Anchoring Fe3O4 Nanoparticles on Carbon Nanotubes for Microwave-Induced Catalytic Degradation of Antibiotics

Magnetic Fe-doped silicon carbide induced microwave activated persulfate for decabromodiphenyl ether removal: Mechanism and unique degradation pathway

In this work, the magnetic nanocomposite Fe@SiC was prepared by a hydrothermal method and determined by SEM, XRD, XPS, FTIR and VNA. Fe3O4 particles were loaded onto SiC with great success, and the synthesized composites had favorable microwave absorption properties. Fe@SiC was used to activate persulfate in a microwave field for the degradation of BDE209 in soil. Specifically, the synergistic interaction between microwaves and Fe@SiC showed excellent catalytic performance in activating PS to degrade BDE209 (90.1% BDE209 degradation in 15 min). The presence of •OH, O2•- and 1O2 was demonstrated based on quench trapping and EPR experiments. LC‒MS was applied to determine the intermediates and propose the possible degradation pathway for BDE209 in the MW/Fe@SiC/PS system, and it was found that BDE209 produced almost no lower brominated diphenyl ethers. Therefore, the toxicity of BDE209 was found to be reduced using toxicity assessment software. Overall, this work provides an effective approach for the degradation of BDE209 in environmental remediation.

Enhanced Adsorption and Evaluation of Tetracycline Removal in an Aquatic System by Modified Silica Nanotubes

In the present study, a nanocomposite adsorbent based on mesoporous silica nanotubes (MSNTs) loaded with 3-aminopropyltriethoxysilane (3-APTES@MSNTs) was synthesized. The nanocomposite was employed as an effective adsorbent for the adsorption of tetracycline (TC) antibiotics from aqueous media. It has an 848.80 mg/g maximal TC adsorption capability. The structure and properties of 3-APTES@MSNT nanoadsorbent were detected by TEM, XRD, SEM, FTIR, and N₂ adsorption-desorption isotherms. The later analysis suggested that the 3-APTES@MSNT nanoadsorbent has abundant surface functional groups, effective pore size distribution, a larger pore volume, and a relatively higher surface area. Furthermore, the influence of key adsorption parameters, including ambient temperature, ionic strength, initial TC concentration, contact time, initial pH, coexisting ions, and adsorbent dosage, had also been investigated. The 3-APTES@MSNT nanoadsorbent's ability to adsorb the TC molecules was found to be more compatible with Langmuir isothermal and pseudo-second-order kinetic models. Moreover, research on temperature profiles pointed to the process' endothermic character. In combination with the characterization findings, it was logically concluded that the 3-APTES@MSNT nanoadsorbent's primary adsorption processes involved interaction, electrostatic interaction, hydrogen bonding interaction, and the pore-fling effect. The synthesized 3-APTES@MSNT nanoadsorbent has an interestingly high recyclability of >84.6 percent up to the fifth cycle. The 3-APTES@MSNT nanoadsorbent, therefore, showed promise for TC removal and environmental cleanup.

Effective degradation of tetracycline via recyclable cellulose nanofibrils/polyvinyl alcohol/Fe3O4 hybrid hydrogel as a photo-Fenton catalyst

In this work, the method of in-situ co-precipitation was used to prepare PVA/CNF/Fe₃O₄ hybrid hydrogel, and the relationship between its structure and performance was explored. The Fe₃O₄NPs prepared by this method were dispersed on the carrier PVA/CNF hydrogel and were easy to recover. The catalytic degradation of tetracycline was investigated using PVA/CNF/Fe₃O₄ hybrid hydrogel as photo-Fenton catalysts. The results showed that light and hydrogel carriers were pivotal factors in promoting Fe²⁺ and Fe³⁺ cycling and that the PVA/CNF/Fe₃O₄ hybrid hydrogel as catalysts were able to activate H₂O₂ to generate a large amount of oxygen radical •OH, resulting in efficient removal of tetracycline. The tetracycline degradation followed a proposed first-order kinetic model and achieved a removal rate of about 98% in 120 min at an optimum pH of 3, H₂O₂ 100 mM, catalyst 0.3 g/L, and a temperature of 25 °C.

