Tsai MH, Chao SJ, Chung KH, Hua LC, Huang C. Destabilization of polystyrene nanoplastics with different surface charge and particle size by Fe electrocoagulation.
THE SCIENCE OF THE TOTAL ENVIRONMENT 2023;
872:162254. [PMID:
36801318 DOI:
10.1016/j.scitotenv.2023.162254]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Revised: 02/06/2023] [Accepted: 02/11/2023] [Indexed: 06/18/2023]
Abstract
Nanoplastics (NPs) discharged from wastewater could pose a major threat to organisms in aquatic environments. Effective removal of NPs by the current conventional coagulation-sedimentation process is not yet satisfactory. This study aimed to investigate the destabilization mechanism of polystyrene NPs (PS-NPs) with different surface properties and sizes (i.e., 90 nm, 200 nm, and 500 nm) by Fe electrocoagulation (EC). Two types of PS-NPs were prepared by a nanoprecipitation method using sodium dodecyl sulfate and cetrimonium bromide solutions to produce negatively-charged SDS-NPs and positively-charged CTAB-NPs. For both NPs, obvious floc aggregation from 7 μm to 14 μm was observed only at pH 7 with particulate Fe accounted for >90 %. At pH 7, Fe EC removed 85.3 %, 82.8 %, and 74.7 % of the negatively-charged SDS-NPs at small-, mid-, and large-sizes from 90 nm, 200 nm, to 500 nm, respectively. Small-size SDS-NPs(90 nm) were destabilized through physical adsorption on the surface of Fe flocs, while the main removal mechanism of mid- and large-SDS-NPs(200 nm and 500 nm) involved the enmeshment of large Fe flocs. Compared to SDS-NPs(200 nm and 500 nm), Fe EC performed similar destabilization behavior to two CTAB-NPs(200 nm and 500 nm), but it resulted in much lower removal rates of 54.8 % - 77.9 %. The Fe EC also exhibited no removal (<1 %) ability toward the small-size and positively-charged CTAB-NPs(90 nm) due to insufficient formation of effective Fe flocs. Our results provide insight into the destabilization of PS in nano-scale with different sizes and surface properties, which clarifies the behavior of complex NPs in a Fe EC-system.
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