Determination Of Sulfide Sulfur In Gas-liquid-solid Phase By Gas-phase Molecular Absorption Spectrometry

This thesis foucses on the determination of sulfide sulfur in gas-liquid-solid phase by gas-phase molecular absorption spectrometry. Simultaneously, principal principle of gas-phase molecular absorption spectrometry, wavelength selection of ultra violet, flow rate of carrier gas, concentration and volume of acid, reaction time and temperature were investigated. Concentration of H2S in biogas, S2- in fermentation broth and acid volatile sulfide(AVS) were detected by this method. Detection limit and quantification limit of sulfide in gas-liquid-solid phase were calculated based on the results of determination. In order to verify the presion and accuracy of this method, inoxidizability of three sulfide antioxidant buffers, AVS in mineral and sediment, and sulfide removal of limonite were discussed. Main conclusions are shown as follows:(1) The optimum absorption wavelength of H2S, obtained by ultraviolet scanning, is 202.6nm. Based on contrast experiment, air is selected as carrier gas,the optimum flow rate is 0.5 L/min and detection time is 20s.6 mol/L of hydrochloric acid is used in the detection process, volume of hydrochloric acid is 2.5 mL. The optimum reaction time of AVS determiantion is 1h, the reaction is heated at the temperature of 100℃.(2) Concentration of H2S in biogas, S2- in fermentation broth and acid volatile sulfide(AVS) were detected by gas-phase molecular absorption spectrometry. Repeatability and recovery of determination are both well. The detection limit of H2S in biogas is 5.1×10-3 mg L-1, the quantification limit is 1.7×10-2 mg L-1; the detection limit of S2- in fermentation broth is 1.2×10-2 mg L-1,the quantification limit is 4.1×10-2 mg L-1 while the detection limit of acid volatile sulfide (AVS) in fermentation residue is 2.7×10-2mg g-1(dry sample) and the quantification limit is 8.9×10-2 mg g-1(dry sample).(3) The components of anaerobic fermentation products are considerablely complex. The gases (CH4, CO2, H2O, H2) have no effect on determination of H2S in biogas. However, some ions (NO2-, SO32-, S2O32-) have deleterious effects on determination of S2- in fermentation broth. A new method based on the application of Cu2+ to precipitate S2- was proposed to eliminate the effects of interference ions on the determination of sulfide in fermentation broth.(4) Application experiments were conducted to verify the presion and accuracy of this method. Contrast experiment on inoxidizability of three sulfide antioxidant buffers: results indicated that the optimum sulfide antioxidant buffer is EDTA, the preservation temperature is 4℃ and the longest preservation time is a week. Determination of AVS in minerals and sediments:detection data illustrated that the content of AVS in minerals and sediments were both within the limits of gas-phase molecular absorption spectrometry. Sulfide removal of limonite:it was found that Yeshan black limonite had the best sulfide removal which reached to 100%. The stable and accurate detection data were obtained in the above experiments, which verified the feasibility of gas-phase molecular absorption spectrometry in practical application.