Effective and selective recovery of Au(III) from WPCBs using quaternary phosphonium adsorbent synthesized by adjusting steric hindrance

With the gradual depletion of natural gold ore , waste printed circuit boards (WPCBs) have become one of the most attractive alternatives to gold ore. Here, a series of quaternary phosphonium adsorbents with a large size were successfully synthesized by adjusting the number of functional groups and carbon chain length of functional monomers , which can be used for selective recovery of gold(III) from WPCBs leaching solution . The quaternary phosphonium adsorbent (PS-TEP) prepared by the nucleophilic substitution reaction between triethyl phosphine with the smallest volume and chloromethylated polystyrene (PS-Cl) exhibited the best gold loading capacity (617.90 mg g −1 ). The adsorption mechanism of gold(III) on PS-TEP surface mainly involves anion exchange between AuCl 4 − and Cl − in the adsorbent. The charge level of the H atom closest to –CH 2 –P + group directly determines the strength of the interaction between the adsorbent and the gold ion . Multiwfn and VMD programs visually confirm the weak interaction between PS-TEP + and AuCl 4 − . After 5 adsorption-stripping cycles, the adsorption rate of gold(III) in solution remained at about 99 %. In addition, PS-TEP exhibited good gold(III) selectivity in both simulated and actual WPCBs gold leaching solutions. These results indicate that the large-particle PS-TEP with high capacity is suitable for selective gold recovery from WPCBs leaching solution.