Synthesis of mesoporous rebar MWCNT/alumina composite (RMAC) nodules for the effective removal of methylene blue and Cr (VI) from an aqueous medium

Synergistic effects of sulfur vacancies and internal electric fields in FeS/MoS2 heterojunctions: A new approach to photocatalytic chromium removal

Molybdenum disulfide (MoS2) is heralded as an exemplary two-dimensional (2D) functional material, largely attributed to its distinctive layered structure. Upon forming heterojunctions with reducing species, MoS2 displays remarkable photocatalytic properties. In this research, we fabricated a novel heterojunction photocatalyst, FeS/MoS2-0.05, through the integration of FeS with hollow MoS2. This composite aims at the efficient photocatalytic reduction of hexavalent chromium (Cr(VI)). A comprehensive array of characterization techniques unveiled that MoS2 flakes, dispersed on FeS, provide numerous active sites for photocatalysis at the heterojunction interface. The inclusion of FeS seemingly promotes the formation of sulfur vacancies on MoS2. Consequently, this heterojunction catalyst exhibits photocatalytic activity surpassing pristine MoS2 by a factor of 3.77. The augmented activity of the FeS/MoS2-0.05 catalyst is attributed chiefly to an internal electric field at the interface. This field enhances the facilitation of charge transfer and separation significantly. Density functional theory (DFT) calculations, coupled with experimental analyses, corroborate this observation. Additionally, DFT calculations indicate that sulfur vacancies act as pivotal sites for Cr(VI) adsorption. Significantly, the adsorption energy of Cr(VI) species shows enhanced favorability under acidic conditions. Our results suggest that the FeS/MoS2-0.05 heterojunction photocatalyst presents substantial potential for the remediation of Cr(VI)-contaminated wastewater.

Selective Oxidation of Cyclohexene over the Mesoporous H-Beta Zeolite on Copper/Nickel Bimetal Catalyst in Continuous Reactor

The copper/nickel-metal on commercial H-Beta zeolite supports was synthesized with different wt % (Ni) of 5, 10, 15, and 20, and was used in the cyclohexene epoxidation process. The synthesized catalyst has been used in a continuous reactor for the cyclohexene epoxidation process, with mild conditions and H2O2 as an oxidant. The catalytic performance was ascertained by adjusting parameters such as the temperature, pressure, WHSV, reaction time, and solvents. The catalytic performance showed the resulting yield in both cyclohexene conversion and selectivity was more than 98.5%. The catalyst's textural attributes, morphology, chemical composition, and stability were determined using FT-IR, XRD, BET, HR-SEM, and TPD. The most active catalyst among those that were synthesized was evaluated, and the reaction parameters were selected to optimize yield and conversion. The H-Beta/Cu/Ni (15%) catalyst has the best conversion (98.5%) and selectivity (100%) for cyclohexene among the catalysts examined. Cu and Ni(15%) metals were successfully added to the H-Beta zeolite, causing little damage to the crystalline structure and resulting in good reusability over five cycles, as well as little loss of catalytic selectivity. Acetonitrile was the solvent that provided the highest conversion and selectivity among the others. These findings show that H-Beta/Cu/Ni bimetallic catalysts have the potential to be effective epoxidation catalysts. Because of their outstanding conversion and selectivity, the continuous reaction technique used in this work makes them appropriate for industrial production-level applications.

Nitrobenzene reduction promoted by the integration of carbon nanotubes and Geobacter sulfurreducens

Electron shuttles (ES) can mediate long-distance electron transfer between extracellular respiratory bacteria (ERB) and the surroundings. However, the effects of graphite structure in ES on the extracellular electron transfer (EET) process remain ambiguous. This work investigated the function of graphite structure in the process of nitrobenzene (NB) degradation by Geobacter sulfurreducens PCA, in which highly aromatic carbon nanotubes (CNTs) was studied as a typical ES. The results showed that the addition of 1.5 g L^-1 of CNTs improved the NB biodegradation up to 81.2%, plus 18.8% NB loss due to the adsorption property of CNTs, achieving complete removal of 200 μM NB within 9 h. The amendment of CNTs greatly increased the EET rate, indicating that graphite structure exhibited excellent electron shuttle performance. Furthermore, Raman spectrum proved that CNTs obtained better graphite structure after 90 h of cultivation with strain PCA, resulting in higher electrochemical performance. Also, CNTs was perceived as the "Contaminant Reservoir", which alleviated the toxic effect of NB and shortened the distance of EET process. Overall, this work focused on the effects of material graphite structure on the EET process, which enriched the understanding of the interaction between CNTs and ERB, and these results might promote their application in the in-situ bioremediation of nitroaromatic-polluted environment.

