Hideyuki Matsunaga

Preparation of porous resin loaded with crystalline hydrous zirconium oxide and its application to the removal of arsenic

Abstract A porous resin loaded with monoclinic or cubic hydrous zirconium oxide was prepared by incorporation of ZrOCl 2 ·8H 2 O into porous spherical polymer beads followed by hydrolysis and hydrothermal treatment of the zirconium salt. Hydrous zirconium oxide appeared to deposit inside the pores with relatively large diameter. The adsorption capacity and distribution coefficients for As(III) and As(V) were determined by batch procedures. The hydrous zirconium oxide-loaded resin (Zr resin) showed a strong adsorption for As(V) at slightly acidic to neutral pH region while As(III) was favorably adsorbed at pH around 9 to 10. The removal of low concentrations of arsenic from the model effluents to meet the demand of Japanese industrial effluent standard (0.1 ppm) was successfully achieved by the column operation packed with the Zr resin. The Zr resin was regenerated by treatment of the column with 1 M sodium hydroxide followed by conditioning with 0.2 M acetate buffer solution. The amount of zirconium leached out during the adsorption and regeneration cycles was negligibly small and the column can be used repeatedly.

Adsorption characteristics of arsenic(III) and arsenic(V) on iron(III)-loaded chelating resin having lysine-Nα,Nα-diacetic acid moiety

Abstract An iron(III)-loaded chelating resin (Fe-LDA) with lysine-N α ,N α -diacetic acid functional groups has been prepared and its adsorption characteristics for arsenic(III) and arsenic(V) have been examined. Arsenic(V) was strongly adsorbed to the resin in the pH range from 2 to 4, while arsenic(III) was moderately adsorbed between pH 8 and 10. The isotherm data for arsenic(V) at pH 3.5 fitted well to a Langmuir equation with a very large binding constant of 7.2 × 10 4 dm 3 mol −1 and a capacity constant of 0.74 mmol g −1 The data for arsenic(III) at pH 9 also fitted to a Langmuir equation, with a binding constant of 190 dm 3 mol −1 and a capacity constant of 0.84 mmol g −1 . Regeneration of the resin was successfully carried out with 0.1 mol dm −3 sodium hydroxide solution. Both arsenic compounds can be almost quantitatively recovered from the resin under these conditions. Only a small amount of ferric ions (less than 0.1 %) was observed to come off the resin during the regeneration with alkaline solutions. Since the Fe-LDA resin showed little affinity for arsenic(III) in acidic media, the present adsorption system can provide satisfactory separation of arsenic(V) from arsenic(III). Arsenic(V) was successfully concentrated in the column packed with Fe-LDA resin from its dilute solution.

Optical sensor for the visual detection of mercury using mesoporous silica anchoring porphyrin moiety

A low cost, solid optical sensor for the rapid detection of low concentrations of Hg2+ in aqueous media was prepared by the monolayer functionalization of mesoporous silica with 5,10,15,20-tetraphenylporphinetetrasulfonic acid (TPPS), anchored by N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TMAC). The detection is based on the color change of TPPS from orange to green as a result of the formation of a charge-transfer complex with Hg2+. The intensity of the charge-transfer band varies linearly with Hg2+ in the concentration range from zero to 2.5 x 10(-7) mol dm(-3). The lower detection limit observed for Hg2+ concentration is 1.75 x 10(-8) mol dm(-3). The material exhibits good chemical and mechanical stability, and did not show any degradation of TPPS for a period of eight months. The sensor was applied for the analysis of various environmental samples. The effects of pH, sample volume, reaction time, amount of material, and the presence of foreign ions on the detection method are discussed.

Extraction of rare earth elements with 2-ethylhexyl hydrogen 2-ethylhexyl phosphonate impregnated resins having different morphology and reagent content

Abstract Extraction of rare earth elements (REEs) with reagent impregnated resins (RIRs) using 2-ethylhexyl hydrogen 2-ethylhexyl phosphonate (PC-88A) and Amberlite XAD-2, XAD-4, XAD-16 and XAD-7 as a polymeric support has been studied. The impregnated resins containing various amounts of PC-88A have been prepared by a dry method. The effect of contact time on the extraction of REEs with PC-88A impregnated resins (PC-88A–resin=20/80, 50/50 wt.%) at pH 3.5 has been chiefly investigated. It was found that the extraction becomes slow when an insufficient amount of PC-88A was impregnated into XAD-2, XAD-4 or XAD-16 resins with respect to their pore volume. Little effect of the amount of PC-88A in XAD-7 on the rate of extraction was observed. The presence of n-dodecane improves the extraction kinetics for XAD-4 and XAD-16 at a small PC-88A content. It is speculated that PC-88A should be filled in the pore of the resin from the bottom to the top under the present impregnation process. It is thus recommended to make RIRs with enough of the reagent to fill up the pores of hydrophobic resins in this impregnation method.

