Influence of Surface Functional Groups on Deposition and Release of TiO2 Nanoparticles

A clear understanding of the factors governing the deposition and release behaviors of engineered nano-particle (NPs), such as TiO2 NPs, is necessary, for prediding their transport and fate in both natural, and engineered, aquatic environments. In this study, impacts of specific chemistries on TiO2 NP deposition, as a function of TiO2 NP concentration and ionic strength/valence, were investigated using self, assembled monolayers (SAMs) with five different ending chemical functionalities ( -CH3, -OH, -COOH, -NH2, and -CONH2). The fastest deposition and Maximum: deposition mass were observed On -NH2 followed by COOH, -CONH2, -CH3, and -OH showing that contact angle and zeta potential of surfaces were not good indicators for predicting the deposition: Specific interactions, for instance) between -COOH and -CONH2 and TiO2, significantly affected their,deposition. Deposition rate, increased linearly with TiO2 NP concentration; however, specific deposition rate was dependent on the type of SAMs. The increase of monovalent (Na+): and divalent (Ca2+) led to different changes in deposition rates for the SAMs due to different functionalities. Results also showed that favorable SAM (e.g, -NH2) had lowered release of NPs compared to unfavorable surface (e.g., -OH). The obtained deposition and release behaviors will support more accurate prediction of the environmental fate of nanoparticles.