Manometric study of CO2 and H2S emission from aqueous solutions and wastewater

The emissions of CO2 and H2S from the aqueous solutions and wastewater were studied to determine and compare the times required to reach the equilibrium of H2S and CO2 between water and gas phases. The solutions of NaHCO3 and NaHS were acidified and the change in the pressure of emitted gases was measured with a manometric OxiTop® system. The average time required to achieve the equilibrium state of distribution of CO2 between two phases was 16.7±1.5 min, and it did not depend on the initial amount of NaHCO3 in the solution. The average time required to achieve the equilibrium of H2S (sulfide) was 19.5±5.5 min, having the same value for solutions with different initial contents of sulfide ions. The average time required to achieve the equilibrium of H2S in the wastewater was 16.2±3.6 min, and it showed the faster emission of gaseous H2S to decrease the oversaturation of the solution. The ratio of measured values of pressure to the calculated values did not depend on the concentration of NaHS in the initial solution, and its average value was 0.86±0.14. The results showed that measured values of pressure of H2S emitted from the wastewater were twice lower than the calculated values and it is necessary to take into account the catalyzed formation of polysulfide in the solution of sulfides.