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Active carbon was oxidised in several oxidising solutions and measured for its surface acidity, specific surface area, X-ray diffraction patterns, ESR spectra and gas adsorption isotherms. The favourable oxidising conditions for acidifying active carbon were speculated. Three kinds of steam activated coconut-shell carbon were treated by solutions of nitric acid, alkaline permanganate, acidic permanganate with nitrate, acidic dichromate and of chlorate in fuming nitric acid. Graphite was similarly treated as a control. When the carbon was oxidised by all the above mentioned reagents except the acidic dichromate, its surface acidity increased unavoidably accompanied by the surface area reduction in almost a linear relation. However, the surface area reduction was extensive in the carbons oxidised by acidic dichromate. Neither the crystalline nor the amorphous carbon fraction was selectively oxidised by any of the oxidants to a significant extent when observed by X-ray diffraction, probably because of the lower levels of crystallisation in the micelles. On the other hand, the change of free radicals was observed by most of the oxidations which indicated the conformational change of the carbon at molecular level. The improved adsorption of ammonia was observed on the oxidised carbon up to 20 times and that of sulphur dioxide and water vapour to a few times. The adsorption of n-hexane was negatively affected by the oxidations.

The adsorption sampling methods of airborne diborane, phosphine, arsine, and silane for the monitoring of workplaces of advanced industries such as the manufacturers of semiconductor integrated circuits and fine ceramics were studied. As those gases are highly toxic and their threshold limit values recommended by American Conference of Governmental Industrial Hygienists are very low, the sampling methods and the successive analytical methods are required to be sensitive. To satisfy the requirement, suitable adsorbents and effective analytical methods were searched or newly developed. This study includes the experimental results on the basic properties of adsorbents such as the impurity contents and the specific surface areas, the gas adsorption capacities, the improvements of the adsorption capacities with chemical modifications, the desorption efficiencies of the adsorbed gases from the adsorbents with various solvents, and the quantitative determination of boron, phosphorus, arsenic, and silico...

Analytical methods for arsine, silane and dichlorosilane by adsorption sampling and elemental analysis with graphite furnace AA were studied to establish convenient methods for atmospheric contamination surveys. This study included the following five items: (1) primary selection of adsorbents applicable to adsorption sampling; (2) examination of the adsorption capacities of the adsorbents for the gases; (3) improvement of the adsorbents by chemical modification; (4) desorption of the gases adsorbed on the adsorbents with solvents; and (5) quantitative analysis of arsenic and silicon in the solutions. Experimental results showed that active carbon made from synthetic thermosetting resin beads contained no aresenic and little silicon as impurities. This active carbon by itself was proved to adsorb arsine and dichlorosilane, but not silane. Impregnation with sodium hydroxide of the active carbon improved the adsorption capacity for all three gases. Refined silica gel, free from arsenic contamination, did not adsorb arsine by itself but potassium permanganate impregnation produced an adsorption capacity for arsine. The adsorbed arsine on the active carbon was desorbed into a hot dilute nitric acid solution with high efficiency (over 90%), but arsine adsorbed on sodium hydroxide impregnated active carbon or on potassium permanganate impregnated silica gel was dissolved into various solutions only at lower efficiencies. Silane adsorbed on sodium hydroxide-impregnated active carbon was desorbed with hot water with an efficiency higher than 90%. Dichlorosilane adsorbed on the active carbon with or without sodium hydroxide impregnation was desorbed with a nitric acid solution with efficiency of 85%. The lower determination limit for arsine able to discriminate from background interference of arsenie was 0.005 ppm, and those for silane and dichlorosilane were each 0.05 ppm for 3-dm3 air samples.

A method for determining phosphine was developed using adsorption sampling followed by colorimetric measurement. Two types of adsorbent used in this study were prepared from silica gel by impregnation with potassium permanganate (1% w/w) or (mercury(II) chloride and sodium chloride) (0.2 + 0.2% w/w). Each adsorbent (150 mg) packed in a glass tube had the capacity to adsorb 0.3 ppm of phosphine in 3 l of test gas passing through at a rate of 300 ml/min without breakthrough. The adsorbed phosphine was desorbed into solutions as phosphate and the recovered phosphate was determined by ICP-AES or by one of two kinds of colorimetric methods for phosphate based on the molybdenum blue method, i.e., the colorimetric method following JIS K 0102 and that following the NIOSH Manual of analytical method, No. S 332. When 0.01 ppm of phosphine in 3 l of test gas was adsorbed on the potassium permanganate adsorbent and determined by the JIS method, 93.8% of the phosphine was recovered as phosphate with a CV of 12.9% (n = 3). This method was applicable to field surveys of phosphine in workplaces. The other method with the mercury(II) chloride adsorbent followed by the NIOSH method resulted in lower recovery of phosphate in low phosphine concentration range. ICP-AES was less sensitive than the colorimetries. The effect of coexistent arsenite or silicate on the colorimetry of phosphate was assessed.

