Spinel cobalt ferrite-based porous activated carbon in conjunction with UV light irradiation for boosting peroxymonosulfate oxidation of bisphenol A

Exploration of the mechanism of levofloxacin removal by N-doped-induced interfacial micro-electric field-activated persulfate

The defects formed by N doping always coexist with pyrrole nitrogen (Po) and pyridine nitrogen (Pd), and the synergistic mechanisms of H2O2 production and PMS activation between the different Po: Pd are unknown. This paper synthesized MOF-derived carbon materials with different nitrogen-type ratios as cathode materials in an electro-Fenton system using precursors with different nitrogen-containing functional groups. Several catalysts with different Po: Pd ratios (0:4, 1:3, 2:2, 3:1, 4:0) were prepared, and the best catalyst for LEV degradation was FC-CN (Po: Pd=3:1). X-ray Photoelectron Spectroscopy (XPS) and density-functional theory (DFT) calculations show that the introduction of nitrogen creates an interfacial micro-electric field (IMEF) in the carbon layer and the metal, accelerates the electron transfer from the carbon layer to the Co atoms, and promotes cycling between the Fe3+/Co2+ redox pairs, with the electron transfer reaching a maximum at Po: Pd = 3:1. FC-CN (Po: Pd=3:1) achieved more than 95 % LEV degradation in 90 min at pH = 3-9, with a lower energy consumption of 0.11 kWh m-3 order-1. and the energy consumption of the catalyst for LEV degradation is lower than that of those catalysts reported. In addition, the degradation pathway of LEV was proposed based on UPLC-MS and Fukui function. This study offers some valuable information for the application of MOF derivatives.

Enhanced Selective Degradation of Pharmaceutical and Personal Care Products by β-Cyclodextrin-Decorated ZIF-67 Nanocomposites in Reclaimed Water

A peroxymonosulfate oxidation system was developed via modification of β-cyclodextrin (β-CD) on the surface of Fe2+-doped ZIF-67 (CD/Fe@ZIF-67) as an activator. The 99.7% carbamazepine, 91.3% bisphenol A (BPA), and 95.4% diclofenac (DCF) degradation efficiency were achieved within 10 min, 60, and 1 min, respectively. The hydrophobicity of these three pollutants is positively correlated with their adsorption kinetic constants by CD/Fe@ZIF-67 due to the introduction of β-CD. Scavenger experiments and electron spin resonance spectra confirmed that carbamazepine was preferentially oxidized by SO4•- [λ(SO4•-)(70.5%) > λ(•OH)(28.2%) > λ(O2•-)(1.3%)], where SO4•- and O2•- played dominant roles in the degradation of BPA [λ(SO4•-)(71.7%) > λ(O2•-)(22.8%) > λ(•OH)(5.5%)], and O2•- was responsible for DCF removal [λ(O2•-) = 93.2%]. Additionally, the particulate catalyst was immobilized in the shell side of a ceramic membrane in a membrane reactor for catalyst recovery. This reactor achieved nearly 100% removal efficiency under optimal conditions: 0.036 wt % catalyst loading, 0.5 mM peroxymonosulfate concentration, 1 L inflow, 10 mg/L initial carbamazepine concentration, and 0.012 L/min hydraulic retention time. In summary, this study elucidates the active role of β-CD in a polymetallic/peroxymonosulfate system and provides valuable insights into the development of effective oxidation methods for pharmaceutical and personal care products in wastewater.

Catalytic ozonation of reverse osmosis membrane concentrates by catalytic ozonation: Properties and mechanisms

Ni-Mn@KL ozone catalyst was prepared for the efficient treatment of reverse osmosis membrane concentrates. The working conditions and reaction mechanism of the ozone-catalyzed oxidation by Ni-Mn@KL were systematically studied. Then, a comprehensive CRITIC weighting-coupling coordination evaluation model was established. Ni-Mn@KL was characterized by scanning electron microscopy, BET, X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive spectrometry, and X-ray fluorescence spectrometry and found to have large specific surface area and homogeneous surface dispersion of striped particles. Under the optimum working conditions with an initial pH of 7.9 (raw water), a reaction height-to-diameter ratio of 10:1, an ozone-aeration intensity of 0.3 L/min, and a catalyst filling rate of 10%, the maximum COD removal rate was 60.5%. Free-radical quenching experiments showed that OH oxidation played a dominant role in the Ni-Mn@KL-catalyzed ozone-oxidation system, and the reaction system conformed to the second-order reaction kinetics law. Ni-Mn@KL catalysts were further confirmed to have good catalytic performance and mechanical performance after repeated utilization. PRACTITIONER POINTS: Ni-Mn@KL catalyst can achieve effective treatment of RO film concentrated liquid. High COD removal rate of RO membrane concentrated liquid was obtained at low cost. Ni-Mn@KL catalyst promotes ozone decomposition to produce ·OH and O2 -· oxidized organic matter. The Ni-Mn@KL catalyst can maintain good stability after repeated use. A CRITIC weight-coupling coordination model was established to evaluate the catalytic ozonation.

