Analysis of the chemical form of iron in water pipes using XAFS measurements

Abstract

Yellow and red metal oxides are commonly found on deteriorated water pipes and it has been reported that their main component is iron. X-ray absorption fine structure (XAFS) spectroscopy is an effective method which can be used to measure the chemical form of metals. However, when the iron concentration in water samples is extremely low, XAFS measurement and analysis can be difficult due to so much noise in the spectra. In this study, we examined various conditions related to XAFS measurements to analyze the chemical form of iron in water taken from water pipes. To optimize the XAFS measurement conditions, the energy range in pattern fitting was set at 7,100–7,140 eV. Piling up multiple pieces of filter paper was effective for improving the accuracy in the analysis of the XAFS spectra. The XAFS measurement of actual water samples was conducted and a low R factor was obtained from pattern fitting analysis. Differences were observed in the XAFS spectra depending on the chemical form of iron. These results showed that the chemical form of the iron of the actual water samples taken from the water pipes was able to be detected from the XAFS measurement.