Arsenic oxidation and removal from flue gas using H2O2/Na2S2O8 solution

- A novel process for removing arsenic was developed based on a composite oxidant.
- SO4− and OH resulting from activation of H2O2/Na2S2O8 were verified as main active species.
- The high removal efficiency of arsenic was reached.

To develop a novel process for removing arsenic from flue gas, a liquid-phase multi-component oxidant (LMO) composed of H2O2 and Na2S2O8 was prepared. The experimental conditions for arsenic oxidation by LMO and then removal were investigated systematically and results showed that the molar ratio of Na2S2O8 to H2O2 had an obvious impact on arsenic oxidation and removal; arsenic oxidation depended closely on reaction temperature and LMO solution pH; flue gases such as SO2 and NO in higher concentrations had an inhibition for arsenic oxidizing, while arsenic removal was inhibited by higher concentration CO2, arsenic oxidation and removal was nearly unaffected by O2. The optimum conditions were determined as 0.01:1 (mol/mol) of molar ratio of Na2S2O8 to H2O2, 5.5 of LMO solution pH, 50 °C of reaction temperature and 1.0 L/min of flue gas velocity, and under the conditions, the average oxidation and removal efficiencies for arsenic reached 96.3% and 100%, respectively. In addition, the reaction mechanism of the oxidation and removal was proposed based on the characteristics of removal products by XRD, HPLC-HG-AFS, AFS, and the literature references.