Silver nanoparticle behaviour in lake water depends on their surface coating

The present study examines the stability of silver nanoparticles (AgNPs) of three different coatings – citrate (CIT), polyvinyl pyrrolidone (PVP) and lipoic acid (LIP) and two sizes - 20 and 50 nm in lake water (LW) over time. Using a combination of asymmetric flow field-flow fractionation (AsFlFFF), surface plasmon resonance (SPR), and single particle inductively coupled plasma mass spectrometry (SP-ICP-MS), the influence of size, surface coating, exposure time, as well as the presence and nature of dissolved organic matter (DOM) on the transformation of AgNPs at low environmental concentrations was thoroughly investigated. The results revealed that the AgNP stability in lake water are complex interplay between the surface coating characteristics, exposure time and presence and nature of DOM. Among the studied variables surface coating was found to play the major role of determining AgNPs behaviour in lake water. PVP-coated AgNPs agglomerated to a lesser extent as compared with the CIT- and LIP-AgNPs. For a given surface coating, DOM of pedogenic and aquagenic origin increased the stability of the AgNPs (LW + EPS > LW + SRHA > LW). Moreover, extracellular polymeric substances (EPS; aquagenic origin) stabilized lipoic acid-coated AgNPs more effectively than Suwannee River Humic Acids (SRHA; pedogenic origin), showing that DOM nature has to be also considered for improved understanding the AgNP stability in aquatic environment

Développement de modèles de plastiques marqués métalliquement

International audienc

Biogenic RH-SiO 2 Nanoparticles for Vanadium Removal from Asphaltenes via GPC-ICP MS and spICP MS Analysis

Based on significant evidence, asphaltenes are found in crude oil and can form stably dispersed nanoaggregates in solution, which can be directly adsorbed onto surfaces by different interactions. These nanoaggregates contain mainly vanadium and nickel compounds, which are effectively adsorbed or occluded in their structure in the form of metal porphyrins. In this study, SiO2 nanoparticles produced from rice husks (RH-SiO2 NPs) were used as adsorbents for asphaltene. Adsorption experiments with asphaltene solutions from Cerro Negro crude oil were conducted, and the vanadium concentrations in the solution and in the material adsorbed were determined. Based on high-resolution analysis techniques, such as gel permeation chromatography with inductively coupled plasma-mass spectrometry (GPC-ICPMS) and single-particle inductively coupled plasma-mass spectrometry (spICP MS), vanadyl compounds associated with asphaltene aggregates were found to be mostly adsorbed on the nanoparticles, with preference in the pores. The analysis of the remnant solution after adsorption using a gel permeation chromatography system with inductively coupled plasma-mass spectrometry showed profiles corresponding to different molar mass ranges, with a decrease in the zone corresponding to larger-molecular-weight aggregates rich in vanadium compounds. The analysis of the solid material before and after adsorption was performed using spICP MS. The results showed that the size and composition of the RH-SiO2 NPs could be accurately determined using this technique; after adsorption, the signals corresponding to vanadium were detected in the nanoparticles with dimensions smaller than the actual nanoparticles. A comparison of the size distributions of nanoparticles and the vanadium signal from the material adsorbed onto nanoparticles indicated that vanadium compounds associated with aggregates were adsorbed and migrated to the pores of the nanoparticles. When simultaneous aggregation is present, the adsorption processes are complex, and the possibility of multilayer adsorption or aggregate adsorption mechanisms is difficult to discern. Using very high-resolution analysis techniques, such as GPC-ICPMS and spICP MS, we acquired reliable evidence that the vanadyl compounds associated with asphaltene aggregates were mostly adsorbed and certified that vanadium in high proportion was strongly adsorbed on the nanoparticles. These results have an important impact on the determination of asphaltene aggregate adsorption mechanisms and facilitate practical applications using nanoparticles to concentrate and separate vanadium compounds from crud