Hydrogen bond interactions in hydrated acetylsalicylic acid

Micro-sized TiO2 as photoactive catalyst coated on industrial porcelain grès tiles to photodegrade drugs in water

Pharmaceutical compounds and their metabolites raise worrying questions because of their continuous release and lack of efficient removal by conventional wastewater treatments; therefore, they are being detected in groundwater, surface water and drinking water in increasing concentrations. Paracetamol and aspirin are two of the most commonly used drugs employed as fever reducer, analgesic and anti-inflammatory. They and their metabolites are very often found in river water, so their degradation is necessary in order to render water suitable for human consumption. The present work is focused on the comparison of the photocatalytic performance of industrial active grés porcelain tiles covered with a commercial micro-sized TiO₂ by industrial process using either conventional spray deposition or innovative digital printing methods. The photodegradation of two commonly used drugs, namely aspirin and paracetamol, was investigated both individually and as a mixture, in both deionized and tap water. The results reveal the full conversion of the drugs and the significant role of the photocatalytic tiles in the mineralization processes leading to harmless inorganic species. In particular, the digitally printed tiles exhibited better photodegradation performance for both drugs compared to the spray deposited tiles. No deactivation was observed on both photocatalytic tiles.

The hydration mechanism and hydrogen bonding structure of 6-carboxylate chitooligosaccharides superabsorbent material prepared by laccase/TEMPO oxidation system

6-carboxylate chitooligosaccharides (6-CCOS), as a superabsorbent material, were prepared by way of the laccase/TEMPO oxidation system. It exhibited a higher moisture-absorption ability and stronger affinity for water. To understand the real reasons for this, the hydrogen bonding structure of 6-CCOS and the hydration mechanism of the molecule were investigated using infrared (IR), differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR). It was found that the introduction of a strongly hydrophilic carboxylate ion on the C6 site of chitooligosaccharides molecule was conducive to the enhancement of the interaction between polysaccharide polymers and water molecules. The most important was the formation of hydrogen bonds connected between carboxylate ion and residual water. In addition, the hydration mechanism of 6-CCOS molecules was presumed to be that more water molecules from outside were incorporated into the already embedded water molecules within the polymer. The whole molecule was woven into a huge water-polymer network structure through intermolecular hydrated hydrogen bonds.

Aspirin and paracetamol removal using a commercial micro-sized TiO2 catalyst in deionized and tap water

Micro-sized TiO₂ catalyst was employed to degrade pharmaceutical compounds, i.e. aspirin and paracetamol, two of the most widely used drugs, purchasable without prescription. Their active agents, acetylsalicylic acid and acetaminophen, are characterized by different substituent groups, linked to the aromatic ring, which affect both the photodegradation and mineralization processes. The experimental conditions highlight the relationship between the nature of the pristine molecules, their degradation mechanisms, their mutual interference and the water's role. The research started from model systems with a single pollutant to the mixture of them and finally by moving from deionized water to tap water.

Variable Temperature Infrared Spectroscopy Studies of Aromatic Acid Adsorbate Effects on Montmorillonite Dehydration

Molecular interactions between benzoic, salicylic, and acetylsalicylic acids and water contained within montmorillonite clay interlayer spaces are characterized by using variable temperature diffuse reflection infrared Fourier transform spectroscopy (VT-DRIFTS). By using sample perturbation and difference spectroscopy, infrared (IR) spectral variations resulting from the removal of interlayer water are used to characterize aromatic acid local environment changes. Difference spectra features representing functional group perturbations are correlated with changes in IR absorptions associated with -O-H and -C = O stretching vibrations. Results suggest that adsorbate carboxylic acid functionalities participate in extensive hydrogen bonding and that the strengths of these interactions are diminished when clays are dehydrated. The nature of these interactions and their temperature-dependent properties are found to depend on adsorbate structure and concentration as well as the clay interlayer cation.