A Strategy for Separating and Recovering Aqueous Ions: Redox-Recyclable Ion-Exchange Materials Containing a Physisorbed, Redox-Active, Organometallic Complex
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- 作者：C. Kevin Chambliss ; Matthew A. Odom ; Christine M. L. Morales ; Charles R. Martin ; and Steven H. Strauss
- 刊名：Analytical Chemistry
- 出版年：1998
- 出版时间：February 15, 1998
- 年：1998
- 卷：70
- 期：4
- 页码：757 - 765
- 全文大小：154K
- 年卷期：v.70,no.4(February 15, 1998)
- ISSN：1520-6882
文摘
A series of anion-exchange materials were prepared byadsorption of the dark-green organometallic saltHEP+NO3-or HEP+ReO4- dissolved inorganic solvents onto threedifferent silica gels (HEP =1,1',3,3'-tetrakis(2-methyl-2-hexyl)ferrocene). Adsorption isotherms showed thattheamount of HEP+ salt adsorbed depended on thechoiceof counteranion, solvent, surface area, and pore sizediameter of the silica gel. After drying theHEP+NO3-/SiO2 andHEP+ReO4-/SiO2solid materials, the organometallic salts did not desorb into the aqueous phase whenthe solids were treated with aqueous solutions containingNaNO3 and/or HNO3. TheHEP+NO3-/SiO2materialsfunctioned as redox-recyclable ion exchangers.Treatmentof the materials with aqueous waste simulants containingKReO4, NaNO3, and HNO3 resulted inNO3-/ReO4-ionexchange as follows:HEP+NO3-/SiO2(s)+ ReO4-(aq) 
HEP+ReO4-/SiO2(s)+ NO3-(aq). The distributioncoefficient for one of the new materials was 100 mL/g (440mL/mmol of HEP+) for an aqueous wastesimulantcontaining ReO4- and 1.0 M HNO3.This can be compared with 290 mL/g (87 mL/mmol of cationic sites) forReillex-HPQ, a commercial non-redox-recyclable ion-exchange resin which has been studied forReO4- andTcO4- extraction. The higherdistribution coefficient permillimole of cationic sites suggests thatHEP+NO3-/SiO2is more selective for ReO4- than Reillex-HPQunder theseconditions. The recovery of adsorbedReO4- was accomplished by treating the exchanged materials withaqueous ferrocyanide, which caused the reduction ofadsorbed HEP+ to adsorbed HEP and concomitantrelease of the adsorbed counterions ReO4- andNO3-.Reactivation of HEP/SiO2 toHEP+NO3-/SiO2was accomplished with aqueous ferric nitrate. Five completeextraction-deactivation/(ReO4-recovery)-reactivationcycles (duty cycle time 94 min) consistently showed a slowdecrease in distribution coefficient (~20% over fivecycles).Nevertheless, the data indicate that redox-recyclableanionexchange is a viable concept and that redox-recyclable ion-exchange materials with improved stability should beconsidered as viable alternatives to traditional anion-exchange resins in the future.
HEP+ReO4-/SiO2(s)+ NO3-(aq). The distributioncoefficient for one of the new materials was 100 mL/g (440mL/mmol of HEP+) for an aqueous wastesimulantcontaining ReO4- and 1.0 M HNO3.This can be compared with 290 mL/g (87 mL/mmol of cationic sites) forReillex-HPQ, a commercial non-redox-recyclable ion-exchange resin which has been studied forReO4- andTcO4- extraction. The higherdistribution coefficient permillimole of cationic sites suggests thatHEP+NO3-/SiO2is more selective for ReO4- than Reillex-HPQunder theseconditions. The recovery of adsorbedReO4- was accomplished by treating the exchanged materials withaqueous ferrocyanide, which caused the reduction ofadsorbed HEP+ to adsorbed HEP and concomitantrelease of the adsorbed counterions ReO4- andNO3-.Reactivation of HEP/SiO2 toHEP+NO3-/SiO2was accomplished with aqueous ferric nitrate. Five completeextraction-deactivation/(ReO4-recovery)-reactivationcycles (duty cycle time 94 min) consistently showed a slowdecrease in distribution coefficient (~20% over fivecycles).Nevertheless, the data indicate that redox-recyclableanionexchange is a viable concept and that redox-recyclable ion-exchange materials with improved stability should beconsidered as viable alternatives to traditional anion-exchange resins in the future.