竹材机械浆顽固发色基团结构解析及其脱除机理初探

Study on the Structural Characteristics and Removal Mechanism of the Inactive Chromophores of Neosinocalamus Affinis Mechanical Pulp

竹类原料木质素含量较高、细胞壁较厚、纹孔少且小、不利于药液渗透等原因使得常规条件下竹材机械浆无法制备高白度纸浆。本研究使用一种温和快速的新型漂白系统——乙醇-水二元介质碱性过氧化氢漂白体系处理慈竹机械浆(TMP),利用木质素在乙醇中良好的溶解性以及碱性条件下乙氧根离子较强的亲核进攻能力,改善药液渗透效果,破坏并溶出慈竹TMP中的顽固发色基团,突破了当前慈竹TMP的漂白上限,将纸浆白度提升至80%ISO以上。本研究对比研究了在相同过氧化氢用量下,常规水相体系与乙醇-水二元介质体系所得慈竹TMP顽固发色基团的结构特点,发现慈竹TMP中的顽固发色基团结构分别为:呋喃类共轭结构、环戊烯酮类共轭结构和木质素结构中的S’、G’、I、FA和pCA五种共轭连接结构。通过分析两种体系漂白终段溶出物结构特征的差异,推测碱性条件下乙醇电离的微量乙氧根离子对顽固发色基团的脱除具有关键性作用。本研究可为开发经济高效和绿色可持续的新型竹类TMP漂白方法提供理论依据和数据支持。

The Neosinocalamus Affinis mechanical pulp(NAMP)from bamboo is hard to prepare high brightness pulp under conventional conditions due to the high lignin content,thick cell wall,and small pores of bamboo,which significantly increase the mass transfer resistance of bleaching liquor.Herein,a facile mild bleaching system,i.e.,alkaline hydrogen peroxide with ethanol-water media bleaching(AHEWB)system was proposed.The stubborn chromophoric groups in NAMP were destructed and dissolved because of the good solubility of lignin in ethanol and the strong nucleophilic attack ability of ethoxylate ion under alkaline conditions,which overcame the ceiling of NAMP brightness and led to an increased pulp brightness to more than 80%ISO.The characteristics of chromophoric groups obtained from NAMP under the traditional aqueous system and the AHEWB system under the same hydrogen peroxide dosage were systematically studied.The results showed that the stubborn chromophoric groups in NAMP mainly consisted of furan conjugated structure,cyclopentenones conjugated structure,and conjugated linkages of S’,G’,I,FA,and pCA.Overall,this study came up with a new guess that the ethoxylate ion of ethanol ionization under alkaline conditions played a key role in removing the stubborn chromophoric groups,which could provide theoretical basis and data support of AHEWB for developing an economically feasible and environmentally sustainable bamboo bleaching industry.