One-step synthesis of Fe2O3 nano-rod modified reduced graphene oxide composites for effective Cr(vi) removal: removal capability and mechanism

Reduced graphene oxide (rGO) supported Fe₂O₃ nanorod composites were prepared via a one-step hydrothermal method and further utilized for hexavalent chromium (Cr(vi)) removal from aqueous environments. The composite material exhibited an excellent removal efficiency for chromium (47.28 mg L⁻¹), which was attributed to the electrostatic attraction and chemical reduction of chromium by the material. The removal mechanism was studied by SEM, BET, XPS, and FTIR. The results demonstrated that rGO was successfully modified by Fe₂O₃ nanorods (approximately 50 nm wide). Compared with graphene oxide (GO), the compound was much more easily separated from the solution after completing the removal. Furthermore, XPS characterization showed that Cr(vi) could also be reduced to low-toxicity Cr(iii) by hydroxyl groups. In the variables test, it was found that the removal process was pH-dependent. The results of the designed experiments for exploring the adsorption kinetics, isotherms and thermodynamics indicated that the removal process obeyed a pseudo-second-order kinetics model, Langmuir isotherm model and that it was a spontaneous exothermal process. This study provides the possibility of hydrothermal synthesis of Fe₂O₃/rGO for use as an excellent material to remove Cr(vi) from aqueous environments.

Reduced graphene oxide (rGO) supported Fe₂O₃ nanorod composites were prepared via a one-step hydrothermal method and further utilized for hexavalent chromium (Cr(vi)) removal from aqueous environments.     

Facile preparation of hybrid porous polyanilines for highly efficient Cr(vi) removal

In the present work, leucoemeraldine-based hybrid porous polyanilines (LHPPs) have been synthesized by the Friedel–Crafts reaction of leucoemeraldine and octavinylsilsesquioxane (OVS) for Cr(vi) removal. The resulting LHPPs were characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and N₂ adsorption–desorption. The findings indiated that the LHPPs were amorphous, with apparent surface areas (S_BET) in the range of 147 to 388 m² g⁻¹ and total volumes in the range of 0.13 to 0.44 cm³ g⁻¹. Cr(vi) removal experiments displayed that the LHPPs exhibited highly efficient Cr(vi) removal performance. The maximum Cr(vi) removal capacity of LHPP-1 was 990.1 mg g⁻¹ at 308 K and pH 1, which is higher than those of other reported polyaniline-based adsorbents. The adsorption process was a spontaneous, endothermic and chemical adsorption process. The adsorption behavior agreed well with Langmuir models and pseudo second-order equations. X-ray photoelectron spectroscopy and Fourier transformed infrared (FTIR) spectroscopy analysis revealed that the highly efficient Cr(vi) removal performance can be mainly attributed to the existence of numerous amine and imine groups on the surface of the LHPPs; these can function as adsorption active sites for Cr(vi) removal through electrostatic adsorption and reduction to Cr(iii) under acidic conditions. Moreover, the LHPPs exhibited excellent adsorption selectivity for Cr(vi) despite the presence of other metal ions (K⁺, Cu²⁺, Mn²⁺) and anions (NO₃⁻, SO₄²⁻). Therefore, the LHPPs have potential applications for Cr(vi) removal in industrial wastewater.

In the present work, leucoemeraldine-based hybrid porous polyanilines (LHPPs) have been synthesized by the Friedel–Crafts reaction of leucoemeraldine and octavinylsilsesquioxane (OVS) for Cr(vi) removal.     

