Air oxidation of aqueous sodium sulfide solutions with coal fly ash

The potential of coal fly ash was studied as a catalyst in the air oxidation of aqueous sodium sulfide (Na2S) solutions in the temperature range of 303–333 K. The rate of oxidation was found to be independent of the initial concentration of Na2S in the range of 5.80×10−2–28.45×10−2 kmol/m3. The effects of fly ash loading, source of fly ash, speed of agitation, air flow rate, fly ash particle size were also studied. Experimental results suggested a film-diffusion controlled reaction mechanism and 4% fly ash loading intensified the reaction rate by a factor of 3.5 over that of without fly ash at 303 K. The deactivation of the catalytic effect of fly ash was found to be less than 31% even after fifth repeated uses.