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Predicting the fate and transport of pharmaceuticals in terrestrial environments requires knowledge of their interactions with complex mineral assemblages. To advance knowledge along this front, we examined the reactivity of pipemidic acid (PIP), a typical quinolone antibiotic, with quartz particles coated with a mixture of manganese oxide (MnO2) and goethite (α-FeOOH) under static and dynamic flow conditions. Batch and dynamic column experiments showed that PIP binding to MnO2 proceeded through a heterogeneous redox reaction, while binding to goethite was not redox-reactive. Mixed columns of aggregated goethite-manganese particles however enhanced redox reactivity because (i) goethite facilitated the transport of dissolved Mn(II) ion and increased the retention of PIP oxidation products, and (ii) MnO2 was protected from passivation. This mobility behavior was predicted using transport models accounting for adsorption and transformation kinetics of PIP on both goethite and MnO2. This work sheds new light on reactivity changes of mixtures of Fe and Mn oxides under flow-through conditions and will have important implications in predicting the fate and transport of redox-active organic compounds as well as development of new geomedia filters for environmental remediation.

Column experiments are more sensitive to surface reactions than batch studies due to the increased surface area to liquid volume ratio. Moreover, these dynamic set-ups allow for stringent tests concerning the validity of equilibrium models for surface protonation and adsorption of pollutants. In the present study, column experiments were carried out at constant pH, where the concentration of background electrolyte consisting of monovalent electrolytes like NaCl at the inlet were varied. Due to the charging phenomena caused by ionic-strength dependent acid-base reaction, the pH at the outlet of column varied. On a positively charged surface (such as alumina at pH 5.8) the increase in salt concentration at the inlet caused a transient increase in pH due to enhanced protonation of surface hydroxyls. On a negatively charged surface (PTFE at pH 5.8) the increase in salt concentration caused a decrease in pH at the column outlet due to enhanced uptake of hydroxide ions at higher salt concentrations. The charging behavior of both surfaces was independently determined by streaming potential measurements. For PTFE column experiments at different pH values were carried out to further relate them to the streaming potential data. Indeed below the isoelectric point, the trend of the pH-jump at the outlet of the column was inversed which suggests pH dependent charging of this inert surface due to protons and hydroxide ions.Overall, the experiments show the high sensitivity of column experiments to changes in solution composition and the kind of experiments may allow for determining points of zero charge in an elegant way.

The current study aimed to explore the public understanding of COVID-19 vaccines and the social representations emerging from a corpus of user-generated comments on YouTube videos posted during the year following the World Health Organization's declaration of the novel coronavirus as pandemic. We used Structural Topic Modelling to process the text and identified a 10-topic solution as the best to represent the corpus of text data. The exploration of the topics showed a complex landscape of social representations underlying a plurality of perspectives, which we interpreted as reflecting different users’ needs to make sense of the unprecedented events. Implications for theory, future research, and intervention for health psychology and policy are discussed.