Determination of Equilibrium Constants for Reactions between Nitric Oxide and Ammoniacal Cobalt(II) Solutions at Temperatures from 298.15 to 309.15 K and pH Values between 9.06 and 9.37 under Atmospheric Pressure in a Bubble Column

Abstract

Experiments were conducted in a bubble column to determine the equilibrium constants of reactions between NO and ammoniacal cobalt(II) solutions at temperatures between 298.15 and 310.15 K and pH values from 9.06 to 9.37 under atmospheric pressure. The two reactions are 2Co(NH 3 ) 5 (H 2 O) 2+ + 2NO ⇌ (NH 3 ) 5 Co(N 2 O 2 )Co(NH 3 ) 5 4+ + 2H 2 O and 2Co(NH 3 ) 6 2+ + 2NO ⇌ (NH 3 ) 5 Co(N 2 O 2 )Co(NH 3 ) 5 4+ + 2NH 3 , respectively. Their equilibrium constants are calculated on the fraction molar basis. All experimental data fit well to the equations ln K NO 5 = 3598.5(1/T) + 16.759 and ln K NO 6 = 1476.4(1/T) + 26.597, which give the enthalpy of reactions between NO and penta-and hexaamminecobalt(II) nitrates: Δ r H 5 °= −29.92kJ•mol −1 and Δ r H 6 °= −12.27kJ•mol −1 .

On the Kinetics of the Absorption of Nitric Oxide into Ammoniacal Cobalt(II) Solutions

“…This analysis was confirmed by Yatsimirskii and Volchenskova using absorption spectra, 23 and it was utilized to study the absorption of oxygen into ammoniacal Co(II) solutions, 24 to investigate the electrochemical oxidation of Co(II) in aqueous ammonia solution, 25 and to determine the equilibrium constants for reactions between nitric oxide (NO) and ammoniacal Co(II) solutions. 26 The reactivity of different ammoniacal Co(II) complexes with NO has also been reported in another paper. 26 Ammoniacal Co(II) complexes that had a coordination number of less than five could not react with NO.…”

“…26 The reactivity of different ammoniacal Co(II) complexes with NO has also been reported in another paper. 26 Ammoniacal Co(II) complexes that had a coordination number of less than five could not react with NO. Parallel reactions b e t w e e n N O a n d p e n t a a m m i n e c o b a l t ( I I ) a n d hexaamminecobalt(II) ions at room temperature or higher can be described, respectively, as follows: 27,28 (2)…”

“…26 Yu and Tan recently determined the relevant equilibrium constants based on an analysis of the Co(II)−ammonia system. 26 However, the kinetics of the absorption of NO into ammoniacal Co(II) solutions still remain unknown. This paper first introduces the experimental setup for s t u d y i n g t h e k i n e t i c s o f N O a b s o r p t i o n i n t o pentaamminecobalt(II) and hexaamminecobalt(II) solutions and explains the theoretical analysis of the rate constants of these two reactions.…”

Experimental investigation of nitric oxide removal from flue gas using hexamminecobalt(II) solution scrubbing in a pilot-scale facility

“…Hexamminecobalt(II) solution (Co(NH 3 ) 6 2+ ) could activate molecular oxygen to form a kind of bridged compound with double core and double oxygen([(NH 3 ) 5 Co-O-O-Co(NH 3 ) 5 ] 4+ ), which has strong oxidation similar to hydrogen peroxide (H 2 O 2 ). At the same time, hexamminecobalt(II) solution could capture NO gas into the solution to form [Co(NH 3 ) 5 NO] 2+ , and [Co(NH 3 ) 5 NO] 2+ is oxidized by [(NH 3 ) 5 Co-O-O-Co(NH 3 ) 5 ] 4+ to form soluble NH 4 NO 3 and NH 4 NO 2 efficiently under the condition of enough presence of oxygen in flue gas (Yu, 2012; Yu et al, 2012; Yu and Tan, 2013; Yu and Tan, 2014). The reaction equations are as follows:…”

“…They also investigated the regeneration and kinetics of the gas–liquid reaction between NO and hexamminecobalt(II) (Long et al, 2004). Yu compared the denitration performances of iron( 2+ )(Fe(II)–EDTA), hexamminecobalt(II) chloride ([Co(NH 3 ) 6 ]Cl 2 ), and hydrogen peroxide (H 2 O 2 ) (Yu, 2012; Yu and Tan, 2013, 2014). Liu Z conducted experimental studies on the influence of operating conditions on NO and SO 2 removal performances (Liu Z et al, 2016) .…”