Magnetic GO/Fe3O4 for rapid malachite green (MG) removal from aqueous solutions: a reversible adsorption

Magnetic GO/Fe₃O₄ was synthesized using co-precipitation of Fe²⁺ and Fe³⁺ composited with graphene oxide (GO) in alkaline conditions. SEM, XPS, FTIR, N₂ adsorption and VSM techniques were employed to characterize the surface peculiarities of GO/Fe₃O₄ and it was then used for removal of malachite green (MG). The key influencing factors on adsorption, such as mass ratio of GO, pH value and dosage of GO/Fe₃O₄, were investigated. The Freundlich isotherm was well fitted to the experimental data, suggesting GO/Fe₃O₄ has more than one type of reactive site. By comparing the adsorption of anionic dyes and cationic dyes onto GO/Fe₃O₄, it was concluded that GO/Fe₃O₄ could be extensively applied to take up cationic dyes mainly for electrostatic interaction. In addition, the spent GO/Fe₃O₄ was almost 100% recovered in a water bath at 80 °C. An ultraviolet-visible (UV-vis) spectrophotometer and an atom adsorption spectrophotometer (AAS) were used to determine leached GO and Fe ions discharged into the treated solutions. Low leaching showed that magnetic GO/Fe₃O₄ is a stable environmentally-friendly material.

MG adsorbed onto magnetic GO/Fe₃O₄ by electrostatic interaction and π–π band.     

Promoted adsorptive removal of chromium(vi) ions from water by a green-synthesized hybrid magnetic nanocomposite (NFe3O4Starch-Glu-NFe3O4ED)

A novel magnetic starch-crosslinked-magnetic ethylenediamine nanocomposite, NFe₃O₄Starch-Glu-NFe₃O₄ED, was synthesized via microwave irradiation. The characteristics of the assembled NFe₃O₄Starch-Glu-NFe₃O₄ED nanocomposite were evaluated via XRD, FT-IR, TGA, BET, SEM and HR-TEM analyses. Its particle size was confirmed to be in the range 11.25–17.16 nm. The effectiveness of the designed nanocomposite for the removal of Cr(vi) ions was explored using the batch adsorption technique. Equilibrium results proved that the adsorptive removal of the target metal ions from aqueous solution was highly dependent on the optimized experimental parameters. The maximum adsorptive removal percentage values (%R) of Cr(vi) ions on NFe₃O₄Starch-Glu-NFe₃O₄ED obtained at pH 2.0 were 85.27%, 91.90%, and 96.47% using 10.0, 25.0, and 50.0 mg L⁻¹ Cr(vi), respectively, for an equilibrium time of 30 min. The adsorption process was found to be strongly influenced by the presence of interfering salts including NaCl, CaCl₂, KCl, MgCl₂, and NH₄Cl. Kinetic studies were performed and it was found that the pseudo-second and Elovich models well fitted the experimental data with the possible suggested ion-pair interaction mechanism. Different isotherm models were employed to assess the adsorption equilibrium, which was revealed by fitting Langmuir, Temkin and Freundlich models. The maximum uptake capacity based on the Langmuir model was 210.741 mg g⁻¹. The effect of temperature and thermodynamics confirmed that adsorption was spontaneous, feasible, and endothermic in nature. Finally, the validity and applicability of using the NFe₃O₄Starch-Glu-NFe₃O₄ED nanocomposite to remove Cr(vi) ions from real water matrices were confirmed in the range of 91.2–94.7 ± 2.2–3.7%.

A novel magnetic starch-crosslinked-magnetic ethylenediamine nanocomposite, NFe₃O₄Starch-Glu-NFe₃O₄ED, was synthesized via microwave irradiation for the removal of Cr(vi) ions from aquous solution using the batch adsorption technique.     

Facile solvothermal preparation of Fe3O4–Ag nanocomposite with excellent catalytic performance

Functional nanocomposites demonstrate excellent comprehensive properties and outstanding characteristics for numerous applications. Magnetic nanocomposites are an important type of composite materials, due to their applications in optics, medicine and catalysis. In this report, a new Fe₃O₄-loaded silver (Fe₃O₄–Ag) nanocomposite has been successfully synthesized via a simple solvothermal method and in situ growth of silver nanowires. The silver nanowires were prepared via the reduction of silver vanadate with the addition of uniformly dispersed Fe₃O₄ nanoparticles. Structural and morphological characterizations of the obtained Fe₃O₄–Ag nanocomposite were carried out using many characterization methods. As a new composite catalyst, the synthesized magnetic Fe₃O₄–Ag nanocomposite displayed a high utilization rate of catalytically active sites in catalytic reaction medium and showed good separation and recovery using an external magnetic field. The facile preparation and good catalytic performance of this Fe₃O₄–Ag nanocomposite material demonstrate its potential applications in catalytic treatment and composite materials.

