Degradation of tetracyclines via calcium peroxide activation by ultrasonic: Roles of reactive species, oxidation mechanism and toxicity evaluation

Optimized Degradation of Doxycycline in Aqueous Systems Using Calcium Peroxide Nanoparticles via Response Surface Methodology

The presence of antibiotic residues in aqueous systems, particularly doxycycline (DOX), is harmful to the environment and public health. In this study, dextran-coated calcium peroxide nanoparticles (DEX@nCPs(DEX)), Fe(II), and oxalic acid (OA) were combined to improve the heterogeneous Fenton-like degradation of DOX. X-ray photoelectron spectroscopy (XPS) demonstrated the successful synthesis of DEX@nCPs(DEX), showing the presence of Ca, O, and C functional groups associated with dextran. Using response surface methodology with a central composite design (RSM-CCD), the optimal conditions (DEX@nCPs(DEX) dosage: 2 g/L, pH: 5, contact time: 420 min) achieved 90% DOX removal, which was 20% higher than using DEX@nCPs(DEX)/Fe(II) alone. The degradation process followed first-order kinetics with a rate constant of k 1 = 0.0047 min-1. Model validation showed high predictive accuracy (R 2 = 0.996; adjusted R 2 = 0.987). Scavenger and photoluminescence analyses revealed hydroxyl radicals (•OH) to be the primary reactive species, accounting for over 80% of the degradation activity. The DEX@nCPs(DEX)/Fe(II)/OA system offers a promising approach for mitigating pharmaceutical pollutants in water, contributing to more sustainable environmental management practices.

Application of calcium peroxide in promoting resource recovery from municipal sludge: A review

The harmless disposal, resource recovery, and synergistic efficiency reduction of municipal sludge have been the research focuses for the last few years. Calcium peroxide (CaO2) is a multifunctional and safe peroxide that produces an alkaline oxidation environment to promote the fermentation of municipal sludge to produce hydrogen (H2) and volatile fatty acids (VFAs), thus realizing sludge resource recovery. This review outlines the research achievements of CaO2 in sludge resource recovery, improvement of sludge dewaterability, and removal of pollutants from sludge in recent years. Meanwhile, the mechanism of CaO2 and its influencing factors have also been comprehensively summarized. Finally, the future development direction of the application of CaO2 in municipal sludge is prospected. This review would provide theoretical reference for the potential engineering applications of CaO2 in improving sludge treatment in the future.