Study on Removal of Iron Rust from Paper Objects with Thiourea Dioxide

Abstract

There are many paper-based documents, archives and books contaminated by iron rust beacuse they were fixed with iron staples or clips. Iron rust not only disfigures the paper, covers the writtings or images of paper, but also makes paper brittle. Iron rust is very difficult to remove due to its insolubility in water and organic solvents. Thiourea dioxide(TDO), an agent with strong reducibility, easy accessibility, stability and safety was applied to remove iron rust in this work. The concentration of TDO solution, iron rust removal effect and removal rate were studied. The results showed that TDO was an effective and safe agents to remove iron rust from paper documents. The concentration was higher, the removal speed was faster. But to get high concentration, TDO need to be dissolved at higher temperature which is damage to paper. In view of the above facts, the proper treatment bath was 5% at 40°C. Results also showed that the combination of 5% TDO and EDTA can remove iron rust from paper completely in 4 hours.