The effect on ozone catalytic performance of prepared-FeOOH by different precursors

Electrochemical reconfiguration of iron-modified Ni3S2 surface induced oxygen vacancies to immobilize sulfate for enhanced oxygen evolution reaction

There is an urgent need for highly active, durable, and low-cost electrocatalysts to overcome the shortcomings of high overpotential in the oxygen evolution reaction (OER) process. In this work, the nickel-iron hydroxysulfate rich in sulfate and oxygen vacancies (SO42-@Fe-NiOOH-Ov/NiS) is legitimately constructed. SO42-@Fe-NiOOH-Ov/NiS only requires a low overpotentials of 190 mV and 232 mV at 10 mA cm-2 and 100 mA cm-2 current densities in 1 M KOH, with excellent stability for 200 h at 100 mA cm-2 current density. In situ Raman spectroscopy and Fourier transform infrared spectroscopy demonstrated the stable adsorption of more SO42- on the surface of catalyst. Density functional theory calculations testify surface reconstruction, doped Fe and oxygen vacancies significantly reduced the adsorption energy of sulfate on the surface. More importantly, the formation of *OOH to O2 is facilitated by the highly hydrogen bonding between SO42- and *OOH, accelerating the OER process.

Preparation and characterization of cellulose-chitosan/β-FeOOH composite hydrogels for adsorption and photocatalytic degradation of methyl orange

Biopolymer-based hydrogels have received great attention in wastewater treatment due to their excellent properties, e.g., high adsorption capacity, fast kinetics, reusability and ease of operation. In the present work, cellulose-chitosan/β-FeOOH composite hydrogels were prepared via co-dissolution and regeneration process as well as hydrothermal in situ synthesis of β-FeOOH. Effect of β-FeOOH loading on the properties of the composite hydrogels and the removal efficiency of methyl orange (MO) was investigated. Results showed that β-FeOOH was uniformly loaded onto the hydrogel framework, and the nanoporous structure of composite hydrogels could increase not only the effective contact area between β-FeOOH and the pollutants but also the active sites. Moreover, the increased β-FeOOH loading led to the enhanced MO removal rate under light conditions. When the loading time was extended from 6 h to 9 h, the MO removal rate increased by 21%, which can be mainly due to the photocatalytic degradation. In addition, MO removal rate reached 97.75% within 40 min under optimal conditions and attained 80.81% after five repetitions. The trapping experiment and EPR results indicated that the main active species were hydrogel radicals and holes. Consequently, this work provides an effective preparation approach for cellulose-chitosan/β-FeOOH composite hydrogel with high adsorption and photocatalytic degradation, which would hold great promise for wastewater treatment applications.

High-Efficiency Photo-Fenton-like Catalyst of FeOOH/g-C3N4 for the Degradation of PNP: Characterization, Catalytic Performance and Mechanism Exploration

The composite photocatalyst FeOOH/g-C3N4 was prepared through thermal polycondensation and co-precipitation methods, followed by XRD, SEM and UV-vis characterization. The stability of FeOOH/g-C3N4 was explored by the recycling test. The active species in the reaction system were investigated by the capture experiment. The results indicated that the optimal preparation condition for g-C3N4 involved calcination at 600 °C for 4 h. XRD analysis revealed that g-C3N4 exhibits a high-purity phase, and Fe in FeOOH/g-C3N4 exists in a highly dispersed amorphous state. SEM analysis showed that FeOOH/g-C3N4 has a rough surface with an irregular layered structure. Element composition analysis confirmed that the content of elements in the prepared catalyst is consistent with the theoretical calculation. FeOOH/g-C3N4 possesses the largest specific surface area of 143.2 m2/g and a suitable pore distribution. UV-vis DRS analysis showed that the absorption intensity of FeOOH/g-C3N4 is stronger than that of g-C3N4. When the catalyst dosage was 1.0 g/L, the H2O2 dosage was 4 mmol/L, the PNP initial concentration was 10 mg/L and the initial pH value was 5, the PNP removal could reach 92% in 120 min. Even after 5 cycles, the efficiency of PNP removal by FeOOH/g-C3N4 remains nearly 80%. The capture experiment indicated that both •OH and •O2- play roles in the photocatalytic degradation of PNP, with •OH being more significant. These findings affirm that FeOOH has been successfully incorporated into g-C3N4, resulting in a conspicuous catalytic effect on the degradation of PNP in the visible light-assisted Fenton-like reaction.

