Selective recovery of silver and palladium from acidic waste solutions using dithiocarbamate-functionalized cellulose

Abstract

The efficient extraction and recovery of precious metals (PMs) such as silver (AgI) and palladium (PdII) from waste sources are of high importance, as natural reserves are limited, and the metals pose an environmental concern. Consequently, a biomass-based adsorbent, dithiocarbamate-modified cellulose (DMC), was used for the selective capture of AgI and PdII from complex aqueous matrices. DMC was found to be an efficient material for the quantitative adsorption of AgI, and PdII from weak to strongly acidic media. The adsorption kinetic data of AgI and PdII were well described by the pseudo-second-order (PSO) model, and the times required to reach equilibrium were 60 min and 90 min, respectively. The Langmuir isotherm model provided the best fitting for the PM ions adsorption, and the maximum uptake capacities of DMC were evaluated as 10.97 and 4.28 mmol g−1 for AgI and PdII, respectively. After extraction, the PM ion-loaded DMC was incinerated and the metals were recovered in their pure and elemental form (Ag0 and Pd0), with a yield of >99%. The proposed technique is more straightforward than the typical adsorption–desorption-based recovery method, as employed in commercial operations. Other advantages include process simplicity, high efficiency, non-utilization of toxic eluents, and recovery of the metals in their elemental form without the use of any reductants. Furthermore, the excellent performance (extraction rate: ~99%) of DMC towards the recovery of Ag and Pd from actual waste solutions indicates the potential for the application of the process at a larger scale.