Adsorptive removal of anionic azo dye by Al3+-modified magnetic biochar obtained from low pyrolysis temperatures of chitosan

Magnetic γ-Fe₂O₃/Al³⁺@chitosan-derived biochar (m-Fe₂O₃/Al³⁺@CB) was prepared by introducing magnetic maghemite (γ-Fe₂O₃) nanoparticles and aluminum sulfate [Al₂(SO₄)₃] into chitosan-derived biochar (CB) obtained at low pyrolysis temperatures. m-Fe₂O₃/Al³⁺@CB was used to remove typical anionic azo dye (Congo red, CR). Effects of initial CR concentration, contact time, initial pH value, background electrolytes, and temperature on CR adsorption by m-Fe₂O₃/Al³⁺@CB were studied. Compared with magnetic chitosan-derived biochar (m-Fe₂O₃@CB), m-Fe₂O₃/Al³⁺@CB exhibited excellent performance for a wider range of pH values (pH 1-7) and in the presence of background electrolyte. The introduction of Al³⁺ is an effective method for improving the properties of magnetic chitosan-derived biochar. High CR adsorption capacity (636.94 mg g^-1) of m-Fe₂O₃/Al³⁺@CB could result from collaborative effect of flocculation/coagulation and electrostatic attraction. These results demonstrated that m-Fe₂O₃/Al³⁺@CB is a potential adsorbent for effective removal of organic dyes from aqueous solution due to its high adsorption capacity and convenient magnetic recovery and stronger anti-interference ability against coexisting anions in wastewater.

Synthesis of graphene oxide-modified porous chitosan cross-linked polyaniline composite for static and dynamic removal of Cr(VI)

A novel ternary composite was synthesized comprising graphene oxide-modified porous chitosan cross-linked polyaniline (GO@CS-PANI) by improved Hummers method, followed by cross-linking and grafting. The morphological, structural, and electrical properties of the composite were characterized by FESEM, BET, XRD, RAMAN, FTIR spectra, and zeta potential. It was found that the composite shows excellent Cr(VI) removal performance both in static and dynamic adsorption. The optimal adsorption parameters were solution at pH of 2.0, adsorbent dosage of 0.4 g/L, time of 45 min, and temperature of 35 °C. The Langmuir isotherm model was the best-fitted model, indicating homogeneous adsorption with maximum uptake of 539.83 mg/g. Pseudo-second-order was the best-fitted kinetic model, and the rate was controlled by film diffusion. Thermodynamic data demonstrated that the process was spontaneous, endothermic, and feasible. From the dynamic study, it was witnessed that a lower flow rate and a higher bed height were suitable for maximum adsorption performance. The Thomas model was the best-fitted model for data obtained from the dynamic study. Competition from interfering ions showed that anions have little effect on Cr(VI) removal, whereas cations have no such effect. The adsorption mechanism involved electrostatic attraction, π-π interaction, ion exchange, and metal ion complexion. After five cycles of adsorption-desorption study, the composite still removed 76% Cr(VI). These findings of the present study and the reusable nature of GO@CS-PANI composite signify the innovative and excellent adsorbent for wastewater treatment.

