Distinctive green recovery of silver species from modified cellulose: mechanism and spectroscopic studies

The present study aimed to recover precious silver in order to identify the adsorption coupled reduction pathways that determine this process. A combination technique of adsorption and nanocrystallization was used to investigate the recovery of silver species from taurine-cellulose (T-DAC) samples. The non-synthetic route of nanocrystallization yielded spherical zero-valent silver sized ∼ 18 nm. Rate-controlling steps were modeled by adsorption parameters by the best fit of Langmuir capacity (55 mg/g), pseudo-second order curves, and exothermic chemical reactions. The T-DAC was an excellent sorbing phase for the treatment of silver-polluted waters over a broad range of pH (2.1-10.1) and varying ionic strengths (8.5-850 mM, as NaCl), which are the conditions often encountered in industrial and mining effluents. A good recovery of silver (40-65%) was also obtained in the presence of Cd(II), Co(II), Cr(VI), Ni(II), and As(V) at lower or equivalent concentrations with Ag(I), either from individually added metals or from all metal ions mixed together. Desorption was compared with a series of five eluents including complexing agents. In these experiments acidified thiourea yielded 86% desorption of Ag(I). Aqueous silver reduced to metallic silver on the surface of the T-DAC samples, which was confirmed by X-ray photo electron spectroscopy.