Nitrate reduction by green rusts modified with trace metals

A kinetic study of nitrate reduction by green rust (GR), a group of layered Fe(II)–Fe(III) hydroxide solids, was performed using a batch reactor system. The reduction rate of nitrate by GRs was affected by the anion content in the interlayer of GRs. GR containing F- (GR-F) showed the fastest reduction rate while GR-SO4 showed 9 times slower reaction rate than GR-F. The addition of 1 mM Pt or Cu to GR that contained 85 mM Fe(II) improved the reduction kinetics of nitrate by up to 200 times. Pt was an effective activating agent for all GRs. The sequential step reaction model that we proposed appropriately simulated the experimental data. The fastest nitrate reduction by GR-F with Pt was achieved at pH 9 among 7.5 to 11. At that condition, 1 mM nitrate transformed completely into ammonium within 23 min.

► The improving method for nitrate reduction was developed by the addition of trace metals into GR.
► Sequential step kinetic model of nitrate reduction was proposed and verified.
► The fastest nitrate reduction by GR-F(Pt) was observed at pH 9.