Toxicity mechanisms and synergies of silver nanoparticles in 2,4-dichlorophenol degradation by Phanerochaete chrysosporium

Abstract

Mechanisms of silver nanoparticles-mediated toxicity to Phanerochaete chrysosporium and the influence of silver nanoparticles (AgNPs) on the biodegradation of 2,4-dichlorophenol (2,4-DCP) have been systematically investigated. AgNPs at low doses (0-60μM) have greatly enhanced the degradation ability of P. chrysosporium to 2,4-DCP with the maximum degradation rates of more than 94%, exhibiting excellent synergies between AgNPs and P. chrysosporium in the degradation of 2,4-DCP. Meanwhile, removal of total Ag was also at high levels and highly pH dependent. However, significant inhibition was highlighted on 2,4-DCP biodegradation and Ag removal upon treatment with AgNPs at high doses and AgNO₃ at low-level exposure. Results also suggested that AgNPs-induced cytotoxicity could arise from the "Trojan-horse" mechanism executing particle effects, ion effects, or both, ruling out extracellularly released Ag⁺. Moreover, under relatively low concentrations of AgNPs exposure, 2,4-DCP was broken into linear chain organics, and eventually turned into CO₂ and H₂O through reductive dechlorination and reaction with hydroxyl radicals. FTIR analysis showed that amino, carboxyl, carbonyl, and sulfur-containing functional groups played crucial roles in Ag transportation and the reduction of Ag⁺ to Ag⁰.

Keywords: 2,4-Dichlorophenol; Biodegradation; Phanerochaete chrysosporium; Silver nanoparticles; Synergies.