Atomic sheets of silver ferrite with universal microwave catalytic behavior

Prompt degradation of organic pollutants renders microwave (MW) catalysis technology extremely lucrative; ideal microwave catalysts are therefore being hunted with an unprecedented urgency. Ideal functional microwave catalyst should be highly crystalline, room temperature ferromagnetic (for magnetic retrieval), highly dielectric (for sufficient microwave absorption) apart from being structurally stable at high temperature. The potential of silver ferrite 2D sheets (2D AFO) synthesized using a novel microwave technique as a microwave catalyst for the degradation of a variety of organic dyes and antibiotics was investigated in this article. While organic dyes like malachite green (MG), brilliant green (BG) and nile blue A (NB) achieved 99.2%, 98.8% and 95.2%, respectively; antibiotic tetracycline hydrochloride (TCH) molecule resulted in 75.8% degradation efficiency. Total organic carbon (TOC) measurements yielded 76%, 59.1%, 49.1% and 47.6% of carbon content for MG, BG, NB and TCH, respectively. The reaction pathway via intermediates and subsequent degradation to CO₂ and H₂O is revealed by liquid chromatography-mass spectrometry (LCMS). Both superoxide and hydroxyl radicals are participating in the process, according to scavenger tests. The evolution of silver ferrite as a new 2D material and its demonstration as an ideal microwave catalyst will lead to a new beginning in catalysis science and technology.

Preparation of Three-Dimensional Mo2C/NC@MXene and Its Efficient Electromagnetic Absorption Properties

The positively charged MoO₃/PDA microspheres are obtained by stacking and assembly of the sheet structure, and the negatively charged MXene nanosheets are wrapped on the surface through the principle of electrostatic self-assembly. After annealing, a nitrogen-doped carbon composite and a MXene-coated Mo₂C wave absorber are obtained. The formation of the wrinkled surface provides a complex pore structure, and the multiple interface reflections between the nanosheets enhance the absorption performance. The existence of heterogeneous interfaces and the uneven distribution of space charges accumulated between the interfaces effectively reduce the minimum reflection loss (RL_min). This work explores the effects of the ratio between MoO₃/PDA and MXene nanosheets and loading amount on the microwave absorption properties. Mo₂C/NC@MXene-2 obtained when the ratio of the two is 3:1 has the best absorption performance under 25% loading. The RL_min is -59.36 dB, and the corresponding effective absorption bandwidth (EAB) is 4.6 GHz at 2.5 mm. This work expands the new applications of MXene-based and Mo₂C-based materials and has a guiding significance for the design of electrostatic self-assembly materials.

Facile and Efficient Photocatalyst for Degradation of Chlortetracycline Promoted by H2O2

The composite photocatalyst based on a cerium (III) metal-organic framework (MOF-1 or 1), graphene oxide (GO), and Fe3O4 was constructed for the first time and was investigated for the degradation...

Sustainable chemical processing of flowing wastewater through microwave energy

Iron oxide nanostructured catalysts have emerged as potential candidates for efficient energy conversion and electrochemical energy storage devices. However, synthesis and design of nanomaterial plays a key role in its performance and efficiency. Herein, we describe a one-pot solution combustion synthesis (SCS) of α-Fe₂O₃ with glycine as a fuel, and a subsequent reduction step to produce iron-containing catalysts (i.e., Fe₃O₄, Fe-Fe₃O₄, and Fe⁰). The synthesized iron-based nanoparticles were investigated for methyl orange (MO) degradation through Microwave (MW) energy under continuous flow conditions. Fe-Fe₃O₄ showed higher MO degradation efficiency than α-Fe₂O₃, Fe₃O₄ and Fe⁰ at low absorbed MW power (i.e. 5-80 W). The enhanced degradation efficiency is associated to the combination of higher availability of electron density and higher heating effect under MW energy. Investigation of dielectric properties showed relative dielectric loss of Fe₃O₄, Fe-Fe₃O₄, and Fe⁰ as 3847, 2010, and 1952, respectively. The calculated average local temperature by the comparative analysis of MW treatment with conventional thermal (CT) treatment showed a marked thermal effect of MW-initiated MO degradation. This work highlights the potential of microwave-driven water depollution under continuous-flow processing conditions and demonstrates the positive impact that earth-abundant Fe catalyst synthesized by green SCS method can have over the treatment of wastewater.

