The Reaction of nitric acid with formaldehyde and with formic acid and its application to the removal of nitric acid from mixtures

Abstract

Efficient methods are given for decreasing or eliminating the nitric acid content of solutions of inorganic nitrates with recovery of oxides of nitrogen and leaving behind no added reagent.The reaction of both formaldehyde and formic acid with nitric acid (2-20N) has been studied at looo. A t constant concentrations of formaldehyde and formic acid the reactions are of apparent third-order over the nitric acid range 2 -1 5~ (rate constants given).Further reaction of formaldehyde or formic acid with nitrate solutions causes precipitation of metal hydroxides as the p H of the solution rises; this may be used as a basis of separation of metals from solution. Nitrates can be converted to other salts such as chloride or sulphate by reaction with formaldehyde after addition of the appropriate acid.Nitrites do not react with formaldehyde in neutral solution, but nitrous acid. liberated by hot acid, decomposes partially into nitric acid which then reacts with formaldehyde as above.

Effect of hydrazine and formaldehyde on the corrosion of SS304L in hot nitric acid environment

“…The self passivation of the stainless steel is attributed to the autocatalytic reduction of nitric acid (Eqs. (6) and (6i)-(6vi)) [16]. The heterogeneous mechanism, has been shown to occur at more anodic potentials (>0.5 V SCE ) and both the mechanisms occur simultaneously at lower potentials.…”

“…(3)- (5). At lower concentrations of nitric acid (<0.5 N), the final products of decomposition are CO 2 , NO and NO 2 [5][6][7][8].…”

Kinetics of reduction of nitric acid by electrochemical method and validation of cell design for plant application

“…Denitration following the induction period can be violent that leads to uncontrollable process conditions and is a significant safety concern. The induction period is reported to depend on the concentration of nitric acid, nitrite content and temperature and can be considerably minimized or suppressed by passing gaseous NO 2 through the acid prior to the addition of HCHO [7]. At 100 C and at acid concentrations above 3 M, the reaction is more or less instantaneous.…”

“…However, bacteria are sensitive to heavy metal ions and to changes in the composition of the influent stream. Though several reductants like sugar, molasses, phosphorous, glycerin, formaldehyde, formic acid and ethyl alcohol are available for chemical denitration, reduction of nitric acid involving a homogeneous reaction with formaldehyde [7][8][9][10][11][12][13] or formic acid [14][15][16][17] and denitration reaction with HCHO/HCOOH induced by nitrite [18][19][20] or catalysts like active carbon [21] and noble metal supported catalysts [22][23][24] have been investigated extensively, owing to the efficiency, simplicity and economic viability of this process. The reaction of HCHO with nitric acid is exothermic and it leaves no residual chemicals, as the products are gaseous NO 2 , NO and CO 2 .…”

Preparation of Ag@mSiO 2 and Pt@mSiO 2 nano composites using trioctylmethyl ammonium hydrogen phthalate (TOMAHP) ionic liquid as reaction medium

“…6H 2 O is mixed with SiO 2 of average mess size of 200 and subsequently reduction of mixture with hydrazine hydrade results into Pt NPs [11,19e22]. However, the uncontrolled particle size, non-uniform distribution of metal NPs on to the inert support, less efficiency and complex chemical processes involved for preparation of such nano composites are the main drawbacks of the process [23]. In recent past, researchers have developed more efficient method called polyol method for preparation of supported metal NPs with desired sizes and shapes [2,16,17].…”