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

Recovery of precious metals (PMs: AuIII and PtIV) 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 AuIII and PtIV extraction from acidic solutions ([H+]: ? 0.2 mol L?1). The adsorption capacity (mmol g?1; AuIII: 5.07, PtIV: 2.41) and rate to reach equilibrium (? 30 min) were significantly higher than most of the reported bioadsorbents. The AuIII or PtIV, after captured in DMC, was subsequently recovered as Au0 and Pt0 (yield 99%) via incineration. The protocol was verified using real waste samples containing AuIII and PtIV in a mixed matrix of base metal ions, and a quantitative (-100%) and selective extraction of AuIII and PtIV 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.