Recovery of platinum(IV) and palladium(II) by bayberry tannin immobilized collagen fiber membrane from water solution

The adsorption of Pt(IV) and Pd(II) on bayberry tannin immobilized collagen fiber (BTICF) membrane was investigated. The optimal pH for the adsorption of Pt(IV) and Pd(II) ions was found to be 3.0 and 4.0, respectively. The time for attaining adsorption equilibrium of Pt(IV) and Pd(II) was 60 and 240 min. The adsorption kinetic data of the two metal ions are well fitted by the pseudo-second-order model. The adsorption capacities of Pt(IV) and Pd(II) on 0.100 g BTICF membrane were 41.7 and 27.5 mg/g at 313 K. The adsorption isotherms of the membrane to both the ions are described by the Langmiur model. The adsorption extent remarkably increases with the increase of temperature and the ratio of membrane material to solution volume. The membrane saturated by Pt(IV) is easily regenerated by 0.1 M thiuorea, but the full regeneration is difficult after adsorption of Pd(II). The continuous adsorption experiments of 58.3 mg/L Pt(IV) and 48.8 mg/L Pd(II) solutions were undertaken by using three layers of membrane (total area 191 cm2), and it was found that no Pt(IV) and Pd(II) ions were detected until 700 and 1000 ml effluents were collected, respectively. Furthermore, competitive adsorption studies revealed that the membrane exhibits ability of selective adsorption to Pt(IV) and Pd(II) in the mixture solutions of metal ions.