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

• Green recovery of gold species from aqueous solutions.
• TDAC samples showed adsorption coupled reduction pathway.
• Desorption and pyro-crystallization yielded good recovery of gold.
• An eco-friendly and effective biomaterial management strategy.

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.