Oxidative cleavage of lignin aromatics during chlorine bleaching of kraft pulp
Methanol liberation and methoxyl loss during chlorine bleaching of softwood kraft pulp were quantitatively investigated to estimate the degree of structural modification of lignin aromatics. An increase in the chlorine multiple led to enhanced methoxyl loss from lignin. Our result, using pH-adjusted chlorine water (pH 5.7), by which chlorination under oxidation-favorable conditions was achieved, strongly supported the importance of the oxidation reaction by chlorine during delignification and lignin degradation. It was also suggested that methanol can be produced not only via catalytic hydrolysis by chlorine but via oxidative cleavage of the ether bond as well. The infrared spectrum of chlorolignins suggested that chlorine oxidation can open aromatic rings to muconic acid derivatives without cleaving ether bonding of the methoxyl group. No straight relation between the methoxyl content and the kappa number of chlorinated pulps was shown. The methoxyl content of bleached kraft pulps subjected to successive chlorination and alkali extraction showed a good relation with the kappa number. This means that almost all the portions of the oxidatively modified lignin structure were successfully removed during these treatments, and the aromatic structures of residual lignin in chlorinated and alkali-extracted pulps were thought to remain intact.
Safety Evaluation of Absorbent Hygiene Pads: A Review on Assessment Framework and Test Methods
Disposable absorbent hygiene products have evolved for superior performance, enhancing the convenience of daily lives. However, the use of disposable hygiene pads has brought safety concerns on chemical exposure, and significant efforts have been made to assess the potential risks associated with use of hygiene pads. This article intends to overview the safety assessment framework of diapers and feminine pads, which includes hazard identification, hazard characterization, exposure assessment, risk characterization, and post-market risk management. Risk assessment of various constituents are reviewed for quantification methods and conservative estimation of exposure parameters. By reviewing the up-to-date considerations in risk assessment, we aim to provide insightful discussion on safety evaluation of current versions of disposable absorbent products. More clinical testing and post-market surveillance are needed for continuous monitoring of potential health impacts of advanced products and constituents.
The unsuitability of AOX as a measure of the organic chlorine content of C-stage effluents
On a fait subir a plusieurs types de pâte kraft un traitement de blanchiment a l'aide de diverses charges de chlore. On a par la suite evalue les quantites de chlore lie organiquement en employant deux methodes : la methode des composes organiques halogenes adsorbables (AOX) et la methode du chlore organique total [COT(diff.)], cette derniere etant definie comme la difference entre le chlore total et le chlorure inorganique. La teneur en ions chlorure a ete determinee au moyen de la chromatographie des ions. Les valeurs AOX etaient beaucoup plus faibles que les valeurs COT(diff.) dans les effluents de chloration, tandis que ces memes valeurs etaient a peu pres egales dans les effluents d'extraction aux alcalis. On attribue cette difference, entre autres, au traitement de l'echantillon avec du H 2 SO 4 durant le processus de mesure des AOX. Dans le cas des effluents du stade C, une partie de chlore organique est facilement liberee sous forme de chlorure inorganique avec l'addition de H 2 SO 4 . Cette difference peut aussi s'expliquer par la presence des composes chlores qui ne sont pas adsorbes par le carbone active.