Magnesium aluminum-layered double hydroxide/graphitic carbon nitride nanocomposite for efficient removal of diclofenac and activation of peroxymonosulfate

The presence of diclofenac sodium (DIF) in water poses a significant risk to public health due to its resistance to biological degradation. Mg Al LDH/g-C₃N₄ nanocomposite was employed as catalyst to activate peroxymonosulfate (PMS) for efficient removal of DIF from aqueous solution. Optimization of operational parameters, including catalyst dose (100–600 mg/L), initial DIF concentration (10–200 mg/L), PMS dose (0.1–1 mM), contact time (10–40 min), and solution pH (3–10), was performed using response surface methodology (RSM) with central composite design (CCD). Under optimized conditions (25 mg/L initial DIF, 381.6 mg/L catalyst, 0.91 mM PMS, pH 6.2, 39.4 min), 98.8% removal was achieved. Radical quenching experiments indicated that sulfate (SO₄• - ) and hydroxyl (•OH) radicals were the dominant reactive species responsible for DIF degradation. Kinetic studies revealed that the process followed a pseudo-second-order model, while equilibrium data were best described by the Langmuir isotherm, suggesting monolayer chemisorption on a homogeneous surface. The nanocomposite showed high stability and reusability over four consecutive cycles. This work presents an efficient, stable, and easily separable catalyst system, offering a promising strategy for the removal of persistent pharmaceutical pollutants from water.