N/ZnFe2O4 codoped biochar as an activator for peroxydisulfate to degrade oxytetracycline: Synthesis, property and mechanism

Graphitic-carbon-nitride-hydrophilicity-dependent photocatalytic degradation of antibiotics with different log Kow

The surface hydrophilicity of a photocatalyst is an important factor that directly influences its interactions with organic pollutants and significantly impacts its degradation. In this study, we investigated the impact of increased hydrophilicity of g-C3N4 (CN) by alkaline solvothermal treatment on the degradations of three antibiotics (oxytetracycline (OTC), oxolinic acid (OA), and sulfamethoxazole (SMX)) with different log Kow values. Scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and Fourier-transform infrared (FT-IR) spectroscopy showed no significant differences in the morphology, crystalline structure, and surface functional groups of CN after alkaline solvothermal treatment (Nv-HPCN). However, contact angle analysis revealed that Nv-HPCN (31.8°) was more hydrophilic than CN (61.1°). To assess the hydrophilicity of the antibiotics, the log Kow values of SMX (0.77), OA (0.43), and OTC (-0.34) were measured. Nv-HPCN showed faster OTC degradation than CN, whereas the opposite pattern was observed for the degradation of OA. Scavenger tests showed that O2•- and h+ mainly contributed to the degradation of these antibiotics. Furthermore, the influences of NOM and coexisting anions on antibiotic degradation were investigated. This study thus offers perspectives on the impact of surface hydrophilicity of photocatalysts on the degradation of antibiotics.

Novel colorimetric detection of oxytetracycline in foods by copper nanozyme

In this study, copper nanozyme (CuNZs) possess good laccase-like activity were synthesized by grinding method with cupric chloride dihydrate as copper source, sodium borohydride as reducing agent and β-cyclodextrin as protective agent. The CuNZs can oxidize colorless 2,4-dinitrophenol (2,4-DP) to red product. When oxytetracycline (OTC) was added to the above three solutions, the color changed from red to orange and the absorbance increased again, indicating that OTC was also an affinity substrate for CuNZs. When CuNZs was mixed with OTC alone, the color changed from colorless to yellow, and the absorption intensity was related to OTC concentration. It has good selectivity and sensitivity, and had a good linear response to the concentration of OTC in the range of 50-500 μM, and the limit of detection was 0.148 μM. Thus, a fast and simple colorimetric assay for the determination of OTC was established by using the laccase-like activity of CuNZs, and it was applied successfully to detect OTC in food samples.

Unveiling the traits of dry and wet pre-magnetized zero-valent iron-activated peroxymonosulfate: Degradation of oxytetracycline

It has been previously reported that pre-magnetization could enhance the efficacy of zero-valent iron (ZVI) in removing contaminants. However, little is known about the effects and persistence of different magnetization methods on pre-magnetized ZVI (Pre-ZVI) when used in advanced oxidation processes (AOPs). Gaining a comprehensive understanding of the durability of various pre-magnetization methods in enhancing the removal efficiency of different pollutants will significantly impact the widespread utilization of Pre-ZVI in practical engineering. Herein, we investigated the efficiency of dry and wet Pre-ZVI-activated peroxymonosulfate (PMS) in eliminating oxytetracycline (OTC) and evaluated the durability of Pre-ZVI. Additionally, we examined several factors that influence the degradation process's efficiency. Our results found that the reaction constant k values corresponding to the dry Pre-ZVI/PMS system at the pH values of 3, 7, and 9 varied from approximately 0.0384, 0.0331, and 0.0349 (day 1) to roughly 0.0297, 0.0278, and 0.0314 (day 30), respectively. Meanwhile, the wet Pre-ZVI/PMS system exhibited k values ranging from approximately 0.0392, 0.0349, and 0.0374 (day 1) to roughly 0.0380, 0.0291, and 0.0322 (day 30), respectively. Moreover, we proposed four OTC degradation pathways using LC-MS/MS and density functional theory calculations. The toxicity of the degradation products was assessed using the ecological structure activity relationship and the toxicity estimation software tool. Overall, this study provides insights into the application of Pre-ZVI/PMS that can be selectively used to eliminate tetracycline antibiotics from water.

