The unintentional release of engineered nanomaterials (ENMs) in environmentally relevant systems is inevitable due to their widespread use in industrial and consumer products. In the agricultural industry, soluble CuO nanoparticles (NPs) are used extensively because of their antifungal and antimicrobial properties. Even though the release of ENMs is increasing, there is a lack of reliable methods that can effectively extract and isolate ENMs from a soil/sediment matrix to subsequently enable quantification and characterization. The objective of this study is to develop and optimize an extraction protocol for CuO NPs from a standard natural soil (LUFA 2.1). The extraction procedure is comprised of three major processes: (i) precondition the soil to increase the sodium adsorption ratio (ii) extraction of colloids/NPs from the soil matrix using a dispersing agent and (iii) separation of the dissolved and nanoparticulate Cu fractions using cloud point extraction. Method parameters of the extraction procedure, including sonication, multiple extraction cycles, and type of dispersing agent were optimized to obtain the highest extraction efficiency of CuO NPs while minimizing their dissolution. Once the method was optimized, an overall maximum recovery of CuO NPs was determined at a concentration 250 and 10 mg-Cu kg-1. NP properties such as surface coating and size were also assessed to determine their influence on the extraction efficiency. The most effective dispersing agent for this extraction protocol was an organic polymer with the highest molecular weight, carboxymethylcellulose 700k. Increasing the sonication treatment time slightly enhanced extraction efficiency, but also increased dissolution and decreased the average particle size, so a short sonication time is recommended. Multiple extraction cycles further increased the recovery of CuO NPs, but the extraction efficiency substantially decreased after three cycles. The addition of a surface coating on the CuO NPs did not influence the extraction efficiency, while decreasing the NP size significantly increased both extraction and dissolution. Using the optimized parameters, the maximum recovery (dissolved and nanoparticulate) was in the range of 62-77% for a NP concentration range of 10-250 mg-Cu kg-1. This procedure is the first to effectively extract soluble NPs from soil and their dissolved fraction, and can be applied to other metal containing natural, incidental, or engineered NP.

Optimization of an extraction method for copper oxide nanoparticles from soil

2019 Spring National Meeting

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