Eiji Shoto

Adsorption and ion exchange of some groundwater anion contaminants in an amine modified coconut coir

The adsorption of nitrate, chromium (VI), arsenic (V) and selenium (VI) anions in an amine modified coconut coir (MCC-AE : with secondary and tertiary amine functionality) were studied to determine the capability of this easily prepared and low-cost material in removing typical groundwater anion contaminants. Batch adsorption-ion exchange experiments were conducted using 200 mg MCC-AE, initially containing chloride as the resident anion, and 50 ml of different anion-containing water of varying concentrations. It is presumed, at this low pH, that only SeO 4 2− remained as a divalent anion, while monovalent species H 2 AsO 4 − and HCrO 4 − predominated in their respective exchanging ion solutions. The adsorption data were fitted using the Freundlich equation and maximum adsorption for each anion was estimated using their respective Freundlich equation constants. MCC-AE exhibited preference for divalent Cr (VI) and Se (VI) anions compared with the Cl − resident ion. Maximum As (V) adsorption was 0.086 mmol/g, while maximum adsorption of Cr (VI), NO 3 − and Se (VI) anions was 0.327 mmol/g, 0.459 mmol/g, and 0.222 mmol/g, respectively. The ion exchange capacity of MCC-AE is estimated, based on its exchange capacity for nitrate, to be within 0.46 mmol of positive charges per gram. Similar adsorption experiments were conducted for comparison using commercial chloride-form Amberlite IRA-900 strong base (quaternary amine functionality) anion exchanger, with an exchange capacity of 4.2 meq/g. Maximum adsorption of the different ions in IRA-900 was about 3 times higher for NO 3 − , 9 times higher for Se (VI), 10 times higher for As (V) and 9 times higher for Cr (VI), than that in MCC-AE. Differences in the ion exchange behavior of MCC-AE and IRA-900 were probably due to the different amine functionalities in the two exchangers. The results suggest that MCC-AE may be used as a low-cost alternative adsorbent/ion exchanger for treatment of anion contaminants in groundwater.

Ion chromatography of inorganic iodine species using C18 reversed-phase columns coated with cetyltrimethylammonium

Abstract Low-capacity anion-exchange columns were developed by sorption of cetyltrimethylammonium on two types of C18 reversed-phase columns which were coated with 1 mM cetyltrimethylammonium in water-methanol mixtures (57:43, v/v, to 45:55, v/v) at 20°C. The exchange capacities of the columns were estimated by three methods. The high separation efficiency for anions was performed by using a 0.1 M sodium chloride-5 mM sodium phosphate buffer (pH 5.8) as mobile phase. An ion chromatographic system for iodide consisted of the column (polymer-coated silica packing) coated with 1 mM cetyltrimethylammonium in water-methanol (56:44%, v/v), the sodium chloride mobile phase, and ultraviolet or amperometric detection. Good chromatograms for iodide in surface sea waters were obtained without interference by an excess of salts.

Radon, Cl− and SO42− anomalies in hot spring water associated with the 1995 earthquake swarm off the east coast of the Izu Peninsula, Central Japan

Abstract Radon concentrations were continuously monitored in hot spring water in a 200-m-deep well in the Yugano hot spring area, Izu Peninsula, Japan from July to December 1995. Concentrations of Cl − and SO 4 2− were measured in the hot spring water about once a month from May to December 1995. The Rn concentrations in the hot spring water increased significantly in September and October 1995, when the 1995 earthquake swarm off the E coast of the Izu Peninsula occurred at a distance of about 30 km from the observation well. The 1995 earthquake swarm began on 11 September and became most active from the end of September to the beginning of October. The Rn concentration rose gradually from 8 September, 3 days before the onset of the swarm activity, increasing by about 50% by 17 September. It remained high in October but had returned to normal by the end of November. However, Cl − and SO 4 2− concentrations doubled suddenly from 22 to 23 September and remained high until the end of November. A good correlation between Cl − and SO 4 2− concentrations suggests the same mechanism for their anomalous increases, probably mixing of water with high Cl − and SO 4 2− concentrations caused by crustal deformation related to the seismic swarm activity. However, the anomalous increase in Rn concentration, which began 15 days before these anion increases, cannot be explained by the same water mixing mechanism. A possible mechanism for the anomalous Rn increase is the formation of microcracks caused by compressional stress, which preceded the onset of the earthquake swarm.

