Citrus pectin derived ultrasmall Fe3O4@C nanoparticles as a high-performance adsorbent toward removal of methylene blue

Cascaded utilization of magnetite nanoparticles@onion-like carbons from wastewater purification to supercapacitive energy storage

Developing high-performance carbon-based materials for environmental and energy-related applications produces solid waste with secondary pollution to the environment at the end of their service lives. It is still challenging to utilize these functional materials in a sustainable manner in different fields. In this study, we demonstrate a cascaded utilization of an Fe3O4@onion-like carbon (Fe3O4@OLC) structure from wastewater adsorbents to a supercapacitor electrode. The structure was formed by carbonizing Fe3O4@oleic acid monodisperse nanoparticles into interconnected Fe3O4@OLCs and subsequent insufficient acid etching. The hollow OLCs in the outside region of the hybrid structure provide high surface area and the encapsulated Fe3O4 nanoparticles in the inside region offer high ferromagnetism. The three-dimensionally interconnected graphitic layers are advantageous for efficient separation and high conductivity. As a result, the maximum saturation adsorption capacity of insufficiently etched interconnected Fe3O4@OLCs can reach up to 90.2 mg g-1 and they can be efficiently separated under a magnetic field. Furthermore, the hybrid structure is thermally transformed into N-doped HOLCs, which are demonstrated to be a high-performance supercapacitor electrode with high specific capacitance and high electrochemical stability. The cascaded utilization of the hybrid structure in this study is meaningful for eco-friendly development of functional materials for environmental and energy storage applications.

Preparation and characterization of pectin/hydroxyethyl cellulose/clay/TiO2 bionanocomposite films for microbial pathogen removal from contaminated water

Some of conventional wastewater disinfectants can have a harmful influence on the environment as well as human health. The aim of this investigation was synthesis and characterizes ecofriendly pectin/hydroxyethyl cellulose (HEC)/clay and pectin/HEC/clay incorporated with titanium dioxide nanoparticles (TiO2NPs) and use the prepared bionanocomposite as microbial disinfectants for real wastewater. Pectin/HEC/clay and pectin/HEC/clay/TiO2 bionanocomposite were characterized by various methods including X-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier-transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA). Mechanical properties and water vapor permeability (WVP) were carried out. The results of SEM showed that, the prepared bionanocomposite had a smooth surface. Additionally, TiO2 nanoparticles to the pectin/HEC/clay composites may lead to changes in the FTIR spectrum. The intensity of XRD peaks indicated that, TiO2NPs was small size crystallite. TGA illustrated that pectin has moderate thermal stability, while HEC generally exhibits good thermal stability. The TEM showed that, TiO2 nanoparticles have diameters <25 nm. On the other hand, antimicrobial activities of pectin/HEC/clay against Escherichia coli (E. coli), Staphylococcus aureus and Candida albicans have been enhanced by adding TiO2NPs. The minimum inhibitory concentration (MIC) of pectin/HEC/clay/TiO2 against E. coli was 200 mg/mL. Moreover, complete eradication of E. coli, Salmonella and Candida spp. from real wastewater was observed by using pectin/HEC/clay/TiO2 bionanocomposite. Finally, it can be concluded that, the synthesized bionanocomposite is environmentally friendly and considered an excellent disinfectant matter for removal of the microbial pathogens from wastewater to safely reuse.

Water-based technologies for improving water quality at the point of use: A review

Water safety concerns are increasing tremendously as a result of the rising population and environmental pollution. As a result, viable water treatment approaches need to be designed to meet the water consumption demands of the population, particularly in developing countries. The recent technological advances in water treatment and purification are well articulated in this review. The efficiency of the materials used for purification and their affordability for people living in rural and remote settlements in various parts of the world have been discussed. Water treatment techniques prior to the rapid advancement of science and technology included a variety of strategies such as coagulation/flocculation, filtration, disinfection, flotation and pH correction. The use of nanotechnology in water treatment and purification has modernized the purification process. Therefore, efficient removal of microbes such as bacteria and viruses are exquisitely accomplished. These technologies may include membrane filtration, ultraviolet irradiation, advanced oxidation ion-exchange and biological filtration technologies. Thus, nanotechnology allows for the fabrication of less expensive systems, allowing even low-income people to benefit from it. Most developing countries find these technologies particularly valuable because access to clean and safe water for drinking and residential needs is critical. This is because access to municipal water supplies is also difficult. This article is categorized under: Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Recyclable magnetic Fe3O4@C for methylene blue removal under microwave-induced reaction system

