International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Removal of heavy metals ions from water sources still represents a challenge and different materials are being developed in order to overcome it. Iron oxide nanomaterials receive a lot of attention because of their small size, high surface area, biocompatibility and low cost. However, most of the reported synthesis methods are multi-step and time-consuming. We investigated the co-precipitation method for the synthesis of nanostructured hematite prepared at different temperatures and different calcination times. The obtained materials were characterized by X-ray powder diffraction, scanning electron microscopy and infrared spectroscopy. The adsorption capacity for Pb(II) ions was found to be about 6–12 mg of adsorbed Pb(II) per gram of adsorbent.

habits of coordinational polyhedras are considered as forms of nanocrystals. Habits for coordination polyhedra with numbers from 1 to 30 are given. It was analazide the cubic and hexagonal lattices. There are the next nanocrystals: primitive, cubic and intercentered and face-centered and diamond-like (all cubic) and hexagonal close packed.

Gel matrix of the natural polymer starch has been employed as template for the preparation of ZnO nanocrystals via solution-solid technique. The template offers selective binding sites for Zn(II) under aqueous conditions. Controlled solvent-exchange, further isolation of solid product by microfiltration and drying, and subsequent removal of the template backbone enable the synthesis of spatially separated ZnO nanocrystals. The crystalline character and near narrow particle size distribution pattern have been confirmed through powder XRD measurements and TEM with SAED observation. The morphology, surface and optical properties of ZnO sample were characterized by SEM observation, BET-surface area, UV–Vis and PL spectra. The UV photocatalytic activity of ZnO nanocrystals was studied by analyzing the degradation of methylene blue in aqueous solution. The nanosized ZnO sample showed greater photocatalytic activity than commercial TiO₂ (P25) photocatalysts. The size and shape factor seems to be of great importance in the observed photocatalytic performance.