Effect of silver sulfide nanoparticles on photochemical degradation of dissolved organic matter in surface water.

Silver sulfide nanoparticles (Ag2SNPs) have shown photocatalytic activity, yet little is known about the effect of Ag2SNPs on the photochemical degradation of dissolved organic matter (DOM) in surface water, which seriously impairs understanding of Ag2SNPs' environmental risks. Herein, this study on the basis of electrospray ionization coupled with Fourier-transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) showed for the first time that photodegradation of natural organic matter (NOM, 2R101 N) could be accelerated by both bared and polyvinylpyrrolidone (PVP)-coated Ag2SNPs; the NOM with Ag2SNPs (e.g., 500 μg/L) exposed to light irradiation for 96 h showed molecular formulas with lower O/C ratios as compared to the NOM alone. Also, added number of points (ranging from 1 to 2 carboxyl groups) having the same Kendrick mass defect (KMD) (COO) values and higher intensity in smaller Kendrick mass (KM) (COO) values were observed in NOM with Ag2SNPs compared to NOM alone. However, negligible effects of Ag2SNPs on photodegradation of humic acid (HA, 2S101H) were observed, even when the concentration of Ag2SNPs was as high as 5 mg/L. Besides molecular characteristics, a great reduction in organic carbon content of NOM within 96 h was only observed in the presence of Ag2SNPs under light condition. More importantly, the enhanced photodegradation of DOM by Ag2SNPs even at a concentration of 100 μg/L was also validated in surface water. These findings suggest that Ag2SNPs have the potential to accelerate the photochemical degradation of DOM in surface water.