Efficient visible light-induced photodegradation of industrial lignin using silver-CuO catalysts derived from Cu-metal organic framework

Degradation of environmental pollutants using renewable solar energy is a low-cost and promising technology. Silver-loaded copper oxide microparticles (Ag/CuO) were prepared using a three-dimensional copper metal–organic framework Ag⁺/[Cu₂(nic)₄(H₂O)]_n (nic = nicotinic acid) as a precursor by the controlled thermal decomposition method and characterized by a variety of physical measurements. The Ag/CuO composites exhibited excellent visible-light-driven photocatalytic activity towards rhodamine B (RB) dye and alkali lignin. Under the catalysis of Ag/CuO composite, over 94% total organic carbon (TOC) removal of alkali lignin was obtained after irradiating for 5 h in an aqueous solution at room temperature. The effects of H₂O₂ dosage and initial pH on the photodegradation efficiency of alkali lignin were investigated in detail. Moreover, 17 phenolic intermediates were detected from the lignin degradation solution by GC–MS analysis. ·OH radicals were found to play the most important role in the photodegradation process. Finally, based on the experimental results, a reasonable mechanism was proposed to interpret the photodegradation process of alkali lignin. The excellent industrial lignin photodegradation performance makes Ag/CuO composites a promising catalyst to purify the paper-making wastewater. Graphical abstract: [Figure not available: see fulltext.] Ag/CuO composite was prepared by calcining an Ag⁺-loaded Cu-MOF, which exhibited high catalytic activity in photodegradation of industrial lignin.