An alternative vapor was explored to replace carbon tetrachloride (CCl4) for testing breakthrough times of cartridges and canisters of gas masks in the National Approval Test of Respirators. Cyclohexane was single out as a candidate for the alternative vapor out of six vapors: trichloroethylene, n-pentane, n-hexane, n-heptane, toluene and cyclohexane from the viewpoints of similarity of vapor pressure and water-solubility to CCl4, lower toxicity than CCl4, and technical feasibility in generating an airflow of 30 L/min containing the vapor ranging from 300 to 5000 ppm. Breakthrough times of cartridges and canisters were examined by generating cyclohexane vapor in a test airflow of 30 L/min in comparison with CCl4 vapor under various test conditions with different vapor concentrations and relative humidities (RH). As the results, the breakthrough times of the cartridges and canisters for cyclohexane were found to almost coincide with those for CCl4 under all examined range of concentrations and RH. By an increase of humidity from 50% RH to 80% RH, the cartridges showed significant shortening of breakthrough times for both of CCl4 and cyclohexane, but the susceptibility of the breakthrough time of cyclohexane to humidity was also similar to that of CCl4. It was, therefore, concluded that cyclohexane can be recommended as the alternative vapor of CCl4 for testing the breakthrough times of gas mask cartridges and canisters in the National Approval Test.

To ensure the effective performance of active carbon tubes for working environment measurements, suitable desorbing solvents were selected for 46 kinds of organic compounds by the phase equilibrium method. The criteria for suitable desorbing solvents in this study was desorption of the objective compounds from active carbon at efficiencies greater than 90% and to give good separation between its own peak and that of the objective compound on a gas chromatogram. For most non-polar or hydrophobic compounds, carbon disulfide was a versatile and effective solvent. But for polar and hydrophilic compounds like alcohol, N, N-dimethylformamide and dimethylsulfoxide were good desorbing solvents if their peaks did not overlap with those of the objective compounds. Mixtures of lower molecular weight alcohols with carbon disulfide or dichloromethane could be alternative solvents for hydrophilic compounds as well. A thermodynamic parameter of the solute-solvent system, i.e., the mixing energy derived from the solubility parameter, gave a rough indication of the effectiveness of solvents but it could not be used as a critical indicator for the efficient desorbing solvents for organic vapors collected on active carbon.

Potentiometric pH-stat titration was performed on alkylated carbon black dispersed in aqueous solution at pH 9.0, 10.0 and 11.0 and alkaline hydrolysis rate constant of the alkylated functional groups on the carbon black was obtained therefrom. Carbon black treated with C 1 -C 8 n -alcohols in vapor or liquid phase was used in this experiment. Hydrolysis proceeded more rapidly for carbon black treated with lower alcohols. For each alkylated carbon black, the hydrolysis rate constant decreased with time and, after the hydrolysis rate diminished, a hydrolysis resistant fraction of alkylated groups remained. For example, the hydrolysis rate constants at 25°C were 24.33, 17.50 and 4.501 · mol −1 · sec −1 at 15 min and 6.00, 6.00 and 3.671 · mol −1 · sec −1 at 45 min after the start of hydrolysis at pH 9.0 for carbon black treated with C 2 , C 3 and C 4 alcohols respectively.

Acid strength distribution on commercial carbon blacks and chemically oxidized carbon blacks was measured by automatic titration using sodium hydroxide solutions as titrants. The titration curves show that the weaker acids with pKa between 7.0 and 11.0 occur in the amount of 0.025–0.490 m eq/g, the stronger ones with pKa between 2.0 and 7.0 in the amount of 0–0.475 m eq/g and trace amount of pKa range below 2.0. The acid strength distribution obtained by this method coincides with that by the Boehm method. The observed amounts of total acid exceed active hydrogen contents obtained by the Zerewitinoff method in the carbon blacks. Three different oxidizing agents were used to determine their effect on carbon black acidity. Nitric acid produced acidic groups at the highest surface density; H2O2 produced a predominance of weaker acids; hot air produced stronger acids with an increase of specific surface area.

