Multifunctional Nb–Cu nanostructured materials as potential adsorbents and oxidation catalysts for real wastewater decontamination

Abstract

Herein, we report the preparation of two niobium(V)–copper(II)-based materials using a bifunctional dicopper(II) complex as a template. Material 1 was prepared via the coprecipitation method in the presence of an aqueous solution of the dicopper(II) complex (n-Bu₄N)₄[Cu₂L₂] (n-Bu₄N⁺ = tetra-n-butylammonium cation and L = N,N′-2,2′-ethylenediphenylenebis(oxamate)), ammonium niobium(V) oxalate (NH₄[NbO(C₂O₄)₂(H₂O)₂]), and ammonia. Material 2 was obtained via the calcination of 1 at 600 °C. Both hybrid materials were characterized via micro-ATR FT-IR and Raman spectroscopy, XRPD, TEM and SEM microscopy, and Brunauer, Emmett and Teller (BET) surface measurements. The microporous nanostructured niobium(V)–copper(II) complex material 1 exhibited a high surface area (200 m² g⁻¹); whereas, material 2 consisted of a crystalline mixture of Nb₂O₅ and CuO phases with a low surface area (40 m² g⁻¹). The ability of both materials to act as adsorbents and heterogeneous catalysts to remove methylene blue dye from real wastewater was evaluated. Material 1 exhibited a remarkable maximum adsorption capacity according to the Langmuir model compared to that of the niobium-based nanostructured material (q_max = 199.20 mg g⁻¹). Both 1 and 2 were used as heterogeneous catalysts for the removal of methylene blue dye from real wastewater by Fenton-like reaction. In the presence of hydrogen peroxide, 2 removed approximately 89% of the dye from water, while 1 removed 85% of the contaminant.