Abstract
Deacidification is an established conservation treatment for the prolongation of the acidic paper stability. Several different deacidification systems are in use today, such as the dispersions of alkaline nanoparticles in organic solvents. The aim of the study was to compare the effects of different calcium nanoparticle dispersions in alcohols on lignocellulosic paper. Commercially available nano calcium hydroxide dispersions for paper deacidification, and laboratory prepared nano calcium carbonate dispersions in ethanol and 2-propanol were investigated and compared as to their effectiveness in increasing the stability of paper. The FE-SEM analyses were used to determine the size of Ca(OH)2 and CaCO3 particles in the dispersions. The SEM–EDS analyses were performed both on the paper surface and its cross-section in order to ascertain the distribution of calcium ions following the deacidification treatment. An evaluation of the changes of color, molecular weight, pH and alkaline reserve on different lignocellulosic papers was performed. In comparison to untreated samples, our results indicate all the investigated deacidification treatments decrease the degradation rate constant of cellulose, as determined by accelerated degradation. However, the treatments involving nano calcium hydroxides in both alcohols noticeably affect the color of the treated lignocellulosic papers. According to the obtained results, nano calcium carbonate is therefore the more suitable deacidification agent for the lignin containing papers.
Highlights
The acidity of paper presents a serious problem for many archive and library collections, motivating the development of many different deacidification treatments
Analytical methods pH measurements The pH of water extracts was measured according to the standard [33], modified to smaller samples: 7 mL of deionised water was added to 100 mg of paper sample. pH was determined in the water extract after one hour using a flat membrane electrode (Metrohm 6.0256.100) connected to a Mettler Toledo MP 220 pH meter
In order to determine the size of the particles, the dispersion was applied to a slide
Summary
The acidity of paper presents a serious problem for many archive and library collections, motivating the development of many different deacidification treatments. Most of the paper deacidification procedures provide an alkaline reserve to neutralize acids that may be introduced later; either generated within the paper itself, or absorbed from its storage environment [5]. Most often weak bases, such as alkaline-earth carbonates, hydroxides, and oxides are used. The pH value of paper after the deacidification is crucial, as an increased alkalinity might induce color changes of the inks, pigments, and dyes [7]. Color changes of watercolor pigments during the deacidification were observed, and it was concluded that calcium and barium hydroxides cause more pronounced color changes compared to the magnesium or calcium hydrogen carbonates [8]. Various metal hydroxides provide a very effective reduction of acidity, they
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