Koichi Ohno

Comparison of natural organic matter adsorption capacities of super-powdered activated carbon and powdered activated carbon.

We examined the natural organic matter (NOM) adsorption characteristics of super-powdered activated carbon (S-PAC) produced by pulverizing commercially available, normal PAC to a submicron particle size range. The adsorption capacities of S-PAC for NOM and polystyrene sulfonates (PSS) with molecular weights (MWs) of 1.1, 1.8, and 4.6 kDa, which we used as model compounds, were considerably higher than those of PAC. The adsorption capacity increases were observed for all five types of carbon tested (two wood-based, two coconut-based, and one coal-based carbon). The adsorption capacities of S-PAC and PAC for polyethylene glycols (PEGs) with MWs of 0.3 and 1.0 were the same. The adsorption capacities of S-PAC for PEGs with MWs of 3.0 and 8.0 kDa were slightly higher than the adsorption capacities of PAC, but the difference in adsorption capacity was not as large as that observed for NOM and the PSSs, even though the MW ranges of the adsorbates were similar. We concluded that the adsorption capacity differences between S-PAC and PAC observed for NOM and PSSs were due to the difference in particle size between the two carbons, rather than to differences in internal pore size or structure, to differences in activation, or to non-attainment of equilibrium that resulted from the change in particle size. The difference in adsorption capacity between S-PAC and PAC was larger for NOM with a high specific UV absorbance (SUVA) value than for low-SUVA NOM. The larger adsorption capacities of S-PAC compared with PAC were explained by the larger specific external surface area per unit mass. We hypothesize that a larger fraction of the internal pore volume is accessible with carbon of smaller particle size because the NOM and PSS molecules preferentially adsorb near the outer surface of the particle and therefore do not completely penetrate the adsorbent particle.

Branched pore kinetic model analysis of geosmin adsorption on super-powdered activated carbon

Super-powdered activated carbon (S-PAC) is activated carbon of much finer particle size than powdered activated carbon (PAC). Geosmin is a naturally occurring taste and odor compound that impairs aesthetic quality in drinking water. Experiments on geosmin adsorption on S-PAC and PAC were conducted, and the results using adsorption kinetic models were analyzed. PAC pulverization, which produced the S-PAC, did not change geosmin adsorption capacity, and geosmin adsorption capacities did not differ between S-PAC and PAC. Geosmin adsorption kinetics, however, were much higher on S-PAC than on PAC. A solution to the branched pore kinetic model (BPKM) was developed, and experimental adsorption kinetic data were analyzed by BPKM and by a homogeneous surface diffusion model (HSDM). The HSDM describing the adsorption behavior of geosmin required different surface diffusivity values for S-PAC and PAC, which indicated a decrease in surface diffusivity apparently associated with activated carbon particle size. The BPKM, consisting of macropore diffusion followed by mass transfer from macropore to micropore, successfully described the batch adsorption kinetics on S-PAC and PAC with the same set of model parameter values, including surface diffusivity. The BPKM simulation clearly showed geosmin removal was improved as activated carbon particle size decreased. The simulation also implied that the rate-determining step in overall mass transfer shifted from intraparticle radial diffusion in macropores to local mass transfer from macropore to micropore. Sensitivity analysis showed that adsorptive removal of geosmin improved with decrease in activated carbon particle size down to 1microm, but further particle size reduction produced little improvement.

Hand-Assisted Endoscopic Esophagectomy for Esophageal Cancer

Abstract.Radical esophagectomy is a highly invasive operation for esophageal cancer, and improved techniques are being sought to reduce the invasiveness of this procedure. We devised a method in which an assistant inserts their left hand into the thoracic cavity, and the operator inserts their left hand into the abdominal cavity through a small incision in the upper quadrant during an endoscopic procedure. Between 1996 and 1999, we performed endoscopic esophagectomy on 18 patients. The median number of mediastinal lymph nodes removed by thoracoscopic surgery was 20.1 ± 9.4 and the median number of abdominal lymph nodes removed by laparoscopic surgery was 11.1 ± 5.6. The number of nodes dissected by endoscopic surgery did not differ significantly from the number of nodes dissected by conventional thoracotomy with laparotomy. Our experience shows that endoscopic esophagectomy with reconstruction of the esophagus assisted by inserting the hand into the thoracic and abdominal cavity, for safety and certainty, is an effective technique that is much less invasive than radical esophagectomy performed by conventional thoracotomy with laparotomy.

