Sonochemical synthesis of Fe3O4/carbon nanotubes using low frequency ultrasonic devices and their performance for heterogeneous sono-persulfate process on inactivation of Microcystis aeruginosa

Magnetic iron oxides nanocomposites: synthetic techniques and environmental applications for wastewater treatment

Nanomaterials are an emerging class of compounds with potential to advance technology for wastewater treatment. There are many toxic substances in industrial wastewater that are dangerous to the aquatic ecosystem and public health. These pollutants require the development of novel techniques to remove them from the environment. Iron oxide nanoparticles are being studied and develop as new technology to address the problem of environmental pollution due to their unique properties and effectiveness against different kind of pollutants. A variety of modified iron oxide nanoparticles have been developed through extensive research that mitigates the shortcomings of aggregation or oxidation and enhances their efficiency as novel remediator against environmental pollutants. In this review, we present synthetic approaches used for the preparation of iron oxide nanoparticles and their corresponding nanocomposites, along with the processes in which the materials are used as adsorbent/photocatalysts for environmental remediation. Applications explored includes adsorption of dyes, photocatalytic degradation of dyes, and adsorption of heavy metal ions. The use of iron oxides nanocomposite in real wastewater samples and recyclability of adsorbents and photocatalysts were also explored.

Nitrogen doped bimetallic sludge biochar composite for synergistic persulfate activation: Reactivity, stability and mechanisms

As a recycling use of waste activated sludge (WAS), we used high-temperature pyrolysis of WAS to support bimetallic Fe-Mn with nitrogen (N) co-doping (FeMn@N-S), a customized composite catalyst that activates peroxysulphate (PS) for the breakdown of tetracycline (TC). First, the performance of TC degradation was evaluated and optimized under different N doping, pH, catalyst dosages, PS dosages, and contaminant concentrations. Activating PS with FeMn@N-S caused the degradation of 91% of the TC in 120 min. Next, characterization of FeMn@N-S by XRD, XPS and FT-IR analysis highlights N doping is beneficial to take shape more active sites and reduces the loss of Fe and Mn during the degradation reaction. As expected, the presence of Fe-Mn bimetallic on the catalyst surface increases the rate of electron transfer, promoting the redox cycle of the catalyst. Other functional groups on the catalyst surface, such as oxygen-containing groups, accelerated the electron transfer during PS activation. Free radical quenching and ESR analysis suggest that the main contributor to TC degradation is surface-bound SO₄^•-, along with the presence of single linear oxygen (¹O₂) oxidation pathway. Finally, the FeMn@N-S composite catalyst exhibits excellent pH suitability and reusability, indicating a solid practicality of this catalyst in PS-based removal of antibiotics from wastewater.

Activated persulfate by iron-carbon micro electrolysis used for refractory organics degradation in wastewater: a review

With the rapid economic development, the discharge of industrial wastewater and municipal wastewater containing many refractory organic pollutants is increasing, so there is an urgent need for processes that can treat refractory organics in wastewater. Iron-carbon micro electrolysis and advanced oxidation based on persulfate radicals (SO₄^-·) have received much attention in the field of organic wastewater treatment. Iron-carbon micro electrolysis activated persulfate (Fe-C/PS) treatment of wastewater is characterized by high oxidation efficiency and no secondary pollution. This paper reviews the mechanism and process of Fe-C/PS, degradation of organics in different wastewater, and the influencing factors. In addition, the degradation efficiency and optimal reaction conditions (oxidant concentration, catalyst concentration, iron-carbon material, and pH) of Fe-C/PS in the treatment of refractory organics in wastewater are summarized. Moreover, the important factors affecting the degradation of organics by Fe-C/PS are presented. Finally, we analyzed the challenges and the prospects for the future of Fe-C/PS in application, and concluded that the main future directions are to improve the degradation efficiency and cost by synthesizing stable and efficient catalysts, optimizing process parameters, and expanding the application scope.

Carbon nanotube-based materials for persulfate activation to degrade organic contaminants: Properties, mechanisms and modification insights

Removal of harmful organic matters from environment has great environmental significance. Carbon nanotube (CNT) materials and their composites have been demonstrated to possess excellent catalytic activity towards persulfate (PS) activation for the degradation of organic contaminants. Herein, detailed information concerning the function, modification methods and relevant mechanisms of CNT in persulfate-based advanced oxidation processes (PS-AOPs) for organic pollutant elimination has been reviewed. The activation mechanism of PS by CNT might include radical and nonradical pathways and their synergistic effects. The common strategies to improve the stability and catalytic capability of CNT-based materials have also been put forward. Furthermore, their practical application potential compared with other catalysts has been described. Finally, the challenges faced by CNT in practical application are clearly highlighted. This review should be of value in promoting the research of PS activation by CNT-based materials for degradation of organic pollutants and the corresponding practical applications.

