption behavior of the composite toward MB, such as the effect of the adsorbent dosage, pH, contact time, dye concentration, and recyclability was observed. In addition, the adsorption isotherm, kinetics and thermodynamics were investigated. According to the experimental data, the adsorption parameters were found to fit well into the Freundlich adsorption isotherm with a correlation coefficient of 0.975 and a maximum predicted adsorption capacity of 39.41 mg g−1 at 25 °C. The adsorption kinetics studies showed that the adsorption behavior followed a pseudo-second-order reaction. On the other hand, the thermodynamics studies showed that the adsorption of MB on GO–PHEMA composite followed spontaneous and endothermic adsorption process with an efficient adsorption temperature at 45 °C. The experimental results also showed that the GO–PHEMA composite could remove 99.8 % of the dye in 45 min. Therefore, GO–PHEMA composite is a favorable green adsorbent for environmental applications. KW - graphene oxide KW - poly (2-hydroxyethyl methacrylate) (PHEMA) KW - adsorption KW - composite materials PY - 2016 DO - https://doi.org/10.1080/09276440.2016.1169707 SN - 0927-6440 SN - 1568-5543 VL - 23 IS - 7 SP - 719 EP - 739 PB - Taylor & Francis CY - London, UK AN - OPUS4-36293 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Haldorai, Y. A1 - Kharismadevi, D. A1 - Tuma, Dirk A1 - Shim, J.-J. T1 - Properties of chitosan/magnetite nanoparticles composites for efficient dye adsorption and antibacterial agent JF - Korean Journal of Chemical Engineering N2 - 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. KW - Chitosan KW - Fe3O4 KW - Composite material KW - Adsorbent KW - Antibacterial agent PY - 2015 DO - https://doi.org/10.1007/s11814-014-0368-9 SN - 0256-1115 SN - 1975-7220 VL - 32 IS - 8 SP - 1688 EP - 1693 PB - Springer US CY - New York AN - OPUS4-35894 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -