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

Perrhenate(ReO4-) was used as nonradioactive surrogate for the radionuclide pertechnetate(99TcO-4) 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 ReO 2 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 0.43h-1 at pH 6.9 and room temperature(25℃).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℃ increased k obs 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 ReO-4-loaded loess was treated with the stabilized nanoparticles suspension([Fe]=560 mg/L),the water leachable ReO-4 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 ReO-4 in soil and groundwater.

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℃）. 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/Cobs 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^--1oaded 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.