Adsorption of Au(III), Pd(II), and Pt(IV) from Aqueous Solution onto Graphene Oxide

Graphene oxide (GO) was prepared and characterized by Fourier transform infrared spectrometry (FT-IR) and scanning electron micrographs (SEM). Batch adsorption studies were carried out to investigate the adsorption data, including the effects of pH, initial concentration, contact time, and temperature. The adsorption of Au(III), Pd(II), and Pt(IV) was optimum at pH 6.0. The adsorption isotherms all obeyed the Langmuir equation in the case of Au(III), Pd(II), and Pt(IV), and the maximum adsorption capacities were 108.342 mg.g(-1), 80.775 mg.g(-1), and 71.378 mg.g(-1), respectively. The adsorption kinetics of Au(III), Pd(II), and Pt(IV) onto GO followed a pseudosecond-order kinetic model, indicating that the chemical adsorption was the rate-limiting step. Thermodynamic parameters such as Gibbs energy (Delta G degrees), enthalpy (Delta H degrees), and entropy (Delta S degrees) were calculated, indicating that the adsorption were spontaneous, endothermic, and feasible. The desorption studies showed that the best desorption reagents were 0.5 mol.dm(-3) thiourea-0.5 mol.dm(-3) HCl for Au(III) and 1.0 mol.dm(-3) thiourea-0.5 mol.dm(-3) HCl for both Pd(II) and Pt(IV).