A Practical and Selective Method for the Analysis of Molybdenum in Grade T91 Tube and P91 Pipe Intended for Power Plants

Abstract:

ASME SA-213 T91 tubes and SA-335 P91 pipes were widely used in combined-cycle steam systems due to their greater increased temperature strength and creep behavior. In this paper, a practical and selective spectrophotometric method for the determination of molybdenum in ASME SA-213 T91 tube and SA-335 P91 pipe samples has been presented. This method was based on the chromogenic reaction between molybdenum(V) and sodium thiocyanate. Employing stannous chloride as a reductant, molybdenum(VI) was reduced to molybdenum(V) at the room temperature. The obtained molybdenum(V) formed an orange-red-colored (1:5) ligand complex with thiocyanate. The absorbance of the complex was measured at 470nm, and the molar extinction coefficient is 1.75´10⁴L·mol^-1·cm^-1. Under the optimum reaction conditions the absorption value was proportional to the concentration of molybdenum in the range of 0.40~1.21%, and the relative standard deviation was less than 3.0%. The proposed method was free from the interference from a large number of analytical important elements and has been applied satisfactorily to the determination of molybdenum in grade T91 tube and P91 pipe samples with the improved accuracy and precision.

• Periodical: Advanced Materials Research (Volumes 284-286)
• Pages: 1510-1515
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.284-286.1510
• Online since: July 2011
• Authors: Ying Li, Wan Qi Huang, Xu Hong Chang, Song Yan Cao, Bao Tong Qi
• Keywords: ASME Sa-213 T91 Tube, ASME Sa-335 P91 Pipe, Molybdenum, Power Plant

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