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Solubility of selenium at high ionic strength under anoxic conditions

還元環境下における高イオン強度溶液中のセレンの溶解度

飯田 芳久; 山口 徹治; 田中 忠夫; 中山 真一

Iida, Yoshihisa; Yamaguchi, Tetsuji; Tanaka, Tadao; Nakayama, Shinichi

還元環境下において、高イオン強度溶液中のセレンの溶解度試験を実施した。支配的な溶存化学形はHSe$$^{-}$$(pH: 5-8), Se$$_{4}$$$$^{2-}$$(pH: 9-13)であった。溶解度制限固相はSe(am)(pH: 5-8), Se(cr)(pH: 9-13)であった。溶解反応とその平衡定数は、Se(am)+H$$^{+}$$+2e$$^{-}$$=HSe$$^{-}$$, logK$$^{0}$$=-6.57$$pm$$0.15, 4Se(cr)+2e$$^{-}$$=Se$$_{4}$$$$^{2-}$$, logK$$^{0}$$=-16.67$$pm$$0.03と決定された。また、イオン相互作用係数は$$varepsilon$$(HSe$$^{-}$$, Na$$^{+}$$)=-0.01$$pm$$0.10, $$varepsilon$$(Se$$_{4}$$$$^{2-}$$, Na$$^{+}$$)=-0.03$$pm$$0.02と決定された。アモルファスセレンの生成自由エネルギーは$$Delta$$$$_{f}$$G$$_{m}$$$$^{0}$$(Se(am))=6.0$$pm$$2.2kJ mol$$^{-1}$$、ポリセレナイド種については$$Delta$$$$_{f}$$G$$_{m}$$$$^{0}$$(Se$$_{2}$$$$^{2-}$$)=111.64$$pm$$1.61kJ mol$$^{-1}$$, $$Delta$$$$_{f}$$G$$_{m}$$$$^{0}$$(Se$$_{3}$$$$^{2-}$$)=98.68$$pm$$1.02kJ mol$$^{-1}$$及び$$Delta$$$$_{f}$$G$$_{m}$$$$^{0}$$(Se$$_{4}$$$$^{2-}$$)=95.14$$pm$$0.17kJ mol$$^{-1}$$と求められた。

Solubility experiments for selenium were performed at high ionic strengths (1.0 and 2.0 M NaCl) under anoxic conditions. Dominant aqueous selenium species were identified as hydrogen selenide, HSe$$^{-}$$, at pH between 5 and 8, and polyselenide, Se$$_{4}$$$$^{2-}$$ at pH between 9 and 13. A solubility-limiting solid was determined to be amorphous selenium at pH between 5 and 8, and crystalline selenium at pH between 9 and 13. The equilibrium constants of Se(am) + H$$^{+}$$ + 2e$$^{-}$$ = HSe$$^{-}$$, logK$$^{0}$$ = -6.57$$pm$$0.15, 4Se(cr) + 2e$$^{-}$$ = Se$$_{4}$$$$^{2-}$$ logK$$^{0}$$ = -16.67$$pm$$0.03 and ion interaction coefficients for HSe$$^{-}$$ and Se$$_{4}$$$$^{2-}$$ versus Na$$^{+}$$, $$varepsilon$$(HSe$$^{-}$$, Na$$^{+}$$) = -0.01$$pm$$0.10 and $$varepsilon$$(Se$$_{4}$$$$^{2-}$$, Na$$^{+}$$) = -0.03$$pm$$0.02, were determined by specific ion interaction theory. The standard molar free energy of formation of amorphous selenium and polyselenide species were determined to be $$Delta$$$$_{f}$$G$$_{m}$$$$^{0}$$ (Se(am)) = 6.0$$pm$$2.2 kJ mol$$^{-1}$$, $$Delta$$$$_{f}$$G$$_{m}$$$$^{0}$$(Se$$_{2}$$$$^{2-}$$) = 111.64$$pm$$1.61 kJ mol$$^{-1}$$, $$Delta$$$$_{f}$$G$$_{m}$$$$^{0}$$(Se$$_{3}$$$$^{2-}$$) = 98.68$$pm$$1.02 kJ mol$$^{-1}$$ and $$Delta$$$$_{f}$$G$$_{m}$$$$^{0}$$ (Se$$_{4}$$$$^{2-}$$) = 95.14$$pm$$0.17 kJ mol$$^{-1}$$, respectively.

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パーセンタイル:33.23

分野:Nuclear Science & Technology

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