Effects of operating conditions on iron (hydr)oxides evolution and ciprofloxacin degradation in potassium ferrate-ozone stepwise oxidation system

In this study, a stepwise oxidation system of potassium ferrate (K2FeO4) combined with ozone (O3) was used to degrade ciprofloxacin (CIP). The effects of pH and pre-oxidation time of K2FeO4 on the evolution of K2FeO4 reduction products (iron (hydr)oxides) and CIP degradation were investigated. It was found that in addition to its own oxidation capacity, K2FeO4 can also influence the treatment effect of CIP by changing the catalyst content. The presence of iron (hydr)oxides effectively enhanced the mineralization rate of CIP by catalyzing ozonation. The pH value can influence the content and types of the components with catalytic ozonation effect in iron (hydr)oxides. The K2FeO4 pre-oxidation stage can produce more iron (hydr)oxides with catalytic components for subsequent ozonation, but the evolution of iron (hydr)oxides components was influenced by O3 treatment. It can also avoid the waste of oxidation capacity owing to the oxidation of iron (hydr)oxides by O3 and free radicals. The intermediate degradation products were identified by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Besides, the degradation pathways were proposed. Among the degradation products of CIP, the product with broken quinolone ring structure only appeared in the stepwise oxidation system.

Fe3O4@uio66 core-shell composite for detection of electrolyte leakage from lithium-ion batteries

Fe₃O₄is an environmentally friendly gas sensing material with high response, but the cross-response to various analytes and poor thermal stability limit its practical applications. In this work, we prepared Fe₃O₄@uio66 core-shell composite via a facile method. The selective response to volatile organic compounds, especially to electrolyte vapors of lithium-ion batteries, as well as long-term stability of Fe₃O₄@uio66 has been dramatically enhanced compared to pure Fe₃O₄, due to the preconcentrator feature and thermal stability of the uio66 thin shell. Real-time detection of electrolyte leakage for an actual punctured lithium-ion battery was further demonstrated. The Fe₃O₄@uio66 sensor, after aging for 3 months, was able to detect the electrolyte leakage in 30 s, while the voltage of the punctured battery was maintained at the same level as that of a pristine battery over 6 h. This practical test results verified ability of the Fe₃O₄@uio66 sensor with long-term aging stability for hours of early safety warning of lithium-ion batteries.

Vortex-assisted dispersive solid phase microextraction using Fe3O4/FeOOH magnetic nanocomposites for high-performance thin-layer chromatographic determination of zolmitriptan in rabbit plasma samples

In this work, a fast, versatile, and convenient dispersive solid-phase micro-extraction (DSPME) method is combined with a spectro-densitometric technique for the analysis of zolmitriptan (ZOLM) in biological fluids. Fe₃O₄/FeOOH magnetic nanocomposites (MNCs) were prepared by a co-precipitation method in aqueous solutions and utilized subsequently as a sorbent in DSPME. By coupling DSPME with high-performance thin-layer chromatography (HPTLC) with fluorescence detection, the preconcentration and determination of (ZOLM) in presence of metoclopramide (MET) and paracetamol (PARA), which are prescribed as an adjuvant therapy with ZOLM, was accomplished. Adsorption capability was assessed using both Langmuir and Freundlich adsorption isotherm models. The adsorption data was fitted to Langmuir adsorption isotherm model as reflected by high determination coefficient (R² = 0.9944). Moreover, adsorption kinetics was assessed by pseudo-first and pseudo-second order kinetic models. The data was fitted to pseudo-second order kinetics, which proves that ZOLM interaction with the adsorbent is a chemisorption process. Surface complexation with MNCs was suggested to explain the pH dependence of ZOLM sorption. The key parameters of extraction and desorption steps (including pH, extraction time, sample volume, magnetic adsorbent amount, and desorption circumstances) were evaluated. Optimized conditions for solid phase microextraction of ZOLM were pH 2.9, 5.0 mg Fe₃O₄/FeOOH MNCs, 15 min vortex-assisted extraction time and 3 × 200 μL of methanol: 33% ammonia; 4:1 as eluent. The analysis was achieved using ACN: dichloromethane: 33% ammonia (22.5: 6.0: 1.5, v/v/v) as a mobile phase and the fluorescence detection was carried out at 223 nm. The proposed DSPME method was successfully applied for trace quantification of ZOLM in rabbits' plasma (n = 6) after oral administration with a linearity range of 50.0 - 400.0 ng mL^-1 (R² = 0.9931), a detection limit of 12.0 ng mL^-1 and extraction recovery of 97.27-99.89% with an RSD < 2% (n = 9). Moreover, the selectivity of the proposed approach for analysis of ZOLM in the presence of MET and PARA is demonstrated.

