Green SO2 conversion from flue gas by pH variation

Abstract

Emissions reduction or conversion by clean technologies has always been a mission for environmental protection and sustainable development. A green, electrochemically driven conversion of SO 2 to NaHSO 4 from flue gas by pH variation was conducted. Experiments were carried out to investigate some factors affecting the conversion process, such as O 2 function in flue gas, selected initial pH (pH 0 ) of solution, and CO 2 effects of high concentration. Experimental results revealed that (i) O 2 was essential for SO 2 absorption, since the pH of solution was decreased more effectively than that of flue gas without O 2 . The lowest pH of absorption solution with pouring O 2 was about 3.2, which was benefit to formatting HSO 3 -but hindering absorption of CO 2 . Meanwhile, O 2 from flue gas accelerated the adsorption of SO 2 for its oxidability to change HSO 3 -and SO 3 2-ions into SO 4 2-. (ii) At the conditions of different pH 0 , the minimum absorption efficiency of SO 2 was 89.3 %, corresponding to pH 0 5.0 and 7.0, while maximum value was 100.1 % corresponding to pH 0 6.0, which meant pH 0 6.0 was more appropriate for SO 2 conversion by electrochemistry under the experimental pH 0 range. (iii) The absorption efficiency of CO 2 was at a very low level under conditions of pH 0 5.0, 6.0, and 7.0, whose value of minimum and maximum was 0.07 and 0.19 %. The result showed that high concentration of CO 2 from flue gas had little affection on desulfurization under the experimental pH 0 range, which enable to infer that byproduct of NaHSO 4 is pure enough.