Enhanced removal of phenol red from water by Cu(ii)-modified Mg–Al composites via adsorption and photocatalysis

Abstract

This study investigates Cu(II)-modified Mg–Al layered double hydroxide (LDH) composites for efficient removal of phenol red (PR) from water through adsorption and visible-light photocatalysis. The aim was to develop a sustainable material capable of addressing dye pollution in textile wastewater. The composites were synthesized via co-precipitation with optional calcination, non-calcined and calcined materials. Structural characterization (XRD, EDX, FT-IR, SEM) confirmed successful Cu²⁺ incorporation by isomorphic substitution, forming mesoporous, less crystalline structures. Uncalcined samples, particularly 5-CuH, retained a layered morphology and removed up to 94% of PR. The removal occurred via electrostatic attraction, π–π interactions, and ion exchange. Cu²⁺ narrowed the bandgap (E_g ≈ 2.1–3.1 eV), enhancing photocatalytic activity. Under visible light, 5-CuH degraded approximately 40% of PR within 60 minutes. Calcined samples (e.g., 5-CuH500) formed CuO particles and performed better under acidic conditions despite reduced structural integrity. Both materials reduced COD by over 90% in real textile wastewater, confirming their dual-function performance, adsorption and photocatalysis. In conclusion, Cu–Mg–Al composites offer an effective, eco-friendly alternative for treating dye-contaminated wastewater.