Microcystis aeruginosa removal by the combination of ultrasound and TiO2/biochar

Harmful cyanobacteria blooms are increasing. They call for novel removal technology, since the required doses of algaecides may cause further environmental pollution or damage treatment facilities. Undesirable intracellular compounds can be released in the water when cyanobacterial cells are damaged. For the first time, ultrasound irradiation was combined with TiO₂/biochar (TiO₂/BC) at relatively low dosage and tested as an alternative for promoting the coagulation of Microcystis aeruginosa in water treatment. This pre-oxidation process removed 92% of cyanobacterial cells after coagulation. With the combination of ultrasound and TiO₂/BC treatment, the dissolved organic carbon and microcystins levels did not increase significantly. The oxidative treatments enhanced the permeability of the cyanobacterial cell membranes, which may be due to the various active species generated from the ultrasound and TiO₂/BC process. The results showed that the TiO₂/BC hybrid catalyst could be a potential candidate for cyanobacterial cells removal in water.

Green and rapid preparation of long-term stable aqueous dispersions of fullerenes and endohedral fullerenes: The pros and cons of an ultrasonic probe

A green, scalable, and sustainable approach to prepare aqueous fullerene dispersions (AFD) C60, C70, endohedral metallofullerene Gd@C82, and their derivatives C60Cl6, C70Cl10, and supramolecular and ester-like derivatives, 10 fullerene species total, is proposed. For the first time, an immersed ultrasonic probe was used to preparing dispersions for pristine fullerenes without addends. Both ultrasound-assisted solvent-exchange and direct sonication techniques for AFD preparation using an immersed probe were tested. The average time for AFD preparation decreases 10-15 times compared to an ultrasound-bath-assisted technique, while final fullerene concentrations in AFDs remained at tens of ppm (up to 80 ppm). The aqueous dispersions showed long-term stability, a negatively charged surface with a zeta potential up to -32 mV with an average nanocluster diameter of no more than 180 nm. The total anionic and cationic compositions of samples were found by inductively coupled plasma atomic emission spectroscopy and chromatographic techniques. The highlights and challenges of using an ultrasound probe for AFD production are discussed.

Recent Advances in Inorganic Nanomaterials Synthesis Using Sonochemistry: A Comprehensive Review on Iron Oxide, Gold and Iron Oxide Coated Gold Nanoparticles

Sonochemistry uses ultrasound to improve or modify chemical reactions. Sonochemistry occurs when the ultrasound causes chemical effects on the reaction system, such as the formation of free radicals, that intensify the reaction. Many studies have investigated the synthesis of nanomaterials by the sonochemical method, but there is still very limited information on the detailed characterization of these physicochemical and morphological nanoparticles. In this comprehensive review, recent advances in the sonochemical synthesis of nanomaterials based on iron oxide nanoparticles (Fe3O4NP), gold nanoparticles (AuNP) and iron oxide-coated gold nanoparticles (Fe3O4@Au NP) are discussed. These materials are the most studied materials for various applications, such as medical and commercial uses. This review will: (1) address the simple processing and observations on the principles of sonochemistry as a starting point for understanding the fundamental mechanisms, (2) summarize and review the most relevant publications and (3) describe the typical shape of the products provided in sonochemistry. All in all, this review's main outcome will provide a comprehensive overview of the available literature knowledge that promotes and encourages future sonochemical work.

Preparation of magnetized iron oxide grafted on graphene oxide for hyperthermia application

Magnetic hyperthermia therapy (MHT) is a highly promising therapeutic modality for the treatment of different kinds of cancers and malignant tumors. The therapy is based on the concept that; iron oxide nanoparticles deposited at cancer sites can generate heat when exposed to an alternating current magnetic field or near infrared radiation and consequently destroying only the cancer cells by exploiting their vulnerability to heat. The fact that the treatment is at molecular level and that iron oxide nanoparticles provide more guided focus heating justifies its efficacy over treatment such as surgery, radiation therapy and chemotherapy. Nevertheless, the spread of MHT as the next-generation therapeutics has been shadowed by insufficient heating especially at the in vivo stage. This can be averted by modifying the iron oxide nanoparticle structure. To this end, various attempts have been made by developing a magnetic hybrid nanostructure capable of generating efficient heat. However, the synthesis method for each component (of the magnetic hybrid nanostructure) and the grafting process is now an issue. This has a direct effect on the performance of the magnetic hybrid nanostructure in MHT and other applications. The main objective of this review is to detail out the different materials, methods and characterization techniques that have been used so far in developing magnetic hybrid nanostructure. In view of this, we conducted a comprehensive review and present a road map for developing a magnetic hybrid nanostructure that is capable of generating optimum heat during MHT. We further summarize the various characterization techniques and necessary parameters to study in validating the efficiency of the magnetic hybrid nanostructure. Hopefully, this contribution will serve as a guide to researchers that are willing to evaluate the properties of their magnetic hybrid nanostructure.

