Binuclear cobalt phthalocyanine supported on manganese octahedral molecular sieve: High-efficiency catalyzer of peroxymonosulfate decomposition for degrading propranolol

Abstract

Propranolol (PRO) is widely detected in the aquatic environment and proved to be detrimental to multifarious aquatic organisms. In view of some virtues of sulfate radicals than hydroxyl radicals, advanced oxidation technologies that involve the activation of peroxymonosulfate (PMS) have stimulated wide-ranging research on the PRO removal. In this paper, a composite (C2NOMS-2) of amino-functionalized manganese octahedral molecular sieve (NOMS-2) and binuclear cobalt phthalocyanine (Co2CPc) was synthesized easily, and utilized as a catalyzer for PMS to degrade PRO in water. The apparent rate constants of PRO degradation by PMS with C2NOMS-2 as a catalyst was found to be higher than with NOMS-2, Co2CPc and the composite of uninuclear cobalt phthalocyanine (CoCPc) and NOMS-2. The catalytic ability of C2NOMS-2 was investigated under various reaction conditions: catalyst dosages (0.5–2.0 g/L), PMS doses (50–500 mg/L), initial pH (5–11), reaction temperature (20–35 °C), and natural water constituents (Cl−, HCO3−, and sodium huminate). Radical scavenging tests and electron paramagnetic resonance spectroscopy showed that 1O2 was the most critical reactive oxygen species, and conceivable mechanisms of PMS activation with C2NOMS-2 were proposed established on the curve estimation of high-resolution XPS spectra, revealing that the generation of reactive oxygen species was mainly resulted from the cycles of Mn3+/Mn4+, Co3+/Co2+ and surface lattice oxygen/surface adsorbed oxygen. The intermediate products of propranolol degradation were identified by LC-MS/MS. Cycling experiments and ion dissolution detection suggested that C2NOMS-2 could maintain satisfactory stability in an aqueous system.