Growth of MWCNTs from Azadirachta indica oil for optimization of chromium(VI) removal efficiency using machine learning approach

The main objective of the present study is to develop artificial neural networks (ANN) to predict the adsorption efficiency of multi-walled carbon nanotubes (MWCNTs) on Cr(VI) removal. Polydisperse MWCNTs were synthesized at 750 °C on alumina supported Fe-Co-Mo catalyst using CVD (chemical vapor deposition)-assisted spray pyrolysis of Azadirachta indica (Neem) oil under inert Argon (Ar) atmosphere. Growth of MCWNTs with inner diameters between 9 and 14 nm was corroborated by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction analysis (XRD), and Raman spectral evidence assessments. The metal-ion adsorbent capacity (Cr-VI) of the as such prepared MWCNTs was examined for industrial purposes. Different parameters such as adsorption isotherms, kinetics, and thermodynamic parameters were analyzed for the removal of metal ions with MWCNTs. The results of isotherm, kinetic, and thermodynamic study indicated that the process suited well with Langmuir isotherm, pseudo second-order kinetics, and followed endothermic reaction, respectively. The effects of parameters such as adsorbent dosage, concentration of chromium ion (Cr-VI), pH, and contact time were studied to optimize the maximum removal of Cr(VI). In order to optimize the process conditions using Artificial Neural Networks, Box-Behnken design (BBD) was used to design the batch adsorption experiments, and the resulting datasets were used as the input for ANN. To predict the adsorption efficiency, various ANN architectures were examined using different training algorithms, number of neurons in the hidden layer, and the transfer function for the hidden and output layers. A neural network structure with Levenberg-Marquardt (LM) training algorithm, 14 hidden neurons, and tangent sigmoid transfer function at the hidden layer and logarithmic sigmoid transfer function at the output layer furnished the best level of prediction results. Comparing with experimental data, the optimal model capitulated mean square error (MSE),and correlation coefficient (R²) of 0.0324 and 0.99512, respectively. The results showed that ANN is well-organized in predicting the adsorption efficiency of MWCNTs for Cr(VI) metal ion removal process.

A comprehensive review on the decontamination of lead(ii) from water and wastewater by low-cost biosorbents

The disadvantages of conventional methods in water and wastewater management including the demand for high energy consumption, the creation of secondary toxic sludge, and operation cost are much too high for developing countries. However, adsorption using low-cost biosorbents is the most efficient non-conventional technique for heavy metals removal. The high adsorption capacities, cost-effectiveness, and the abundance of agricultural waste materials in nature are the important parameters that explain why these biosorbents are economical for heavy metals removal. The present investigation sought to review the biosorption of lead [Pb(ii)] onto low-cost biosorbents to understand their adsorption mechanism. The review shows that biosorption using low-cost biosorbents is eco-friendly, cost-effective, and is a simple technique for water and wastewater treatment containing lead(ii) ions. The batch biosorption tests carried out in most studies show that Pb(ii) biosorption by the low-cost biosorbents is dependent on biosorption variables such as pH of the aqueous solution, contact time, biosorbent dose, Pb(ii) initial concentration, and temperature. Furthermore, batch equilibrium data have been explored in many studies by evaluating the kinetics, isothermal and thermodynamic variables. Most of the studies on the adsorptive removal of Pb(ii) were found to follow the pseudo-second kinetic and Langmuir isotherm models with the thermodynamics variables suggesting the feasibility and spontaneous nature of Pb(ii) sequestration. However, gaps exist to increase biosorption ability, economic feasibility, optimization of the biosorption system, and desorption and regeneration of the used agricultural biosorbents.

Removal of Congo red dyes from aqueous solutions by porous γ-alumina nanoshells

Porous alumina has been shown to be an excellent adsorbent for Congo Red (CR) dye. In this work, highly porous g-Al₂O₃ nanoshells were synthesized from alumina coated carbon black (CB) obtained from a new deposition technique and used for removal of CR dye from aqueous solutions. Adsorption experiments were conducted in a batch mode and a series of parameters were investigated, including contact time, initial dye concentrations, ionic strength and pH of the solutions. It was found that equilibrium for CR adsorption can be reached within 30 min, much faster than reported by other studies in the literature on similar adsorbents. It was also found that the adsorption capacity of Al₂O₃ nanoshells is 44.8 % higher than that of alumina/CB. The adsorption capacity of Al₂O₃ nanoshells was more favorable at lower pH, and the optimal adsorption ability was achieved at pH 4.0 with a removal efficiency at 98.6 %. The Al₂O₃ nanoshells have a maximum adsorption capacity of 370.4 mg g^-1 (25 °C; pH 7; no salt added), better than or comparable to those reported in the literature. A pseudo-second-order kinetics model can best fit the kinetics of CR adsorption, which follows the Langmuir isotherm. The high adsorption capacity is attributed to the strong hydrogen-bonding interactions between the anionic dye and Al₂O₃ nanoshells surface as well as to the electrostatic interactions between CR dye and the Al₂O₃ nanoshells.

