Activation of Persulfate by NiFe-Layered Double Hydroxides Toward Efficient Degradation of Doxycycline in Water

In recent years, the excessive use and improper disposal of antibiotics have led to their pervasive presence in the environment, resulting in significant antibiotic pollution. To address this pressing issue, the present study synthesized nickel–iron-layered double hydroxides (NiFe-LDHs) with varying molar ratios using a hydrothermal method, employing these LDHs as catalysts for the oxidative degradation of doxycycline, with peroxymonosulfate (PMS) serving as the oxidant. X-ray diffraction analysis confirmed that the synthesized NiFe-LDHs exhibited a hexagonal crystal structure characteristic of layered double hydroxides. Experimental results demonstrated that the catalytic efficiency of NiFe-LDHs increased with both the dosage of the catalyst and the concentration of PMS, achieving a high degradation efficiency for doxycycline at a catalyst concentration of 0.5 g/L. Furthermore, the catalytic performance was notably effective across a range of pH conditions, with the highest degradation efficiency being observed at a Ni–Fe molar ratio of 3:1. The activation of PMS by NiFe-LDHs for the catalytic degradation of pollutants primarily occurs through singlet oxygen (1O2), superoxide radicals (O2−·), and sulfate radicals (SO4−·). The study also proposed three potential degradation pathways for doxycycline, indicating that the final degradation products have lower environmental toxicity. This research offers novel approaches and methodologies for the treatment of antibiotic-contaminated wastewater.