ELECTROCHEMICAL SYNTHESIS OF AMMONIUM PERSULFATE (NH4)2S2O8 USING OXYGEN-DEPOLARIZED POROUS SILVER CATHODES PRODUCED BY POWDER METALLURGY METHODS

V.A.†Lavrenko,
   
A.Zolotarenko
 

I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Omeliana Pritsaka str.,3, Kyiv, 03142, Ukraine
Powder Metallurgy - Kiev: Frantsevich Institute for Problems of Materials Science NASU, 2018, #09/10
http://www.materials.kiev.ua/article/2660

Abstract

The stage-by-stage mechanism of the reduction process proceeding in an acidic environment in the cathodic depolarization of ammonium sulfate (NH4)2SO4 (including the primary process such as synthesis of hydrogen peroxide H2O2 on a porous silver cathode by equation 2H2O2 + 2SO2-4= S2O2-8  +O2↑ + H2O and the main final process such as 2NH2+4 + S2O2-8 = (NH4)2S2O8) along with the anodic reaction, 4HO-2 = 3O2↑ + 2H2O + 4e, on a platinum plate has been established. The silver cathodes were produced by powder metallurgy methods (compaction of silver nanopowder with particles 10–30 nm in diameter at 450 kg/cm2 followed by sintering of the samples in a purified hydrogen atmosphere at 450 ºС). The silver nanopowder was obtained as individual acicular nanocrystals that branched out and were held in pairs on a Pt plate in electrolysis in a 2% AgNO3 solution with addition of 1% nitric acid. The nanostate of the silver powder was verified with the BET method (Brunauer, Emmett, Teller) by low-temperature nitrogen adsorption. The ammonium persulfate synthesis kinetics and mechanism indicate that the replacement of commercial lead cathodes with oxygen-polarized silver cathodes leads to 17.5% decrease in the electricity consumed. The polarization properties of the cellular silver cathode remain unchanged for 100 h of (NH4)2SO4 electrolysis.


AMMONIUM PERSULFATE, AMMONIUM SULFATE, ELECTROCHEMICAL SYNTHESIS MECHANISM, ELECTROLYSIS, OXYGEN-DEPOLARIZED POROUS SILVER CATHODES, POWDER METALLURGY, ROCKET ENGINEERING