Facile synthesis of core\shell Fe3O4@mSiO2(Hb) and its application for organic wastewater treatment

Magnetic solid-phase extraction of tetracyclines from milk using metal-organic framework MIL-101(Cr)-NH2 functionalised hydrophilic magnetic nanoparticles

Novel metal-organic framework MIL-101(Cr)-NH2 functionalised hydrophilic polydopamine-modified Fe3O4 magnetic nanoparticles (Fe3O4@PDA@MIL-101(Cr)-NH2) were synthesised and used as magnetic solid-phase extraction (MSPE) adsorbents for extracting tetracyclines (TCs) from milk samples. The integrated Fe3O4@PDA@MIL-101(Cr)-NH2 exhibited convenient magnetic separation and exceptional multi-target binding capabilities. Furthermore, the PDA coating significantly enhanced the hydrophilicity and extraction efficiency of the material, thereby facilitating the extraction of trace TCs. Various factors affecting MSPE, such as adsorbent dosage, extraction time, pH value, and desorption conditions, were optimised. The developed MSPE method coupled with high-performance liquid chromatography demonstrated good linearity (R2 ≥ 0.9989), acceptable accuracy (82.2%-106.1%), good repeatability (intra-day precision of 0.8%-4.7% and inter-day precision of 1.1%-4.5%), low limits of detection (2.18-6.25 μg L-1), and low limits of quantification (6.54-18.75 μg L-1) in TCs detection. The approach was successfully used for the quantification of trace TCs in real milk samples.

Enhanced cadmium removal by a magnetic potassium ferrocyanide framework: Performance and mechanism study

Polluted environments often contain large amounts of toxic metals, such as cadmium, which pose a major threat to ecosystems and public health. Contamination by cadmium and its compounds is often observed in areas surrounding zinc mining sites and electroplating factories, and the control of cadmium pollution is essential for environmental safety and health. In this study, a highly efficient and straightforward separation strategy for K4Fe(CN)6@Fe3O4 nanocomposites is successfully developed to capture the Cd ions in the water environment. Batch adsorption experiments revealed that K4Fe(CN)6@Fe3O4 exhibited a high cadmium removal rate (greater than 98 %) at a pH level of 6.0 and solid-liquid ratio of 1.0 g/L at room temperature (298 K). Kinetic analysis revealed that the adsorption process followed a pseudo-second-order model and cadmium was rapidly removed in the first 10 min, with chemisorption dominating the capture of Cd2+ by K4Fe(CN)6@Fe3O4. Adsorption isotherms revealed a heterogeneous adsorption behavior, with a maximum adsorption capacity of 40.78 mg/g. The intrinsic adsorption of Cd2+ by K4Fe(CN)6@Fe3O4 occurring primarily through electrostatic interaction and ion exchange. In addition, K4Fe(CN)6@Fe3O4 exhibited an excellent regeneration capacity. Therefore, integrating Fe3O4 into the metal cyanide not only provided the composite material with excellent chemical stability and selective adsorption sites for Cd2+, but also facilitated subsequent sorbent collection and recovery. Overall, this study presents a simple and feasible approach for integrating Fe3O4 into potassium ferrocyanide frameworks for efficient cadmium removal from contaminated water.

Multi-point immobilization of GH 11 endo-β-1,4-xylanase on magnetic MOF composites for higher yield of xylo-oligosaccharides

GH 11 endo-β-1,4-xylanase (Xy) was a crucial enzyme for xylooligosaccharides (XOS) production. The lower reusability and higher cost of purification has limited the industrial application of Xy. Addressing these challenges, our study utilized various immobilization techniques, different supports and forces for Xy immobilization. This study presents a new method in the development of Fe3O4@PDA@MOF-Xy which is immobilized via multi-point interaction forces, demonstrating a significant advancement in protein loading capacity (80.67 mg/g), and exhibiting remarkable tolerance to acidic and alkaline conditions. This method significantly improved Xy reusability and efficiency for industrial applications, maintaining 60 % activity over 10 cycles. Approximately 23 % XOS production was achieved by Fe3O4@PDA@MOF-Xy. Moreover, the yield of XOS from cobcorn xylan using this system was 1.15 times higher than that of the free enzyme system. These results provide a theoretical and applicative basis for enzyme immobilization and XOS industrial production.

