The removal of heavy metals from drinking water has attracted great interest in water purification technology. In this study, a biocompatible Polyaniline (PANI) polymer filled with TiO₂ and ZnO nanoparticles (NPs) is considered as an adsorbent of cadmium iodide from water. Theoretical investigation of the van der Waals (vdW) interactions deduced from the Hamaker constant calculated on the basis of Lifshitz theory was presented. It was found that the surface energy as well as the work of adhesion between water and PANI/NPs across air increases with an increasing volume fraction of the TiO₂ and ZnO nanoparticles. Consequently, an increase in the Laplace pressure around the cavities/porosities was found, which leads to the enhancement of the specific contact surface between water and PANI/NPs. On the other hand, for the interactions between CdI₂ particles and PANI/NPs surface across water, we show that the interactions are governed principally by the attractive London dispersion forces. The vdW energy and force increase proportionally with the augmentation of the volume fraction of nanoparticles and of the radius of the CdI₂ particle. Particularly, the PANI/TiO₂ has been proved to be a better candidate for adsorption of cadmium iodide from water than PANI/ZnO.

Thin films of physical mixture of Hausmannite Mn₃O₄ and lithium (Li) are synthesized by spray pyrolysis technique. Structural, morphological, optical, electrical, wettability, and photocatalytic properties have been investigated. X-ray diffraction (XRD) and Raman spectra, Scanning electron microscope (SEM) images, and electrical measurements show that Li nanoparticles are formed both on top surface of the film and inside grain boundaries. Bandgap and Urbach energies and optical relaxation time have been determined from transmittance T and reflectance R spectra. Impedance spectroscopy shows that charge separation increases with Li content, which improves photocatalytic efficiency of the film. The best photocatalytic efficiency is obtained for Li/Mn ratio of 15%. Indeed, the degradation of methylene blue (MB) under ultraviolet (UV) and visible light exposure, is improved by a factor of 5.7 and 2.4, respectively, when compared to undoped Mn₃O₄. In addition, this film exhibits a high photostability (10 cycles consecutively) under solar light. On the other hand, hydrophobicity reveals the hydrophilic character of the films.