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Adsorption is a preferred decontamination process for the treatment of industrial effluents, and various materials have been developed for this purpose. In the present work, esters based on sulfonated poly(ether ketone)/ionic liquids were prepared and their structures were evaluated by Fourier transform Infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies. Batch adsorption experiments were carried out on a mixed solution comprising Pb2+, Cu2+, Cd2+ and Zn2+ ions with concentration ranging from 4 to 10 μg L-1. The adsorption affinity of the esters expressed as the equilibrium metal ions uptake capacity, qe (mg g-1) was in the order: Pb2+ (6.2), Cd2+ (5.1), Cu2+ (2.8) and Zn2+ (0.8). It was interesting to observe the low values of qe of all adsorbents for Zn2+, which is advantageous in the treatments of wastewater as Zn2+ present in high concentration and could reduce the ion exchange capacity of the adsorbent largely toward other metal ions pollutant. Esterification with ionic liquids open the opportunity to upcycle polymer wastes that can be sulfonated, such as polystyrene, PEEK and its cross-linked form.

Crotonaldehyde semicarbazone {systematic name: (E)-2-[(E)-but-2-en-1-ylidene]hydrazinecarboxamide}, C5H9N3O, (I), and crotonaldehyde thiosemicarbazone {systematic name: (E)-2-[(E)-but-2-en-1-yldene]hydrazinecarbothioamide}, C5H9N3S, (II), show the same E conformation around the imine C=N bond. Compounds (I) and (II) were obtained by the condensation of crotonaldehyde with semicarbazide hydrochloride and thiosemicarbazide, respectively. Each molecule has an intramolecular N—H...N hydrogen bond, which generates an S(5) ring. In (I), the crotonaldehyde fragment is twisted by 2.59 (5)° from the semicarbazide mean plane, while in (II) the corresponding angle (with the thiosemicarbazide mean plane) is 9.12 (5)°. The crystal packing is different in the two compounds: in (I) intermolecular N—H...O hydrogen bonds link the molecules into layers parallel to the bc plane, while weak intermolecular N—H...S hydrogen bonds in (II) link the molecules into chains propagating in [110].

The structure of the title compound, C6H7N3O2, is of interest with respect to radiopharmacueticals. The crystal packing is characterized by N—H...O and O—H...N hydrogen bonds, which form a three-dimensional network. The molecule is planar except for one of the amine H atoms.