According to Llorens, Lloret, Picouet, and Fernandez (2012), when
copper is used as antimicrobial, cellulose fibers are impregnated with
copper metal ions immersed in aqueous solution of copper sulfate
(1%) resulting in the adsorption of copper ions. The authors have indicated
that copper ions can be transformed into elementary copper or
copper oxide by means of physical or chemical methods. Physical
methods include heating at 180 °C for 2 h or a combination of a heating
process (155 °C for 10 min) and UV light exposure (low pressure mercury
lamp), while chemical methods consist on a reduction reaction
with sodium borohydride (0.5 M).