Recycling of Pd(0) catalysts by magnetic nanocomposites-microbial extracellular polymeric substances@Fe3O4.

Abstract Palladium (Pd) is extremely expensive due to its scarcity and excellent catalytic performance. Thus, the recovery of Pd has become increasingly important. Herein, microbial extracellular polymeric substances (EPS) and magnetic nanocomposite EPS@Fe3O4 were applied to recover Pd catalysts from Pd(II) wastewater. Results indicated that Pd(II) was reduced to Pd (0), which was then adsorbed by EPS (101.21 mg/g) and EPS@Fe3O4 (126.30 mg/(g EPS)). After adsorbing Pd, EPS@Fe3O4 could be collected by magnetic separation. The recovered Pd showed excellent catalytic activity in the reduction of methylene blue (MB). The pseudo-second-order kinetic model and Redlich-Peterson model best fit the adsorption results. According to spectral analysis, Pd(II) was reduced to Pd (0) by chemical groups in EPS and EPS@Fe3O4, and the hydroxyl had a chelating effect on adsorbed Pd. Therefore, EPS@Fe3O4 is an efficient adsorbent for recovering Pd from Pd(II) wastewater.