Using plasma-induced graft polymerization technique which is well known as a surface modification method, the grafted polymer was formed in pores of the porous material. Although plasma treatment made polymer radicals primarily on the outer surface of the porous substrate, the treatment also formed a few radicals inside the substrate. The radicals inside the substrate reacted with monomer and grafted polymer formed in the pores. The location of grafted polymer depended on the balance between monomer diffusivity and reactivity. The technique can be utilized for functionalization of pores of the porous substrate. Several applications are also explained.

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Most biofilms have redox stratification where aerobic and anaerobic zones are stratified. This inherent property can be potentially applied to removals of persistent organic pollutants and simultaneous carbon and nitrogen. Biofilm reactors, therefore, have been numerously developed; however, their downsides are long-term startup and difficulty to maintain stable reactor performance since the reactor might experience sloughing events. The engineering challenges are to reduce startup time and to create rigid biofilm resistant to such sloughing events. Given that initial bacterial adhesion is an important factor to govern biofilm cohesiveness, enhancement of initial bacterial adhesion to a substratum is required. Here, we applied radiation-induced graft polymerization (RIGP) in terms of modification of a substratum to enhance bacterial adhesion and finally to develop a novel biofilm reactor system. Polyethylene sheets and hollow-fibers were modified with either amino or sulfonic acid groups. RIGP provides precise degree of grafting and density of the functional groups. Bacterial adhesion test on surface-modified membrane has revealed that membrane potential, i.e., electrostatic interaction, mainly governs bacterial adhesion rate, indicating that positivelycharged surfaces are favorable for initial bacterial adhesion. On the contrary, these surfaces potentially decrease bacterial activity, which is probably dependent on cell wall structures of Gram-positive and -negative bacteria. Even though bacteria attaching to the surfaces decrease the activity, flow cell test has demonstrated that these surfaces enhanced and maintained E. coli biofilm growth whereas the biofilm on negatively-charged surfaces did not grow well, paving the way for the effectiveness of the positively charged surfaces for bacterial immobilization carriers. Membrane-aerated biofilm reactors with positively-charged surface have been developed for controllable nitritation (conversion from ammonium to nitrite) and for simultaneous nitrification and denitrification, which achieved high oxygen utilization efficiency and high nitrogen removal rates. Therefore, we conclude that surface-modification by RIGP provides a suitable surface where rigid biofilm grows rapidly, leading to development of the novel biofilm reactor system for wastewater treatment.

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Polytetrafluoroethylene (PTFE)-based polymer electrolyte membranes were developed by radiation-grafting of styrene onto PTFE films and subsequent sulfonation. However, the PTFE is a radiation-degradation material. To overcome this disadvantage, we introduced the γ-crosslinked structure into the PTFE to increase its radiation-resistance before grafting. On the contrary, the UV method is very useful as an irradiation source for grafting. Under the UV irradiation, the mechanical properties of the PTFE films were almost not affected, while the radicals were generated on the surface of the film. The surface radicals initialed the styrene grafting, and the graft chains were readily propagated into the PTFE films. The resultant grafted films were sulfonated to obtain the polymer electrolyte membranes. Even through the degree of grafting was lower than 10%, the proton conductivity of the newly prepared electrolyte membranes can reach a value similar to Nafion. In comparison with γ-ray radiation grafting, the photografting technique is very simple and safe, and causes less damages to the membranes because the significant degradation of the PTFE main chains can be avoided.

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A novel method for impregnating extractants to a polymeric porous membrane of hollow-fiber form was suggested to collect metal ions at high rate by permeating a metal-ion-containing solution through the pores of the extractantimpregnated porous membrane. The extractants, such as HDEHP, Cyanex 272, TOPO, and Aliquat 336, were impregnated to the polymer chain grafted onto the pore surface of the porous membrane via a hydrophobic interaction between the hydrophobic moiety contained in the extractant and the long alkyl chain introduced into the graft chain. The amounts of extractants impregnated ranged from 1.2 to 2.1 mole per kg of the GMA-grafted porous membrane, which was comparable to and higher than those of conventional extractant-impregnated beadous resins. For the impregnation of the neutral and basic extractants, the diol and carboxypentylamino groups, respectively, coexisting with hydrophobic groups of the graft chain worked well to retain the permeability after impregnation and to increase the amount of the extractant impregnated. The extractants impregnated to the graft chain were found to bind the metal ions efficiently, i.e., at a molar binding efficiency of 100%. In addition, no deterioration of the amount of metal ions adsorbed after the repeated uses of adsorption and elution procedures revealed that the leakage of the extractants from the graft chain was negligible.

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The electrodialysis with ion-exchange membranes is a very useful method for separating an objective amino acid from mixed amino acids. The values of the limiting current density in the electrodialysis for various kinds of amino acids and pH were measured in this work. It was found that the values of limiting current density decreased with increasing the molecular weight of amino acids, viz., glycine (Gly), alanine (Ala), and arginine (Arg). It was evident that the relationship between the concentration of total ions in the feed solution and the limiting current density showed a straight line which passed through the origin. The value of the limiting current density of amino acids is smaller than that of inorganic ions.

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Harnal D is a fast-disintegrating tablet containing fine, modified-release (MR) particles. The dissolution-controlled film on the MR particles consisted of a mixture of water-soluble and -insoluble polymers, with a very smooth particle surface (as determined by SEM observation). During dissolution testing, very fine pores on the surface of the MR particles were formed, and the drug release rate was controlled through these pores. The dissolution-controlled film was usually damaged during the compression process, and thus the dissolution rate increased. However WOWTAB technology, which was applied to Harnal D, can be manufactured at a low compression pressure, thereby avoiding damage to the dissolution-controlled film. In fact, there was no difference in the dissolution rate between the MR particles and tablet.

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