A new Fe₃O₄–Ag nanocomposite was prepared via solvothermal method, demonstrating potential application in catalytic degradation of wastewater treatment and composite materials.     

Surfactant-assisted hydrothermal synthesis of rGO/SnIn4S8 nanosheets and their application in complete removal of Cr(vi)

To solve the problem of contamination of hexavalent chromium (Cr(vi)), visible-light-driven graphene-based ternary metal chalcogenide nanosheets (rGO/SnIn₄S₈) were synthesized via a one-pot surfactant-assisted hydrothermal method for the photoreduction of Cr(vi). Characterizations demonstrated that SnIn₄S₈ nanosheets were uniformly distributed on the surface of rGO and the as-synthesized nanosheets exhibited excellent photocatalytic activity under visible light. In addition, the effects of pH, concentration of critic acid, holes and electron scavengers on the reduction of Cr(vi) were systematically investigated. It was found that 50 mg L⁻¹ of Cr(vi) could be completely removed within 30 min at pH 2 when citric acid served as a hole scavenger. Kinetic studies showed that the photocatalytic reduction of Cr(vi) processes obeyed the pseudo first order model. Further study indicated that the Cr(iii) species was immediately adsorbed onto the surface of the rGO/SnIn₄S₈ nanosheets after photocatalytic reduction of Cr(vi). Additionally, recycling results suggested that rGO/SnIn₄S₈ nanosheets possessed high recycle ability and stability after repeated use (5 times). This effective and promising work might provide a new strategy for the photoreduction of Cr(vi) and complete removal of chromium from effluent through the novel photocatalyst rGO/SnIn₄S₈.

Fabrication of visible-light-responsive photocatalyst (rGO/SnIn₄S₈) for photoreduction of Cr(vi) and adsorption of Cr(iii).     

Self-assembly preparation of lignin–graphene oxide composite nanospheres for highly efficient Cr(vi) removal

Recently, research interest in the application of lignin is growing, especially as adsorbent material. However, single lignin shows unsatisfactory adsorption performance, and thus, construction of lignin-based nanocomposites is worth considering. Herein, we introduced graphene oxide (GO) into lignin to form lignin/GO (LGNs) composite nanospheres by a self-assembly method. FTIR and ¹H NMR spectroscopy illustrated that lignin and GO are tightly connected by hydrogen bonds. The LGNs as an environmental friendly material, also exhibit excellent performance for Cr(vi) removal. The maximum sorption capacity of LGNs is 368.78 mg g⁻¹, and the sorption efficiency is 1.5 times than that of lignin nanospheres (LNs). The removal process of Cr(vi) via LGNs mainly relies on electrostatic interaction, and it also involves the reduction of Cr(vi) to Cr(iii). Moreover, LGNs still have high adsorption performance after repeating five times with the sorption capacity of 150.4 mg g⁻¹ in 200 mg g⁻¹ Cr(vi) solution. Therefore, the prepared lignin–GO composite nanospheres have enormous potential as a low-cost, high-absorbent and recyclable adsorbent, and can be used in wastewater treatment.

Lignin/GO (LGNs) composite nanospheres were prepared by self-assembly method, which showed excellent adsorption performance for Cr(vi) removal.     

