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Spectroscopic Study of Tempo-Oxidized Deinked Pulp

Abstract Deinked pulps are not currently used in value-added paper manufacturing. To implement their use, both strength and optical properties must be improved. TEMPO oxidation has been shown to improve strength properties of thermomechanical and deinked pulps. However, a significant reduction of the pulp brightness results due to yellowing of mechanical fibers. Spectroscopic techniques were used to investigate the effect of TEMPO oxidation on deinked fiber properties. Fourier transform infra-red (FTIR) spectroscopy and UV/VIS spectrum showed that oxidation conditions are driving important chemical reactions that affect optical properties. Results indicated that ortho-quinone compounds as well as carboxylic groups are generated depending on oxidation conditions resulting in pulp brightness decrease. Spectroscopic studies also revealed that residual ink detachment from fiber surfaces is occurring during oxidation contributing to improve pulp brightness.