Critical role of zero-valent iron in the efficient activation of H2O2 for 4-CP degradation by bimetallic peroxidase-like

Peroxidase-like based on double transition metals have higher catalytic activity and are considered to have great potential for application in the field of pollutant degradation. First, in this paper, a novel Fe0-doped three-dimensional porous Fe0@FeMn-NC-like peroxidase was synthesized by a simple one-step thermal reduction method. The doping of manganese was able to reduce part of the iron in Fe-Mn binary oxides to Fe0 at high temperatures. In addition, Fe0@FeMn-NC has excellent peroxidase-like mimetic activity, and thus, it was used for the rapid degradation of p-chlorophenol (4-CP). During the degradation process, Fe0 was able to rapidly replenish the constantly depleted Fe2+ in the reaction system and brought in a large number of additional electrons. The ineffective decomposition of H2O2 due to the use of H2O2 as an electron donor in the reduction reactions from Fe3+ to Fe2+ and from Mn3+ to Mn2+ was avoided. Finally, based on the experimental results of LC-MS and combined with theoretical calculations, the degradation process of 4-CP was rationally analyzed, in which the intermediates were mainly p-chloro-catechol, p-chloro resorcinol, and p-benzoquinone. Fe0@FeMn-NC nano-enzymes have excellent catalytic activity as well as structural stability and perform well in the treatment of simulated wastewater containing a variety of phenolic pollutants as well as real chemical wastewater. It provides some insights and methods for the application of peroxidase-like enzymes in the degradation of organic pollutants.

Evaluation of immobilized microspheres of Clonostachys rosea on Botrytis cinerea and tomato seedlings

Tomato (Solanum lycopersicum L.) is a popular vegetable crop which is widely cultivated around the world. However, the production of tomatoes is threatened by several phytopathogenic agents, including gray mold (Botrytis cinerea Pers.). Biological control using fungal agents such as Clonostachys rosea plays a pivotal role in managing gray mold. However, these biological agents can negatively be influenced by environmental factors. However, immobilization is a promising approach to tackle this issue. In this research, we used a nontoxic chemical material, sodium alginate as a carrier to immobilize C. rosea. For this, sodium alginate microspheres were prepared using sodium alginate prior to embedding C. rosea. The results showed that C. rosea was successfully embedded in sodium alginate microspheres, and immobilization enhanced the stability of the fungi. The embedded C. rosea was able to suppress the growth of gray mold efficiently. In addition, the activity of stress related enzymes, peroxidase superoxidase dismutase and polyphenol oxidation was promoted in tomatoes treated with the embedded C. rosea. By measuring photosynthetic efficiency, it was noted that the embedded C. rosea has positive impacts on tomato plants. Taken together, these results indicate that immobilization of C. rosea improved its stability without detrimentally affecting its efficiency on gray mold suppression and tomato growth. The results of this research can be used as a basis for research and development of new immobilized biocontrol agents.

A vortex-enhanced magnetic solid phase extraction for the selective enrichment of four quaternary ammonium alkaloids from Zanthoxyli Radix

Zanthoxyli Radix, the dried root of Zanthozylum nitidum (Roxb.) DC, one of traditional Chinese medicines (TCMs), exhibits various pharmacological activities such as anti-bacterial, anti-inflammatory, anti-tumor, analgesic activity. A sustainable vortex-enhanced magnetic solid phase extraction (VE-MSPE) method combined with ultra-high performance liquid chromatography (UHPLC) was established to enrich and analyze the bioactive quaternary ammonium alkaloids (QAAs) of Zanthoxyli Radix. Fe₃O₄@C@CMCS magnetic nanoparticles (MNPs) was first synthesized for selectively adsorbing target QAAs (magnolinine, sanguinarine, nitidine chloride and chelerythrine), which possess excellent adsorption performance after being reused 10 times. The results revealed that the great adsorption rate of Fe₃O₄@C@CMCS MNPs for the four QAAs could reach 55.1-78.7 %. In addition, a reliable linear relationship (r ≥ 0.9995) and good recovery (97.5-104 %) was obtained. Consequently, the VE-MSPE method applying Fe₃O₄@C@CMCS MNPs as a sustainable adsorbent exhibited great potential in the selective enrichment of QAAs in TCM.

