Surface weak acid-base pair of FeOOH/Al2O3 for enhanced peroxymonosulfate activation in degradation of humic substances from water

Abstract Three oxides (SiO2, Al2O3 and FeOOH/Al2O3) made of earth-abundant elements (O, Si, Al and Fe) were prepared to activate peroxymonosulfate (PMS). Humic acid (HA) as a representative of humic substances in water was used to evaluate their PMS activation performance. FeOOH/Al2O3 exhibited the highest catalytic activity towards HA degradation with a pseudo-first order reaction rate constant of 0.0204 min−1, but almost no HA was degraded over SiO2. The results of Electron Spin Resonance (ESR) analysis and radical quenching experiments verified that singlet oxygen (1O2) was the sole reactive species for HA degradation. The relationship between surface properties of tested oxides and their PMS activation efficiency was investigated. According to the characterization results of powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), nitrogen adsorption-desorption experiment, temperature programmed desorption of adsorbed CO2 (CO2-TPD) and Pyridine-FTIR spectroscopy, the surface acid-base property was proven to be responsible to excellent PMS activation performance of FeOOH/Al2O3 for 1O2 generation. A dual-reaction-site mechanism was proposed and the contribution of weak Lewis acid site and weak basic site to HA degradation in PMS-FeOOH/Al2O3 system was discussed based on all the experimental results.