Hisashi Tamai

Dye adsorption on mesoporous activated carbon fiber obtained from pitch containing yttrium complex

Abstract The adsorption of acid dyes (Acid Blue 9, Acid Blue 74, Acid Orange 10, and Acid Orange 51), direct dyes (Direct Black 19, Direct Yellow 11, and Direct Yellow 50), and basic dyes (Basic Brown 1 and Basic Violet 3) on a highly mesoporous activated carbon fiber (Y-ACF) obtained from pitch containing yttrium acetylacetonate was investigated in terms of size of dye molecules, and pore size and surface charge of the activated carbon fiber. The results were compared with that on a microporous activated carbon fiber (A-20). The high amounts of sterically small size of acid dyes and basic dyes were adsorbed on both Y-ACF and A-20. The amounts of direct dyes, which are large in one or two dimensions of molecular structures, adsorbed on a mesoporous Y-ACF were much higher than those on microporous A-20. The adsorbed amounts of direct dyes decreased with increasing pH in alkaline pH, in which the ζ potentials of Y-ACF show negative values. From these results, we can suggest that the adsorption of dyes on activated carbon fiber varies greatly by changing pore size and surface charge of activated carbon fiber.

Highly Mesoporous Carbon Electrodes for Electric Double-Layer Capacitors

High Brunauer-Emmett-Teller method (BET) surface area and mesoporous activated carbons (ACs) were prepared by carbonization followed by activation of vinylidene chloride copolymer containing yttrium acetylacetonate Y(acac) 3 . Their performance as electrodes for electric double-layer capacitors (EDLCs) in nonaqueous electrolyte solution was evaluated and compared with those of commercial microporous ACs. The specific EDLC capacitances of the ACs with high BET surface area are higher than those of the low BET surface area ACs at low discharge current. At high discharge current, the capacitances of the mesoporous ACs are higher than those of microporous ones. This is attributed to smooth movement of organic electrolyte ions in mesopores.

Surface characterization of styrene/sodium styrenesulfonate copolymer latex particles

Abstract The surface characteristics of styrene/sodium styrenesulfonate copolymer latex particles prepared by seed polymerization in the absence of emulsifier were investigated. The surface charge densities, determined by conductometric and potentiometric titrations, increase with increasing sodium styrenesulfonate content and are higher than those of the seed latices. Also, the ζ-potentials were found to decrease with increasing sodium styrenesulfonate content, which is suggestive of an outward shift of the slipping plane, due to increased water solubility of the polymer. It was suggested that in addition to the increase in surface charge density, water-soluble polyelectrolyte at the particle surface enhances the colloidal stability of styrene/sodium styrenesulfonate copolymer latex.

Colloidal stability of polymer latices coated with bovine serum albumin

Abstract The colloidal stability of polystyrene (PS), styrene/methacrylic acid copolymer (P(St/MAA)), styrene/acrylamide copolymer (P(St/AAm)), and its hydrolyzate (P(St/AAm-H)) latices coated with bovine serum albumin (BSA) at different coverages was studied. The rates of flocculation were measured as a function of NaCl concentration by the stopped-flow spectrophotometric method. The results are considered in terms of the surface characteristics of the latex particles such as ζ-potentials. The slow flocculation of BSA-coated PS and P(St/MAA) latices was observed at low NaCl concentration where no flocculation of bare latices was detected. The contribution of the bridging effect by adsorbed BSA is suggested. The maximum rates of flocculation of PS and P(St/MAA) latices at high NaCl concentrations decrease with increasing surface coverage of BSA. At high NaCl concentrations, a steric repulsive interaction due to adsorbed BSA plays an important role. No flocculation of bare and BSA-coated P(St/AAm) and P(St/AAm-H) latices was observed at all NaCl concentrations tested. This high colloidal stability could be attributed to the steric stabilization effect due to a water-soluble polymer layer at the surface of bare latex particles.

Latex deposition on fibers. VI. Deposition state and interaction energy

Abstract The deposition of polystyrene latex particles on polyamide fiber (Nylon 6) and polyacrylonitrile fiber (Vonnel) was studied by observing the deposited latex particles with a scanning electron microscope as a function of deposition time and pH. The latex particles on Nylon fiber at low pH were connected to each other, e.g., like a rosary, with increasing deposition time. The deposition of the latex particles onto Vonnel fiber seemed to proceed along the many grooves, which were present on the fiber surface, and it was scarcely influenced by pH. On the Nylon fiber, the deposition states as a function of time and pH were conveniently interpreted by the interaction energy estimated from the Hogg, Healy, and Fuerstenau theory using a sphere-plate model and the consideration of the heterogeneous distribution of surface groups of the fiber. On the Vonnel fiber, the interaction energy of electrical double layers calculated by regarding the fiber surface as a plate possessing cylindrical holes correctly accounted for the deposition phenomena.

