Synthesis and characterization of nanocomposite Fe3O4/SiO2 core–shell abrasives for high-efficiency ultrasound-assisted magneto-rheological polishing of sapphire

A functional Fe₃O₄/SiO₂ core–shell abrasive was synthesized via hydrolysis of tetraethyl orthosilicate. A silica shell was successfully coated on a Fe₃O₄ core, resulting in a core-shell particle with an average diameter of 140 nm. The prepared core–shell abrasives was utilized for ultrasound-assisted magneto-rheological polishing (UAMP) of sapphire substrate. The experimental results showed that the Fe₃O₄/SiO₂ core–shell abrasives exhibited a remarkable polishing performance for the sapphire material, resulting in smooth and detect-free surfaces with a high material removal rate (MRR) compared to mixed abrasives (Fe₃O₄ and SiO₂) and pure Fe₃O₄ particles. The application of ultrasonic vibration to the sapphire wafer further improved the MRR, which was approximately 3.4 times higher than that of traditional magneto-rheological polishing. The largest MRR (1.974 μm/h) and comparatively low surface roughness (0.442 nm) of the polished sapphire wafer were achieved by UAMP with the Fe₃O₄/SiO₂ core–shell abrasives. The polishing mechanism of the sapphire wafer is discussed in terms of chemical reactions and mechanical polishing.     

Facile Synthesis of Fe3O4−SiO2 Nanocomposites for Wastewater Treatment

Water constitutes ≈70–90% of the organism's body by mass and is highly important for its survival. Water contains a variety of chemical contaminants introduced by various sectors, resulting in contamination that has a direct impact on the ecosystem. Various approaches are in practice to tackle these issues. Among these, semiconductor photocatalysis appears to be the cutting-edge technology for the degradation of wastewater contaminants. Herein, the fabrication of Fe₃O₄−SiO₂ nanocomposite via facile co-precipitation and Stober methods are reported. Various characterization techniques are employed for the structural elucidation, morphology, crystallinity, and stability of the as-prepared composite. The nanocomposite is employed in catalytic and photocatalytic applications toward the removal of methylene blue (MB) and methyl orange (MO) dyes from a comparative perspective. It is observed that the composite can remove about 93% of MB and 51% of MO within 7 and 6 h, respectively. These findings indicate that the nanocomposite has a higher MB removal effectiveness than the MO. This trend can be accredited to the difference in the chemical structure of both dyes. The nanocomposite is also evaluated for antioxidant and antileishmanial activity, and it is shown to be quite effective even at very low concentrations.     

Fe3O4–carbon black nanocomposite as a highly efficient counter electrode material for dye-sensitized solar cell

Iron oxide–carbon black (Fe₃O₄–CB) nanocomposite has been proposed as a cost–effective alternative counter electrode (CE) to the conventional Pt in a dye sensitized solar cell (DSSC). The Fe₃O₄–CB nanocomposite at three different weight ratio (1:1, 1:2 and 2:1) was prepared by a simple solution mixing process and the material was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning and transmission electron microscopy techniques. The performance of the three Fe₃O₄–CB nanocomposite CEs was assessed with respect to Fe₃O₄, CB and Pt in a conventional DSSC consisting of N719 dye sensitized TiO₂ (P25) photoanode in contact with an electrolyte containing the I⁻/I₃⁻ redox couple. The electrocatalytic activities of the various CEs towards triiodide (I₃⁻) reduction were analyzed by cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization analysis. The photocurrent voltage (J–V) characteristics of the DSSCs assembled with various counter electrodes were assessed at a light intensity of 80 mW cm⁻². The DSSC assembled with Fe₃O₄–CB nanocomposite (1:2) CE showed the best photovoltaic performance in terms of a high power conversion efficiency of 6.1% which is superior to that of sputtered Pt (4.1%). The simple preparation, excellent electrocatalytic activity and low-cost nature allow the Fe₃O₄–CB nanocomposite to be a promising alternative CE to Pt for use in DSSCs.     

