Simultaneous and Rapid Analysis of Hydroxide, Sulfide, and Carbonate in Kraft Liquors by Attenuated Total Reflection UV Spectroscopy, 2000 Pulping / Process & Product Quality Conference Proceedings

X. S. Chai, J. Li, J. Y. Zhu--This study experimentally demonstrated Attenuated Total Reflection (ATR) UV Spectroscopy for rapid and simultaneous determination of hydroxide, sulfide, and carbonate in kraft liquors. On-line measurements were achieved using an ATR flow cell integrated with a commercial UV spectrophotometer. A multi-variant partial least-square fitting procedure was employed to develop a species concentration predictive model. The model is calibrated using a set of eighteen modified kraft liquor samples made from a mixture of a kraft mill green and white liquor (base liquor) through dilutions and additions of sodium hydroxide, sulfide, and carbonate. The concentrations of hydroxide, sulfide, and carbonate in these liquors were obtained by standard ABC titration. The ATR-UV measurements were then directly applied to one green and three white liquor samples collected from the same kraft mill. Very good agreements between ATR-UV measured and titrated concentrations of hydroxide, sulfide, and carbonate were obtained. The ATR-UV measurement is rapid and accurate and does not require sample pretreatment or dilution; therefore, it can be implemented on-line for process control in mill environments. Because of the low cost and ease in maintenance, the ATR-UV technique may provide a better alternative to ATR-NIR or -FTIR methods.