Kazuyuki Chihara

Control of micropore diffusivities of molecular sieving carbon by deposition of hydrocarbons

Abstract Adsorption of ethylbenzene and styrene at 150–400°C followed by heat treatment at 400°C was tried for controlling diffusivities in micropores of Molecular Sieving Carbon. The amount of carbon deposited after heat treatment is a function of adsorption temperature. Diffusivities of oxygen and nitrogen were measured using the Chromatographic method and found to decrease sharply with the small increase of the amount of carbon deposited. The ratio of O 2 N 2 diffusivities, however, was little affected by this treatment.

Interpretation for the micropore diffusivities of gases in molecular-sieving carbon

Abstract Physical interpretations were tried for the experimental data on micropore diffusivity of gases in molecular-sieving carbon (MSC) reported by the authors elsewhere. Micropore diffusion is so-called activated diffusion in the space between graphite layer planes and diffusion coefficient is expressed as D = D 0 exp( −E/RT ). The experimentally determined D 0 for Ar, Kr, Xe, N 2 , and CH 4 agreed with D 0 estimated theoretically from the activation energy, E , and structural parameters of MSC by using the absolute rate theory. The isosteric heats of adsorption, q st , and E are compared with those calculated on the basis of Lennard-Jones potential with London expressions for the space between two graphitized carbon surfaces. The values of q st and E for Ar, Kr, and Xe suggested that the distance of the two graphite layers was 4.4 ± 0.1 A.

Heterogeneous coagulation of organic colloid and powdered activated carbon

Abstract For the treatment of wastewaters containing both dissolved and suspended organics, powdered activated carbon may well be applied to remove dissolved organics by adsorption, and suspended solid organics by heterogeneous coagulation, at the same time. The condition for this heterogeneous coagulation was studied here. First, control of surface charge of activated carbon by heat treatment was examined. It was found that it is possible to shift the surface charge of the powdered activated carbon in a positive direction. Secondly, heterogeneous coagulation of organic colloid by heat-treated carbon or carbon black was attempted. Coagulation was found to be successful. Stoichiometry of the coagulation was well explained by charge neutralization using surface charge density determined by colloid titration.

Mechanisms of Biological Clogging in Soil Infiltration Treatment Systems

土壌浄化法の大きな問題点のひとつである目詰まりについて, その機構の解明と, 浸透不良を防ぐための排水供給量の推算を試みた。まず, 微生物が土壌透水係数に及ぼす影響を, カラム実験により実測した。土壌中の微生物密度には最大値が存在し, それに対応する最小の透水係数が求められた。次にトレンチを模擬した小型の実験装置で, 人工下水を定水頭差で浸透させ, 浸透水量の減少を追跡した。浸透水量は20日程度で定常状態となった。カラム実験の結果と, 土壌中の微生物分布, TOCのバランスから, 目詰まりの機構を明らかにした。さらに, 以上の知見をもとに数理モデルを作成し, 浸透不良を生じないための排水供給量を推算した。計算の結果, BOD100mg・l-1の排水に対して, 40l・m-1 (trench) day-1という許容排水供給量が得られた。