Photo- and thermo-chemical transformation of AgCl and Ag2S in environmental matrices and its implication.
AgCl and Ag2S prevalently exist in the environment as minerals and/or the chlorination and sulfidation products of ionic silver and elemental silver nanoparticles (AgNPs). In this work, we investigated the chemical transformation of AgCl and Ag2S under simulated sunlight (in water) and incineration (in sludge and simulated municipal solid waste, SMSW). In the presence of natural organic matter, AgCl in river water was observed to be transformed into AgNPs under simulated sunlight, while photo-reduction of Ag2S could not take place under the same experimental conditions. During the course of incineration, pure Ag2S was transformed into elemental silver while AgCl remained stable; however, both Ag2S in sludge and AgCl in SMSW can be transformed to elemental silver under incineration, evident by the results of X-ray absorption spectroscopy and scanning electron microscopy measurements. Incineration temperature played an important role in the transformation of Ag2S and AgCl into elemental silver. These results suggest that chemical transformations of Ag2S and AgCl into elemental silver could be a possible source of naturally occurring or unintentionally produced AgNPs, affecting the fate, transport, bioavailability and toxicity of silver. Therefore, it is necessary to include the contributions of this transformation process when assessing the risk of ionic silver/AgNPs and the utilization and management of incineration residues.
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Institute of Environment and Health, Jianghan University, Wuhan 430056, China.
Yongguang
Y
Yin
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
Wei
W
Xu
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Zhiqiang
Z
Tan
Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China.
Yanbin
Y
Li
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Weidong
W
Wang
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Xiaoru
X
Guo
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Sujuan
S
Yu
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China. Electronic address: jfliu@rcees.ac.cn.
Jingfu
J
Liu
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Guibin
G
Jiang
D004785:Environmental Pollutants / Q000737:chemistry* / Q000528:radiation effects; D005618:Fresh Water; D017745:Incineration; D053768:Metal Nanoparticles / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D012834:Silver / Q000737:chemistry; D018030:Silver Compounds / Q000737:chemistry* / Q000528:radiation effects; D062611:Solid Waste; D013472:Sunlight; D013696:Temperature; D056928:X-Ray Absorption Spectroscopy
D004785:Environmental Pollutants; D018030:Silver Compounds; D062611:Solid Waste; D012834:Silver; C013251:silver sulfide; C037548:silver chloride
Ag(2)S; AgCl; Incineration; Silver nanoparticle; Sunlight; Transformation