TiO2/Fe2O3 heterostructures with enhanced photocatalytic reduction of Cr(vi) under visible light irradiation

We report a study on the synthesis of TiO₂/Fe₂O₃ (TF) nanocomposites and their photocatalytic performance under visible-light irradiation. The characterization of structure and morphology shows that hematite Fe₂O₃ was deposited on anatase TiO₂ nanoparticles with particle sizes in the range of 20–100 nm. In contrast to pure TiO₂ and pure Fe₂O₃, the nanocomposites exhibited remarkable photocatalytic activity. For example, the photoreduction efficiency of TF0.5 reaches 100% for a 100 ppm Cr(vi) solution within 160 minutes. The photochemical properties were studied by various methods. Finally, we conclude that the excellent performance of the photocatalysts is mainly attributed to two aspects: the enhanced absorption of visible light and the synergistic effect of an internal electric field at the heterojunction and citric acid for promoting the separation of electron–hole pairs.

A TiO₂/Fe₂O₃ heterojunction with an internal electric field was constructed for enhancing photocatalytic reduction efficiency of Cr(vi).     

Removal of arsenic(v) from aqueous solutions using sulfur-doped Fe3O4 nanoparticles

In this study, magnetic sulfur-doped Fe₃O₄ nanoparticles (Fe₃O₄:S NPs) were applied as adsorbents for the removal of As(v). Fe₃O₄:S NPs were fabricated by a two-step route, which included low-temperature mixing and high-temperature sintering. The as-prepared Fe₃O₄:S NPs could effectively remove As(v) under a wide pH range of 2–10 and presented a high As(v) adsorption capacity of 58.38 mg g⁻¹, which was much better than undoped Fe₃O₄ nanoparticles (20.24 mg g⁻¹). Adsorption experiments exhibited a pseudo-second-order model of adsorption kinetics and a Langmuir isotherm model of adsorption isotherms. Additionally, the coexisting ions such as NO₃⁻, SO₄²⁻, and CO₃²⁻ had no significant effect on As(v) adsorption and the adsorbent worked well in actual smelting wastewater. XPS and FTIR spectra of Fe₃O₄:S NPs before and after As(v) adsorption showed that Fe–OH groups played a significant role in the adsorption mechanisms. Moreover, the magnetic Fe₃O₄:S NPs adsorbents after adsorption could be rapidly separated from wastewater with an external magnetic field. Therefore, Fe₃O₄:S NPs could be an ideal candidate for the removal of As(v) from water.

Magnetic Fe₃O₄:S NPs presented a much better As(v) adsorption performance than undoped Fe₃O₄ NPs due to sulfur doping.     

Fe(iii) and Cr(vi) ions' removal using AgNPs/GO/chitosan nanocomposite as an adsorbent for wastewater treatment

Heavy metal ions in water refer to significant risks to the biological system due to their high toxicity. Therefore, the decontamination of water polluted by heavy metal ions attracts significant interest of researchers. Adsorption by nanomaterials has been a widely used technique for removing heavy metal ions from water. Chitosan was extracted from shrimp shellfish and mixed with laboratory-prepared AgNPs/GO in the ratio of 3 : 1. A series of tests evaluates the best condition of pH, amount of adsorbent, retention time, stirring speed, temp, and initial concentration. The research was conducted under various conditions. Langmuir, Freundlich, Tempkin, and Dubinin–Radushkevich isotherms were also tested. Also, the column adsorption experiment was carried out on industrial wastewater at different flow rates and column bed heights. The optimal values of the contact time, pH, and adsorbent dose of Cr(vi) were found to be 80 min, 4, and 0.1 g 100 mL⁻¹, respectively, at room temperature (30 °C), agitation at 150 rpm, and initial concentration of 50 ppm. On the other hand, the optimal value of contact time, pH, and adsorbent dose of Fe(iii) were found to be 30 min, 6, and 0.02 g 100 mL⁻¹, respectively, at room temp (30 °C) with a stirring speed of 250 rpm and an initial concentration of 40 ppm. For Cr(vi) and Fe(iii), equilibrium studies show that the data fit the Freundlich isotherm well (correlation coefficient, R² = 0.98) (III). A link between the pseudo-second order active model and data fitting the pseudo-first order active models were made. Within the intraparticle diffusion model, there are four stages that the mechanism must go through before it is at equilibrium. The adsorbent was tested in an industrial adsorbent column. This test proves that the nanocomposite''s adsorption capacity can be restored by washing it with 0.1 M HCl, as shown by the periodicity test. After four cycles, the amount of Cr(vi) adsorbed on AgNPs/GO/chitosan was just 20%, which is insufficient for further adsorption experiments. Cr(vi) removal rates (%R) decreased slightly.