The reclamation and removal of organic pollutants are difficult issues of world concern. In this study, a microwave-induced reaction system (MIRS) is applied to synthesize the multifunctional composite of Fe₃O₄@C, which is employed to adsorb, separate and catalytic oxide the typical organic dye of methylene blue (MB). SEM, TEM, VSM, XPS, pHpzc, and N₂ adsorption performances are carried out to characterize the Fe₃O₄@C. Results show that the Fe₃O₄@C mainly consists of activated Fe-O-C microspheres, which possess plentiful mesopore and macropore structures on surfaces. Batch adsorption experiments were carried out by varying key reaction conditions to optimize these. The maximum adsorption capacity of MB onto the Fe₃O₄@C was 305.0 mg g^-1 in 120 min, at pH 10, and at a temperature of 323 K. MIRS was also assisted to regenerate the spent Fe₃O₄@C which presented good regeneration efficiency by sustaining 16 regeneration cycles without any oxidizing agent. SEM images and FTIR spectrum verified that MB would translate into greater or smaller-sized carbon microspheres. What's more, the adsorption of MB onto both initial and the 16th regenerated Fe₃O₄@C obeyed the Langmuir isotherm model and followed the pseudo-second-order adsorption kinetics, indicating the adsorptive stability after regeneration. In this study, the Fe₃O₄@C combined with MIRS may be one innovative strategy for organic pollutants' complete removal in the future.

Facile Preparation of Porous Carbon Derived from Pomelo Peel for Efficient Adsorption of Methylene Blue

Pomelo peel waste-derived porous carbon (PPPC) was prepared by a facile one-step ZnCl₂ activation method. The preparation parameters of PPPC were the mass ratio of ZnCl₂ to pomelo peel of 2:1, carbonization temperature of 500 °C, and carbonization time of 1 h. This obtained PPPC possessed abundant macro-,meso-, and micro-porous structures, and a large specific surface area of 939.4 m² g^-1. Surprisingly, it had excellent adsorption ability for methylene blue, including a high adsorption capacity of 602.4 mg g^-1 and good reusability. The adsorption isotherm and kinetic fitted with Langmuir and pseudo-second order kinetic models. This work provides a novel strategy for pomelo peel waste utilization and a potential adsorbent for treating dye wastewater.

Synthesis of amorphous carbon functionalized Fe3O4 nanoparticles as a smart nanosorbent for organic dyes removal

Illustration of process for synthesis of carbon coated Fe3O4 (CCF) nanocomposites and their application as nanosorbents with recoverability and regenerability for the sorption of organic dyes.

A Novel Nonenzymatic Hydrogen Peroxide Sensor Based on Magnetic Core-Shell Fe3O4@C/Au Nanoparticle Nanocomposite

Fe₃O₄@C/Au nanoparticle (AuNP) nanocomposites were prepared through electrostatic adsorption of AuNPs onto PDDA-functionalized core/shell Fe₃O₄@C magnetic nanospheres, which had been synthesized by a facile solvothermal method. The morphology and composition of the nanocomposites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), etc. Moreover, highly electrocatalytic activity to the reduction of hydrogen peroxide (H₂O₂) was also exhibited on the Fe₃O₄@C/AuNP-modified indium tin oxide (ITO) electrode. The effect of solution pH and the modification amount of Fe₃O₄@C/AuNPs on the performance of electrocatalytic H₂O₂ reduction was investigated. Under the optimal conditions, the catalytic current showed a linear relationship with the increase of H₂O₂ concentration in the range of 0.007–15 mM and a detection limit of 5 μM. The H₂O₂ sensor showed high selectivity for H₂O₂ detection, which could effectively resist the interference of ascorbic acid (AA), uric acid (UA), and citric acid (CA). Finally, the H₂O₂ sensor was used in the real fetal bovine serum to detect H₂O₂ and obtained satisfactory results with the recovery values ranging from 95.14 to 103.6%.

