Milled cashmere guard hair powders: Absorption properties to heavy metal ions

Cashmere guard hair was milled into fine particles using a wet milling system. The metal ion absorption properties of cashmere guard hair, both in the milled powder and its parent fibre forms, in comparison with wool and silk, were examined towards oppositely charged ionic metal species (Zn2 + and anionic species of Cr6 +) using respective gamma emitting radioisotopes. The absorption of metal ions was found to be governed by ionic interactions over different pH ranges. The absorption performance of the powder sorbents towards Zn2 + ions (silk powder > wool powder > cashmere guard hair powder) showed an opposite trend to Cr6 + (cashmere guard hair powder > wool powder > silk power). The breakdown of cashmere guard hair cuticle cells and oxidation of powder surface during milling enhanced the initial rate of metal ion absorption. The absorption yield of all the studied sorbents increased with increasing the initial Cr6 + ion concentration in the solution. However, Zn2 + ion concentration in solution showed a very little effect on absorption in the powder sorbents studied.