Steps of AgNPs/GO/chitosan nanocomposite preparation.     

As(iii) removal through catalytic oxidation and Fe(iii) precipitation

To remove arsenite (As(iii)) from wastewater effectively, the catalytic oxidation of As(iii) to arsenate (As(v)) and As(v) precipitation with iron ions (Fe(iii)) was investigated. The Pt/SiO₂ catalyst functioned as a reaction site for As(iii) with oxygen in the atmosphere. The combination of the Pt/SiO₂ catalyst and Fe(iii) precipitant improved the removal of As(iii) in the precipitate; Pt/SiO₂ worked as both an As(iii) oxidation site and precipitation site with Fe(iii) precipitant.

A Pt/SiO₂ catalyst promoted an oxidative reaction of arsenite to arsenate with air, and it also functioned as a nucleation site of its precipitate with iron precipitant, achieving high removal efficiency from water.     

Characterization of CMC–LDH beads and their application in the removal of Cr(vi) from aqueous solution

In this study, CMC–LDH beads were prepared and characterized using SEM, FTIR and TG analysis. The beads were applied for the removal of Cr(vi) from aqueous solution. The effects of adsorbent dosage, initial pH and initial concentration of Cr(vi) solution on Cr(vi) uptake were investigated in detail. Moreover, adsorption isotherms and adsorption kinetic models were employed to analyze the adsorption process, and a preliminary study of the reusability of the adsorbent was performed. The experimental results showed that the CMC–LDH beads could remove Cr(vi) from aqueous solution efficiently. When the initial concentration of the Cr(vi) solution was 100 mg L⁻¹ and the adsorbent dosage was 12 g L⁻¹, the removal efficiency of Cr(vi) reached 96.2%. After the CMC–LDH beads were reused 10 times, the removal efficiency of Cr(vi) still remained at 89.6%.

CMC–LDH beads were prepared, characterized and applied for the removal of heavy metal ions in this study.     

Retraction: Experimental and theoretical studies of the nanostructured {Fe3O4@SiO2@(CH2)3Im}C(CN)3 catalyst for 2-amino-3-cyanopyridine preparation via an anomeric based oxidation

Retraction of ‘Experimental and theoretical studies of the nanostructured {Fe₃O₄@SiO₂@(CH₂)₃Im}C(CN)₃ catalyst for 2-amino-3-cyanopyridine preparation via an anomeric based oxidation’ by Mohammad Ali Zolfigol et al., RSC Adv., 2016, 6, 50100–50111, https://doi.org/10.1039/C6RA12299J.

