Selective recovery of palladium by wool resin and woven wool fabric resinrbents

Protein fibers, including wool fibers, selectively adsorb precious-metal ions; hence, they can potentially be used in wastewater treatment applications. Herein, we examined metal-ion adsorption by woven wool fabric and wool resins, especially the adsorption of Pd(II). When woven wool fabrics are treated with chlorine, the cuticle layer is removed from the fiber surface; this treated fabric showed superior Pd(II)-adsorption performance compared with untreated fabric, with a Pd recovery of 81% from an aqueous solution containing 500 mg L−1 Pd(II) for 24 h at 25 °C, which is superior to that of lignin-based adsorbents. The chlorine-treated woven wool fabric and wool resin prepared from this fabric preferentially adsorb Pd when placed in simulated industrial wastewater, even if it contains a variety of other metal ions (e.g., Pd(II), Ni(II), and Cu(II)). Therefore, wool fabrics and resins produced from wool waste can be used as selective adsorbents for the recovery of precious metals such as Pd. •Chlorine-treated wool fiber has a better absorption performance than untreated wool fiber.•The maximum Pd recovery of wool adsorbent is 81% in aqueous nitrate solution containing 500 mg L−1.•Chlorine-treated wool selectively adsorbs precious-metal ions including Au, Pd, Pt, and Rh from mixed solutions.•The chlorine-treated wool adsorbent preferentially adsorbs Pd in simulated industrial wastewater containing Ni and Cu.•Waste or poor-quality wool can be formed into resin to form an effective and easy-to-handle adsorbent.