Surface properties of Langmuir–Blodgett films and nanodispersed oxides containing nickel and copper

Abstract

The structures exhibiting specific sorption properties have recently attracted considerable attention [1]. Sorbents containing a metal ion strongly bound at the substrate are of special interest for metal-affine chromatography [2][3][4]. Earlier we have shown that such structures containing Fe III ions can be used as metal-affine sorbents [5,6]. Therefore we assumed that Langmuir-Blodgett films based on metal stearates and nanodispersed metal oxides with a developed surface can exhibit such specific sorption properties [7,8]. To verify this assumption, we prepared collapsed films of copper and nickel stearates and nanosized oxides of the same metals.The films of copper and nickel stearates with average mass of 0.002 g per 100 cm 2 were prepared via the Langmuir-Blodgett method. Chemical analysis of the metals contents showed that the fraction of copper (nickel) at the surface of stearic acid monolayer was of 0.5, pointing at the complete conversion of stearic acid into distearate of the corresponding metal. Scanning electronic microscopy (SEM) examination of the collapsed monolayers of copper and nickel stearates revealed the layered structures that were further used in the study of the electrokinetic potential as a function of the solution рН. The isoelectric points were found at 3.9 and 3.5 рН units for the films based on nickel and copper stearates, respectively.Nickel and copper oxides were synthesized via microwave treatment of aqueous solutions containing carbamide and the corresponding metal nitrate. The Xray analysis revealed that the single-phase oxides without any admixtures of the starting compounds were formed; the recorded reflexes were well resolved, and no splitting was observed. Nickel and copper oxides had the bunsenite and the tenorite structures, respectively. In the both cases, the peaks were somewhat broadened, possibly pointing at sufficiently high dispersity and small particle size of the resulting oxides. The SEM method showed that the formed oxides contained spherical aggregates of about 500 nm.The synthesized oxides were studied with nitrogen low-temperature sorption (BET). The hysteresis loop and characteristic inflection at low relative pressure allowed assignment of the sorption isotherm to the type IV according to the IUPAC nomenclature, evidencing about the mesoporous structure of the oxides. The specific surface area of copper and nickel oxides was of 2 and 90 m 2 /g, respectively.It was found that both the films of copper and nickel stearates and the oxides of those metals exhibited the metal-affine activity towards N-(phosphonomethyl)glycine and aminomethylphosphonic acid, i.e. they could be used as sorbents. After extraction

Holmium-Containing Metal-Organic Frameworks as Modifiers for PEBA-Based Membranes

“…Membranes and thin solid films with metal ions [ 32 , 33 , 34 ] have been used in many fields, such as seawater desalination, wastewater treatment and gas separation [ 35 , 36 , 37 ]. Most modern research into the use of membrane technologies for the separation of components is based on the use of mixed matrix membranes (MMMs) containing various additives, such as metal oxides, fullerene and its derivatives, MOFs, etc.…”