The Royal Society of Chemistry hereby wholly retracts this RSC Advances article as the synthesis of {Fe₃O₄@SiO₂@(CH₂)₃Im}C(CN)₃ reported in the article, whereby tricyanomethane is used as a starting material, is not reproducible. The authors stated that they did not report the synthesis of tricyanomethane in the published paper as they purchased this compound from a commercial center and used it in the synthesis of ionic liquids, molten salts and various kinds of catalysts. The authors thought the reaction between tricyanomethane and organic bases is a simple acid–base reaction, therefore they did not cite the previously reported literature and its related history for the preparation of tricyanomethane. However, according to papers by Banert et al.,^1,2 and based on their obtained analysis of the chemical sold to them as tricyanomethane, it became clear to the authors that this purchased compound was not tricyanomethane as there were differences in the ¹H NMR and ¹³C NMR chemical shift between the purchased compound and the reports of Banert et al.¹ According to these documents, the authors believe that the compound sold to them as tricyanomethane was fake. While the authors have now re-prepared {Fe₃O₄@SiO₂@(CH₂)₃Im}C(CN)₃, by synthesising potassium tricyanomethanide as a starting material for the synthesis,^3–5 the synthesis reported in this article is not accurate. Therefore, this article is being retracted to avoid misleading readers and to protect the accuracy and integrity of the scientific record.Mohammad Ali Zolfigol and Meysam Yarie oppose the retraction. Mahya Kiafar, Avat (Arman) Taherpour and Mahdi Saeidi-Rad were contacted but did not respond.Signed: Laura Fisher, Executive Editor, RSC AdvancesDate: 17^th August 2022     

High capacity and fast removal of Cr(vi) by alkali lignin-based poly(tetraethylene pentamine-pyrogallol) sorbent

In this work, a novel alkali lignin-based adsorption material, alkali lignin-based poly(tetraethylene pentamine-pyrogallol) (AL-PTAP), was prepared using a Mannich reaction and catechol-amine reaction for removal of Cr(vi). It was characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The effects of tetraethylene pentamine (TEPA) dosage, pyrogallol (PL) dosage, contact time, pH, temperature and other factors on the adsorption behavior of the adsorbent were systematically investigated. These experimental data show that the adsorption behavior conforms to the pseudo-second-order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity is 769.2 mg g⁻¹ at 303 K, which is much higher than that of alkali lignin (AL). AL-PTAP can achieve a removal rate of almost 100% for Cr(vi) solutions with a concentration of less than 90 mg L⁻¹ at 1 min. Furthermore, the toxic Cr(vi) is partly reduced to nontoxic Cr(iii) during the adsorption process. Therefore, AL-PTAP is a fast and efficient alkali lignin-based adsorbent, which is expected to improve the utilization value of alkali lignin in Cr(vi) wastewater treatment.

The alkali lignin-based poly(tetraethylene pentamine-pyrogallol) (AL-PTAP) was prepared with an adsorption capacity of 769.2 mg g⁻¹ and a removal percentage of almost 100% within 1 min at an initial concentration of less than 90 mg L⁻¹.     

The enhanced visible-light-induced photocatalytic activities of bimetallic Mn–Fe MOFs for the highly efficient reductive removal of Cr(vi)

The photocatalytic efficiencies of bimetallic MOFs, namely STA-12-Mn–Fe, for the reductive removal of Cr(vi) were explored. The best effective variable values were obtained and correlation between the response and influential variables was optimized via experimental design methodology. Complete Cr(vi) removal was achieved under natural sunlight and fluorescent 40 W lamp radiation at pH 2, with an initial Cr(vi) concentration of 20 mg L⁻¹, and 10 mg of photocatalyst within 30 min. A pseudo-first-order rate constant of 0.132 min⁻¹ at T = 298 K was obtained for the Cr(vi) reduction reaction. The title catalysts revealed high performance in the visible region based on photoefficiency measurements, while improved activity was observed compared to the corresponding single-metal MOFs under natural sunlight, highlighting the synergistic effect between the two metal ions. Trapping experiment results proved that direct electron transfer is the main pathway during the photocatalytic Cr(vi) reduction process.

The photocatalytic efficiencies of bimetallic MOFs for the reductive removal of Cr(vi) were explored. The catalysts revealed higher performance compared to the corresponding single-metal MOFs, highlighting the synergistic effect between the two metal ions.     

