Use of highly stable phosphonate coordination polymers as adsorbents for wastewater

A series of coordination polymers (CPs) based on phosphonates, M‐VP, and M‐Phen‐VP (M = Ce, La, Phen = 1,10‐phenanthroline, Im‐imidazole, VP = vinylphosphonate) were obtained by hydrothermal reactions in different conditions: room temperature, 75°C, 180°C, at pH 1.5–7 aqueous solutions. The materials were characterized by Fourier‐transform infrared (FTIR), X‐ray powder diffraction, and thermogravimetric analysis. The samples are characterized by a high degree of crystallinity, judging from the intensity of the peak in the 2θ region 8–9°. Thermogravimetric analysis performed on cerium and lanthanum CPs crystals indicate that the compounds are stable up to 360°C, after which it undergoes degradation corresponding to loss of the organic unit. The obtained materials were further used as adsorbent in the removal process of cesium (Cs(I)) and thalium ions (Tl(I)) from aqueous solutions. In order to establish the maximum adsorption capacity of the studied CPs and for the interpretation of the results obtained in the equilibrium study, several empirical isotherms were used: Freundlich, Temkin, Langmuir, and Dubinin–Radushkevich. The particular parameters for each isotherm and correlation coefficient (R2) have been determined. This work examines the synthesis of a series of metal organic frameworks based on phosphonates, M‐VP, and metal phosphonates with coligands M‐Phen‐VP and M‐Im‐VP (M = Ce, La, Phen = 1,10‐phenanthroline, Im = imidazole, VP = vinylphosphonate) that were obtained by hydrothermal reactions in different conditions. These materials were characterized by FTIR, X‐ray powder diffraction, Scanning electron microscope (SEM), Energy‐dispersive X‐ray (EDX) and thermogravimetric analysis. The prepared materials were further used as adsorbent in the removal process of Rare Earth Elements (Cs(I), Tl(I)) from aqueous solutions, using atomic emission spectrophotometry.