Removal and Recovery of Au(III) from Aqueous Solution Using a Low-Cost Lignin-Based Biosorbent

A lignin-based composite, PANI-EHL, was prepared in a facile manner from enzymatic hydrolysis lignin (EHL) and aniline. The effects of initial pH value, biosorbent concentration, sorption time, and initial adsorbate concentration on the biosorption of Au(III) ions onto PANI-EHL composite were investigated. The results showed that the biosorbent exhibited high biosorption of Au(III) ions. The PANI-EHL composite favored treatment of Au(III) ions with concentrations below 2 mmol L-1 with an adsorptivity of 100%. The maximum biosorption capacity and adsorptivity for Au(III) ions were up to 4193.0 mg g(-1) and 70.9%, respectively, at a Au(III) ion concentration of 20 mmol L-1 at 30 degrees C. Furthermore, the biosorption of Au(III) ions was found to be a redox sorption process, as confirmed by XRD, TEM, and FTIR and UV-vis spectroscopic analyses of the biosorption product. The sorption kinetic and equilibrium data were described well with the pseudo-second-order model and the Freundlich isotherm model, respectively, for the Au(III) ion biosorption process.