Study of isotachophoretic separation behaviour of metal cations by means of particle-induced X-ray emission: III. Analysis of a crude rare earth chloride from monazite

Abstract A crude rare earth chloride produced from monazite was analysed by coupled isotachophoresis-particle-induced X-ray emission (ITP-PIXE). The sample was separated and fractionated by the use of a micro-preparative isotachophoretic analyser and the dropwise fractions containing nanomole amounts of rare earth elements were analysed off-line by PIXE. By mens of ITP-PIXE, the minor elements (Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) co-existing with the other major lanthanoids (La, Ce, Pr and Nd) were determined accurately, because the “matrix effect” in X-ray analysis was reduced by isotachophoretic removal of the major elements. The maximum abundance found was for Ce at 47.4% with respect to total rare earths and the minimum abundance was 0.001% for Lu. The separation efficiency of the crude rare earth chloride was ca. 500 nmol/C. The method for the fractionation of minor elements and PIXE analysis is discussed in detail. The analytical results obtained by ITP-PIXE were confirmed by means of inductively coupled plasma atomic emission spectrometry.

Ion chromatographic separation of alkali metal and ammonium cations on a C18 reversed-phase column

Abstract The separation of alkali metal (Li + , Na + , K + , Rb + and Cs + ) and ammonium cations on a C 18 reversed-phase column using three anionic surfactants [sodium 1-eicosyl sulphate, sodium dodecyl benzenesulphonate and sodium dodecyl sulphate (SDS)] is described. Two methods were examined: (a) “permanent” coating, with the use of a C 18 reversed-phase column previously coated with the surfactants; and (b) dynamic coating, with addition of the surfactants to the mobile phase. With method (a) the separation of the six cations was achieved with SDS. However, the retention times gradually decreased owing to dissolution of the SDS coating. Good separation was obtained with method (b), where 10 m M HNO 3 containing 0.1 m M SDS was used as the mobile phase with conductivity detection, and it was applied satisfactorily to real samples. The effect of system peaks on determination is also discussed.

ANALYSIS OF TRACE RARE EARTH ELEMENTS IN MISCH METAL BY MEANS OF ITP-PIXE METHOD

A misch metal, an alloy of light rare earth elements, was analyzed by a new coupled analytical method, ITP-PIXE(isotachophoresis—Particle Induced X-ray Emission) : The sample solution containing ca.1 mg misch metal was separated and fractionated by the use of a preparative isotacho-phoretic analyzer. The dropwise fractions containing nanomole rare earth elements were analyzed off-line by PIXE. The matrix effect in X-ray measurement was reduced by the isotachophoretic removing of the dominant lanthanoids and preconcentration of the trace elements of interest. Consequently the minor elements, Sm, Gd, Tb, Dy, Ho, Er, Yb and Y could be determined accurately. The most trace element found was Yb (4ppm, 4ng in 1mg sample). The good accuracy of ITP-PIXE method was also demonstrated for several model samples of lanthanoids, where La was the dominant element and the thirteen lanthanoids were the minor elements. The ratio was varied from 500:1 to 50000:1. Even in the case of 50000:1, ca. 10% accuracy was achieved for each minor element except for Sm(23%), Gd(17%) and Yb(18%). The analytical results by ITP-PIXE were compared with those by means of ICP-AES(Inductively Coupled Plasma—Atomic Emission Spectrometry).

Study of Solidification of Chromium-Containing Sludge by Heating with Silicates (3)

著者等は有害金属を含むスラッジを無害固形化する方法に関する一連の実験を行っている.こまれでにCr2O3をスラッジのモデルとし, Na2O-CaO-SiO2三成分系ケイ酸塩の組成が化学的固定化剤として有効かどうかを調べた.そのため, Cr2O3にNa2CO3, CaCO3およびSiO2を調合して焼成し, クロムの溶出試験を行った.本研究では焼成の際に少量の活性炭を加えることによる還元効果が, クロムの溶出濃度に及ぼす影響について調べた.

TRACE ANALYSIS OF ALUMINUM METAL REFERENCE STANDARDS BY PIXE METHOD

Trace elements in thick samples of aluminum metal reference standards were analyzed by means of PIXE and ICP-AES. The samples were SRM1258 and SRM1259 from National Institute of Standards and Technology (U.S.A.) and 1-A, 3, 4-A and 83 from Japan light metal association. The observed PIXE spectrum was converted “into that of a hypothetical thin target and it was analyzed using a relative intensity database for thin target. A good agreement was obtained between the certified and the found amount of the trace elements. The analytical results for SRM1258 and SRM1259 obtained by ICP-AES method also agreed well with the present results confirming the analytical accuracy.