Modeling high adsorption capacity and kinetics of organic macromolecules on super-powdered activated carbon

The capacity to adsorb natural organic matter (NOM) and polystyrene sulfonates (PSSs) on small particle-size activated carbon (super-powdered activated carbon, SPAC) is higher than that on larger particle-size activated carbon (powdered-activated carbon, PAC). Increased adsorption capacity is likely attributable to the larger external surface area because the NOM and PSS molecules do not completely penetrate the adsorbent particle; they preferentially adsorb near the outer surface of the particle. In this study, we propose a new isotherm equation, the Shell Adsorption Model (SAM), to explain the higher adsorption capacity on smaller adsorbent particles and to describe quantitatively adsorption isotherms of activated carbons of different particle sizes: PAC and SPAC. The SAM was verified with the experimental data of PSS adsorption kinetics as well as equilibrium. SAM successfully characterized PSS adsorption isotherm data for SPACs and PAC simultaneously with the same model parameters. When SAM was incorporated into an adsorption kinetic model, kinetic decay curves for PSSs adsorbing onto activated carbons of different particle sizes could be simultaneously described with a single kinetics parameter value. On the other hand, when SAM was not incorporated into such an adsorption kinetic model and instead isotherms were described by the Freundlich model, the kinetic decay curves were not well described. The success of the SAM further supports the adsorption mechanism of PSSs preferentially adsorbing near the outer surface of activated carbon particles.

Exposure assessment of metal intakes from drinking water relative to those from total diet in Japan

Daily intakes of 17 metals (boron, aluminium, chromium, manganese, nickel, copper, zinc, arsenic, selenium, molybdenum, cadmium, antimony, lead, uranium, magnesium, calcium, and iron) via drinking water and total diet were investigated in six cities in Japan. The daily metal intakes were estimated and compared with tolerable daily intake (TDI) values proposed by the WHO or Joint FAO/WHO Expert Committee on Food Additives for toxic metals and with recommended dietary allowances (RDAs) or adequate intake (AI) values proposed for essential metals by the Japanese Ministry of Health, Labour and Welfare. Among the 13 toxic metals, mean dietary intakes of 10 (except arsenic, selenium, and molybdenum) were less than 50% of TDI, suggesting that for these 10 metals the allocation of intake to drinking water in establishing guidelines or standards could possibly be increased from the normal allocation of 10-20% of TDI. For the 13 toxic metals, the contribution of drinking water to TDI was 2% or less in all six cities. Mean dietary intakes of the essential elements magnesium, calcium, and iron were less than the RDA or AI values. Drinking water did not contribute much to essential metal intake, accounting for less than 10% of RDA or AI.

Modification of the Nuss procedure for pectus excavatum to prevent cardiac perforation

PURPOSE In a few patients, cardiac perforation and aortic injury have occurred during the Nuss procedure for pectus excavatum. The article details a modification of this procedure that enables the prevention of fatal complications. METHODS Our subjects were 22 males and 13 females with pectus excavatum who were aged 8.2 +/- 3.7 years. Their Hallers computed tomography index was 5.2 +/- 1.5. An introducer is inserted into the pleura between the sternum and thymus instead of the thoracic depression under right thoracoscopic guidance. After the introducer reaches the internal cranial position of the left nipple, the thoracoscope is shifted to the left thoracic cavity. The introducer is subsequently guided to the left highest intercostal space under left thoracoscopic guidance. RESULTS A single bar was inserted in 34 patients; 2 bars were required in 1 patient. The operating time was 95 +/- 27 minutes and blood loss was 11 +/- 6 g. Cardiac perforation did not occur in any patient. CONCLUSIONS Our modified technique has certain advantages: (1) the introducer does not rub against the pericardium and heart; (2) the tip of the introducer can be observed at all times with a thoracoscope; (3) the anterior mediastinum between the left and right thoracic cavities is very narrow at the cranial level; (4) the introducer can be accurately directed to the left highest intercostal space; and (5) hemostasis and no injury of the bilateral thoracic organs can be confirmed.

Effect of rice-cooking water to the daily arsenic intake in Bangladesh: results of field surveys and rice-cooking experiments.

The effect of rice-cooking water to the daily arsenic intake of Bangladeshi people was investigated. At the first field survey, uncooked rice and cooked rice of 29 families were collected. Their arsenic concentrations were 0.22+/-0.11 and 0.26+/-0.15 mg/kg dry wt, respectively. In 15 families, arsenic concentration in rice increased after cooking. Good correlation (R(2)=0.89) was observed between arsenic in rice-cooking water and the difference of arsenic concentration in rice by cooking. In the second survey, we collected one-day duplicated food of 18 families. As a result, we estimated that six of 18 families likely used the arsenic contaminated water for cooking rice even they drank less arsenic-contaminated water for drinking purpose. We also conducted rice-cooking experiments in the laboratory, changing arsenic concentration in rice-cooking water. Clear linear relationships were obtained between the arsenic in rice-cooking water and the difference of arsenic concentration in rice by cooking. Factors that affect arsenic concentration in cooked rice are suggested as follows: (1) arsenic concentration in uncooked rice, (2) that in rice-cooking water, (3) difference in water content of rice before and after cooking, and (4) types of rice, especially, the difference between parboiled and non-parboiled rice.

