Mechanistic insight into visible light photocatalytic removal of meropenem from wastewater utilizing nickel based LDH nanostructures with synergistic adsorption effects

In this work, two complementary synthesis routes were developed to prepare novel Ni-containing layered double hydroxide (LDH) catalysts. In Route 1, a trivalent-metal composite precursor was fabricated by compositing MIL-101(Cr) and MIL-88 A(Fe) MOFs and subsequently converted into Ni-[MCr/MFe] LDH via Ni2+ incorporation. In Route 2, Ni-MCr LDH and Ni-MFe LDH were individually derived from MIL-101(Cr) and MIL-88 A(Fe) in the presence of Ni2+ and then combined to Ni-MCr LDH/Ni-MFe LDH composite. The synthesized materials were systematically characterized and applied to meropenem (MER) removal through a combined adsorption–photocatalysis process. Catalytic performance was evaluated by varying catalyst dosage, MER initial concentration, solution pH, and reaction temperature. Under optimized conditions (50 mg catalyst, 25 mg L−1 MER, visible-light irradiation), Ni-[MCr/MFe] LDH achieved 98.1% MER degradation and maintained 93.4% efficiency after five cycles, while post-reaction XRD, FTIR, and ICP analyses confirmed structural stability, heterogeneity, and recyclability. Adsorption followed the pseudo-second-order kinetic model and Temkin isotherm, whereas photocatalytic degradation obeyed pseudo-first-order kinetics. A comprehensive and previously unreported MER degradation pathway was elucidated using HPLC–MS/MS, radical scavenger tests, intermediate identification, and literature comparison, demonstrating that Ni-[MCr/MFe] LDH is a robust, reusable, and synergistic platform for visible-light-driven remediation of persistent pharmaceutical pollutants.