ADSORPTION CHARACTERISTICS AND REMOVAL OF OXO-ANIONS OF ARSENIC AND SELENIUM ON THE POROUS POLYMERS LOADED WITH MONOCLINIC HYDROUS ZIRCONIUM OXIDE

Adsorption properties for oxoanions of Se(IV), Se(VI), As(III), As(V), and methyl derivatives of As(V) have been examined by the porous polymer beads loaded with monoclinic hydrous zirconium oxide (Zr-resin). The retention of these ions on the Zr-resin has been analyzed using Langmuir model of adsorption. The equilibrium constants and the capacities for above ions have been determined. The equilibrium constants for monomethyl arsinic acid and dimethyl arsinic acid are similar to that of As(V) but the adsorption capacity depends on the number of methyl groups. As(V) and Se(IV) are effectively retained on the Zr-resin from an aqueous solution of acidic to neutral pH region, whereas As(III) is removed from neutral to alkaline solution. The column system packed with the present Zr-resin can quantitatively remove low levels of As(V) and Se(IV) from aqueous solution.

Chromatographic separation and inductively coupled plasma atomic emission spectrometric determination of the rare earth metals contained in terbium

Abstract The chromatographic separation of rare earth elements (REEs), prior to inductively coupled plasma atomic emission spectrometric (ICP-AES) measurements, using a column packed with 2-ethylhexyl hydrogen 2-ethyl-hexylphosphonate (PC-88A)-loaded polymer resin in order to exclude spectral interferences was examined. A favourable separation of trace amounts of metals (La, Nd and Sm) from a large amount of terbium was achieved simply by elution with dilute hydrochloric acid. Trace lanthanum and neodymium in metallic terbium were determined by separation of the analyte ions from the matrix element followed by ICP-AES analysis.

Naked-eye detection of trace arsenic(V) in aqueous media using molybdenum-loaded chelating resin having β-hydroxypropyl-di(β-hydroxyethyl)amino moiety

A naked-eye detection method for a trace amount of arsenic in aqueous samples has been newly developed. The proposed method is based on the formation of a hetero poly acid in a chelating resin phase. Molybdenum loaded on a chelating resin having beta-hydroxypropyl-di(beta-hydroxyethyl) amino moiety reacts with arsenic(V) to form the hetero poly acid, which makes the resin beads greenish blue in the presence of a reducing agent under acidic conditions. It was also found that the intensity of the color of the resin depends on the concentration of arsenic(V) in the sample solutions. Since the development of the color occurs in 20min by heating of the mixture at 40 degrees C, this system can provide a simple, rapid and low-cost detection method of a trace amount of arsenic(V) in an aqueous media. The detection limit of this method is 1x10(-6)moldm(-3). A longer preconcentration time with the same resin gave the higher sensitivity of 1x10(-7)moldm(-3) that is comparable with that of the instrumental analysis. The present method comprises both the concentration and detection step with the same solid material, and hence it gives higher sensitivity and easier handling than the ordinary colorimetric methods using a liquid medium.

Fluorometric detection of fluoride ion by ligand exchange reaction with 3-hydroxyflavone coordinated to a zirconium(IV)–EDTA complex

An aqueous solution composed of [Zr(H2O)2edta]·2H2O and 3-hydroxyflavone (flavonol) exhibits an intense blue fluorescence (λmax = 460 nm) upon excitation at 400 nm and the signal intensity decreases with the addition of fluoride ion. This observation has been interpreted by the ligand exchange of flavonol coordinated to Zr(IV) with fluoride ion. Based on this phenomenon, we have fabricated a simple fluorescent detection system of fluoride ion available in aqueous media. The present signaling system provides a simple, rapid and selective detection method of fluoride ion, which covers the concentration range from 1 × 10−3 to 3 × 10−6 M without any significant interference from common anions.

Extraction Characteristics of Niobium(V) and Tantalum(V) on Trioctylmethyl Ammonium Chloride-Impregnated Polyurethane Foam

Abstract A reagent-impregnated polymer material has been prepared with trioctylmethyl ammonium chloride (TOMAC) and polyurethane foam as a new type of extractant for niobium and tantalum. Niobium(V) and tantalum(V) can be easily concentrated from their hydrofluoric acid solutions with TOMAC-impregnated polyurethane foam. The log D value for tantalum(V) is more than 4 in the HF concentration range from 0.5 to 2 mol·L−1. The recovery of tantalum(V) from hydrofluoric acid solutions containing a large amount of niobium(V) has been successfully carried out by a batch technique. Extraction characteristics of the present system are similar to solvent extraction rather than to conventional anion-exchangers with respect to the dependence of the value of log D on hydrofluoric acid concentration.

PREPARATION AND ADSORPTION PROPERTIES OF THE POLYSTYRENE RESIN HAVING DIETHYLENETRIAMINE-N,N′- BIS(METHYLENEPHOSPHONATE) GROUP

ABSTRACT Styrene-divinylbenzene copolymer beads containing diethylenetriamine-N,N′-bis(methylenephosphonate) group have been synthesized. The adsorption properties, of the present resin for some trivalent and bivalent metal ions have been examined. The selectivity sequence of the present resin at pH lower than 2.0 is as follows: Ga(III)> A1(III)> Sm(III)>Cu(II)>Co(II)>Zn(II)>Ca(II). The present resin reveals remarkable selectivity for the trivalent metal ions. The selective concentration of In(III) Ga(III) and Sm(III) from an acidic aqueous solution has been demonstrated by using a column of the present resin.