Mechanism and kinetics of Fe(II)EDTANO reduction by iron powder under anaerobic condition

•Fe(II)EDTANO was first reduced by Fe powder.•Fe(II)EDTANO reduction by Fe powder was a first-order reaction with respect to Fe(II)EDTANO.•Reaction stoichiometry of Fe(II)EDTANO reduction by Fe powder was proposed.•Fe(III)EDTA reduction was restricted by Fe(II)EDTANO, and Fe(III)EDTA had little effect on the reduction of Fe(II)EDTANO.

Reduction of Fe(II)EDTANO as well as Fe(III)EDTA is the main process for simultaneous removing nitric oxide and sulfur dioxide with Fe(II)EDTA solution. In this paper, iron powder was proposed to reduce the Fe(II)EDTANO. The mechanism and kinetics of Fe(II)EDTANO reduction by Fe powder were studied with respect to the Fe(II)EDTANO concentration, pH value, and temperature. The experimental results indicated that the bonded NO was converted to ammonium. Fe(II)EDTANO reduction by Fe powder was a first-order reaction concerning Fe(II)EDTANO. The reaction rate increased with the decrease of pH value as well as the increase of temperature. In addition, the energy of activation (Ea) and the entropy of activation (ΔS‡) of the Fe(II)EDTANO reduction by Fe powder were 23.229 kJ mol−1 and −215.251 J K−1 mol−1, respectively. Finally, the simultaneous reduction of Fe(III)EDTA and Fe(II)EDTANO by Fe powder was investigated. The results showed that Fe(III)EDTA reduction was restricted by Fe(II)EDTANO, and Fe(III)EDTA had little effect on the reduction of Fe(II)EDTANO. Besides, the reduction of Fe(II)EDTANO was the determining step in the whole process of Fe(II)EDTA regeneration. These findings can provide constructive instruction for the NO removal in industrial applications with mixed Fe(II)EDTA and Fe powder system.