Recovery of palladium (II) from aqueous solution through photocatalytic deposition in presence of ZnO under UV/Visible-light radiation

Systematic Assessment of Precious Metal Recovery to Improve Environmental and Resource Protection

“…Dai et al made a typical photocatalyst TiO 2 into a filter membrane and modified amino or thiol groups on its surface to achieve functionalization . In addition, photocatalysts such as zinc oxide (ZnO) can also recover palladium ions under ultraviolet or visible light, in which ethanol is used as a hole sacrificial agent . At room temperature, when flowing continuously at a rate of 1 mL/min, up to 99.95% of Pd 2+ can be removed from a stock solution with an initial concentration of 100 ppm.…”

“…79 In addition, photocatalysts such as zinc oxide (ZnO) can also recover palladium ions under ultraviolet or visible light, in which ethanol is used as a hole sacrificial agent. 80 At room temperature, when flowing continuously at a rate of 1 mL/min, up to 99.95% of Pd 2+ can be removed from a stock solution with an initial concentration of 100 ppm. The captured Pd 2+ can be converted into nanoparticles and applied in a Suzuki coupling reaction as the catalyst.…”

A new process for the recovery of palladium from a spent Pd/TiO2 catalyst through a combination of mild acidic leaching and photodeposition on ZnO nanoparticles

“…Nowadays, the leaching solutions containing the dissolved palladium are generally treated by means of different processes such as precipitation, membrane separation as well as electrodeposition, for which low selectivities are recorded and numerous operating units are required 24,[36][37][38][39][40][41] . An alternative was proposed in a recent work by some of the authors 42 , in which the recovery of palladium from the leaching solution was achieved through its photocatalytic deposition in the presence of ZnO under visible and UV-Visible light radiation.…”

“…The resulting Pd/ZnO composite material is separated from the solution by filtration and washed, originating a waste solution containing NaCl, Cu 1+ and ethanol. As for the effective palladium recovery, the dissolution of zinc oxide nanoparticles, by adjusting the pH of the suspension below 6.30, was studied in the previous work 43 . Therefore, the metallic palladium precipitates are recovered, while a stream containing zinc ions and nitrates is generated (4).…”

“…Table 1 shows the theoretical composition of the spent streams generated within the two processes, calculated according to the indications reported in the previous papers 35,42 when the total recovery of palladium was achieved starting from a synthetic waste containing about 100 milligrams of the metal. It is evident from the scheme in Figure 2 (B) that the streams (3) and ( 4) have to be considered as waste for which a proper treatment has to be arranged to allow their disposal.…”