Microwave synthesized strontium hexaferrite 2D sheets as versatile and efficient microwave catalysts for degradation of organic dyes and antibiotics

Microwave catalysis is extremely lucrative due to prompt mineralization and superior efficiency. Ideal microwave catalysts should possess crystalline nature, large surface area, room temperature ferromagnetic, high dielectric properties apart from structural stability at elevated temperature. In the present article, the candidature of microwave synthesized strontium hexaferrite 2D sheets (2D SFO) has been explored as microwave catalysts for the degradation of a host of organic dyes and antibiotics. Malachite green (MG) and nile blue A (NB) in particular exhibited 99.8% and 97.6% degradation, respectively. Degradation reaction is established to follow pseudo-second-order kinetics. Total organic carbon (TOC) measurements hint at 52% and 60% mineralization for MG and NB, respectively. Liquid chromatography-mass spectroscopy (LCMS) measurements indicate the reaction pathways via intermediates and eventual mineralization to CO₂ and H₂O. Mott-Schottky measurements along with scavenger tests hint that both hydroxyl and superoxide radicals participate in the reaction. Having superior efficiency apart from the versatile nature of the 2D SFO microwave catalyst, the present research will guide to the emergence of microwave catalysis as a new technology.

Microwave-assisted high-efficiency degradation of methyl orange by using CuFe2O4/CNT catalysts and insight into degradation mechanism

Microwave-assisted catalytic oxidation technology has become an effective technology for rapid removal of organic pollutants in wastewater. In this research, the removal of methyl orange (MO) from aqueous solution by CuFe₂O₄ loaded on carbon nanotubes (CuFe₂O₄/CNTs) under microwave irradiation was studied. The effects of different loadings (1:2, 1:4, 1:8) of CuFe₂O₄ on the dielectric loss, magnetic loss, dielectric loss factor, magnetic loss factor, and reflection loss of composite materials were studied. The results showed that the microwave adsorption performance was improved by loading CuFe₂O₄ on CNTs. These different composites were further characterized by SEM, FTIR, and XRD techniques. In addition, this article also studied the effects of different microwave irradiation time, pH, and ionic factors on the degradation of MO. In particular, the mechanism of MO degradation by composite materials under different pH conditions was also studied in detail. The results showed that the removal rate reaches 97% with 5 min under the best conditions, and the composite material had good anti-interference performance. This study may provide a new option to degrade organic dye in wastewater treating.

Fabrication of one dimensional hierarchical WO3/BiOI heterojunctions with enhanced visible light activity for degradation of pollutants

One-dimensional (1D) hierarchical WO₃/BiOI p–n (WB) heterojunctions with different mass percentages of WO₃ were fabricated through a precipitation process. Various analytical techniques were employed to characterize the resulting WB composites, and their photocatalytic properties were measured by the degradation of rhodamine B (RhB) and methylene blue (MB) under irradiation of visible light. The WB heterojunctions showed largely enhanced photocatalytic performance as compared to the pure photocatalysts. Notably, the degradation rate constant of RhB by WB-10 was 3.3 and 33.6 times higher than those of pure BiOI and WO₃, respectively. The enhanced activity could be attributed to the hierarchical p–n heterostructures, which can supply more reaction sites and effectively promote the separation of photogenerated charge carriers, as confirmed by PL and photocurrent. Trapping experiments implied that holes (h⁺) and superoxide anion radicals (˙O₂⁻) were the dominant active species for organic pollutants decomposition on the WB composites. This work may benefit the construction of hierarchical heterostructures with high photocatalytic efficiency.

One-dimensional (1D) hierarchical WO₃/BiOI p–n (WB) heterojunctions with different mass percentages of WO₃ were fabricated through a precipitation process.

Sustainable plant and microbes-mediated preparation of Fe3O4 nanoparticles and industrial application of its chitosan, starch, cellulose, and dextrin-based nanocomposites as catalysts

Iron oxide nanoparticles (Fe₃O₄ NPs) attracted significant scientific interest, considering their immense diversity of usage and biocompatibility. Perceiving the growing importance of sustainable chemistry, many efforts have been made to prepare these NPs using naturally occurring materials mostly plant extracts and microbes. Magnetic NPs (MNPs) are commonly used as composites and are considered in two matters: synthesis and modification of their functional groups. Biopolymeric nanocomposites are a group of hybrid materials composed of natural polymers and inorganic nanomaterials. Biopolymers such as alginate, cellulose, starch, gelatin, chitosan, etc. have been considered extensively and provided composites with better electrical and mechanical thermal properties. Fe₃O₄ NPs incorporated in a polymer and biopolymer matrix is a good instance of the functional nanostructure, which has been able to enhance the properties of both ingredients. These hybrids can have impressive applications in various scopes such as magneto-optical storage, electromagnetic interference shielding, catalyst, water remediation, biomedical sensing, and so on. In this study, we have tried to briefly introduce Fe₃O₄ NPs, investigate the green and sustainable methods that have been suggested for its synthesis and review recent utilization of their biopolymeric nanocomposite (NC) including starch, chitosan, dextrin, etc. as catalysts and photocatalysts.