Synthesis of Fe3O4@SiO2@Ption–TiO2 hybrid composites with high efficient UV–visible light photoactivity

Platinum ion doped magnetic TiO₂ (Fe₃O₄@SiO₂@Pt_ion–TiO₂) hybrid microspheres with uniform magnetic cores were synthesized and characterized in this work. The results indicate that the photoactivity of Fe₃O₄@SiO₂@Pt_ion–TiO₂ is much higher than Fe₃O₄@SiO₂@TiO₂ for the decolorization of acid orange 20 under UV–visible light irradiation. The trend for the final degradation ratio with Fe₃O₄@SiO₂@Pt_ion–TiO₂ is quite small, even after seven repetitive experiments. These data indicate that the magnetic microspheres possess the potential to be effective and stable catalysts. The results demonstrate that the Pt ion doped magnetic catalyst meets the needs for both immobilization and high photoactivity.     

Fe3O4@SiO2的表面改性

采用溶胶凝胶法在磁性Fe3O4纳米粒子的表面包覆SiO2,采用正交试验法,以表面Si-OH含量为指标,考察温度、时间和醇/水三因素对表面Si-OH含量的影响,利用X射线光电子能谱分析(XPS)测试Fe3O4@SiO2复合粒子表面Si-OH含量,结果表明在80%、回流时间为1h、醇/水为6∶1是改性Fe3O4@SiO2的...     

The use of κ-carrageenan/Fe3O4 nanocomposite as a nanomagnetic catalyst for clean synthesis of rhodanines

In this work, magnetically separable Fe₃O₄ nanoparticles were synthesized in the presence of natural κ-carrageenan (KCAR) biopolymer to provide Fe₃O₄@KCAR. FT-IR analysis, scanning electron microscopy (SEM), X-ray diffraction, VSM analysis, and SEM-EDAX were incorporated for the characterization of Fe₃O₄@KCAR nanocomposite. And then, the first catalytic report of Fe₃O₄@KCAR with no post-modification was achieved by studying its catalytic activity in the multicomponent reaction of rhodanine synthesis. Based on this study, Fe₃O₄@KCAR was an efficient, magnetically separable and recyclable, water-dispersible and green catalyst with natural source. This catalyst also showed 9-run recyclability with no significant yield decrease.     

Epoxide functionalized γ-Al2O3/Fe3O4/SiO2 nanocomposite and comparative adsorption behavior of a model reactive azo dye

In this investigation, magnetic γ-Al₂O₃ nanocomposite polymer particles with epoxide functionality were prepared following a multistep process. The prepared nanocomposite polymer particle was named as γ-Al₂O₃/Fe₃O₄/SiO₂/poly(glycidyl methacrylate (PGMA). The surface property was evaluated by carrying out the adsorption study of Remazol Navy RGB (RN), a model reactive azo dye, on both γ-Al₂O₃/Fe₃O₄/SiO₂ and γ-Al₂O₃/Fe₃O₄/SiO₂/PGMA nanocomposite particles, that is, before and after epoxide functionalization. A contact time, temperature, adsorbent dose, and dye concentration dependent change in adsorption behavior was observed on both nanocomposite particles. The adsorption amount reached equilibrium (q_e) value within 5 minutes at the respective point of zero charge (PZC). The adsorption density of RN per unit specific surface area on epoxide functional γ-Al₂O₃/Fe₃O₄/SiO₂/PGMA nanocomposite polymer particles (1.30 mg/m²) was higher relative to that on γ-Al₂O₃/Fe₃O₄/SiO₂ nanocomposite particles (0.87 mg/m²). The optimum adsorbent dose for obtaining the maximum adsorption density was 0.01 g. Comparatively, Langmuir isotherm model was better to describe the adsorption process and the adsorption process was favorable at low temperature (283 K). Batch kinetic adsorption experiment suggested that a pseudo-second-order rate kinetic model is more appropriate. Nanocomposite polymer particles were used as adsorbent up to third cycle with almost 99% adsorption efficiency.     

