Yuhan Wang,Longzhen Ding,Chang Liu,Yao Lu,Qianyuan Wu,Chao Wang,Qing Hu
A series of environmental-friendly and cost-effective 0D/2D/2D ZnFe 2 O 4 /Bi 2 O 2 CO 3 /BiOBr double Z-scheme heterojunctions (abbreviated as xZnCB) were fabricated by a hydrothermal method using an electrostatic self-assembly strategy. The removal efficiencies toward tetracycline (TC), oxytetracycline (OTC), and doxycycline (DOX) were 93%, 90.1%, and 89.4% in 10ZnCB/sunlight/permonosulfate (PMS) systems within 20 min, and the degradation rate constants of 10ZnCB were 5.7–8.2 times higher than those of ZnFe 2 O 4 and 2.6–2.9 times higher than those of Bi 2 O 2 CO 3 /BiOBr (CB) under the same conditions. XPS valence band spectra, quenching experiments, EPR measurements, and density functional theory (DFT) calculations demonstrated the existence of the double Z-scheme heterojunctions. The coexistence of radical and non-radical pathways caused by photocatalytic and non-photocatalytic degradation mechanisms was also elucidated. PMS was effectively activated by a photoinduced e − , · O 2 − , and Fe(II)/Fe(III) pathway, and active species including · O 2 − , 1 O 2 , SO 4 · − , · OH, and h + participated in the catalytic processes. Unexpectedly, 1 O 2 , and · OH were determined to be the primary species during the degradation processes instead of SO 4 · − . Recycling experiments, metal leaching measurements, and TC degradation experiments in the secondary effluent demonstrated the excellent catalytic and structural properties of these xZnCB hybrid materials.
Tetracycline hydrochloride (TC) water pollution poses a serious threat to human health. Preparation of a high-efficiency TC treatment agent is one of the key tasks in TC wastewater treatment. The present work innovatively designed and successfully prepared a three-dimensional layered double hydroxide nanocage (H-NiCo-LDH) to efficiently remove TC through synergistic adsorption and non-photocatalytic degradation. The nanocage structure, derived from Co-ZIF through the Kirkendall effect, featured ultrathin nanosheets with a high specific surface area of 659 m2 g−1 and abundant oxygen vacancies (Ovs). The material showed excellent TC removal performance in a wide pH (5–11) and temperature (5–45 °C) range, and the removal rate of 20 mg L−1 of TC reached 99.6% in 5 min. In addition, the maximum removal amount reached 630 mg g−1, which was higher than that of most reported LDHs. The removal mechanism was confirmed to be the combined effect of adsorption and 1O2 driven degradation. Remarkably, the degradation pathway, independent of light, relied on Ov-mediated dissolved oxygen. Liquid chromatography-mass spectrometry (LC-MS) gave the primary intermediates of TC degradation, and toxicity assessment showed that the degradation process decreased the environmental risks of TC. The work provides a paradigm for designing self-sustaining catalysts for antibiotic removal in complex aquatic environments.
Minshu Cui,Kangping Cui,Xueyan Liu,Xing Chen,Zhenhu Hu
The metal-free nature of carbon nitride endows it the advantages of low cost and less secondary pollution when uses in peroxymonosulfate (PMS)-based advanced oxidation processes. However, practical applications call for continued efforts on developing modification protocols to achieve higher catalytic efficiency while breaking its dependence on visible light. Herein, a one-step carbon fragments doping method was developed to synthesis a series modified carbon nitride. The obtained catalyst DCNs showed high efficiency on non-photocatalytic activation of PMS for organic pollutant removal. Characterization results proved that carbon fragments were incorporated into the skeleton of carbon nitride during the thermal treatment process. Along with the rise of doping amount, the system efficiency on pollutant removal increased first then decreased. The dominant reactive species was identified as singlet oxygen, which was deduced to originate from the electron loss process of HSO 5 − at the carbon sites on DCN. Density functional theory calculations suggest that appropriate doping of carbon fragments on carbon nitride improves the adsorption energy and charge transfer efficiency of PMS on the catalyst surface, thereby elevating the catalytic efficiency on pollutant removal. In addition, as a non-radical species dominated process, the DCN catalyst well resisted the interference from water matrices to degrade pollutants in high efficiency. At the same time, DCN had good reusability, exhibiting considerable prospects for practical applications.
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