Some colloidal considerations on the surface characteristics of various emulsifier-free polymer latices

Abstract The home-coagulations and the hetero-coagulations between the various kinds of emulsifier-free polymer latices having 400–500 nm of uniform particle diameters were investigated as a function of KCl concentration, and the surface characteristics of their latex particles were considered on the basis of the interaction energies due to electrostatic and van der Waals forces at the critical coagulation concentrations determined. The homo- and the hetero-coagulations between styrene/acrylamide copolymer (P(St/AAm)), its hydrolyzate, and poly(vinyl acetate) latices were not observed even at high KCl concentrations, and those between polystyrene, poly(methyl methacrylate), styrene/methacrylic acid copolymer (P(St/MAA)), and styrene/2-hydroxyethyl methacrylate copolymer (P(St/HEMA)) latices took place at low interaction energies. The rapid hetero-coagulations of P(St/AAm) latex to another latex except P(St/HEMA) latex took place in spite of the presence of large interaction energy. These results on the coagulations of styrene/ hydrophilic monomer copolymer latices suggest that the particle surface of P(St/AAm) latex has a water-soluble polymer layer which exhibits a steric repulsion or bridging effects. On the other hand, the surfaces of P(St/MAA) and P(St/HEMA) latex particles seem not to give those effects.

Latex deposition on fibers: Effect of electrolytes on rate and interaction energy☆

Abstract The rate of deposition of anionic polymethyl methacrylate latex on polyamide, polyester, and polyacrylonitrile fabrics and its relation to the interaction energy were investigated as a function of electrolyte concentration. With increasing the concentration of electrolytes, the total interaction energy between latex particles and fabrics decreased and the rates of deposition on polyamide and polyester fabrics increased. The rates of deposition on polyacrylonitrile fabric were constant above a certain concentration of electolytes. The rate constants of deposition on polyacrylonitrile fabric were constant below a certain value of the estimated maximum total interaction energy ( V Tmax ) as a function of the separation distance between latex particles and fabric and decreased with further increasing V Tmax . The rate constants on polyamide fabric and polyester fabric decreased gradually with increasing V Tmax , however, latex particles deposited in spite of large values estimated for V Tmax . At the same value of V Tmax with respect to the three kinds of fabrics, the rate constants decreased in the order of polyacrylonitrile fabric, polyamide fabric, and polyester fabric.

The surface characterization of styrene-acrylamide copolymer latex particles and their deposition onto fibers

The surface characteristics of styrene-acrylamide (St-AAm) copolymer latex particles were investigated and their deposition onto polyamide (Nylon 6), polyester (polyethylene terephthalate) and polyacrylonitrile fibers was studied. Conductometric titrations and viscosity measurements of latex dispersions revealed the presence of a water-soluble polymer layer on the particle surface and the thickness of its polymer layer increased with increasing acrylamide fraction in a latex particle. The deposition rates of St-AAm copolymer latices onto Nylon 6 and polyester fibers increased with increasing acrylamide fraction and decreasing pH at a constant ionic strength. These deposition phenomena onto Nylon 6 and polyester fibers agreed qualitatively with prediction based on the electrokinetic data of the latices and the fibers. However, a participation of attractive interaction due to an increase in acrylamide fraction was also suggested.The deposition rate onto polyacrylonitrile fiber decreased with increasing acrylamide fraction in spite of a decrease in electrostatic repulsive interaction, and it was found that a specific large repulsive interaction acts between polyacrylonitrile fiber and St-AAm copolymer latex particles.

NO decomposition by ultrafine noble metals dispersed on the rare earth phosphate hollow particles

Novel fine polymer particles containing ultrafine Pd, Pt or Rh metal dispersed on the core-shell [core, poly(styrene-co-acrylamide) or poly(styrene-co-acrylic acid); shell, LnPO4(Ln = Ce, Nd, Pr, Sm, La)] type microsphere were prepared by the emulsifier-free emulsion polymerization of styrene with acrylamide or acrylic acid followed by the addition of PdCl2, HPtCl6, or RhCl3 and finally by the addition of a mixture of Ln(NO3)3 and NaH2PO4. Pyrolysis of the resulting polymer particles at 700–900°C provides polymer-free hollow particles (diameter 450–550 nm) composed of noble metals and LnPO4. The excellent catalytic reduction of NO gas into N2 and O2 was observed at 500–700°C using the rersulting particles as catalyst.

Antibacterial activated carbons prepared from pitch containing organometallics

Abstract A simple method for the preparation of antibacterial activated carbons was reported. The antibacterial activated carbons uniformly contain metal oxides, i.e. CaO, MgO, NiO, CoO and ZnO. These activated carbons were readily prepared by steam activation of pitch containing organometallics, i.e. CaI 2 , t -BuMgBr, Ni(acac) 2 , Co(acac) 3 , and Zn(acac) 2 . The antibacterial activities for B . subtilis , S . aureus , and E . coli were estimated by the growing inhibitory effect in the solutions containing activated carbons and by haloes at surrounding of activated carbons on agar. The CaO, MgO, CoO, and ZnO dispersed activated carbons exhibited obviously the antibacterial activity for B . subtilis both in the solutions and on agar. The MgO and CoO dispersed ones exhibited a growing inhibition effect for S . aureus . On the other hand, no inhibitory effect was observed for the growing of E . coli .