Removal of Stabilized Silver Nanoparticles from Surface Water by Conventional Treatment Processes.

Hafiz H M Salih,Thabet M Tolaymat,Amro M El Badawy,Craig L Patterson

doi:10.4236/anp.2019.82002

Abstract

Engineered nanomaterials are used in many applications, including pollution sensors, photovoltaics, medical imaging, drug delivery and environmental remediation. Due to their numerous applications, silver nanoparticles (Ag NPs) are receiving a large amount of attention. Ag NPs may occur in drinking water sources either during manufacturing, consumption and/or disposal processes. This potentially leads to the presence of Ag NPs in finished drinking water, which could have public health impacts. The objective of this research was to investigate the removal of several types of stabilized Ag NPs by potable water treatment processes. Specifically, this research achieved these objectives through; 1) Synthesis of Citrate-reduced Ag NPs, Polyvinylpyrrolidone stabilized (PVP) Ag NPs and Branched polyethyleneimine stabilized (BPEI) Ag NPs, 2) Characterization of synthesized Ag NPs to determine their aggregation potential, Zeta potential profiles, (pHpzc) and obtain morphological data from SEM images, and 3) An evaluation of the efficacy of conventional water treatment processes (i.e., coagulation, flocculation, sedimentation and sand filtration) in removing stabilized Ag NPs from natural water. The three NPs were found to be stable at the nano size in natural water. Alum coagulation had no impact on the PVP and BPEI Ag NPs. Flocculation and settling were found to be key steps for removal of these NPs. The three Ag NPs were not permanently removed by means of conventional water treatment processes employed in this study.

Highlights

Nanoparticles (NPs) are emerging as a new type of contaminant in water and wastewater
Characterization and aggregation studies were conducted on three Ag NPs to confirm their stability in natural water
Charge stabilization is attributed to the adsorption of counter ions on the colloidal particle surface or the protonation of specific functional groups adsorbed on the particle surface

Summary

Introduction

Nanoparticles (NPs) are emerging as a new type of contaminant in water and wastewater. Synthesized NM is being used in over 1000 products, including food/beverage, sport merchandise, tires, stain resistant clothing, cosmetics, electronics, household tools and in medicine [1] This high production and use of NPs will likely to result in the release of NPs into the environment and to natural water [2] [3]. This characteristic prompts the use of Ag NPs in many consumer products such as cosmetics, fabrics, and air and water filters, in addition to their use in medical equipment and textiles [5] [6] Due to their extensive use, Ag NPs may occur in drinking water sources either during manufacturing, consumption and/or disposal processes. Once released into the environment they may be considered an emerging contaminant in water and wastewater [8]

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Conclusion