Calcium Phytate as a Pretreatment for Iron-contaminated Papers Prior to Hydrogen Peroxide Bleaching

ABSTRACT

Among bleaching agents available in paper conservation, hydrogen peroxide (HP) is a versatile choice that has many advantages in the removal of discoloration from paper. However, its well-known radical formation in the presence of iron impurities in paper poses the risk of cellulose degradation and color reversion, i.e. return of staining. This study explores a method to diminish undesired HP reactions by adding an additional step using a calcium phytate solution as complexing agent to the recommended treatment sequence. Tests on model papers impregnated with different molar concentrations of iron ions to trace the effects of simulated HP treatments on weight average molar mass, carbonyl group content, and color indicate that the iron phytate complex is sufficiently stable to sustain limited HP bleaching and thereby keeps the iron ions to a certain extent from the reaction system.

KEYWORDS:

• Bleaching
• calcium phytate
• iron contamination
• weight average molar mass
• carbonyl group content
• color

Acknowledgements

Melanie Diesner and Thomas Prohaska, both from Department of Chemistry, Division of Analytical chemistry at BOKU University for the iron content determination by ICP-QMS. Sonja Schiehser and Antje Potthast, both from Department of Chemistry, Division of Chemistry of Renewable Resources for the determination of carbonyl group content and molar mass moments by fluorescence labeling and GPC-MALLS-RI.

Disclosure statement

No potential conflict of interest was reported by the author(s).