Evaluating solubility, aggregation and sorption of nanosilver particles and silver ions in soils

Abstract: Engineered nanoparticles (ENPs) are used in so many different products. ENPs are released into different environmental compartments. Silver nanoparticle (AgNP) is one of the most used ENPs. AgNPs may cause damage to the environment due to their toxicity and wide exposure. In this thesis possible exposure ways of AgNPs to the environment was reported. Also sorption-solubility and aggregation of AgNPs and AgNO3 based on the different concentration of Ag and pH function in clayey and sandy soil was investigated. Results showed that sorption of both silver nanoparticles and silver ions by the soils were increased with increasing pH. Silver (nano/ion) sorption ratio in clayey treatment was slightly higher than sandy one. It can be due to having higher CEC value and finer texture in clay in comparison with sand. Partitioning between nanosilver and free silver ions was investigated by help of ultrafiltration. It can be concluded that a significant fraction of the silver nanoparticles were oxidized and transformed to free Ag+ during the oxic experimental conditions. The aggregation of AgNPs and silver ions was investigated based on the different concentration of silver in a constant pH. Aggregation of silver nanoparticulate by help of SEM and XRD were identified in 2.5 ppm concentration of AgNPs in sandy soil. No aggregation was found at low concentration of silver nanoparticles. No silver aggregated spot could be recognized at 6.7, 0.65 and 0.05 ppm concentration of silver in silver nitrate polluted soil samples.