A Novel Method for Quantification of Residual Toners in Deinked Pulp, 2010 TAPPI PEERS Conference

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Pulp brightness and ERIC (Effective Residual Ink Concentration) have been commonly used to evaluate ink removal efficiency in paper recycling operations. Because these two methods are based on the measurements of light reflection, absorption and transmission, they can only provide indirect or relative values of residual ink in a pulp. As a result, deinking efficiency cannot be accurately quantified, which can result in over dosage of deinking chemicals or excess operation of flotation. This study developed a novel technique for accurate quantification of residual toner content in pulp based on the measurements of Fe concentration. In non-contacted printing, Fe was used as the common element in toners to facilitate imaging. As a metallic element, Fe can be traced in recycling processes. Meanwhile, the Fe content in a given toner is a constant. Therefore, residual ink content in pulp can be determined by analyzing Fe in the deinked pulp. The deinking efficiency determined by Fe Measurement is in qualitative agreement with those from brightness and ERIC measurements. However, both the ERIC and brightness method under predict deinking efficiency when compared with the present method based on Fe measurement. The significance of this study lies in the fact that accurate determination of deinking efficiency can help to effectively control production casts such as chemicals and energy.