Interfacial charge-transfer in CoAl-LDH/CoOx for photocatalytic dye degradation and UV/H2O2 assisted real-wastewater treatment

Abstract

Photocatalysis can decolorize dye-laden wastewaters using light, but practical catalysts often suffer from narrow absorption, charge recombination, and stability limits. Here we synthesize a carbonate-intercalated cobalt–aluminum layered double hydroxide hosting cobalt-oxide nanocluster (CoAl-LDH/CoO_x) via a one-pot hydrothermal route and evaluate its performance for dye decolorization and UV/H₂O₂ treatment of real textile wastewater. Under UV irradiation, CoAl-LDH/CoO_x accelerates discoloration of methyl orange (MO) and Congo red (CR), following pseudo-first-order kinetics (e.g., MO: ∼98% removal at 5 mg L⁻¹ in 100 min; CR: ∼100% at 100 mg L⁻¹ in 100 min; k_app up to 0.14 min⁻¹). On real textile wastewater (ADMI₀ = 608.1), UV/H₂O₂ with 0.5 g L⁻¹ catalyst achieved ∼80% American Dye Manufacturer's Institute (ADMI) removal in 120 min at 48.96 mM H₂O₂; outdoor sunlight tests removed 82.5% (raw influent) and 50.8% (biologically treated effluent) over 20 h. Scavenger tests and EPR spin-trapping implicate h⁺ and ˙O₂⁻ as dominant species under UV, with ˙OH contributing when H₂O₂ is present. Five-cycle tests indicate stable activity. The one-pot CoAl-LDH/CoO_x heterostructure provides a robust, recyclable platform for interfacial charge-transfer-assisted photocatalysis on realistic effluents and motivates follow-up on mineralization and leaching.