Sodium sulfonate functionalized magnetic Fe3O4@SiO2 towards the preparation of sorbent for Cu(Ⅱ) removal

通过化学一步共沉淀法制备了疏水性的Fe3O4纳米粒子,然后采用反相微乳液法制备出分散性良好、粒径均匀的Fe3O4@SiO2复合磁性纳米粒子,紧接着用2-(4-氯磺酰苯基)乙基三甲氧基硅烷对其表面进行修饰,最终再经过1.0 M NaCl溶液处理得到富含磺酸基官能团磁性纳米吸附剂(Fe3O4@SiO2-SO3Na).通过透射电镜(TEM)、X射线衍射(XRD)、红外光谱(FT-IR)、振动样品磁强计(VSM)等对其进行了表征,着重研究了其对水溶液中Cu(Ⅱ)离子的吸附性能.结果表明,溶液的pH值能显著影响吸附剂对Cu(Ⅱ)离子的吸附效果,其中pH值为5.1时吸附效果最佳,即Cu(Ⅱ)从初始的20mg·L-1降低至0.45mg·L-1,意味着97.8％的Cu(Ⅱ)从溶液中除去,通过用0.1M HCl洗涤可把Cu(Ⅱ)从吸附剂中脱离下来并且可以重复使用.     

Synthesis of K2O–MgO–SiO2 compounds as slow-release fertilisers from acid-leached biotite residues

For the utilisation of mineral residues and improving the nutrient use efficiency in fertilisers, the K₂O–MgO–SiO₂ compounds prepared as slow-release K fertilisers by using the acid-leached biotite residues, K₂CO₃, and Mg(OH)₂ as the starting materials were systematically studied and evaluated in this work. Sintering experiments were performed at 700–1000 °C and solubility experiments were conducted by dissolving the sintered samples in 0.50 M HCl solution, 0.10 M citric acid solution, and water. The results showed that K₂MgSiO₄ (KMS), KMS-K_1.14Mg_0.57Si_1.43O₄(K₂M₂S₅)–K₂MgSi₃O₈(KMS₃) mixtures, and K₂MgSi₅O₁₂ (KMS₅) were synthesised at 800 °C, 850–900 °C, and 950 °C, respectively. These compounds are citrate-soluble, and the solubilities followed the order KMS > K₂M₂S₅ ≫ KMS₃ > KMS₅. The release properties of the K₂O accumulated in water for all the K₂O–MgO–SiO₂ compounds fit the release kinetics Elovich equations, which suggest that KMS and KMS-K₂M₂S₅-KMS₃ can be used as slow-release K fertilisers and that KMS₅ with a much slower release of K₂O may be more suitable as a soil conditioner. Evaluation of the raw materials, synthesis approach, product properties, and environmental benefits shows that K₂O–MgO–SiO₂ slow-release fertilisers are eco-friendly and offer plenty of advantages with regard to soil fertility, environmental protection, resource utilisation, and energy consumption.     

Phase transformations as a result of thermal annealing of nanocomposite Fe–Ni / Fe–Ni–O particles

The paper presents the results of a study of changes in structural and magnetic characteristics, as well as phase transformations in Fe–Ni/Fe–Ni–O nanoparticles obtained by chemical synthesis and subsequent thermal annealing. It was found that the initial nanoparticles are a three-phase system consisting of Fe–Ni–O oxide with a spinel structure and a Fe–Ni alloy with a face- and body-centered cubic lattices. As a result of thermal annealing, a decrease in the Fe–Ni phase was established with subsequent ordering of the Fe–Ni–O phase with a decrease in the crystal lattice parameter and an increase in the degree of crystallinity. During resurces tests, it was found that for single-phase Fe–Ni–O nanoparticles, the lifetime is close to 500 discharge/charge cycles, which is a good indicator of the working life and makes it promising to use Fe–Ni/Fe–Ni–O nanoparticles as anode materials for lithium-ion batteries.     

Cerium dioxide nanoparticles decorated on CuFe2O4 nanofibers as an effective adsorbent for removal of estrogenic contaminants (bisphenol A and 17-α ethinylestradiol) from water

CeO₂/CuFe₂O₄ nanofibers with high adsorption selectivity for bisphenol A (BPA) and 17-α ethinylestradiol (EE2) were synthesized by support of CeO₂ on the CuFe₂O₄ nanofibers. The characteristics of nanocomposite were investigated via using XRD analysis, FT-IR, SEM, pH_pzc, and Brunauer, Emmett, and Teller methods. The results showed that the maximum adsorption capacities of adsorbent for BPA and EE2 were 226.9 and 179 mg g^?1, respectively. Moreover, the regeneration experiments illustrated that synthesized adsorbent could be recovered, and it showed good recycling ability after being used for six cycles. The isotherm analysis indicated that the equilibrium data could be represented by the Langmuir–Freundlich model. The thermodynamic study showed that the adsorption processes were spontaneous and endothermic under studied conditions.     

