Application of the Cu@PET Composite Track-Etched Membranes for Catalytic Removal of Cr(VI) Ions

Abstract

This research examines the features of obtaining composite track-etched membranes based on copper microtubes using various compositions of a deposition solution and various types of reducing agents, such as formaldehyde (Cu_CHOH@PET), dimethylamine borane (Cu_DMAB@PET), glyoxylic acid (Cu_Gly@PET). The structure and composition of the membrane composites were studied by scanning electron microscopy and X-ray phase analysis. It was shown that in the case of using dimethylamine borane as a reducing agent, the obtained composites consisted of copper(I) oxide (37.4 %) and copper(0) (62.6 %), in other cases single-component copper microtubes were obtained. The reduction reaction of chromium(VI) ions was used to evaluate the catalytic ability of prepared composites. It was found that the removal efficiency of chromium ions reached up to 95–97 % in the case of single-component composites; the presence of a copper( I) oxide phase in the structure of the Cu_DMAB@PET composites significantly reduced the activity of catalysts and under similar conditions, only 41% of the contaminant was removed from the reaction system. The degradation reaction of Cr(VI) was found to follow the Langmuir-Hinshelwood mechanism and a pseudo- first-order kinetic model. The calculated value of the reaction rate constant ka for composites of the Cu_DMAB@PET composition (0.017 min–1) was more than 9 times less than that of composites obtained using glyoxylic acid (0.156 min–1) and more than 15 times less than the ka value of Cu_CHOH@PET samples (0.249 min–1). Effect of temperatures on the catalytic ability of composites was studied in the temperature range of 10–38 °C. Some thermodynamic characteristics such as activation energy, enthalpy, and entropy of activation were calculated. It was found that the minimum value of the activation energy was obtained for the Cu_CHOH@PET samples.