Efficient and selective adsorption of Pd(II) by amino acid-functionalized cellulose microspheres and their applications in palladium recovery from PCBs leaching solution

Recovery of palladium from secondary resources has become attractive due to the sharp increase in demand. In order to develop cost-effective and environment-friendly adsorbents, four eco-friendly amino acids (arginine (Arg), histidine (His), methionine (Met) and cysteine (Cys)) functionalized cellulose microspheres (ArgR, HisR, MetR and CysR) were synthesized by radiation method, and applied to Pd(II) capture. The batch experiments showed that these amino acid resins exhibited outstanding selectivity for Pd(II). The batch adsorption processes were better in accordance with Langmuir and pseudo-second-order kinetics model. The maximum adsorption capacity of CysR was 143.47 mg/g, and was the highest of the four adsorbents. It was also found that MetR and CysR showed great acid tolerance and CysR also exhibited ultrastrong salt resistance. The maximum adsorption capacities of MetR and CysR at 5 mol/L HCl were 65.95 and 80.44 mg/g, respectively. Remarkably, the column experiments showed that MetR and CysR can selectively uptake and recover Pd(II) from simulated acidic waste effluent. Finally, the practical application of the amino acid resins showed that they can selectively and effectively capture trace Pd from the PCBs leachate. The adsorption performance certified that these amino acid resins are promising for high-efficiency recovery of Pd(II) from secondary resources.