Imparting Silver into Wool and the Influence of Chloride

Abstract

The following study is concerned with imparting silver ions to wool fibres to study the uptake in the presence of chloride ions. The primary concern is that silver nitrate uptake in tap water implicates the precipitation of silver chloride when silver ions are exposed to chloride. The procedure involved the use of distilled water, tap water and saline solutions as a comparison. The purpose of introducing silver to wool is to impart the fibres with antimicrobial properties, in order to further understand how silver propagates when silver ion and silver chloride uptake are competing processes. Despite silver exhibiting useful antimicrobial properties, these properties are counterbalanced with high silver(I) reactivity to sunlight and halides. Results from AAS, argentometric Cl– titration and SEM-EDS provide insight that the mechanism is strongly dependent on the temperature and rate of diffusion, both into and within the fibre. Firstly, wool rapidly adsorbs Ag+ and spreads it through the fibre. If AgCl is present, a partial decoupling of AgCl to Ag+ and Cl– occurs due to the common-ion effect, contact with the wool and partial solubility at elevated temperatures. Additionally, Ag+ scavenges impurities in the wool, giving rise to colour in both the wool and the resulting solution. AgCl adsorbs onto the surface of the wool more slowly than Ag+, marginally penetrating the cross-section, while both surface and core Ag+ migrates to the inner rim of the fibre. If there is sufficient Ag+, it binds to sulfur, primarily at the fibre paracortex. Overall, silver uptake into wool is a fragile process that has strong dependence on silver and chloride concentrations, the temperature and the presence of other entities such as dyes or impurities.