Recovery of gold from aqueous solutions by taurine modified cellulose: An adsorptive-reduction pathway

The aim of the study was to develop green techniques to recover precious gold by the taurine-modified cellulose (TDAC samples) from the aqueous solution. Adsorption, followed by reduction offered a method for the recovery of ionic and zerovalent gold. The spherical gold nanoparticles (5 nm average size) were investigated in the nanoparticle-embedded gel. Potential rate controlling steps of chemical reactions are modeled by the best-fit of thermodynamic (an endothermic process), kinetic curve (pseudo second order), and isotherm (Sips and 34.5 mg/g Langmuir adsorption capacity) parameters. The pH (2-6) and competing heavy metals (Cd, Co, Cr, Ni, and As) showed least interference, however, gold recovery altered at the high ionic strength (as NaCl). A complexing agent (acidic thiourea) desorbed 86% of ionic gold and pyro-crystallization technique yielded 90% metallic gold. The characterization including X-ray photoelectron spectroscopy detected metallic gold on the surface of TDAC, supporting the adsorptive-reduction mechanism. Performance characteristic of TDAC to concentrate gold in various forms can be viewed as a controllable technique in the water treatment applications. (C) 2014 Elsevier BM. All rights reserved.