[Raman Spectroscopic Study on the Determination of SO4(2-) Concentration in Aqueous Solution under High Temperature...

In the present work, the Raman spectra of SO4(2-) ions in aqueous solutions were studied. The quantitative analysis shows that there is a significant correlation between the Raman intensity ratio(R) and the SO4(2-) concentration. The SO4(2-) concentration in aqueous solution at ambient temperature and pressure can be determined by the Raman intensity according to the linear fitting equation c (SO4(2-) = 4.779 6R (r2 = 0.999 4). Furthermore, the research proves that the temperature and pressure will af- fect the relationship between the Raman intensity ratio and the concentration of SO4(2-) ions. The quantitative equation for measur- ing the SO4(2-) concentration in aqueous solution at high temperature and high pressure is c(SO4(2-)) = 4.779 6(R + 1.469 x 10(-4)ΔT + 1.340 x 10(-4)ΔP), where R is defined as the ratio of the SO4(2-) ions band intensity to the OH stretching single band intensity, T is the temperature relative to 23 °C, ΔP is the pressure relative to 0.1 MPa, 23 °C ≤ T ≤ 390 °C, the concentration range of the SO4(2-) ions is 0.5-1.5 mol · L(-1), and the uncertainty of the equation is 6.5%. Raman spectroscopy can be used to measure the concentration of the Raman-active species in aqueous solutions.