LaCuFe mixed metal oxide as catalyst for degradation of refractory pollutants from water by hybrid ultrasonic/peroxymonosulfate process

Refractory organic pollutants (ROPs) pose a significant challenge to water treatment because of their persistence and toxic effects on aquatic environments. Here, we developed a hybrid ultrasonic/peroxymonosulfate process using LaCuFe mixed metal oxide (MMO) derived from an LDH precursor by co-precipitation method, followed by calcination . The absence of LDH peaks in the X-ray diffraction (XRD) analysis of the calcined product revealed that the LDH structure collapsed and a new mixed metal oxide was formed. High-resolution transmission electron microscopy images revealed clear lattice fringes indicative of distinct metal oxide phases. The sonocatalytic activity of the LaCuFe MMO was determined in the degradation of phenazopyridine (PHP) under varying operational parameters, including catalyst dosage, PMS concentration, US power, solution pH, and PHP concentration. PMS alone achieved 21.8% removal, US alone 17.0%, and LaCuFe MMO adsorption 25.9%, while the binary US/PMS system yielded 32.3%. In contrast, the hybrid LaCuFe/US/PMS process achieved 81.2% degradation with a synergy factor of 2.48, confirming a strong non-additive enhancement. Radical scavenging tests confirmed that SO₄^•⁻, O₂^•⁻, and h+ played a role in the PHP degradation. LC-MS analysis identified several transformation products of PHP, and ECOSAR predictions indicated the process could reduce the toxicity. Additionally, the process showed high performance in removing five alternative pollutants, including rhodamine B, pymetrozine, rifampicin, tetracycline, and levofloxacin. Catalyst reusability tests showing stable performance over multiple cycles and the effectiveness of the process at treating types of organic pollutants support the practical applicability of the process.