Synthesis of a starch–acrylic acid–chitosan copolymer as flocculant for dye removal

Flocculants prepared with modified natural polymers have recently attracted extensive attention in the field of water treatment. In this work, acrylic acid was successfully grafted onto the backbones of starch and chitosan by free radical polymerization. The synthesis parameters of initiator concentration, reaction temperature, and neutralization degree of acrylic acid were optimized as 0.4 wt %, 50 °C, and 70%, respectively, according to the flocculation performance. The ternary copolymer starch–acrylic acid–chitosan (SAAC) could completely remove Acid Blue 113 from 100 mg/L of simulated wastewater (color removal efficiency 99.7%) at the flocculant dosage of 100 mg/L. The SAAC also had effective flocculation capability in a wide range of flocculant dosages and pH values of wastewater. The ternary copolymer based on two natural polymers has enormous potential as flocculant with its advantages of low price, ecofriendliness, and high performance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47437.     

Self-assembly of α-MoO3 flower as a highly effective organics adsorbent for water purification

We report α-MoO₃ flowers as a highly effective organics adsorbent for the first time. With α-MoO₃ microfibers (MFs), α-MoO₃ flowers uniformly self-assemble on a carbon cloth, serving as a great organics scavenger. They not only provide a high specific surface area but also possess van der Waals force, both of which guarantee a high adsorption efficiency for multiple organics. Nearly 100% of Rhodamine B (RhB), methylene blue (MB), and crystal violet (CV) are rapidly adsorbed while flowing through the designed α-MoO₃ flower-based filtration device. Even after five recycling times, its high adsorption efficiency toward RhB remains unaffected. The adsorption capacity of α-MoO₃ flowers for RhB, MB, and CV reaches up to 4974, 6217, and 3886 mg/m², respectively. Additionally, this novel adsorbent can adapt to a wide pH range, maintaining the excellent capacity of 4774 and 4473 mg/m² toward RhB at pH of 2.0 and 12.0. The α-MoO₃ flowers can also adsorb other organics, including MO, noroxin, and tetracycline hydrochloride. Moreover, the free-standing α-MoO₃ flowers on a carbon cloth realize the adsorptive filtration for organics removal, which not only require no conditions and no energy consumption but also avoid secondary pollution to the water as compared to the powdery adsorbents.     

Preparation and photocatalytic properties of a novel kind of loaded photocatalyst of TiO2/SiO2/γ‐Fe2O3

A novel kind of loaded photocatalyst of TiO₂/SiO₂/γ‐Fe₂O₃ (TSF) that can photodegrade effectively organic pollutants in the dispersion system and can be recycled easily by a magnetic field is reported in this paper. The γ‐Fe₂O₃ cores in TiO₂/γ‐Fe₂O₃ are found to reduce the activity of the TiO₂ photocatalyst in the photodegradation of dyes under either UV or visible light irradiation. Addition of a SiO₂ membrane between the γ‐Fe₂O₃ core and the TiO₂ shell weakens efficiently the influence of the γ‐Fe₂O₃ cores on the TiO₂ photocatalytic activity and leads to a highly active and magnetically separable photocatalyst on TSF. Comparison of the photodegradation processes of dyes under UV and visible irradiation is also carried out. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis of menthols from citral on Ni/SiO2–Al2O3 catalysts

The one-pot synthesis of menthols from citral was studied on Ni/SiO₂–AlO₃ catalysts containing 3.6%, 8.8% and 11.4% Ni. The yield of menthols increased with the amount of Ni up to 94% on Ni(11.4%)/SiO₂–AlO₃, reflecting the diminution of byproducts formation via acid-catalyzed reactions. The sample deactivation was studied by performing two consecutive catalytic tests. Results showed that Ni(11.4%)/SiO₂–AlO₃ was a stable, active, and highly selective catalyst because it contained the appropriate density and strength of bifunctional acid/Ni⁰ active sites to efficiently promote the hydrogenation/isomerization pathway involved in the reaction network while avoiding coke formation.