Formation of NH4 + ions in reaction between urea and nitrous acid

Abstract

The interaction of urea and nitrogen oxides produces N 2. This reaction is used in neutralization of nitrogencontaining technological gases and wastes of power, metallurgic, and metal working plants. 1 It is generally accepted 2-4 that urea reacts with nitrous acid according to the equation CO(NH2) 2 + 2 HNO 2 9 2 N 2 + CO 2 +3 H20.However, in acidic solutions urea may also undergo hydrolysis producing CO: and NH4 + ions. 4 Available data on the product composition and kinetics of urea reactions with nitrogen oxides and nitrous acid are insufficient for complete description of occurring processes.We investigated in detail the interaction of HNO 2 with urea in aqueous solutions of HNO3 containing 0.05--0.2 M CO(NH2) 2 and NaNO2 and 0.02--1.0 M HNO 3 with magnetic stirring. Time variation of the solution contents was monitored by titrimetry (determination of H +, HNO 2 and CO(NH2)2) and ionometry . .with use .of.ion-selective electrodes _(NH4~" .andNO.if).Gaseous products were identified by IR spectroscopy and with the use of a ~I'esto-3Y' automatic gas analyzer. We found that the reaction between CO(NH2)2 and HNO 2 within a temperature range of 10--50 ~ follows the stoichiometric equation CO(NH2) 2 + HNO 2 + H + ,, 9 N 2 + NH4 + + CO 2 + H20.The reaction orders with respect to CO(NH2)2 and HNO 2 are equal to unity. The effective reaction rate constant keff grows proportionally to the H * ion concentration within the range from 0.01 L tool -t s -I when [H +] = 0.02 tool L -I to 0.30 L mo1-1 s -1 when [H +] = 1.0 mol L -1 (25.0+_0.1 ~ In our opinion, the essential determining factor in the H + concentration range under study is the fraction of the protonated form of CO(NH2) 2. Assuming that the reaction involves H2NCONH3 +, we calculated the rate constant /c o independent of the H + ion concentration with the use of the dissociation constant of the urea protonated formS:The concentration of the urea protonated form is determined by the expression K+[H +1

A highly stabilized–inhibited nitric acid/ferric nitrate-based solder stripping solution

“…Gladyshev et al [18] found that this reaction is of first-order with respect to both N 2 HSO 3 H and HNO 2 . The following rate equation has been suggested by these authors [18]:…”

“…Gladyshev et al [18] stated that HNO 2 first accumulates in solutions containing metal ions and nitric acid and then decomposes to nitrogen oxides. The reactions showing the possible products of decomposition of nitrous acid are presented elsewhere [19,20].…”

“…However, reduction of nitric acid by metals can be essentially avoided through incorporation of sulfamic acid and its salts [18,19,21]. Sulfamate ions are capable of reacting with nitrous acid and convert it to sulfuric acid [21,23] according to Equation (2):…”

Sulfamic Acid and Its N- and O-Substituted Derivatives

“…64 A kinetic study of the reaction of nitrous acid with sulfamic acid and urea has been reported, and kinetic equations have been derived. 65…”