Measurement and Control of Peroxide Bleaching Indicators

ABSTRACT The complicated chemical processes that occur during peroxide bleaching of pulp may be monitored by analysis of the dissolved substances in peroxide bleaching pressates with UV-visible spectroscopy. Sample preparation using filtration, pH adjustment and data manipulation assist in the extraction of information using UV absorbance spectroscopy. This information may be used to model peroxide residual, pulp brightness, wood species and other parameters that contribute to or describe the efficiency and quality of the pulp bleaching process. The use of multiple ratios of UV absorbance values is described and shown to provide superior information compared to partial least squares methods on the raw data. The efficiency of the bleaching process is optimized when the amount of peroxide compared to dissolved lignin is maximized and the amount of chromophores on the lignin is minimized.