Physicochemical properties and biodegradability of organically functionalized colloidal silica particles in aqueous environment.
Engineered sub-micron particles are being used in many technical applications, leading to an increasing introduction into the aquatic environment. Only a few studies have dealt with the biodegradability of non-functionalized organic particles. In fact the knowledge of organically surface functionalized colloids is nearly non-existent. We have investigated the biodegradability of organically surface functionalized silica (SiO2) particles bearing technically relevant groups such as amino-, carboxyl-, benzyl-, sulfonate-, chloro-, and phosphatoethyl-derivatized alkyls. Essential physicochemical properties including zeta potential, isoelectric point, morphology, surface area, porosity, surface density, and elemental composition of the particles were investigated, followed by biodegradability testing using the Closed Bottle Test (OECD 301D). None of the particles met the biodegradability threshold value of 60%. Only a slight biodegradation was revealed for SiO2-Benzyl (13.7±6.7%) and for SiO2-3-Chlorpropane (10.8±1.5%). For the other particles biodegradability was below the normal background fluctuation of 5%. The results were different of those obtained from structurally similar chemicals not being functionalized on the particle surface and from general rules of structure-biodegradation prediction of organic molecules. Therefore, our results suggest that the attachment of the organic groups heavily reduces their biodegradability, increases their residence time and possibility for adverse effects to environmental species.
Institute of Sustainable and Environmental Chemistry, Leuphana University of Lüneburg, Scharnhorststraße 1, DE-21335 Lüneburg, Germany. Electronic address: mandy.schneider@leuphana.de.
Mandy
M
Schneider
Advanced Ceramics, University of Bremen, Am Biologischen Garten 2, D-28359 Bremen, Germany. Electronic address: meder@uni-bremen.de.
Fabian
F
Meder
Institute of Sustainable and Environmental Chemistry, Leuphana University of Lüneburg, Scharnhorststraße 1, DE-21335 Lüneburg, Germany. Electronic address: haiss@leuphana.de.
Annette
A
Haiß
Advanced Ceramics, University of Bremen, Am Biologischen Garten 2, D-28359 Bremen, Germany. Electronic address: treccani@uni-bremen.de.
Laura
L
Treccani
Advanced Ceramics, University of Bremen, Am Biologischen Garten 2, D-28359 Bremen, Germany. Electronic address: krezwan@uni-bremen.de.
Kurosch
K
Rezwan
Institute of Sustainable and Environmental Chemistry, Leuphana University of Lüneburg, Scharnhorststraße 1, DE-21335 Lüneburg, Germany. Electronic address: klaus.kuemmerer@leuphana.de.
Klaus
K
Kümmerer
D001673:Biodegradation, Environmental; D003102:Colloids / Q000737:chemistry*; D008956:Models, Chemical; D012822:Silicon Dioxide / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
D003102:Colloids; D014874:Water Pollutants, Chemical; D012822:Silicon Dioxide
Biodegradation; Colloidal silica particles; Environmental fate; Organic functionalization; Physicochemical characteristics