Magnetic solid-phase extraction using polydopamine-coated magnetic multiwalled carbon nanotube composites coupled with high performance liquid chromatography for the determination of chlorophenols

Polydopamine (PDA)-coated magnetic multiwalled carbon nanotube (M-MWCNT) composites were synthesized in two facile preparation steps, and were used as adsorbents for magnetic solid-phase extraction (MSPE) coupled with high-performance liquid chromatography (HPLC) for simultaneous extraction, enrichment and determination of five kinds of typical chlorophenols (CPs) in water samples. The as-prepared magnetic composites showed excellent magnetic properties and high thermal stability. Various main parameters influencing the extraction efficiency of MSPE were systematically investigated. Under the optimized MSPE-HPLC conditions, a high enrichment factor (EF) was obtained in the range of 85-112 for 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), 2,6-dichlorophenol (2,6-DCP), 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP). Good linearity was obtained in the range of 2.0-200 μg L^-1 for 2-CP and 4-CP and 1.0-200 μg L^-1 for 2,6-DCP, 2,4-DCP and 2,4,6-TCP, with a correlation coefficient (R²) higher than 0.9964. The limits of detection (LODs) and the limits of quantification (LOQs) were in the range of 0.10-0.31 μg L^-1 and 0.35-1.03 μg L^-1, respectively. The intraday and interday precisions evaluated using relative standard deviation (RSD) values were in the range of 1.05-2.25% and 1.88-2.83%, respectively. The validated MSPE-HPLC method was also successfully applied to analyze five kinds of CPs in tap water, lake water, river water and seawater samples, and satisfactory recoveries were obtained in the range of 76.87-106.5% with RSDs of 1.64-6.78%.

Polypyrrole functionalized Cobalt oxide Graphene (COPYGO) nanocomposite for the efficient removal of dyes and heavy metal pollutants from aqueous effluents

A cobalt oxide graphene nanocomposite functionalized with polypyrrole (COPYGO) having a heterogenous porous structure was synthesized using hydrothermal method. Microscopic imaging of the COPYGO surface revealed its highly porous and ordered features. The adsorption performance of the COPYGO composite was systemically investigated for Methylene Blue (MB), Congo red (CR) dyes and toxic lead (Pb(II)) and Cadmium (Cd(II)) metals. These were selected as they are the common pollutants in industrial wastewater. The COPYGO was found to be thermally stable up to 195 ^oC with a specific surface area of 133 m² g^-1. Experimental data indicates that the COPYGO follows Langmuir and Temkin adsorption isotherm. The COPYGO was efficient in removing MB (92.8%), CR (92.2%), Pb(II) (93.08%) and Cd(II) (95.28%) pollutants at pH 7.2, 5.0, 5.5 and 6.1 respectively from the simulated effluents. The maximum adsorption capacity (Q_max) observed for MB 663.018 mg g^-1, CR 659.056 mg g^-1, Pb(II) 780.363 mg g^-1 and Cd(II) 794.188 mg g^-1 pollutants. The thermodynamic analysis of the COPYGO indicates that the adsorption is endothermic and spontaneous in nature. COPYGO showed very high efficient removal rate for the pollutants in simulated effluents which guaranteed its benefits and efficacy in industrial wastewater treatment.

Decorating graphene oxide with zeolitic imidazolate framework (ZIF-8) and pseudo-boehmite offers ultra-high adsorption capacity of diclofenac in hospital effluents

