title: Fate of fluorescent core-shell silica nanoparticles during simulated secondary wastewater treatment.
abstract: Increasing use of silica nanoparticles (SiO2 NPs) in consumer products and industrial processes leads to SiO2 NP discharge into wastewater. Thus, there is a need to understand the fate of SiO2 NPs during wastewater treatment. However, the detection of SiO2 NPs in environmental systems is hindered by the elevated background levels of natural silicon. In this work, laboratory-synthesized fluorescent core-shell SiO2 NPs were used to study the fate of these NPs during secondary wastewater treatment. Fluorescent measurements provided an easy and fast method for SiO2 NP tracking. A laboratory-scale activated sludge system consisting of an aeration tank and a settler was fed with synthetic wastewater containing ca. 7.5 mg L(-1) of fluorescent SiO2 NPs for 30 days. SiO2 NPs were effectively removed from the wastewater (>96%) during the first 6 days, however the concentration of SiO2 NPs in the effluent gradually increased afterwards and the NP discharge was as high as 65% of the input after 30 days of NP dosing. The poor removal of the SiO2 NPs was related to the high colloidal stability of the NPs in the wastewater and their limited propensity to biosorption. Although some degree of NP adsorption on the biomass was observed using fluorescence microscopy, the affinity of SiO2 NPs for the activated sludge was not enough for a sustained and effective removal of the SiO2 NPs from the wastewater.
authors: Department of Chemical and Environmental Engineering, University of Arizona, P.O. Box 210011, Tucson, AZ 85721, USA. Electronic address: lilaoter@email.arizona.edu.
authors: Lila
authors: L
authors: Otero-González
authors: Department of Chemical and Environmental Engineering, University of Arizona, P.O. Box 210011, Tucson, AZ 85721, USA.
authors: Jim A
authors: JA
authors: Field
authors: Department of Chemistry and Biochemistry, University of Arizona, P.O. Box 210041, Tucson, AZ 85721, USA.
authors: Isen A C
authors: IAC
authors: Calderon
authors: Department of Chemistry and Biochemistry, University of Arizona, P.O. Box 210041, Tucson, AZ 85721, USA.
authors: Craig A
authors: CA
authors: Aspinwall
authors: Department of Chemical and Environmental Engineering, University of Arizona, P.O. Box 210011, Tucson, AZ 85721, USA.
authors: Farhang
authors: F
authors: Shadman
authors: Department of Chemical and Environmental Engineering, University of Arizona, P.O. Box 210011, Tucson, AZ 85721, USA.
authors: Chao
authors: C
authors: Zeng
authors: Department of Chemical and Environmental Engineering, University of Arizona, P.O. Box 210011, Tucson, AZ 85721, USA.
authors: Reyes
authors: R
authors: Sierra-Alvarez
mesh_terms: D000327:Adsorption; D018533:Biomass; D005456:Fluorescent Dyes; D008856:Microscopy, Fluorescence; D053758:Nanoparticles / Q000032:analysis*; D012722:Sewage; D012822:Silicon Dioxide / Q000032:analysis*; D013194:Staining and Labeling; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification / Q000379:methods*
chemical_list: D005456:Fluorescent Dyes; D012722:Sewage; D012822:Silicon Dioxide; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Activated sludge; CMP; Engineered nanomaterials; Municipal wastewater treatment; Nanoparticle adsorption; SiO(2)