Nanoparticles of Mg(OH)₂:  Synthesis and Application to Paper Conservation

Abstract

We report an investigation on the effects of counterions of magnesium salts on the homogeneous phase precipitation reaction to yield nanoparticles. The results provide new parameters to guide the control of the size, monodispersity, crystallinity, and morphology of Mg(OH)(2) nanoparticles. Evidence emerged that magnesium counterions affect the size of crystallites. The particle size increases from about 50 to 200 nm and follows the Hofmeister anion series: sulfate < chloride < nitrate </= perchlorate. All of the results show that a proper choice of counterion and composition of reaction mixture allows one to modulate and set conditions that predetermine production of nanoparticles with desired size. The Mg(OH)(2) nanoparticles have been applied to the successful conservation of paper. To demonstrate the efficacy of nanoparticles as deacidifying agent and as protection against cellulose aging, some samples of paper from the 18th century were treated with the nanoparticles and artificially aged by subjecting them to hydrothermal and photooxidative degradation. The treatment with nanoparticles preserved the mechanical features of paper, and the deterioration was consistently reduced. The comparison with the Wei t'O method (based on magnesium alkoxides), one of the most common and largely used methods for paper deacidification, indicates the following: (1) nanoparticles present a higher efficacy in the deacidification treatment since they are much more reactive; (2) nanoparticles are less aggressive since they are easily converted into the carbonate form; (3) they present minor disadvantages related to the chemical nature of the solvent used in the Wei t'O (i.e., CFC); (4) papers/books can be treated with very simple procedures, and do not require any special apparatus; (5) nanoparticle treatments have substantial economic benefits.

Deacidification of Acidic Books and Paper by Means of Non-aqueous Dispersions of Alkaline Particles: A Review Focusing on Completeness of the Reaction

“…nanoparticles. Thus, it has been proposed to deacidify paper by addition of nano-sized Ca(OH)2 (Giorgi et al 2002;Sequeira et al 2006;Stefanis and Panayiotou 2007), or Mg(OH)2 (Giorgi et al 2005;Stefanis and Panayiotou 2007;Giorgi 2015;Amornkitbamrung et al 2015;Wojciak 2015). More research is needed to follow up in this area.…”

Functional polypropylene composites filled with ultra-fine magnesium hydroxide

“…Magnesium hydroxide has been used to neutralize pollutants [1], in pharmaceutical production [2,3], in fertilizers [4], as a paper preservative [5], and as a magnesium oxide precursor [6−8]. Its varied morphology, hydrophilicity, basicity, non-toxicity and antibacterial activity have recently stimulated new applications, ranging from membrane production, [9] biomaterials [2], compound detection [10] to modern polymer composites [11−16].…”

A stabilizer-free non-polar dispersion for the deacidification of contemporary art on paper

“…Since then, research efforts have been devoted to the refinement of synthetic procedures, with the aim of tailoring physico-chemical particles characteristics to different case studies, including paper [13,16,17], iron gall inked manuscripts [18,19] and archeological wood [21,22]. The efficacy of these systems in hampering cellulose degradation has been assessed in several studies [37][38][39][40].…”

“…About fifteen years ago, the use of dispersions of alkaline nanoparticles, mainly calcium and magnesium hydroxide in short-chain alcohols, was proposed as an efficient way for the deacidification and pH control of several cellulose-based works of art [13][14][15]. Since then, several systems have been formulated and applied to paper [16,17], iron gall inked manuscripts [18][19][20] and archeological wood [21][22][23]. Nanoparticles high reactivity grants a fast neutralization of acidity, providing a neutral environment due to the conversion of hydroxides into carbonates, which are milder alkaline species.…”