A co-precipitation synthesized BiOI/(BiO) 2 CO 3 nanocatalyst: An experimental design and mechanism study towards photodegradation of sulfasalazine

Increased antibiotic consumption residues a large amount of antibiotics in the bacterial communities and ecosystems, leading to bacterial persistence against them. Thus, in recent decades, an urgent need has been to introduce/develop novel catalysts/adsorbents/methods to diminish the pollution extent of the aquatic environment by various organic pollutants like antibiotics. BiOI/(BiO) 2 CO 3 was synthesized by adding ammonium iodide to the aqueous suspension of (BiO) 2 CO 3 (BOC) under hydrothermal conditions. The individual BiOI and (BiO) 2 CO 3 and their p-n heterojunction system were characterized by some identification techniques like UV–vis diffuse reflectance spectroscopy (DRS) and electrochemical impedance spectroscopy (EIS). The direct band gap energies of 1.99, 3.54, and 2.42 eV were obtained for BiOI, (BiO) 2 CO 3, and BiOI/(BiO) 2 CO 3 samples from the Tauc plots. Both CVs and EIS results confirmed better charge transfer in the coupled catalyst. pHpzc for BiOI, (BiO) 2 CO 3 and BiOI/(BiO) 2 CO 3 was 6.3, 10.1, and 6.5. The response surface methodology (RSM) approach was used to construct a design model to investigate the interaction effects of the most influencing variables on the boosted catalytic effect of the coupled catalyst toward sulfasalazine (SSZ) as a model antibiotic pollutant. The model goodness was confirmed based on model F-value=20.59 > F 0.05, 14, 13  = 2.55 and lake of fit (LOF) F-value = 0.364 < F 0.05, 10, 3  = 8.73, as well as by adequate regression coefficient (R 2 ) of 0.9705, adjusted R 2 (0.9699), and predicted R 2 (0.9575) values. RSM optimal run included pH 6.0, catalyst dose: 0.55 g/L, irradiation time: 50 min, and SSZ concentration of 6 ppm, which resulted in a 95.3 % photodegradation efficiency. The relative role of photoinduced holes> photoinduced electrons > hydroxyl radicals> superoxide radicals was obtained in the photodegradation efficiency by the results obtained in the presence of some scavenging species. Accordingly, the photodegradation pathway was suggested. We believe simple preparation of the BiOI/(BiO) 2 CO 3 photocatalyst via a co-precipitation anion-exchanged consisted procedure by adding iodide anion to the aqueous suspension of (BiO) 2 CO 3 is an advantage of this work.