Synthetic resin active carbon beads were applied to adsorption sampling of arsine in the air, and the accompanying analytical procedures including desorption of arsenic from the adsorbent and graphite furnace atomic absorption spectrophotometry to determine desorbed arsenic were studied.Results showed that active carbon produced from synthetic thermosetting resin beads was not contaminated with arsenic, an advantage over coconut-shell active carbon. The sampling tube, which was 4 mm in inside diameter and packed with 150 mg of the resin active carbon, was able to adsorb arsine at 0.5 ppm in 51 of dry air only with negligible breakthrough. The same tube previously humidified had a lower adsorption capacity: 0.5 ppm in 41 air. The adsorbed arsine on the resin active carbon was desorbed to 80%-94% with 2 ml or 10 ml of 0.01 M HNO3 solution with or without 10% ethyl alcohol under heat treatment at 75°C for 1 h. Arsenic desorbed into nitric acid solution was determined by atomic absorption spectrophotometry with pyrocoated graphite furnace and electrodeless discharge lamp, and the lower determination limit of arsenic in the final solution was 5 ng/ml (n =6, CV =0.12).

Recovery of rhodium and nickel ions from plating waste water was investigated. It was found that a hydrogen form cation-exchange resin can be used for the removal of the noble metal ions and that these ions, especially rhodium, can easily be eluted from the resin with 1 N sulfuric acid; the eluted solution can be recycled to the rhodium plating bath.

The toxic volatile components in acrylamide and urea formaldehyde resins which were industrially manufactured as soil consolidating agents were analyzed by gas chromatography and gas chromatography-mass spectrometry before and after poly-merization. In acrylamide monomer solution, acrylonitrile was contained up to 0.3mg/ml as an impurity and after gelation of the solution by polymerization with sand, it evaporated to air up to 4440mg/m3 at equilibrium. In the solution of urea formaldehyde condensate prior to the gelation, formaldehyde up to 192mg/ml, formic acid up to 20.6mg/ml, trace amount of associated formaldehyde and another higher molecular compound were contained and after gelation of the resin with sand by further condensation, trace ammonia, formaldehyde up to 14900mg/m3, formic acid up to 96mg/m3 and associated formaldehyde up to 1800mg/m3 evaporated from the gel to air at equilibrium. DTA and TG curves were observed on the gels which revealed the dehydration of the gels at 80-180°C and the thermal decomposition at 500-600°C.

Adsorption capacities of sampling tubes packed with various kinds of active carbons for collecting vinyl chloride vapor were measured. Among the active carbons with identical particle size, those made from coconut shell and wood were more effective than those from petroleum pitch giving longer breakthrough times. The tubes packed with active carbons of smaller particle sizes adsorbed vinyl chloride vapor for longer periods than those with larger particle sizes. The break-through time in adsorbing vinyl chloride flow using active carbon tubes containing 150 mg carbon of a definite type in a glass tube of 4 mm inside diameter varied depending on the sampling conditions, i.e., the active carbon tube adsorbed the vapor for a longer period when the sampling rate was slower and the humidity in the flow was low.

Potentiometric titration, in which carbon black was reduced in aqueous medium with excess NaBH4 and then titrated backwards with I2, showed the presence of two kinds of reducible surface groups on carbon black, i.e. reversibly reducible and irreversibly reducible groups. The former was attributed to quinone groups and the latter to the other structures. The quinone groups were detected in the potential range between −50 and −456 mV (vs N.H.E.) at pH 10. The total amounts of titratable quinone in three commercial carbon black products were 0.91, 0.98 and 1.18meq/g respectively.

Applying the theory and the technique of gas chromatography, adsorption effectiveness of surface was studied on a pulse flow system of active carbon and acetone. The adsorp-tion effectiveness "f" was defined as the ratio of the following two distribution coefficients at the same vapor pressure and temperature; one (μ1) was for the pulse flow adsorption obtained gas chromatographically and the other (μ2) was that for the adsorption equilibrium from the adsorption isotherm measurements. Gas chromatographic observations were carried out on the column packed with active carbon, and under helium carrier gas, liquid acetone of 0.05 ml, 0.10 ml and 0.20 ml was injected respectively.Values of μ1 varied with sample volumes, whereas the μ2 values were remained con-stant in this experimental conditions, in which the vapor pressure was as low as 10-2 to 10-4 mmHg. Consequently the adsorption effectiveness of the surface "f" varied with the change of μ1 values, and the maximum obtained was 53% at the smallest sample volume and the higher temperature.The ratio of "f" to the gas-solid contact time was almost constant in this experimental range. This fact indicates that the "f" increases with increasing contact time. Greater ratio of surface effectiveness to contact time at 72°C may be due to higher adsorption velocity at higher temperature.