Magnetic ethylene-based periodic mesoporous organosilica supported palladium: An efficient and recoverable nanocatalyst for Suzuki reaction

In the present study, a novel magnetic ethylene-based periodic mesoporous organosilica supported Pd-Schiff base complex (Fe₃O₄@PMO/SB-Pd) was prepared, characterized and applied as a recoverable nanocatalyst for green synthesis of Suzuki products. Chemical composition, magnetic and thermal behavior, morphology and particle size of Fe₃O₄@PMO/SB-Pd were investigated by using FT-IR, TGA, EDX, VSM, PXRD, TEM and Scanning electron microscopy (SEM) analyses. The Fe₃O₄@PMO/SB-Pd nanocomposite was applied as an efficient nanocatalyst in the Suzuki reaction under ultrasonic conditions giving corresponding products in high yield. Some advantages of this study are simple purification of products, the use of water solvent, easy catalyst separation, short reaction time and high catalyst efficiency and recoverability.

Polyethylenimine-grafted nitrogen-doping magnetic biochar for efficient Cr(VI) decontamination: Insights into synthesis and adsorption mechanisms

Herein, polyethylenimine (PEI)-grafted nitrogen (N)-doping magnetic biochar (PEI_MW@MNBC_BM) was synthesized, and characterization results showed that the microwave-assisted PEI grafting and ball milling-assisted N doping introduced abundant amino, pyridine N and pyrrole N structures onto biochar, which possessed high affinity to Cr(VI) in the anion form. The as-prepared PEI_MW@MNBC_BM displayed pH-dependence adsorption performance and high tolerance to co-existing ions with maximum uptake capacity of Cr(VI) identified as 183.02 mg/g. Furthermore, PEI_MW@MNBC_BM could bind Cr(VI) through electrostatic attraction, complexion, precipitation, reduction and pore filling. Especially, effective reduction of Cr(VI) was ascribed to cooperative electron transfer of partial oxygen-containing functional groups, intramolecular pyridine/pyrrole N, protonated amino and Fe²⁺ on the adsorbent, while oxygen-containing and amino functional groups from N-doping biochar and PEI synergistically complexed Cr(III) via providing lone pair electrons to form coordinate bonds. Furthermore, the stable precipitation was formed between Fe³⁺ and Cr(III). Additionally, the Cr(VI) elimination efficiency could maintain 95.83% even after four adsorption-desorption cycles, suggesting PEI_MW@MNBC_BM as a high-performance adsorbent for Cr(VI) contaminated water remediation.

Novel hollow α-Fe2O3 nanofibers with robust performance enabled multi-functional applications

The synthetic strategies of achieving low-cost and high-performance nanofibers are of great significance in the field of catalysis and detection. In this work, a series of electrospun α-Fe₂O₃ nanofibers with hollow structure were prepared via combination technology of electrospinning, hydrothermal synthesis, and controlled calcination process. Especially, the influences of the crystal structure and morphology on the comprehensive properties of nanofibers have been explored in detail. The results indicated that α-Fe₂O₃ nanofibers could be obtained via the calcination at 600-800 °C. Rice-like α-Fe₂O₃ particles were observed to assemble a stable exoskeleton, supporting a robust tubular cavity. And this tubular structure turned gradually into groove-like structure as the calcination temperature increased, accompanied by tunable crystallization, specific surface area and magnetic property. Finally, combined with series of validation tests, including dye decolorization, electrochemical detection of trace cadmium ions and Fenton degradation of polyvinyl alcohol, the resultant α-Fe₂O₃ nanofibers have been demonstrated to show the potential application prospects.