离子色谱法测定烟气脱硫海水中的亚硫酸根离子

摘要

The technology for flue gas desulfurization (FGD) with seawater is widely adopted by coal-fired power plants in coastal areas. SO_2 in the flue gas is absorbed by alkaline seawater and transfered in aqueous phase as sulfite (SO~(2-)_3) , and most SO~(2-)_3 is transformed to sulfate (SO~(2-)_4) after an aeration process. The remaining SO~(2-)_3 in the seawater discharged to sea area may be harmful to marine organism because of its biological toxicity, thus it is necessary to determine the concentration of SO~(2-)_3 in the seawater for desulfurization. In this study, the method of determination of SO~(2-)_3 in the seawater by ion chromatography was investigated. The separation was achieved on an IonPac ASH A column with 14 mmol/L NaOH-12 mmol/L Na_2CO_3 solution as the mobile phase at a flow rate of 1.2 mL/min, and the detection was performed by a pulsed amperometric detector. Formaldehyde was added as a protective agent when sampling because the SO~(2-)_3 is easy to be oxidized. To avoid the formation of Mg(OH)_2 in the mobile phase with high pH value which might block the column, the Mg~(2+) in seawater was precipitated by NaOH solution (pH 12. 0) before sample determination. The method showed good linearity within the range of 0-100 mg/L with an average recovery of 116. 8%. The meth-od detection limit ( MDL) reached as low as 0. 05 mg/L. The relative standard deviations (RSD) for seawater matrix samples spiked at levels of 7. 5, 25. 0 and 75.0 mg/L were 2. 1%, 3. 1% and 4.0% (n =9) , respectively. The method has been applied for the determination of SO~(2-)_3 in flue gas desulfurization seawater with the advantages of being fast, sensitive and selective.%建立了燃煤电厂烟气脱硫海水中亚硫酸根(SO~(2-)_3)的离子色谱-脉冲安培检测方法.色谱柱为IonPac AS14A阴离子交换柱,流动相为14 mmol/L NaOH-12 mmol/L Na_2CO_3溶液(pH 11.7),流速1.2 mL/min,脉冲安培法检测.因SO~(2-)_3 易被氧化,故在采样时加入甲醛作为保护剂,使之稳定存在.在测定海水样品前,用NaOH溶液(pH 12.0)沉淀海水中的Mg~(2+),以避免其在pH较高的流动相中生成沉淀堵塞色谱柱.采用该方法检测SO~(2-)_3 的线性范围为0～100 mg/L,平均回收率为116.8%,检出限为0.05 mg/L;对7.5,25.0和75.0 mg/L 的海水基底加标溶液分别进行9次平行测定,其相对标准偏差(RSD)分别为2.1%,3.1%和4.0% .该方法具有快速、灵敏、选择性好等特点,用于烟气脱硫的海水中SO~(2-)_3 的检测,可得到令人满意的结果.