Biogenic palladium nanoparticles for wastewater treatment: Formation, applications, limitations, and future directions

Biological wastewater treatment is currently the most cost-effective and sustainable method, but it is necessary to supplement it with environmentally friendly physicochemical methods because of its inefficiency in the removal of some recalcitrant pollutants. Nano-sized palladium represents a promising catalyst for the remediation of multiple recalcitrant pollutants. Microorganisms can reduce ionic palladium to palladium nanoparticles under mild conditions and act as dispersants, stabilizers, and support materials for palladium catalysts, forming microbial-loaded biologenic palladium. Biologenic palladium combines the advantages of biological treatment and palladium catalysis, providing a novel solution to wastewater purification. Herein, this review was focused on the formation and the wastewater treatment performance of biologenic palladium. In this work, the formation mechanism of biologenic palladium is elucidated. The synergistic effect of microorganisms and palladium nanoparticles in removing pollutants is analyzed. The pollutants and wastewater treatment scenarios suitable for biologenic palladium treatment, as well as the purification efficiency, are summarized. This review also provides insights into the limitations faced by the large-scale application of biologenic palladium and future research directions that may assist in improving its efficiency and practical application. [Display omitted] •Synergistic effects between microorganisms and PdNPs enhance the removal of pollutants.•Bio-Pd is suitable for multiple pollutant removal and wastewater treatment scenarios.•Deactivation and loss are the main limitations of bioPd' practicality.•Enhancing the durability and efficiency of bio-Pd can be a future research direction.