Monitoring pH Variations in Aqueous Saline Systems by NIR Spectroscopy and Chemometric Modeling

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Resumo

pH control in saline aqueous systems is a recurring challenge in industrial processes, especially in oil production and treatment units, where acid-base variations affect corrosion, scaling, and chemical stability. Traditional electrochemical techniques are limited in high salinity, temperature, and pressure environments, motivating the use of optical approaches. In this study, the application of near-infrared (NIR) spectroscopy, combined with partial least squares (PLS) regression, was evaluated to monitor pH variations between 5500-7900 cm-1 in saline aqueous systems containing cations at 40 °C and ambient pressure. The measurements were performed in a temperature-controlled, jacketed glass reactor. A NIR probe was inserted into the system. Measurements were taken with a spectrophotometer in the range of 10000-5500 cm-1, using a transflectance cell with a 1 mm optical path. The results revealed a correlation between actual and predicted values, with an R2 for calibration of 0.99006 and for validation of 0.98589, in addition to mean absolute errors of 0.00045 and 0.00064, respectively. These indices demonstrate the accuracy and stability of the model, reinforced by the symmetrical distribution of residuals and the linearity observed in the prediction versus actual value graph. Spectral analysis indicated that variations in pH are reflected in discrete changes in the vibrational regions associated with O-H bonds, allowing for pH determination even in the presence of dissolved salts. The high sensitivity obtained proves that the NIR-PLS coupling is capable of detecting pH fluctuations of less than 1%. These characteristics make the technique suitable for continuous, non-invasive, and real-time monitoring of industrial processes, with potential application in CO2 injection systems, produced water treatment, and mitigation of fouling in pipelines and heat exchangers.

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Programação
15:15 até 16:00 em 18/05/2026
Área Externa do Aud…
Instituições
  • 1 Programa de Pós-graduação em Engenharia de Processos, Universidade Tiradentes
  • 2 Unit - Universidade Tiradentes
  • 3 Universidade Tiradentes
  • 4 Instituto de Tecnologia e Pesquisa
  • 5 Petrobras (Brazil)
Eixo Temático
  • Petróleo, gás e combustíveis
Palavras-chave
NIR Spectroscopy
pH
Chemometrics Analyses
PLS Model
Process Monitoring