Magnetically separable Bi2O2CO3/MIL-101(Fe)/CoFe2O4 nanostructured catalysts for heterogeneous reductive remediation of nitrophenols and organic dyes

Abstract

A new magnetically separable nanocomposite, Bi₂O₂CO₃/MIL-101(Fe)/CoFe₂O₄, was successfully synthesized through a hydrothermal method. The composite was characterized through various analytical techniques. The nanocomposite demonstrated good catalytic efficiency in reducing nitroaromatic compounds and organic dyes by using NaBH₄ reducing agent in aqueous solutions at room temperature. The apparent rate constant (k_app) values for 4-nitrophenol, 2-nitrophenol, 2-nitroaniline, and 4-nitroaniline were recorded at 0.457, 0.253, 1.52, and 0.564 min⁻¹, respectively, achieving complete conversion in just 2 to 9 min. Under similar conditions, methylene blue, methyl orange, rhodamine B, congo red, and crystal violet organic dyes were reduced to 98–100 % within 4 to 20 min, with k_app values ranging from 0.157 to 0.885 min⁻¹. Furthermore, the influence of catalyst dosage, NaBH₄ concentration, and substrate concentration on the reduction process was examined. Importantly, the nanocomposite can be recovered using an external magnet and reused over four consecutive cycles without a significant reduction in catalytic efficiency.