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.
The effects of La^3＋ on proliferation, cell cycles, apoptosis and ion channels were investigated in mouse embryo fibroblast NIH 3T3 cells and its possible mechanisms were explored. Our data showed that La^3＋ promoted cell proliferation with increased S-phase entry and inhibited the outward potassium currents in a concentration-dependent manner in NIH 3T3 cells. La^3＋ and Ca^2＋ had synergistic effect on cell proliferation and cell cycles. It showed that Ca^2＋ was needed for La^3＋ promoted cell cycle progression. Using the whole-cell voltage-clamp technique, we found that La^3＋ blocked the outward potassium current in a Lanthanum ions can increase intracellular Ca^2＋ concentration concentration-dependent manner in NIH 3T3 cells. through inhibition of potassium currents, which induce a series of physiological changes and improve proliferation of cells. This may be one of the molecular mechanisms of lanthanum ions induced cell proliferation. The present work provides a new perspective for understanding the biological and toxicological effects of lanthanum.