Adsorption, degradation, and mineralization of emerging pollutants (pharmaceuticals and agrochemicals) by nanostructures: a comprehensive review

This review discusses a fresh pool of research findings reported on the multiple roles played by metal-based, magnetic, graphene-type, chitosan-derived, and sonicated nanoparticles in the treatment of pharmaceutical- and agrochemical-contaminated waters. Some main points from this review are as follows: (i) there is an extensive number of nanoparticles with diverse physicochemical and morphological properties which have been synthesized and then assessed in their respective roles in the degradation and mineralization of many pharmaceuticals and agrochemicals, (ii) the exceptional removal efficiencies of graphene-based nanomaterials for different pharmaceuticals and agrochemicals molecules support arguably well a high potential of these nanomaterials for futuristic applications in remediating water pollution issues, (iii) the need for specific surface modifications and functionalization of parent nanostructures and the design of economically feasible production methods of such tunable nanomaterials tend to hinder their widespread applicability at this stage, (iv) supplementary research is also required to comprehensively elucidate the life cycle ecotoxicity characteristics and behaviors of each type of engineered nanostructures seeded for remediation of pharmaceuticals and agrochemicals in real contaminated media, and last but not the least, (v) real wastewaters are extremely complex in composition due to the mix of inorganic and organic species in different concentrations, and the presence of such mixed species have different radical scavenging effects on the sonocatalytic degradation and mineralization of pharmaceuticals and agrochemicals. Moreover, the formulation of viable full-scale implementation strategies and reactor configurations which can use multifunctional nanostructures for the effective remediation of pharmaceuticals and agrochemicals remains a major area of further research.

A Case Study of Waste Scrap Tyre-Derived Carbon Black Tested for Nitrogen, Carbon Dioxide, and Cyclohexane Adsorption

Waste scrap tyres were thermally decomposed at the temperature of 600 °C and heating rate of 10 °C·min^-1. Decomposition was followed by the TG analysis. The resulting pyrolytic carbon black was chemically activated by a KOH solution at 800 °C. Activated and non-activated carbon black were investigated using high pressure thermogravimetry, where adsorption isotherms of N₂, CO₂, and cyclohexane were determined. Isotherms were determined over a wide range of pressure, 0.03-4.5 MPa for N₂ and 0.03-2 MPa for CO₂. In non-activated carbon black, for the same pressure and temperature, a five times greater gas uptake of CO₂ than N₂ was determined. Contrary to non-activated carbon black, activated carbon black showed improved textural properties with a well-developed irregular mesoporous-macroporous structure with a significant amount of micropores. The sorption capacity of pyrolytic carbon black was also increased by activation. The uptake of CO₂ was three times and for cyclohexane ten times higher in activated carbon black than in the non-activated one. Specific surface areas evaluated from linearized forms of Langmuir isotherm and the BET isotherm revealed that for both methods, the values are comparable for non-activated carbon black measured by CO₂ and for activated carbon black measured by cyclohexane. It was found out that the N₂ sorption capacity of carbon black depends only on its specific surface area size, contrary to CO₂ sorption capacity, which is affected by both the size of specific surface area and the nature of carbon black.

