NaHS regenerated Fe(II) EDTA denitrification mechanism and kinetics investigation

Abstract

Fe(II) EDTA regeneration is a hot research topic in wet denitrification. In this study, NaHS was used to regenerate Fe(II)EDTA. The effects of Fe(II)EDTA-NO concentration, temperature and pH on the reduction of NaHS were investigated separately. On this basis, the reduction reaction mechanism and kinetics are clarified. A comparison was made with other reductants in terms of reduction efficiency and cost. The experimental results show that the reduction of Fe(II)EDTA-NO by NaHS is a first-order reaction for Fe(II)EDTA-NO. The NaHS reduction rate increases with increasing temperature. The destination of N in the reduction reaction is N2 and the destination of S is mainly S monomer. In addition, the activation energy (Ea) for the reduction of Fe(II)EDTA-NO by NaHS was 34.328 kJmol-1, the enthalpy of activation (ΔH#) was31.7879 kJmol-1, and the entropy of activation (ΔS#) was −160.3614 Jk-1mol-1. In addition, NaHS can simultaneously reduce Fe(II)EDTA-NO and Fe(III)EDTA, and Fe(II)EDTA-NO will reduce the efficiency of NaHS reduction of Fe(III)EDTA. These data can further promote the industrial denitrification of Fe(II)EDTA.