Fe3O4@C Nanoparticles Synthesized by In Situ Solid-Phase Method for Removal of Methylene Blue

Fe3O4@C nanoparticles were prepared by an in situ, solid-phase reaction, without any precursor, using FeSO4, FeS2, and PVP K30 as raw materials. The nanoparticles were utilized to decolorize high concentrations methylene blue (MB). The results indicated that the maximum adsorption capacity of the Fe3O4@C nanoparticles was 18.52 mg/g, and that the adsorption process was exothermic. Additionally, by employing H2O2 as the initiator of a Fenton-like reaction, the removal efficiency of 100 mg/L MB reached ~99% with Fe3O4@C nanoparticles, while that of MB was only ~34% using pure Fe3O4 nanoparticles. The mechanism of H2O2 activated on the Fe3O4@C nanoparticles and the possible degradation pathways of MB are discussed. The Fe3O4@C nanoparticles retained high catalytic activity after five usage cycles. This work describes a facile method for producing Fe3O4@C nanoparticles with excellent catalytic reactivity, and therefore, represents a promising approach for the industrial production of Fe3O4@C nanoparticles for the treatment of high concentrations of dyes in wastewater.

Preparation, surface functionalization and application of Fe3O4 magnetic nanoparticles

This paper reviews recent developments in the preparation, surface functionalization, and applications of Fe₃O₄ magnetic nanoparticles. Especially, it includes preparation methods (such as electrodeposition, polyol methods, etc.), organic materials (such as polymers, small molecules, surfactants, biomolecules, etc.) or inorganic materials (such as silica, metals, and metal oxidation/sulfide, functionalized coating of carbon surface, graphene, etc.) and its applications (such as magnetic separation, protein fixation, magnetic catalyst, environmental treatment, medical research, etc.). In the end, some existing challenges and possible future trends in the field were discussed.

Ginger Straw Waste-Derived Porous Carbons as Effective Adsorbents toward Methylene Blue

In this work, ginger straw waste-derived porous carbons, with high adsorption capacity, high adsorption rate, and good reusability for removing the toxic dye of methylene blue from wastewater, were prepared by a facile method under oxygen-limiting conditions. This study opens a new approach for the utilization of ginger straw waste, and the porous materials can be employed as great potential adsorbents for treating dye wastewater.

Carbon-Based Fe₃O₄ Nanocomposites Derived from Waste Pomelo Peels for Magnetic Solid-Phase Extraction of 11 Triazole Fungicides in Fruit Samples

Carbon-based Fe₃O₄ nanocomposites (C/Fe₃O₄ NCs) were synthesized by a simple one-step hydrothermal method using waste pomelo peels as the carbon precursors. The characterization results showed that they had good structures and physicochemical properties. The prepared C/Fe₃O₄ NCs could be applied as excellent and recyclable adsorbents for magnetic solid phase extraction (MSPE) of 11 triazole fungicides in fruit samples. In the MSPE procedure, several parameters including the amount of adsorbents, extraction time, the type and volume of desorption solvent, and desorption time were optimized in detail. Under the optimized conditions, the good linearity (R² > 0.9916), the limits of detection (LOD), and quantification (LOQ) were obtained in the range of 1–100, 0.12–0.55, and 0.39–1.85 μg/kg for 11 pesticides, respectively. Lastly, the proposed MSPE method was successfully applied to analyze triazole fungicides in real apple, pear, orange, peach, and banana samples with recoveries in the range of 82.1% to 109.9% and relative standard deviations (RSDs) below 8.4%. Therefore, the C/Fe₃O₄ NCs based MSPE method has a great potential for isolating and pre-concentrating trace levels of triazole fungicides in fruits.

Citrus Pectin-Derived Carbon Microspheres with Superior Adsorption Ability for Methylene Blue

In this study, citrus pectin-derived, green, and tunable carbon microspheres with superior adsorption capacity and high adsorption rate, as well as good reusability toward methylene blue adsorption, were prepared by a facile hydrothermal method without any hazardous chemicals. The materials hold great potential for the treatment of methylene blue wastewater.