This study reports on an easy and scalable synthesis method of a novel magnetic nanocomposite (GO/ZIF-8/γ-AlOOH) based on graphene oxide (GO) nanosheets decorated with zeolitic imidazolate framework-8 (ZIF-8), pseudo-boehmite (γ-AlOOH), and iron oxide (Fe₃O₄) nanoparticles by combining solvothermal and solid-state dispersion (SSD) methods. The nanocomposite was successfully applied to remove of diclofenac sodium (DCF) - a widely used pharmaceutical - from water. Response Surface Methodology (RSM) was used to optimize the adsorption process and assess the interactions among the influencing factors on DCF removal efficiency; including contact time, adsorbent dosage, initial pH, solution temperature, and DCF concentration. Adsorption isotherm results showed a good fitting with the Langmuir isotherm model with an exceptional adsorption capacity value of 2594 mg g^-1 at 30 °C, which was highly superior to the previously reported adsorbents. In addition, kinetic and thermodynamic investigations further illustrated that the adsorption process was fast (equilibrium time = 50 min) and endothermic. The regeneration of GO/ZIF-8/γ-AlOOH nanocomposite using acetic acid solution (10% v/v) after a simple magnetic separation was confirmed in five consecutive cycles, which eliminate the usage of organic solvents. The nanocomposite has also shown a superior performance in treating a simulated hospital effluent that contained various pharmaceuticals as well as other organic, and inorganic constituents.

Bionic chitosan-carbon imprinted aerogel for high selective recovery of Gd(Ⅲ) from end-of-life rare earth productions

High selective recovery of Gd(Ⅲ) from end-of-life rare earth productions is essential for cleaner production. Chitosan(CS), a biomaterial, has shown excellent results in water treatment. The amino and hydroxyl groups on the surface of CS play a vital role in adsorbing metal ions. Polydopamine has good stability, strong water dispersibility, and excellent biocompatibility. As a bio-crosslinking agent, the amino and phenolic hydroxyl groups on its surface can be combined with metal ions to help the material absorb metal ions. This paper combines the active groups of biomimetic materials and the mechanical properties of new nanomaterials multi-walled carbon nanotubes and graphene oxide, and prepared a high-performance chitosan-based aerogel MWCNT-PDA-CS-GO through heat and mass transfer at low temperature and low pressure. The adsorption mechanism of MWCNT-PDA-CS-GO for Gd(Ⅲ) was analyzed through a series of characterization and adsorption experiments. At pH 7.0, the maximum adsorption capacity of aerogel for Gd(Ⅲ) reached 150.86 mg g^-1. The relative selectivity of imprinted ions is 48.02 times higher than other ions. All the results indict MWCNT-PDA-CS-GO aerogel exhibits excellent selectivity and stability for effective recovery of Gd(Ⅲ).

Adsorption of Methylene blue and Congo red from aqueous solution using synthesized alumina-zirconia composite

Alumina-zirconia (Al₂O₃-ZrO₂) composite was prepared by combustion method and used to remove Congo red and Methylene blue from aqueous solutions. It was characterized using SEM-EDS, XRD and gas adsorption techniques. The results obtained from gas adsorption and SEM agree with each other, showing meso- and macro-porosity of inter-agglomerate pores. The removal of the two dyes was pH dependent, acidic pH favoured Congo red removal, while basic pH favoured Methylene blue. The, mechanism of adsorption was not limited to electrostatic attraction between the adsorbent and the dye molecules. Adsorption kinetic of both dyes was consistent with Pseudo-second-order model. The data obtained fitted to Langmuir and Liu isotherm models, with the maximum adsorption capacity of 57. 50 and 53.44 mg g^-1 for Congo red and Methylene blue, respectively. The thermodynamic parameters indicated that the adsorption is spontaneous and exothermic. The mechanism of adsorption was elucidated using XRD and FTIR techniques.

Fabrication of an electrochemical sensor with Au nanorods-graphene oxide hybrid nanocomposites for in situ measurement of cloxacillin

