ハイドロタルサイトを用いる淡水中の鉛及びカドミウムの固相抽出／黒鉛炉原子吸光分析

摘要

ハイドロタルサイト（HT）の有する陽イオン交換能及び塩基性化合物としての特性を活かしたPb（II）及びCd（II）の固相抽出法について検討を行った．その結果，Pb（II）及びCd（II）はいずれも水溶液のpH 4.0～10.0の範囲で良好にHTに吸着された．吸着実験の結果をLangmuir式で検討したところ，Pb（II）はK＝6.11×10~5（dm~3/mol），b＝4.53×10~(-4)（mol/g），Cd（II）はK＝4.46×10~5（dm~3／mol），b＝1.53×10~(-4)（mol/g）であり，HTがPb（II）及びCd（II）の吸着体として有効であることが示唆された．さらに，Pb（II）及びCd（II）を捕捉したHTを希塩酸に溶解後，黒鉛炉に導入し，灰化温度をPbが300℃，Cdが250℃，原子化温度をPbが2150℃，Cdが1600℃とすることで微量分析が可能になった．検量線はPb（II）05μg/100mL，Cd（II）は0.05μg/100mL以下で原点を通る良好な直線関係を示した・得られた定量法を水道水，河川水，溜め池水中の微量Pb（II）及びCd（II）の定量に応用し，良好な結果を得ることができた．%The solid-phase extraction (SPE) method for the preconcentration of trace amounts of Pb(II) and Cd(II) using hydrotalcite (HT), and its determination by graphite furnace atomic absorption spectrometry (GFAAS) were investigated. The Pb(II) and Cd(II) were quantitatively adsorbed onto HT at pH 4.0-10.0, respectively. The adsorption isotherms were found to be fitted by the Langmuir equation. After the solid-phase (metal ions adsorbed HT) was separated from the sample solution by a membrane filter, it was dissolved in 1.5 mol dm~(-3) hydrochloric acid. An aliquot of the resulting solution was injected into a cup-type graphite furnace, and the absorbances of Pb and Cd were measured by AAS. An ashing temperature of 300 ℃ and an atomizing temperature of 2150 ℃ were selected for Pb, and an ashing temperature of 250 ℃ and an atomizing temperature of 1600 ℃ were selected for Cd, respectively. The detection limit for Pb(II) was 0.01 μg/100 mL, and that for Cd(II) was 0.0008 μg/100 mL. The proposed method was applied to the determination of trace amounts of Pb(II) and Cd(II) in fresh-water samples.