Reduction of nitrate by resin-supported nanoscale zero-valent iron

Abstract

For environmental remediation of a contaminated groundwater, the use of nanosized zero-valent iron (nZVI) represents one of the latest innovative technologies. However, nZVI gets easily agglomerated due to its colloidal characteristics and has limited applications. To overcome this drawback, nZVI was immobilized on a supporting material. In this study, nZVI was formed and bound to ion-exchange resin spheres at the same time through the borohydride reduction of an iron salt. The pore structures and physical characteristics of the supported nZVI were investigated and its reactivity was measured using nitrate. The degradation of nitrate appeared to be a pseudo first-order reaction with the observed reaction rate constant of 0.425 h(-1) without pH control. The reduction process continued but at a much lower rate with a rate constant of 0.044 h(-1). When the simulated groundwater was used to assess the effects of coexisting ions, the rate constant was 0.078 h(-1) and it also reduced to 0.0021 h(-1) in later phase. The major limitation of ZVI use for nitrate reduction is ammonium production. By using a support material with ion-exchange capacity, this problem can be solved. The ammonium was not detected in our batch tests.