Catalytic effect of γ-Al(OH)3, α-FeOOH, and α-Fe2O3 on the ozonation-based decomposition of diethyl phthalate adsorbed on sand and soil

Diethyl phthalate (DEP) is a pollutant which can be found on soils as a result of its widespread application in plastic industry. Soil contaminated with DEP requires the application of different chemical methods to attain its remediation. Among these methods, ozonation has proven to be effective against toxic soil pollutants. The presence of metal oxides in soil is a possible source of catalytic effect. In this study, it was analyzed the catalytic effect of goethite (α-FeOOH), hematite (α-Fe₂O₃), and gibbsite (γ-Al(OH)₃) in combination with O₃ to achieve DEP decomposition. The DEP elimination efficiency by ozonation on the sand increased according to the following order: without catalyst < γ-Al(OH)₃ < α-Fe₂O₃ < α-FeOOH. Among these three oxides, goethite has the highest OH groups density. The reaction of OH groups and O₃ favors the formation of oxidant species, such as O₂•^- and OH•. The effect of the moisture content, the catalyst concentration, and the type of soil (sand and calcined soil) were also studied. The latter had a significant influence on the total organic carbon (TOC) removal. The mineralization degree was 84% in the O₃-soil system, while only 40% was obtained with O₃-sand (α-FeOOH) in dry sand after 8 h of treatment. Calcined soil promoted the increase of TOC removal due to the presence of different metal oxides, which were active centers for O₃ decomposition. The toxicity tests of the three reaction systems (O₃-sand, O₃-sand (α-FeOOH), and O₃-soil) were evaluated on lettuce seed germination before and after DEP ozonation.

Catalytic ozonation for water and wastewater treatment: Recent advances and perspective

Ozonation process has been widely applied in water and wastewater treatment, such as for disinfection, for degradation of toxic organic pollutants. However, the utilization efficiency of ozone is low and the mineralization of organic pollutants by ozone oxidation is ineffective, and some toxic disinfection byproducts (DBPs) may be formed during ozonation process. Catalytic ozonation process can overcome these problems to some extent, which has received increasing attention in recent years. During catalytic ozonation, catalysts can promote O₃ decomposition and generate active free radicals, which can enhance the degradation and mineralization of organic pollutants. In this paper, the history of ozonation application in water treatment was briefly reviewed. The properties of the ozone molecule, the ozonation types and several ozone-based water treatment processes were briefly introduced. Various catalysts for catalytic ozonation, including homogeneous and heterogeneous catalysts, such as metal ions, metal oxidizes, carbon-based materials and their possible catalytic mechanisms were analyzed and summarized in detail. Furthermore, some inconsistent results of previous research on catalytic ozonation were analyzed and discussed. The application of catalytic oxidation for the degradation of toxic organic pollutants, including phenols, pesticides, dyes, pharmaceuticals and others, was summarized. Finally, several key aspects of catalytic ozonation, such as pH effect, the catalyst performance, the catalytic mechanism were proposed, to which more attention should be paid in future study.

Application of Heterogeneous Catalytic Ozonation for Refractory Organics in Wastewater

Catalytic ozonation is believed to belong to advanced oxidation processes (AOPs). Over the past decades, heterogeneous catalytic ozonation has received remarkable attention as an effective process for the degradation of refractory organics in wastewater, which can overcome some disadvantages of ozonation alone. Metal oxides, metals, and metal oxides supported on oxides, minerals modified with metals, and carbon materials are widely used as catalysts in heterogeneous catalytic ozonation processes due to their excellent catalytic ability. An understanding of the application can provide theoretical support for selecting suitable catalysts aimed at different kinds of wastewater to obtain higher pollutant removal efficiency. Therefore, the main objective of this review article is to provide a summary of the accomplishments concerning catalytic ozonation to point to the major directions for choosing the catalysts in catalytic ozonation in the future.