ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Kinetic study of non-reactive iron removal from iron-gall inks

Antonio C A da Costa, Fernanda do N Corrêa, Gustavo de S Sant’Anna, Gisele B Tonietto, José Marcus de O Godoy, Rodrigo de A Gonçalves, and Márcia T S Lutterbach

^aMuseu de Astronomia e Cięncias Afins, Rua General Bruce 586, Bairro Imperial de São Cristóvão, 20921-030, Rio de Janeiro, RJ, Brasil

E-mail: antoniocosta@mast.br

Abstract: The removal of non-reactive iron for different combinations of Fe²⁺ and tannic acid in iron-gall inks, via calcium phytate solutions, was studied. In parallel, the non-reactive iron removal kinetics was investigated using the pseudo first-order and second-order kinetic models. The results showed that the use of a dilute solution of calcium phytate to wash the impregnated paper strips removed the non-reactive iron from iron-gall inks in approximately 15 min in stoichiometric and non-stoichiometric combinations of iron and tannic acid. A second washing of the paper strips after an accelerated ageing, showed a distinct kinetic behaviour, with iron removal taking place simultaneously but apparently via a different mechanism. The use of a reference calcium phytate solution exhibited the same behaviour, suggesting that the use of dilute solutions as iron removal agents would represent less damage to historical documents. The results of kinetic modelling showed that all the combinations of Fe²⁺ and tannic acid used fitted the pseudo first-order kinetic model, when dilute and reference phytate solutions were tested as iron-desorbing agents.

Keywords: iron-gall ink – phytate – kinetic modelling – iron stabilisation

Full paper is available at www.springerlink.com.

DOI: 10.1515/chempap-2015-0227

Chemical Papers 70 (5) 602–609 (2016)