Facet-controlled activation of persulfate by goethite for tetracycline degradation in aqueous solution

Advanced oxidation processes (AOPs) based on the activation of persulfate (PS) by minerals have been widely used in environmental remediation. Herein, two goethite materials with different contents of exposed {0 2 1} facet were synthesized and used as the catalysts for PS activation to degrade tetracycline. Results showed that exposed facets significantly affected their catalytic activity. Goethite exposed with more {0 2 1} facet exhibited better catalytic performance. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical analysis suggested that the surface Fe(II)/Fe(III) redox cycle, the abundant surface hydroxyl density and the easier generation of active radicals by activating PS were responsible for the excellent catalytic performance of goethite with more {0 2 1} facet exposed. Furthermore, the density functional theory (DFT) calculations further confirmed that {0 2 1} facet was more favorable for the activation of PS than {1 1 0} facet. The electron paramagnetic resonance (EPR) and radical scavenging experiments indicated that both sulfate radicals and hydroxyl radicals participated in the degradation process. This study provides new insights into the PS heterogeneous activation by facet-dependent goethite in environmental catalysis.