Development of Quantitative Structure–Activity Relationships for Nanoparticle Titanium Dioxide Aggregation in the Presence of Organic Contaminants

Abstract

Abstract

This study investigated the influence of organic wastewater contaminants (OWCs) on the aggregation of nanoparticle titanium dioxide (n-TiO₂) because aggregation experiments are important to obtain fundamental information about the potential fate of n-TiO₂ in environmental systems. Aggregation experiments showed that surface modification of n-TiO₂ such as different aggregation behaviors and changes of zeta potentials was clearly influenced by the adsorption of OWCs based on t-test results. Largest diameter changes of n-TiO₂ were observed by chlorothalonil (359 nm) at 0 h and alachlor (436 nm) at 12 h, while smallest diameter changes of n-TiO₂ were observed by cyanazine (84 nm) at 0 h and butylate (53 nm) at 12 h. The most significant zeta potential changes of n-TiO₂ were observed by pendimethalin and butylate with −15.2 mV at 0 h and with −16.7 mV and −17.1 mV at 12 h, respectively. These results may demonstrate insights into the microscopic and/or molecular interaction between n-TiO₂ and OWCs that result in surface modification of n-TiO₂. Thus, we developed quantitative structure–activity relationships (QSARs) between n-TiO₂ aggregation rate kinetics and representative seven descriptors of OWCs including pK_a, Solubility (C_w), log K_ow, molecular weight, polar surface area (P.S.A.), molar volume, and # of H Bond Donor (# of H.B.D.). The developed QSARs showed that experimental n-TiO₂ aggregation rate kinetics were strongly related to seven descriptors of all OWCs except for butylate. Particularly, some polarity descriptors such as C_w, log K_ow, P.S.A., and # of H.B.D. seem to have influences on the developed QSARs. Therefore, our developed QSARs for n-TiO₂ aggregation rate kinetics according to seven descriptors of OWCs provide solid information to the general nanoparticle (NP) researches and significant insights about the effects of emerging OWCs on microscopic and/or molecular interaction with NPs, which would demonstrate the roles of physicochemical descriptors of OWCs on n-TiO₂ aggregation.