In recent years, considering the increasing use of antibiotics, and their continued entry into the environment, extensive research has been conducted on the impact of antibiotics on human health, water resources, and the environment. In this study, a suitable method has been proposed for detecting and elimination the trace amounts of the antibiotic cloxacillin in aqueous. For identify trace amounts of cloxacillin in solution, a new electrochemical nanosensor based on a screen printed carbon electrode (SPCE) modified with gold nanorods/graphene oxide was proposed. This nanosensor, which was prepared by self-assembling method, was capable of measuring cloxacillin in the 5.0-775.0 nM with a detection limit of 1.6 nM. In order to reduce the amount of antibiotics in the environment, a novel carbon nanocomposite based on sol-gel method was prepared and its application as a high-capacity adsorbent for the removal of cloxacillin was studied. In the antibiotic removal experiments, the effect of pH, contact time, different mass ratios of SWCNT and amount of nanocomposite adsorbent were also optimized by response surface methodology (RSM). The prepared nanosensor and synthesized carbon nanocomposites were then characterized by commonly identical techniques involve SEM, EDAX, BET and FT-IR. The presented nanosensor was successfully used for the in situ determination of Clox in adsorptive tests with reliable recovery. As well, the AuNR/GO/SPC electrode presented well stability, repeatability and reproducibility. In addition, good performance and high adsorption capacity make developed adsorbent as a suitable case for the removal of water-soluble pharmaceutical contaminants.

Treatment of Yellow Phosphorus Slag and Reuse of It as an Absorbent of Chromium (VI) Ions and Methylene Blue

Yellow phosphorus is used widely in the world for production of phosphoric acid, various phosphates, flame retardant, detergent, water treatment, metal surface treatment, etc. After the production of yellow phosphorus, a large amount of phosphorus sludge is discharged to environment, causing environment pollution. This work focused on treatment of yellow phosphorus slag (YPS) and application of it as an absorbent for chromium (VI) ion and methylene blue. The YPS was first washed with water to remove phosphoferrite (FeP) and impurities and then being milled and transferred to a float sorting system to obtain YPS particles. The characteristics of YPS particles were determined by inductively coupled plasma-mass-spectrometry (ICP-MS), energy-dispersive X-ray spectroscopy (EDX), infrared spectroscopy (IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), zeta potential, and nitrogen adsorption methods. The YPS particles were retreated with NaOH, HNO3, and EDTA solutions to evaluate the influence of these agents on metal ion and organic compound adsorption ability by YPS. The adsorption parameters of chromium (VI) ion and methylene blue (MB) by treated YPS particles were recognized by the ultraviolet-visible (UV-Vis) spectrometer. The effects of temperature, pH solution, and initial concentration of absorbed substances on the adsorption ability were investigated. The adsorption isotherms and adsorption kinetics of chromium (VI) ion and MB by YPS particles were also determined. The obtained results confirmed that the green technology used to treat the YPS2 particles is suitable to obtain an effective absorbent. The adsorption efficiency of YPS2 particles for removal of chromium (VI) ions is smaller than that for removal of MB in aqueous solutions. The adsorption isotherm of MB adsorption process is complied with the Langmuir isotherm while the adsorption kinetic fits well with the pseudo-second-order reaction model. The thermodynamic parameters of MB adsorption processed on YPS2 were calculated and discussed.

Adsorption of methylene blue onto porous carbon materials prepared from Na2EDTA

A simple self-activation preparation procedure and excellent adsorption performance for methylene blue.

Sequestrating anionic and cationic dyes from wastewater using spray dried biopolymeric magnetic composite: Experimental and theoretical studies

Spray dried cross-linked chitosan/cobalt ferrite composite was synthesized and applied as an adsorbent for the removal of acid orange II and methylene blue. The composite was structurally, thermally, morphologically and magnetically characterized. The result obtained shows that the magnetic composite was in form of microspheres, while cobalt ferrite was encapsulated in the cross-linked chitosan with saturation magnetization of 10.79 emu g^-1. Adsorption studies revealed that acid orange II adsorbed more favorably on the composite than methylene blue. The adsorption process is spontaneous and exothermic. Liu isotherm model was found to be applicable for the adsorption process. Computational studies showed that the formation of hydrogen bond between acid orange II and the magnetic composite (at both acidic and alkaline pH) contributed to its better adsorption than methylene blue. Adsorption capacity of acid orange II at pH 3 and methylene blue at pH 12 are 542 and 173 mg g^-1 respectively at 303 K base on Liu isotherm model.

