Highly selective and straightforward recovery of gold and platinum from acidic waste effluents using cellulose-based...

Recovery of precious metals (PMs: Au^III and Pt^IV) from waste resources is of high importance due to the environmental concern and imbalance in the supply-demand ratio. A new approach has been explored for the recovery of PM using earlier developed bio-adsorbent, dithiocarbamate-modified cellulose (DMC). The adsorbent exhibits excellent adsorption efficiency (~99%) over a wide range of pH (< 1-6) and high selectivity towards Au^III and Pt^IV extraction from acidic solutions ([H⁺]: ≥ 0.2 mol L^-1). The adsorption capacity (mmol g^-1; Au^III: 5.07, Pt^IV: 2.41) and rate to reach equilibrium (≤ 30 min) were significantly higher than most of the reported bio-adsorbents. The Au^III or Pt^IV, after captured in DMC, was subsequently recovered as Au⁰ and Pt⁰ (yield > 99%) via incineration. The protocol was verified using real waste samples containing Au^III and Pt^IV in a mixed matrix of base metal ions, and a quantitative (~100%) and selective extraction of Au^III and Pt^IV were observed. The proposed technique is more effective and straightforward than the typical adsorption-desorption-reduction based method, because of the advantages like no-use of toxic eluents, and no-addition of any reductants to collect the PMs in elemental form.