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

Abstract

The features of obtaining composite track-etched membranes based on copper microtubes using various com-positions 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) were studied in this research. The structure and composition of the membrane composites were studied by scanning elec-tron 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 in order to evaluate the catalytic ability of prepared composites. It was shown that the removal effi-ciency of chromium ions reached up to the 95–97 % in the case of single-component composites; the pres-ence 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 us-ing 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.