Synthesis of azo metal complexes for efficient photocatalytic diclofenac degradation: experimental studies and...

In the present study, two azo ligands (L1 and L2) were synthesized and subsequently reacted with Ni(ii), Cu(ii), Co(ii), and Zn(ii) metal ions to afford a series of eight corresponding azo metal complexes (C1-C8). The successful synthesis and structural features of the azo ligands and their metal complexes were confirmed through comprehensive spectroscopic characterization using UV-visible spectroscopy, FTIR, mass spectrometry, and NMR spectroscopy. The photocatalytic activity of the synthesized metal complexes C1-C8 was investigated using diclofenac sodium (DCF) as a target pollutant. Among different compositions, C8 showed exceptional performance attributed to the synergy of extended π-conjugation and the favorable redox cycle of Cu²⁺/Cu¹⁺. The photocatalytic process was optimized through response surface methodology (RSM) employing central composite design (CCD). Herein, the influence of different reaction parameters on DCF degradation and their interactive effects was examined. Maximum degradation efficiency of 90.2% was recorded for C8 at a catalyst loading of 20 mg using 11 mg L^-1 of DCF under mildly acidic conditions (pH = 5.1) for an irradiation time of 79 min. Furthermore, C8 displayed reasonable reusability up to four repeated runs with only a slight drop of 1.8% in photocatalytic activity, suggesting the viable photocatalytic potential of such materials in wastewater treatment.