Porous NiFe-oxide nanocubes derived from prussian blue analogue as efficient adsorbents for the removal of toxic metal ions and organic dyes

A novel porous NiFe-oxide nanocubes (NiFe NCs) binary material was successfully fabricated via a facile and scalable tactic, which involved a morphology-inherited heat treating of Ni₃[Fe(CN)₆]₂·xH₂O prussian blue analogue nanocubes as self-sacrificial templates. Consequently, it was demonstrated that the NiFe NCs consisted of primary nanostructure units and interconnected pores, with an average size of ˜80 nm. When employed as adsorbents, the as-prepared NiFe NCs displayed remarkable adsorption capacities for heavy metal ions (232.3 mg g^-1 for As(V) and 350.71 mg g^-1 for Cr(VI)) and organic dyes (284.99 mg g^-1 for XO and 31.97 mg g^-1 for CR at 298 K). The resulting NiFe NCs further revealed efficient regeneration and reusability even after five consecutive adsorption/desorption cycles. The microscopic spectrum analysis demonstrated that the interaction between As(V) and NiFe NCs was mainly ascribed to the metal-oxide bonds (MO) and hydroxyl groups (OH), while Cr(VI) adsorption was in conjunction with the reduction reaction of Cr(VI) to Cr(III). Furthermore, the adsorption of organic dyes on NiFe NCs depended on the pore structure and molecule sizes of the organic dye molecules. These findings make cost-efficient NiFe NCs materials a powerful candidate for remediating water contaminated with inorganic and organic contaminants.

Enteromorpha prolifera-derived Fe3C/C composite as advanced catalyst for hydroxyl radical generation and efficient removal for organic dye and antibiotic

Enteromorpha prolifera-derived Fe₃C/C composite has been fabricated through a facile one-step calcination method. As an advanced Fenton-like catalyst, the obtained Fe₃C/C composite displayed high catalytic reactivity to generate hydroxyl radicals. It is worth to note that the removal rate of methylene blue (MB) could effectively reach 100% in a wide pH range (pH = 2˜12) and the maximum degradation capacity of the composite is 660 mg/g. The stability and reusability of Fe₃C/C composite catalyst have also been tested, which could remain the removal rate at 100% after 6 consecutive runs. To illustrate the practical application possibility, the Fe₃C/C composite catalyst was used for degradation of papermaking and dyeing waste water, which could reduce the COD (chemical oxygen demand) value to less than 50. Additionally, the antibiotic norfloxacin (NOR) could also be catalytically removed by the Fe₃C/C composite and the possible removal pathway has also been proposed. The excellent removal performance of Fe₃C/C composite for MB and NOR may be attributed to the synergistic effect between porous carbon adsorption and Fe₃C catalysis. This study not only provides novel insights into recycling of waste biomass, but also paves a new way for the application of Fe₃C/C in dyes and antibiotics waste water treatment areas.

Construction of novel graphene-based materials GO@SiO2@C@Ni for Cr(VI) removal from aqueous solution

A series of novel sandwich-like GO@SiO₂@C@Ni composites were developed. The morphologies and adsorption capacities of the materials sintered at different carbonization temperatures were investigated. The formed GO@SiO₂@C@Ni-400 possessed of wonderful dispersion, large surface area (229.88 m²/g) and high saturation magnetization. Batch experimental results revealed that maximum adsorption capacities of these materials towards Cr(VI) were as follows: GO@SiO₂@C@Ni-400 (299.20 mg/g) > GO@SiO₂@C@Ni-500 (244.05 mg/g) > GO (202.39 mg/g) > Graphene@C@Ni (188.80 mg/g) > GO@SiO₂@C@Ni-600 (165.51 mg/g) > GO@SiO₂@C@Ni-700 (93.36 mg/g). Moreover, the influence of hydrochemistry, such as contact time, pH, co-existing ions and solution temperature, on Cr(VI) adsorption was researched as well. It was demonstrated that GO@SiO₂@C@Ni-400 had remarkable adsorption capacity for Cr(VI) removal under the acidic condition, hardly disturbed by other anions, and showed better adsorption performance at 328 K. Besides, On the base of X-ray photoelectron spectroscopy analysis, mechanisms of adsorption could be explained that Cr(VI) was reduced to Cr(III) by nitrogen dopant, and the complexation was existed between Cr(VI) and oxygen-containing functional groups. Additionally, GO@SiO₂@C@Ni-400 could be easily separated under the external magnetic field and displayed outstanding reusability. Herein, GO@SiO₂@C@Ni-400 opens up the possibility of future practical applications.