Degradation Kinetics of Fe-EDTA in Hydrogen Sulfide Removal Process

Available data on the degradation of Fe-EDTA liquid redox H2S removal processes are reviewed, and the effect of H2S molar flow rate, the initial concentration of Fe(III)EDTA, and the presence of sodium citrate in Fe-EDTA solution were investigated in this study. The semibatch with continuous flow of H2S containing biogas was used under a wide range of experimental conditions; , H2S molar flow rate, (1.08 × 10−3–3.40 × 10−3 mol/h), the initial concentration of Fe(III)EDTA, (2.17–8.16 mol/m3), and the concentration of sodium citrate, (0–300 mol/m3). The result showed that sodium citrate acted as stabilizer with a good ability to reduce the degradation rate. The degradation rate of Fe-EDTA was found to follow pseudo first-order kinetics. Empirical correlations expressed the degradation rate constant as a function of significant H2S molar flow rate, and the initial Fe(III)EDTA and sodium citrate concentration were successfully developed for the prediction of Fe-EDTA degradation rate. Moreover, the precipitated solid, called sulfur cake, was recovered, and its composition was investigated. The result revealed that the sulfur cake contained more than 98% sulfur element and almost balances with iron, and no significant EDTA was degraded into the solid form.