微量の金属または金属イオンをイオン交換薄層によって展開し, 定量する方法の開発を試みた。この方法は一定量の陽イオン交換基を含むセルローズ粉末の薄層を用いて金属イオンの弱酸性緩衡溶液を薄層クロマトグラフィーと同様の技術で展開し, 金属イオンを薄層上にイオン交換によって保持し, これを発色させて試料中の金属イオン量を呈色層の長さから求めようとする方法である。その主な操作は, (1) 被検試料の弱酸性緩衡溶液による溶解, (2) 一定濃度の陽イオン交換基を含むセルロ一ズ粉末の薄層作製, (3) 試料溶液の薄層上への展開, (4) 薄層上に保持された金属イオンの発色, (5) 発色した薄層部分の長さの測定による金属イオン量の定量より成る。この報告においては主としてカドミウムの分析例について, 分析感度と分析条件 (セルローズ粉末中の陽イオン交換基濃度, セルローズ薄層の幅, 展開する試料の量, 試料液の pH および金属イオン濃度, 金属イオンの発色方法) との関係を検討した。この方法によって 1～300μg のカドミウムイオンの定量が可能であった。

When binding agents are used at high temperatures, workers often suffer from the poisoning by hydrogen cyanide generated by their decomposition. The authors investigated the relation between the heating temperature and the amount of produced hydrogen cyanide on thermal degradation of binding agents which contain nitrogen atoms in their original compositions. Hydrogen cyanide was not recognized from any binding agents tested below 250°C, while its considerable amounts were generated from nitril rubber and urea resin above 350°C. The mechanisms of production of hydrogen cyanide from these binding agents were considered. In the case of nitril rubber, acid amide would be produced by its hydrolysis at first, and this acid amide may then turn to hydrogen cyanide. In heating urea resin, cyanuric acid may be an intermediate product which turns to hydrogen cyanide gradually.

This paper is concerned with the theories and the experimental results on the breakdown of dynamic adsorption of gas streams through active carbon column.Kinetic theory of dynamic gas adsorption has been developed as the concept of adsorption wave by many investigators, and it interpretes the observed data in the wide range of adsorption conditions, except both of the effluent gas concentration at the initial range of breakdown and of the relation between the influent gas concentration and the breakdown time. Here, the theory was discussed in comparison of the observed results.Also, the reviews are given on some semiempirical methods, like Mecklenberg's concept, MTZ approach and the pulse test methods.The relation between the dynamic and static adsorption was considered at last, which lead to the new and convenient method to obtain the general relation between the influent gas concentration and the breakdown time.

An adsorption sampling method for airborne silane was developed using active carbon made from synthetic thermosetting resin beads, and an ac-companying procedure to determine silane concentration was established. The resin active carbon had very low silicon contamination (0.31-3.14 μg Si/g), and its ca-pacity for adsorbing silane was improved by impregnating sodium hydroxide up to 20 wt.% of the carbon. This sodium hydroxide-impregnated-active carbon (200 mg) had the capacity to adsorb 5 ppm of silane in 6l of air drawn at the rate of 200 m//min, without breakthrough. To quantify the silane, the adsorbed silane was desorbed into 4 ml of water at 80°C with more than 90% efficiency, and the final solution of silicate ions in the sodium hydroxide solution was analyzed by graphite furnace AAS with a pyrocoated graphite tube. From the results, adsorp-tion sampling tubes were formed by packing 200 mg and 100 mg of the resin active carbon impregnated with sodium hydroxide as two separate beds in a polyethylene tube of 4 mm inside diameter. The lower limit of slilane determination by this method was less than 1 ppm in 1l of air.

Adsorption characteristics of the tri-iodide and iodide forms of an anion-exchange resin (R—I–3 and R—I–) have been probed by microcalorimetry, dynamic adsorption of vapour-phase mercury and organic compounds, and the oxidation of naphthalenediol.At first, a transformation of the nature of the R—I– surface from hydrophilic to hydrophobic by the exchange of I– with I–3 was seen. This transformation is complete when two thirds of the I– in the resin is exchanged with I–3. The hydrophobic nature of I2 in I–3 ions screens the hydrophilic I– ions. The I–3 content in the resin is decreased by evacuation, after which only stable I–3 ions remain on the surface.Secondly, vaporized organic compounds such as benzene, stryrene and n-hexane were adsorbed on R—I–; their adsorbed amounts on R—I–3 decreased according to the degree of exchange of I– with I–3.Thirdly, it was found that mercury vapour is adsorbed on the surface of the resin. Mercury was sensitive to all I–3 ions, both stable and unstable. However, 1,4-naphthalenediol was sensitive only to some of the stable I–3 ions by which it was oxidized to 1,4-naphthoquinone in a buffer solution at pH 10.These results imply that the R—I–3 resin has a chemically active surface with both hydrophilic and hydrophobic sites.