Efficient degradation of venlafaxine using intimately coupled high-active crystal facets exposed TiO2 and biodegradation system: Kinetic studies, biofilm stress behavior and transformation mechanism

Intimately coupled photocatalysis and biodegradation (ICPB) system is a potential wastewater treatment technology, of which TiO2-based ICPB system has been widely studied. There are many ways to improve the degradation efficiency of the ICPB process, but no crystal facet engineering method has been reported yet. In this work, a new ICPB system coated with NaF-TiO2 exposing high energy facets was designed to degrade biorecalcitrant psychotropic drug - venlafaxine (VNF). Initially, the TiO2 crystal surface was modified with NaF, resulting in the formation of NaF-TiO2 with a 14.4% increase in the exposure ratio of (001). The contribution rate of ·OH was increased by 9.5%, and the contribution rate of h+ was increased by 33.2%. Next, NaF-TiO2 was loaded onto the surface of the sponge carrier, and then the ICPB system was constructed after about 15 days of biofilm formation. After the ICPB system was acclimated with VNF, the removal rate of COD decreased significantly (the lowest was 62.7%), but that of ammonia nitrogen remained at 50.5 ± 6.0% and the extracellular polymeric substance (EPS) secretion increased by 84.1 mg/g VSS. According to the high throughput results, at the phylum level, Proteobacteria and Chloroflexi together maintain the nitrogen removal capability and structural stability of the ICPB system. The relative abundance of Bacteroidota was significantly increased by 14.2%, suggesting that there may be some correlation between Bacteroidota and certain metabolites of the anti-depressant active ingredients. At the genus level, the Thauera (3.1%∼11.5%) is the major bacterial group that secretes EPS, protecting biofilm against external influences. Most of the changes in microorganisms are consistent with the decontamination properties and macroscopic appearance of EPS in the ICPB system. Finally, the degradation efficiency of ICPB system for VNF was investigated (92.7 ± 3.8%) and it was mostly through hydroxylation and demethylation pathways, with more small molecular products detected, providing the basis for biological assimilation of VNF. Collectively, the NaF-TiO2 based ICPB system would be lucrative for the future degradation of venlafaxine.

Tungsten-based nanocatalysts with different structures for visible light responsive photocatalytic degradation of bisphenol A

Environmental pollution, such as water contamination, is a critical issue that must be absolutely addressed. Here, three different morphologies of tungsten-based photocatalysts (WO3 nanorods, WO3/WS2 nanobricks, WO3/WS2 nanorods) are made using a simple hydrothermal method by changing the solvents (H2O, DMF, aqueous HCl solution). The as-prepared nanocatalysts have excellent thermal stability, large porosity, and high hydrophilicity. The results show all materials have good photocatalytic activity in aqueous media, with WO3/WS2 nanorods (NRs) having the best activity in the photodegradation of bisphenol A (BPA) under visible-light irradiation. This may originate from increased migration of charge carriers and effective prevention of electron‒hole recombination in WO3/WS2 NRs, whereby this photocatalyst is able to generate more reactive •OH and •O2- species, leading to greater photocatalytic activity. About 99.6% of BPA is photodegraded within 60 min when using 1.5 g/L WO3/WS2 NRs and 5.0 mg/L BPA at pH 7.0. Additionally, the optimal conditions (pH, catalyst dosage, initial BPA concentration) for WO3/WS2 NRs are also elaborately investigated. These rod-like heterostructures are expressed as potential catalysts with excellent photostability, efficient reusability, and highly active effectivity in different types of water. In particular, the removal efficiency of BPA by WO3/WS2 NRs reduces by only 1.5% after five recycling runs and even reaches 89.1% in contaminated lake water. This study provides promising insights for the nearly complete removal of BPA from wastewater or different water resources, which is advantageous to various applications in environmental remediation.

Cobalt-aluminum spinel supported on modified γ-alumina for peroxymonosulfate activation: Si-Al ratio of support to optimize performance and reusability

The development of cobalt-based supported catalysts with high PMS catalytic activity and stability by adjusting the composition of the support is highly desirable yet remains scarce. In the work, a series of catalysts (Co2AlO4/Al2O3-xSiO2) were prepared by impregnation and high-temperature calcination using Al2O3-xSiO2 with a low Si-Al ratio as the support. Measurement techniques such as XRD, XPS, UV-DRS, FTIR, BET, SEM and HRTEM were used to characterize textural and chemical properties (ratio of Co3+/Co2+, specific surface area, pore size, pore volume, etc.). The ratio of Co3+/Co2+ and pore volume of Co2AlO4/Al2O3-xSiO2 can be turned by controlling the ratio of Si to Al, which are closely related to the catalytic performance and reusability of the catalysts. The optimized catalyst (Co2AlO4/Al2O3-0.25SiO2) can completely degrade 10 mg/L p-nitrophenol (PNP) in 40 min in the pH range of 3-9 with excellent reusability. The effects of several reaction parameters (i.e., PMS dosage, Co2AlO4/Al2O3-0.25SiO2 dosage, reaction temperature, initial pH value, and inorganic ions) on PNP removal were comprehensively investigated. Sulfate radical (SO4•-) and singlet oxygen (1O2) are making a major contribution to the degradation of PNP. Moreover, a millimeter-scale catalyst (CoSiAl-0.25/Al2O3 pellet) was prepared by sol adsorption and high-temperature calcination method, which maintained high oxidation activity after treatment of 18 L wastewater (PNP of 10 mg/L) in a continuous flow process. The method is simple and easy to operate on a large scale, providing a new perspective on the design and preparation of cobalt-aluminum spinel catalysts for activated PMS.