Controlled pyrolysis of MIL-88A to prepare iron/carbon composites for synergistic persulfate oxidation of phenol: Catalytic performance and mechanism

In this study, based on the extensive discussion of the phase transformation process of metal-organic frameworks (MOFs)--MIL-88A(Fe) under thermal treatment, the catalytic performance of MIL-88A-derived iron/carbon (FexC) composites on persulfate (PS) activation for phenol degradation was investigated. FexC-600 (γ-Fe₂O₃/C) exhibited a superior catalytic activity on PS activation for phenol degradation due to higher carbon content, more sp²-hybridized structure, carbonyl group and defective sites in composites, in which 98.23% of phenol (20 mg/L) was degraded after 60 min with 0.3 g/L catalyst and 0.3 g/L PS at ambient pH (6.1). The phenol degradation experiments and mechanism studies revealed that there was a catalytic synergism between iron oxides and carbon component in FexC 400-600 composites. Moreover, sulfate radicals (SO₄^-), hydroxyl radical (•OH), singlet oxygen (¹O₂) and interfacial electron transfer process all involved in the degradation of phenol by FexC 400-600 composites, but the ¹O₂-mediated non-radical oxidation was the dominant pathway rather than reactive radicals. Finally, the possible mechanism of PS activation on FexC 400-600 composites was proposed. This work discusses the synergistic catalytic mechanism of FexC composites on PS activation, and favors to provide a better understanding of the metal species and carbon component interaction in iron/carbon-based materials.

Impact of sonochemical synthesis condition on the structural and physical properties of MnFe2O4 spinel ferrite nanoparticles

Herein, we report sonochemical synthesis of MnFe₂O₄ spinel ferrite nanoparticles using UZ SONOPULS HD 2070 Ultrasonic homogenizer (frequency: 20 kHz and power: 70 W). The sonication time and percentage amplitude of ultrasonic power input cause appreciable changes in the structural, cation distribution and physical properties of MnFe₂O₄ nanoparticles. The average crystallite size of synthesized MnFe₂O₄ nanoparticles was increased with increase of sonication time and percentage amplitude of ultrasonic power input. The occupational formula by X-ray photoelectron spectroscopy for prepared spinel ferrite nanoparticles was (Mn_0.29Fe_0.42)[Mn_0.71Fe_1.58]O₄ and (Mn_0.28Fe_0.54) [Mn_0.72Fe_1.46]O₄ at sonication time 20 min and 80 min, respectively. The value of the saturation magnetization was increased from 1.9 emu/g to 52.5 emu/g with increase of sonication time 20 min to 80 min at constant 50% amplitude of ultrasonic power input, whereas, it was increased from 30.2 emu/g to 59.4 emu/g with increase of the percentage amplitude of ultrasonic power input at constant sonication time 60 min. The highest value of dielectric constant (ε') was 499 at 1 kHz for nanoparticles at sonication time 20 min, whereas, ac conductivity was 368 × 10^-9 S/cm at 1 kHz for spinel ferrite nanoparticles at sonication time 20 min. The demonstrated controllable physical characteristics over sonication time and percentage amplitude of ultrasonic power input are a key step to design spinel ferrite material of desired properties for specific application. The investigation of microwave operating frequency suggest that these prepared spinel ferrite nanoparticles are potential candidate for fabrication of devices at high frequency applications.

Ultrasound-assisted coagulation for Microcystis aeruginosa removal using Fe3O4-loaded carbon nanotubes

Harmful cyanobacterial blooms are increasing environmental issues and require novel removal technology since the required doses of algaecides may cause further environmental pollution or treatment facility damage. Herein, we firstly introduce the combination of ultrasound and Fe₃O₄/CNTs as an alternative strategy to enhance coagulation for the removal of Microcystis aeruginosa cells in water. It remarkably enhanced cyanobacterial cell removal and microcystins control, compared with sonication alone (40 kHz ultrasonic bath, 4.2 mJ mL⁻¹). 94.4% cyanobacterial cells were removed using 20 second sonication with 20 mg L⁻¹ Fe₃O₄/CNTs, Al₂(SO₄)₃ coagulation (20 μM). Both sonication time and catalyst dose significantly influenced the cyanobacterial removal. Ultrasound with Fe₃O₄/CNTs only induced a slight increase of cell permeability, which may contribute to the effective control of DOC and microcystins' release in water. The enhanced settlement of the cyanobacterial cells may result from the moderate oxidation on the cell surface. This study suggested a novel ultrasound-Fe₃O₄/CNT process to promote cyanobacteria removal with efficient DOC and microcystin release control, which is a green and safe technology for drinking water treatment.

The combination of sonication and Fe₃O₄/CNTs were applied on Microcystis aeruginosa removal for the first time.