Investigation of manganese-iron oxide nanocomposite immobilized on powdered activated carbon as an efficient activator of peroxymonosulfate for antibiotics degradation: Conjunction of adsorption, radical and nonradical processes

Peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) have gained considerable attention for their efficient oxidation of persistent pollutants. A two-step chemical co-precipitation method was used to prepare a bimetallic nanocomposite (MnOx@Fe3O4) consisting of manganese oxides and ferroferric oxides, supported by powdered activated carbon (PAC). The synthesis of MnOx@Fe3O4-PAC (MFP) was aimed to enhance the degradation efficiency of oxytetracycline (OTC) via the simultaneous adsorption and oxidation processes on the solid-liquid interface. The OTC degradation process in the MFP/PMS system could be well described by pseudo-first-order kinetics. A wide pH range (3-6) was acceptable for MFP to degrade OTC via PMS activation with the highest removal efficiency reaching up to 85.6% (OTC0 = 150 mg/L), while a 60.8% removal efficiency of total organic carbon (TOC) was also attained simultaneously. SO4•- and 1O2, which were bound to the surface, played a crucial role as reactive oxygen species in the degradation of OTC. The combination of PAC, Fe3O4, and MnOx of MFP could enhance the degradation efficiency of OTC and fetch up their defects of separate application. The deduced OTC degradation pathway relied on the findings from UPLC-MS analysis and density functional theory (DFT) calculations. Noteworthy, MFP maintained efficient catalysis performance in the five cycles of stability experiment with neglectable loss of manganese and iron. These results provide valuable understanding of the conjunction of adsorption, radical, and nonradical processes driven by MFP for OTC degradation.

Degradation of oxytetracycline by iron-manganese modified industrial lignin-based biochar activated peroxy-disulfate: Pathway and mechanistic analysis

In this study, high-performance Fe-Mn-modified industrial lignin-based biochar (FMBC) was successfully prepared to facilitate the efficient degradation of oxytetracycline by its driven sulfate radical-based advanced oxidation process with 90% degradation within 30 min. The results showed that oxygenated functional groups (e. g. hydroxyl, carbonyl, etc.) in industrial lignin-based biochar, the synergistic effect of transition metals Fe and Mn, and defective structures were the active sites for activation of peroxy-disulfate. SO₄^·- produced during the degradation process assumed a key function. Significantly, 38 intermediates were innovatively proposed for the first time in the system, and oxytetracycline was degraded in 7 ways, including deamidation, demethylation, hydroxylation, secondary alcohol oxidation, ring opening, dehydration, and carbonylation. A new perspective on the application of industrial lignin in the advanced oxidative degradation of organic pollutants was provided by this study.

Enhanced Heterogeneous Peroxymonosulfate Activation by MOF-Derived Magnetic Carbonaceous Nanocomposite for Phenol Degradation

Degradation efficiency and catalyst stability are crucial issues in the control of organic compounds in wastewater by advanced oxidation processes (AOPs). However, it is difficult for catalysts used in AOPs to have both high catalytic activity and high stability. Combined with the excellent activity of cobalt/copper oxides and the good stability of carbon, highly dispersed cobalt-oxide and copper-oxide nanoparticles embedded in carbon-matrix composites (Co-Cu@C) were prepared for the catalytic activation of peroxymonosulfate (PMS). The catalysts exhibited a stable structure and excellent performance for complete phenol degradation (20 mg L^-1) within 5 min in the Cu-Co@C-5/PMS system, as well as low metal-ion-leaching rates and great reusability. Moreover, a quenching test and an EPR analysis revealed that ·OH, O₂·^-, and ¹O₂ were generated in the Co-Cu@C/PMS system for phenol degradation. The possible mechanism for the radical and non-radical pathways in the activation of the PMS by the Co-Cu@C was proposed. The present study provides a new strategy with which to construct heterostructures for environmentally friendly and efficient PMS-activation catalysts.

Electrochemical-enhanced Fe3O4/biochar activates peroxymonosulfate (E/nano-Fe3O4/BC/PMS) for degradation of oxytetracycline

To find cost-effective and environmentally friendly free radical activators to stimulate peroxymonosulfate (PMS) oxidative degradation of organic pollutants, nano-Fe₃O₄/biochar (BC) composites were prepared and characterized in this work to examine their effectiveness in stimulating PMS oxidative degradation of Oxytetracycline (OTC) in water enhanced with electrochemical degradation. When the mass ratio of nano-Fe₃O₄ to BC is 1:1, the catalyst nano-Fe₃O₄/BC exhibits the most obvious degradation effect on OTC. After 4 h of degradation, the OTC concentrations were reduced from 20 to 2.65 mg L^-1, while treated with a single nano-Fe₃O₄ and a single BC are reduced by only 67.7% and 61.8%. Anions HCO₃^- and H₂PO₄^- significantly inhibit OTC degradation, and HCO₃^- has a stronger inhibitory effect than H₂PO₄^-, while Cl^- and NO₃^- can promote OTC degradation. Quenching test and electron spin paramagnetic resonance (EPR) detection showed that singlet oxygen (¹O₂) was the main active species in the degradation process, followed by hydroxyl radical (·OH). When reused for the third time, the removal rate of OTC by nano-Fe₃O₄/BC composites with mass ratios of 1:4, 1:2 and 1:1 was still more than 70%. Therefore, the nano-Fe₃O₄/BC composite is a promising PMS activator, which can realize the rapid oxidative degradation of OTC.