Effects of particle size and solution chemistry on Triclosan sorption on polystyrene microplastic

PS microplastic particle (<5 mm) is an emerging contaminant of concern in aquatic and sediment systems with reported negative impacts on environmental and human health. TCS is a broad-spectrum antimicrobial which can affect ecosystems and result in long-term human health risks. The interaction between TCS and PS microplastic, partly determines the behavior and dispersion of TCS in the environment. In this study, the sorption kinetics and isotherms for TCS and PS microplastic were investigated. The influences of temperature, pH, ionic strength and coexisting heavy metals were assessed in batch experiments. The pseudo-second-order model (PSOM) was found to effectively describe the sorption kinetics of TCS on PS. TCS sorption on PS was found to be higher within the pH range of 3.0-6.0, while a decrease occurred at pH > 6.0. This result indicates that TCS⁰ was the major species contributing to the sorption process through hydrophobic interaction. Temperature did not affect the sorption of TCS on polystyrene, with sorption K_d values of 0.15, 0.16, 0.18 and 0.17 L/g at 288, 298, 308 and 318 K, respectively. Furthermore, the sorption amount of TCS showed no obvious variation with NaCl concentrations varying between 0.001 and 0.1 M. Finally, the coexistence of Cu(II)/Zn(II) had no significant influence on TCS sorption on PS, as Cu(II)/Zn(II) and TCS had different mechanisms of sorption on PS.