Absorption and Oxidation of Nitric Oxide (NO) by Aqueous Solutions of Sodium Persulfate in a Bubble Column Reactor

Abstract

The absorption-oxidation of nitric oxide (NO) by aqueous solution of sodium persulfate (Na 2 S 2 O 8 ) has been studied in a bubble column reactor operated in semibatch mode. The effects of different process variables such as the persulfate concentration (0.01-0.2 M), temperature (23-90°C), pH (4-12), sodium chloride concentration (0-0.5 M), and NO concentration (500-1000 ppm) were studied. In general, the NO fractional conversion (percent of inlet NO removed) at all temperatures increased almost linearly with persulfate concentration up to about 0.1 M, after which it started to level off. Increased temperature led to an increased fractional conversion of NO at all persulfate levels. At 0.1 M persulfate concentration, conversions of up to 69% and 92% were observed at 70 and 90°C, respectively. Solution pH and chloride concentration were both found to affect NO absorption at higher temperatures. The effect of pH was moderate, but sodium chloride showed a significant effect on NO absorption at 70°C, to the point of causing complete removal of NO. The effect of initial NO concentration in the gas phase was found to be marginal. The results demonstrate the feasibility of NO removal using aqueous solutions of sodium persulfate.

Thermally activated persulfate (TAP) oxidation of antiepileptic drug carbamazepine in water

“…It is noted that the redox potentials of the Cl À containing radicals are much lower than 2.6 V of sulfate radicals [14]. Furthermore, the generated Cl ÀÅ 2 and Cl Å could further react with itself to form Cl 2 and Cl À [31,32]. CO 2À 3 and HCO À 3 are the good scavengers for hydroxyl radicals, similar findings were reported everywhere [33].…”

Degradation of trichloroethylene in aqueous solution by persulfate activated with citric acid chelated ferrous ion

“…For instance, on the persulfate oxidation of TCE at pH 7 and 20°C, Liang et al [45] demonstrated that TCE degradation in the presence of chlorides revealed no effect on the degradation rate especially at chloride levels below 0.2 M, but at chloride levels greater than 0.2 M, TCE degradation rate reduced with an increase of the chloride ion concentration. However, Khan and Adewuyi [46] reported that the absorption and oxidation of nitric oxide (NO) significantly improved with the addition of NaCl in sodium persulfate solutions. In addition, in our previous study of 1,1,1-trichloroethane oxidation stimulated by thermally activated persulfate [47], we found anions Cl À and HCO 3 À had negative effects on TCA removal over the range of 1 to 100 mM.…”

Nitric oxide removal by combined persulfate and ferrous–EDTA reaction systems

“…Therefore, alternative cost-effective and environmentally friendlier processes such as using wet scrubbing agents, capable of significantly increasing the solubility of NO in water, are of ardent interest. [3][4][5][6][7] As a result, the uses of aqueous solutions of H 2 O 2 , NaClO 2 , KMnO 4 , iron and cobalt chelated compounds, and sonochemical oxidation processes for NO removal, are the subjects of a number of recent studies. [8][9][10][11][12][13][14][15] In 2010, Khan and Adewuyi reported, for the first time, the use of aqueous sodium persulfate (Na 2 S 2 O 8 ) activated by temperature for NO removal, and commented on its safety, stability and environmental benign nature.…”

“…The thermal and Fe 2+ ion activation of the persulfate anion leads to the production of the sulfate radicals (SO 4 •− ), which is responsible for the production of OH • that acts as the main oxidant for the conversion of NO in the aqueous solution. [5,6,[21][22][23] The following major pathways have been proposed: Finally, the respective concentration values were multiplied by their respective dilution factors, and then averaged to determine the concentration of a particular sample. The concentration profiles of the species were then obtained.…”