Surface modification of biomaterials based on cocoa shell with improved nitrate and Cr(vi) removal

The present work addresses the development of simple, low-cost and eco-friendly cocoa-shell-based materials for efficient removal of heavy metal hexavalent chromium (Cr(vi)), and toxic nitrate (NO₃⁻) from aqueous solution. A conventional treatment process was used to purify cocoa shell (CS) into an adsorbent, followed by chemical grafting of dendrimers to promote its surface properties for nitrate and Cr(vi) removal. The morphology, surface charge, structure and stability of the new adsorbent were investigated by scanning electron microscopy, Fourier transform infrared and UV-visible spectroscopies, zeta potential, X-ray photoelectron spectrometry, and differential scanning calorimetry. The successful chemical grafting of the dendrimer (polyethyleneimine, PEI) onto purified CS was confirmed. CS-T-PEI-P proved to be a very efficient candidate for the removal of nitrate and chromium(vi). Removal of the two pollutants at different initial concentrations and pH values was studied and discussed. Sorption of chromium and nitrate was found to obey 2^nd-order kinetics and a Freundlich-type isotherm, affording an uptake adsorption of 16.92 mg g⁻¹ for NO₃⁻ and 24.78 mg g⁻¹ for Cr(vi). These results open promising prospects for its potential applications as a low cost catalyst in wastewater treatment.

The present work addresses the development of simple, low-cost and eco-friendly cocoa-shell-based materials for efficient removal of heavy metal hexavalent chromium (Cr(vi)), and toxic nitrate (NO₃⁻) from aqueous solution.     

Preparation and application synthesis of magnetic nanocomposite using waste toner for the removal of Cr(vi)

In this study, a novel magnetic nanocomposite was prepared using waste toner (WT) through high temperature decomposition, and calcination was conducted in different atmospheres (air, ammonia, and vacuum). WT calcined in ammonia (WT(NH₃)), and it was then utilized as an efficient absorbent for the reduction of Cr(vi) in aqueous solutions; a batch experiment with different conditions was performed to investigate its Cr(vi) removal ability. The effects of two pH-regulating acid (HCl and H₂SO₄) treatments were also studied. It was found that WT(NH₃) could remove about 99% Cr(vi) at pH 2 under H₂SO₄ treatment. The XRD and TEM results coupled with VSM results confirmed that WT(NH₃) is an Fe₃O₄/Fe₂N nanohybrid, which possesses excellent water-dispersibility and remarkable magnetic properties. XPS analysis showed the presence of Cr(vi) and Cr(iii) on the surface of WT(NH₃), which indicated that Cr(vi) was reduced to Cr(iii). Furthermore, H₂SO₄ regulation also promoted the reduction of Cr(vi) by WT(NH₃), and this reduction was higher than that obtained by HCl regulation.

A novel magnetic nanocomposite is prepared using waste toner via calcination in ammonia, which exhibits excellent magnetic properties and high efficiency for the removal of Cr(vi) via pH regulation using H₂SO₄.     

超顺磁Fe3O4/SiO2-聚乙烯亚胺复合微球的制备及基因传递应用

背景：在基因治疗中选择合适、低毒、对人体和环境无害的载体,使基因高效地转移至靶向部位并有效表达相关产物尤为关键。目的：制备超顺磁性Fe3O4/SiO2-聚乙酰亚胺复合微球。方法：通过乳化溶剂挥发法制备Fe3O4纳米粒子聚集体,再利用stober法合成超顺磁性Fe3O4/SiO2核壳型微球,进一步在该微球表面修饰聚乙酰亚胺,得到超顺磁性Fe3O4/SiO2-聚乙酰亚胺复合微球,并对其进行透射电镜、Zeta电位和磁性等结构性能表征。将Fe3O4/SiO2-聚乙酰亚胺复合微球与Plasmid DNA按照不同的质量比（29∶1,39∶1,49∶1,59∶1,68∶1,78∶1,88∶1）混合,通过凝胶电泳测定该复合微球与绿色荧光蛋白基因的结合能力。将Plasmid DNA分别与Fe3O4/SiO2-聚乙酰亚胺、聚乙酰亚胺混合,通过共聚焦荧光显微镜观测其在HeLa细胞中转染绿色荧光蛋白基因的情况。结果与结论：成功合成了Fe3O4/SiO2-聚乙酰亚胺复合微球,分散性良好,粒径分布均匀,约为100 nm,表面电荷为21.07 mV,饱和磁化强度为28.05 emu/g,为超顺磁性。随着复合微球与Plasmid DNA质量比的不断增加,越来越多的Plasmid DNA质粒被吸附在Fe3O4/SiO2-聚乙酰亚胺复合微球上,此时Plasmid DNA质粒过量,当质量比达到59∶1时,所有的pDNA质粒都被吸附在复合微球上;质量比大于59∶1时,复合微球过量,因此质量比为59∶1时二者均无过量,结果较好,用于 HeLa 细胞转染。与聚乙酰亚胺相比, Fe3O4/SiO2-聚乙酰亚胺复合微球可显著提高Plasmid DNA的转染效率。     

