Mg‐Al LDH‐Based Polymeric Nanocomposites for Effective Removal of Congo Red Dye from Wastewater

Abstract

Abstract This study investigates the adsorption performance of polyethylene glycol‐400 (PEG400)‐modified Mg‐Al layered double hydroxide (LDH‐P400) for removing Congo red (CR) dye from aqueous solutions. X‐ray diffraction confirmed that LDH‐P400 preserved the characteristic layered structure of LDH, with an expanded interlayer spacing (7.92 → 8.27 Å) due to PEG intercalation. BET analysis further indicated an increase in surface area from 7.52 to 33.16 m 2 /g, facilitating enhanced dye uptake. Batch adsorption studies showed that LDH‐P400 achieved a capacity of ∼243.90 mg/g, surpassing unmodified LDH (150 mg/g), with 98.75% CR removal within 20 min under optimal conditions (pH 4, 0.5 g/L). Thermodynamic analysis confirmed the spontaneity of adsorption (negative Δ G ), while kinetic modeling yielded an excellent fit ( R 2 = 0.998) to the pseudo‐second‐order model. Isotherm analysis revealed that the Temkin model best described the process, indicating uniform binding energies and physisorption‐driven interactions, whereas the Dubinin–Radushkevich model suggested additional contributions from ion‐exchange mechanisms. The Elovich model supported heterogeneous surface adsorption, and intra‐particle diffusion analysis indicated a multi‐stage uptake pathway. Recyclability tests showed LDH‐P400 retained 86% and 71% efficiency after 4 and 7 cycles, respectively, demonstrating its promise as a low‐cost, sustainable adsorbent for dye‐laden wastewater.