One-step electrochemical sensor based on an integrated probe toward sub-ppt level Pb2+ detection by fast scan voltammetry

Herein, a one-step electrochemical sensor for selective and sensitive detection of lead ion Pb²⁺ was developed based on an integrated probe meso-tetra(4-carboxyphenyl) porphine (TCPP)-multi-walled carbon nanotubes (MWCNTs)@Fe₃O₄, which is TCPP-modified magnetic multi-walled carbon nanotubes. In the integrated probe, TCPP is a porphyrin with a specific cavity structure which could selectively chelate with Pb²⁺, MWCNTs with good electric conductivity provide a place to load TCPP and form a specific adsorption state of Pb²⁺ on the electrode surface, and Fe₃O₄ enables the rapid separation and one-step fabrication of the electrochemical sensor. Based on it, the sample pre-enrichment, separation and determination can be integrated, making the whole process very fast and simple. In addition, fast scan voltammetry (FSV) with a scan rate up to 200 V/s could be used to improve the detection sensitivity greatly, benefitting from the specific adsorption state formed. Under the optimal conditions obtained through orthogonal experiments including adsorption time, integrated probe dosage and solution pH, there was a good linear relationship between the peak current and Pb²⁺ concentration ranging from 2.0 × 10^-4 μg L^-1 to 2.0 × 10^-3 μg L^-1, with the limit of detection (LOD) being 6.7 × 10^-5 μg L^-1 (S/N = 3) i.e. 0.067 ppt. Analysis of actual water samples was successful. Therefore, being simple, fast, selective and sensitive, the one-step electrochemical sensor proposed has a good potential in practical applications.

Microwave-induced release and degradation of airborne antibiotic resistance genes (ARGs) from Escherichia coli bioaerosol based on microwave absorbing material

Antibiotic resistance genes (ARGs) have been detected in the atmosphere. Airborne ARGs transmission threatens human health. In the present study, we investigated the release and degradation of airborne ARGs from Escherichia coli bioaerosol through microwave (MW) irradiation. In this study, a new MW absorbing material (Fe₃O₄@SiC ceramic foam) that contributed to its stronger MW absorption is presented. When the MW input energy density was 7.4 × 10³ kJ/m³, the concentration of airborne Escherichia coli decreased by 4.4 log. Different DNA forms were found in the air because MW irradiation ruptured cell membranes. The bound particles provide more protection for bound DNA in the degradation process than free DNA. After the self-degradation of the released airborne free ARGs, some of them would remain and continue to spread in the atmosphere. The released airborne free ARGs cannot be ignored. Total ARGs concentrations decrease rapidly with increased temperature. The inactivation rate constant of ARGs through MW irradiation is higher than that through the Fenton and UV, however, the energy efficiency per order of MW irradiation is lower. Therefore, MW irradiation with Fe₃O₄@SiC ceramic foam could efficiently degrade the distribution of ARGs in the atmosphere.

Bifunctional reusable Co0.5Ni0.5Fe2O4 nanoparticle-grafted carbon nanotubes for aqueous dye removal from contaminated water

Highly stable and reusable CNF-grafted CNTs for efficient and effective aqueous dye removal from contaminated waters.

Synthesis of a Novel Catalyst MnO/CNTs for Microwave-Induced Degradation of Tetracycline

Microwave-induced catalytic degradation (MICD) has been considered as one of the most prospective approaches to remove organic contaminants from water. High-performance catalysts, ideally offering efficient degradation ability, are essential to this process. This work reports the fabrication of manganese oxide on carbon nanotubes (MnO/CNTs) as an efficient catalyst under microwave irradiation (MI) to remove tetracycline (TC) from aqueous solution. The hybrid MnO/CNTs structure shows excellent performance in TC degradation. Combining experimental characterization and theoretical calculations, synergistic mechanisms are revealed: (i) Strong MnO/CNTs interaction stabilizes Mn(II) through interfacial bonding; (ii) high-spin states associated with low coordinated Mn(II) play a major role in MICD; and (iii) superoxide radicals (•O2−) and hydroxyl radicals (•OH) induced by microwave input are identified as the major active species.

Preparation of FeOOH/Cu with High Catalytic Activity for Degradation of Organic Dyes

In this study, high-frequency electromagnetic-assisted ball-milling was used to prepare FeOOH/Cu catalyst. The combined effect of the high-frequency electromagnetic field and ball-milling resulted in the complete conversion of raw materials into FeOOH/Cu nanomagnetic hybrid at ~40 °C in only 30 h. Experiments showed that Rhodamine B was completely degraded within only 3 min, which was much faster than with previously reported catalysts. The combination effect of ball milling and microwave afforded excellent catalytic activity. Furthermore, the produced catalyst could be recovered easily using an external magnetic field for reuse. The influence of pH on the catalytic activity for degrading Rhodamine B, Phenol Red, Methyl Orange, and Methylene Blue were also investigated; Rhodamine B was completely degraded at pH 9 within only 2 min.