Reductive immobilization of perrhenate in soil and groundwater using starch-stabilized ZVI nanoparticles

Abstract

Perrhenate (ReO4-) was used as nonradioactive surrogate for the radionuclide pertechnetate (99TcO4-) to investigate the potential of using starch-stabilized zero valent iron (ZVI) nanoparticles for reductive immobilization of pertechnetate in soil and groundwater. Batch kinetic tests indicated that the starch-stabilized ZVI nanoparticles were able to reductively remove ~96% of perrhenate (10 mg/L) from water within 8 h. XRD analyses confirmed that ReO2 was the reduction product. A pseudo-first-order kinetic model was able to interpret the kinetic data, which gave a pseudo first order rate constant (kobs) value of 0. 43 h-1 at pH 6. 9 and room temperature (25°C). Increasing solution pH up to 8 progressively increased the reaction rate. However, highly alkaline pH (10) resulted in much inhibited reaction rate. Consequently, the optimal pH range was identified to be from 7 to 8. Increasing solution temperature from 15 to 45°C increased kobs from 0. 38 to 0. 53 h-1. The classical Arrhenius equation was able to interpret the temperature effect, which gave a low activation energy value of 7. 61 kJ/mol. When the ReO4--loaded loess was treated with the stabilized nanoparticles suspension ([Fe]=560 mg/L), the water leachable ReO4- was reduced by 57% and nearly all eluted Re was in the form of ReO2. This finding indicates that starch-stabilized ZVI nanoparticles are promising for facilitating in situ immobilization of ReO4- in soil and groundwater. © 2012 The Author(s).