Enhanced removal of chromium(vi) by Fe(iii)-reducing bacterium coated ZVI for wastewater treatment: batch and column experiments

In order to effectively destroy the structure of the passive oxidation film that covers zero-valent iron (ZVI), an Fe(iii)-reducing strain, namely Morganella sp., was isolated from anaerobic activated sludge and coated on ZVI, which was distributed in porous ceramsite made of iron dust, kaolin and straw, with a ratio of 7 : 3 : 1. Batch experiments showed that under the optimized conditions, the maximum removal amount of Cr(vi) by ZVI increased from 7.33 mg g⁻¹ to 26.87 mg g⁻¹ in the presence of the Fe(iii)-reducing bacterium. The column experiment was performed with the addition of the agar globules to supply nutrients to the strain. Compared with ZVI, the column penetration time and maximum capture amount of RB-ZVI increased to 17 h and 112.5 mg g⁻¹, respectively, on the 15^th day. Furthermore, the service life of RB-ZVI was prolonged in the existence of the strain. Based on X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy analyses, the key mechanisms for the removal of Cr(vi) by ZVI coated with Fe(iii)-reducing bacterium were determined to be adsorption, reduction, coprecipitation and biomineralization.

To effectively destroy the structure of the passive oxidation film covering zero-valent iron (ZVI), an Fe(iii)-reducing strain, Morganella sp., was isolated from anaerobic activated sludge and coated on the ZVI.     

Copper(ii)-containing tungstotellurates(vi): syntheses,structures and their catalytic performances in selective oxidation of thioethers

We report the syntheses and structures of two new copper(ii)-containing tungstotellurates(vi) Na₁₂[Te^VI₂W₈O₃₈Cu₂(H₂O)₂]·7H₂O (Te₂W₈Cu₂) and Na₆[Te^VIW₆O₂₄Cu(NH₂CH₂CO₂)₂]·6H₂O (TeW₆Cu). The two compounds were synthesized by a simple one-pot method and characterized by single-crystal X-ray diffraction (XRD), powder XRD, FT-IR spectroscopy, elemental analysis, and thermogravimetric analysis in the solid state. Furthermore, their catalytic properties for the selective oxidation of thioethers were also studied systematically. The catalytic experiment results indicate that the tungstotellurate(vi) Te₂W₈Cu₂ is an effective heterogeneous catalyst for the selective oxidation of thioethers to sulfoxides or sulfones by an H₂O₂ oxidant at room temperature. Under the ambient conditions, Te₂W₈Cu₂ can convert 99% of methyl(phenyl)sulfane to sulfoxides or sulfones with 96% or 99% selectivity, respectively, and the utilization rate of H₂O₂ is up to 80%. Furthermore, Te₂W₈Cu₂ as a heterogeneous catalyst is stable in the reaction and could be reused at least five cycles with conserved activity.

Two copper(ii)-containing tungstotellurates(vi) were synthesized and present very high catalytic activity for the selective oxidation of thioethers under ambient conditions.