Ultra-adsorption enhancing peroxymonosulfate activation by ultrathin NiAl-layered double hydroxides for efficient degradation of sulfonamide antibiotics

Sulfonamides have attracted special attention due to their widespread use and refractory nature in the aquatic environment. Heterogeneous catalytic peroxymonosulfate (PMS) activation for sulfonamide degradation has been demonstrated to be an encouraging strategy. Herein, ultrathin nickel aluminium layered double hydroxide (U–NiAl-LDH) was employed as an efficient peroxymonosulfate activator. The adsorption kinetics experiment showed that U–NiAl-LDH exhibited a super-adsorption phenomenon for sulfonamide antibiotics, such as sulfamethoxazole (SMX) and sulfachloropyridazine (SCP). U–NiAl-LDH was composed of 6 layers of a NiAl bimetallic layer structure. The degradation performance of organic contaminants via PMS activation was greatly accelerated by decreasing the number of LDH layers. Ni(II) on the surface of U–NiAl-LDH activated PMS to produce surface-bound hydroxyl radicals and sulfate radicals by donating electrons to cleave the O–O bond of PMS. These in-situ generated reactive oxygen species (ROS) on the surface of U–NiAl-LDH could directly attack adjacent adsorbed SMX or SCP molecules, where the migration distance between the ROS and target contaminants was reduced. Consequently, super-adsorption synergistically promoted the degradation efficiency of SMX and SCP, which decreased the demand for PMS. The newly found ultra-adsorption enhancing peroxymonosulfate activation effect was pioneered for the ultrafast elimination of sulfonamide antibiotics in real water. This proposed mechanism provides preliminary guiding significance to design PMS catalysts with dual reaction sites for the treatment of targeted refractory organic contaminant wastewater.