Adsorption recovery of Pd(II) from aqueous solutions by persimmon residual based bio-sorbent

A low cost bio-sorbent, named “PPF resin”, was prepared by immobilizing persimmon residual with formaldehyde and it was characterized before and after adsorption of Pd(II). The adsorption behavior of PPF resin towards Pd(II) from aqueous solutions was studied by batch and column adsorption methods. The adsorption equilibrium of Pd(II) on PPF resin was achieved within 840 min, and the experimental data were well fitted with the pseudo-second-order rate model. Higher initial concentration and adsorption temperature led to higher equilibrium adsorption amount, and the adsorption isotherms could be well described by Langmuir model. The column studies suggested that the resin was effective for the adsorption of Pd(II) from aqueous solutions, and the loaded Pd(II) could be easily desorbed by acidic thiourea solution. The adsorption process of Pd(II) on PPF resin might be the multiple reactions of electrostatic interaction and reductive adsorption, in which Pd(II) was reduced to Pd(0) as confirmed by the XRD pattern of PPF resin after adsorption of Pd(II). The resin exhibited outstanding selective adsorption towards Pd(II) from actual leach liquor of waste PCBs at a high concentration of HNO3. The results suggested that the PPF resin can be used as an active bio-sorbent for the recovery of Pd(II) from aqueous environment.