Abstract This study intends to explain the difference in brightness stability between hardwood ECF and TCFz kraft pulps bleached by DEpDD and A(ZEo)(ZEo)(ZP) sequences respectively, using UV Resonance Raman (UVRR) spectroscopy. The brightness stability of the pulps was tested via dry aging experiments where the Post-Color Number (PCN) of the ECF pulp was twice that of the TCF pulp. The aged and non-aged bleached pulps were analyzed with UVRR spectroscopy to identify the cause of the large difference in PCN. The spectra of ECF and TCF bleached pulps presented clear differences in the intensities of the Raman shifts associated to lignin, lignin-like compounds, and degradation products such as muconic acids. To identify more specifically the compounds affecting the PCN, several post-bleaching treatments were applied on the ECF pulp including single stages (E, B, P, Z) or combinations (ZE, ZB, ZP), and their UVRR spectra analyzed. It was found that alkaline-soluble compounds were the main culprits for the difference in PCN values between ECF and TCFz pulps. ZP combination was the most efficient in eliminating residual lignin and other unsaturated components and for the development of brightness and brightness stability.

中文翻译：

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使用紫外共振拉曼光谱评估臭氧 TCF 漂白纸浆的亮度稳定性

摘要 本研究旨在利用紫外共振拉曼 (UVRR) 光谱来解释分别经 DEpDD 和 A(ZEo)(ZEo)(ZP) 序列漂白的阔叶木 ECF 和 TCFz 牛皮纸浆在亮度稳定性方面的差异。通过干老化实验测试纸浆的亮度稳定性，其中 ECF 纸浆的后色值 (PCN) 是 TCF 纸浆的两倍。使用 UVRR 光谱分析老化和未老化的漂白纸浆，以确定 PCN 存在较大差异的原因。ECF 和 TCF 漂白纸浆的光谱在与木质素、木质素类化合物和降解产物（如粘康酸）相关的拉曼位移强度方面存在明显差异。为了更具体地确定影响 PCN 的化合物，对 ECF 纸浆进行了几种后漂白处理，包括单阶段（E、B、P、Z）或组合（ZE、ZB、ZP），并分析了它们的 UVRR 光谱。结果表明，碱溶性化合物是导致 ECF 和 TCFz 纸浆 PCN 值差异的主要原因。ZP 组合在消除残留木质素和其他不饱和成分以及提高亮度和亮度稳定性方面最有效。