Singlet oxygen-dominated transformation of oxytetracycline by peroxymonosulfate with CoAl-LDH modified hierarchical porous ceramics: Toxicity assessment

Singlet oxygen (1O2) dominated advanced oxidation processes have gained much attention due to their ability to transform or even detoxify organic pollutants. Herein we report that CoAl-LDH modified 3D printed hierarchical porous ceramics (3DP-HPC@CoAl-LDH) were able to efficiently activate peroxymonosulfate to degrade oxytetracycline (OTC) at pH 6.2 (over 99% removal in 30 min) and transform it into less toxic by-products. Cl- and natural organic matter showed an inhibitory effect on OTC degradation. Quenching experiments and ESR results identified the main contribution of 1O2 to OTC oxidation besides SO4•−, O2•– and •OH. Several possible pathways of OTC degradation were proposed based on the by-products detected using LC-MS. T.E.S.T calculation based on quantitative structure–activity relationships (QSARs) revealed detoxification of transformation products. Flow cytometry method was applied to quantify the cytotoxic effects of the reaction solution including the degradation products at various reaction times. Density functional theory simulation suggested that the strong electronic interaction between Co (II) and PMS allowed the 3DP-HPC@CoAl-LDH to effectively adsorb HSO5- and split the O-O bond. Moreover, the 3DP-HPC@CoAl-LDH can be separated directly from water and reused with a degradation efficiency of more than 83% after 11 cycles, demonstrating high recyclability and sustainable catalytic efficiency. Furthermore, a 3D printed impeller-agitator was fabricated and evaluated for potential practical application. The strategy proposed in this study may provide alternative approach to design functional devices as PMS activators and treat bio-refractive contaminants for practical applications.