Mitigation of interference in heavy metal analysis in highly alkaline FGD wastewater by Taguchi method

• Main Authors: Shi-Zhe Zhang, 詹仕哲
• Other Authors: 張書奇
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/s6wwvq

碩士 === 國立中興大學 === 環境工程學系所 === 106 === Heavy metal quantification in complex matrix is a very challenging task, especially in flue gas desulfurization (FGD) wastewater from steam power generators. Since the discharge standards on arsenic and selenium will be further tightened to lower ppb levels, the interference can cause significant errors on quantification results. This study investigated the interference of major constituents in FGD wastewater on quantification of the aforementioned heavy metals by flame atomic absorption spectrometry (FAAS) coupled with a hydride generator in both synthetic and real FGD wastewater samples. To minimize the numbers of experiments, Taguchi method was employed to determine the most influential ions or ligands based on the interfering extent as well as effective pretreatment steps that can reduce the interference. Eight major ions or ligands were chosen based on historical records, i.e., ammonia nitrogen, nitrate, sulfate, chloride, boron, calcium, sodium, and magnesium. An orthogonal table L18(21x37) was used to check the interfering strengths of these eight controlling factors on the quantification of arsenic and selenium. The result showed that influential factors are nitrate and sulfate. Furthermore, in this study, four different pretreatment steps with three different levels were tested using an orthogonal table L9(34) to define an optimum pretreatment procedure to reduce the interference on quantifying real FGD wastewater samples. As a result, these pretreatment steps were determined and these heavy metals can be detected consistently in a satisfactory recovery range and all QA/QC parameters such as RSD and method detection limits are satisfactory.