Investigating naproxen removal from pharmaceutical factory effluents using UVA/MIL-88-A/PS and solar/MIL-88-A/PS systems

MIL-88-A, an iron-based metal–organic framework (MOF), was synthesized and investigated for its potential as a mediator in a solar-powered system for the activation of persulfate (PS). Solar/MIL-88-A/PS and UVA/MIL-88-A/PS systems were evaluated for the degradation of naproxen (NAP) in water. Control experiments were conducted to study the activation of PS by MIL-88-A in the absence and presence of either UVA lamps or sunlight. Both systems were optimized and tested for their recyclability and matrix variations by varying water-quality parameters, including pH, salinity, bicarbonates, and phosphates. The results indicated that (i) 87% of NAP ([NAP]0 = 50 mg L−1) was degraded within a period of 100 min in UVA/MIL-88-A/PS system, whereas complete degradation occurred in 10–15 min in solar/MIL-88-A/PS system; (ii) MIL-88-A can be recycled over five cycles for PS activation without any regeneration process; and (iii) carbonates and phosphates have inhibitory effect on the degradation of NAP in both systems. The degradation mechanism was elucidated using EPR, TOF-SIMs, and HPLC-MS, which revealed that the degradation mechanism is based on oxidation by hydroxyl (HRs) and sulfate radicals (SRs). Three NAP degradation products were identified using an HPLC-QTOF high-resolution mass spectrometer.