Sustainabilityin the Metallurgical Industry: ChemicallyModified Cellulose for Selective Biosorption of Gold from Mixturesof Base Metals in Chloride Media.

Inan effort to develop sustainable materials and methods for therecovery and recycling of precious metals, we recently developed twodifferent adsorbents by cross-linking pure cellulose with either epichlorohydrinor concentrated sulfuric acid and then modifying the surface with N-aminoguanidine functional groups. The adsorption behaviorof these sorption materials toward Au(III) from a multicomponent mixtureof Pt(IV), Pd(II), and some base-metal ions was studied in hydrochloricacid media. Both of the adsorbents exhibited outstanding selectivitytoward precious metals, with a selectivity order of Au(III) ≫Pd(II) > Pt(IV), over base metals in a wide range of acid concentrations.These materials contain a number of positive centers in HCl mediathat function as sorption active sites for chloroanionic species ofAu(III), Pd(II), and Pt(IV). The chloroanionic species of the correspondingprecious metals were thus adsorbed on these materials through anion-exchange-coupledelectrostatic interaction. The sulfuric acid cross-linked materialexhibited improved selectivity and greater adsorption capacity comparedto the epichlorohydrin cross-linked adsorbent. As equilibrium wasachieved within an hour with quantitative adsorption, the effectivenessof the sulfuric acid cross-linked material with regard to Au(III)was exemplified by the fact that 1 kg of the dry adsorbent materialhad a capacity to load 9.2 mol, that is, nearly 1.8 kg of Au(III).Moreover, the adsorbed Au(III) was subsequently reduced to the elementalform, yielding metallic gold particles, thereby demonstrating theconsiderable improvements in efficiency and effectiveness of the noveladsorbents for the recovery of gold in comparison to current commercialresins. [ABSTRACT FROM AUTHOR]