ASSESSING THE RISKS OF ALKALINE DAMAGE DURING DEACIDIFICATION TREATMENTS OF OXIDIZED PAPER

The sensitivity of oxidized cellulose to damaging beta-elimination reactions was studied to define safe pH conditions and treatment times beyond which damage from alkaline treatment may occur; whether damage caused by alkaline treatment was affected by the type or amount of oxidation was also investigated. Cotton paper was oxidized using UV-A radiation, a hydrogen peroxide solution, or a sodium metaperiodate solution. Following oxidation, samples were soaked at room temperature in carbon-dioxide-free calcium hydroxide baths, at pH 8.5, 10.0, or 12.5, for 20 or 60 minutes. Changes to the molecular weight of the cellulose as a function of the amount of oxidation, treatment bath pH, and treatment time, were monitored to understand which conditions cause degradation to occur. The UV-A and hydrogen peroxide oxidized samples, simulating naturally oxidized papers, showed minimal sensitivity to beta-elimination reactions in baths up to pH 10.0; slight degradation was observed during treatment at pH 12.5. By contrast, sodium metaperiodate oxidized samples, which did not mimic naturally oxidized papers, were markedly degraded in pH 10.0 and 12.5 baths, with more degradation occurring at higher pH. For the oxidized papers found to be sensitive to beta-elimination reactions, longer treatment times led to more degradation.