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

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 (kapp) 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 kapp 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.