Direct observation of solid-phase adsorbate concentration profile in powdered activated carbon particle to elucidate mechanism of high adsorption capacity on super-powdered activated carbon

Decreasing the particle size of powdered activated carbon (PAC) by pulverization increases its adsorption capacities for natural organic matter (NOM) and polystyrene sulfonate (PSS, which is used as a model adsorbate). A shell adsorption mechanism in which NOM and PSS molecules do not completely penetrate the adsorbent particle and instead preferentially adsorb near the outer surface of the particle has been proposed as an explanation for this adsorption capacity increase. In this report, we present direct evidence to support the shell adsorption mechanism. PAC particles containing adsorbed PSS were sectioned with a focused ion beam, and the solid-phase PSS concentration profiles of the particle cross-sections were directly observed by means of field emission-scanning electron microscopy/energy-dispersive X-ray spectrometry (FE-SEM/EDXS). X-ray emission from sulfur, an index of PSS concentration, was higher in the shell region than in the inner region of the particles. The X-ray emission profile observed by EDXS did not agree completely with the solid-phase PSS concentration profile predicted by shell adsorption model analysis of the PSS isotherm data, but the observed and predicted profiles were not inconsistent when the analytical errors were considered. These EDXS results provide the first direct evidence that PSS is adsorbed mainly in the vicinity of the external surface of the PAC particles, and thus the results support the proposition that the increase in NOM and PSS adsorption capacity with decreasing particle size is due to the increase in external surface area on which the molecules can be adsorbed.

Contribution of tap water to chlorate and perchlorate intake: a market basket study.

The contributions of water to total levels of chlorate and perchlorate intake were determined using food and water samples from a market basket study from 10 locations in Japan between 2008 and 2009. Foods were categorized into 13 groups and analyzed along with tap water. The average total chlorate intake was 333 (min. 193-max. 486) μg/day for samples cooked with tap water. The contribution of tap water to total chlorate intake was as high as 47%-58%, although total chlorate intake was less than 32% of the tolerable daily intake, 1500 μg/day for body weight of 50 kg. For perchlorate, daily intake from water was 0.7 (0.1-4.4) μg/day, which is not high compared to the average total intake of 14 (2.5-84) μg/day, while the reference dose (RfD) is 35 μg/day and the provisional maximum tolerable daily intake (PMTDI) is 500 μg/day for body weight of 50 kg. The highest intake of perchlorate was 84 μg/day, where concentrations in foods were high, but not in water. The contribution of water to total perchlorate intake ranged from 0.5% to 22%, while the ratio of highest daily intake to RfD was 240% and that to PMTDI was 17%. Eight baby formulas were also tested--total chlorate and perchlorate intakes were 147 (42-332) μg/day and 1.11 (0.05-4.5) μg/day, respectively, for an ingestion volume of 1 L/day if prepared with tap water.

Integrated watershed modeling for simulation of spatiotemporal redistribution of post-fallout radionuclides

Simulation of the watershed-scale fate and transport of radionuclides is required in order to predict the consequences of contamination redistribution. Integrated watershed modeling is a suitable technique for this task, but it requires fully coupled investigation of radionuclide behavior in surface water, suspended sediment and subsurface aquifers. We developed a novel simulator for computing the spatiotemporal redistribution of fallout radionuclides in watersheds. The simulator was applied to an actual reservoir basin contaminated by fallout radionuclides from the Fukushima Dai-Ichi Nuclear Power Plant accident in 2011. As a result, the simulated 137Cs concentration in bottom sediment showed a reasonably close match with the measurement data. The distribution coefficient of 137Cs consistent with the latest measurement data was identified as being at least 400,000?L/kg, and it was estimated that more than 90% of the total 137Cs distributed in the fallout remains in the catchment area. We propose a new simulator to assess environmental impact of fallout radionuclide.Simulation treats surface and subsurface fully coupled hydrological processes.Spatiotemporal variation of the deposited 137Cs can be successfully reproduced.Deposited 137Cs is predominantly transported with the suspended sediment.Results indicate that most of the deposited 137Cs remains within the catchment.