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The greatest problem in conventional Fenton reaction is the slow production of ROS (reactive oxygen species) because of the inefficient Fe 3+ /Fe 2+ conversion. Based on the extraordinary photo-response property of two-dimensional molybdenite (2DM), photogenerated electrons can be easy separated to accelerate the regeneration of Fe 2+ . In this work, Fe 2+ -anchored 2DM (2DM-Fe) was prepared and used as a heterogeneous Fenton catalyst to investigate the degradation efficiency to Methylene Blue (MB) in the presence of light. According to experimental results, 2DM-Fe exhibited extraordinary catalytic activity in MB elimination, which ascribed to the synergetic effect of photogenerated carriers and anchored Fe 2+ to H 2 O 2 activation. In addition, 2DM-Fe showed nearly 100% degradation efficiency to MB within 5 cycles with slight leaching amount of Mo and Fe ions, implying the strong stability and reusability in H 2 O 2 system. Furthermore, the influences of H 2 O 2 and 2DM-Fe dosages, pH values as well as the degradation efficiency to different dyes were also investigated. According to quenching experiments and EPR (electron paramagnetic resonance) test, the degradation mechanism of MB mainly ascribed to the oxidation of HO• and •O 2 - . This finding provides a novel strategy to design rational Fenton catalyst and has great significance to water remediation in the future., (Copyright © 2021. Published by Elsevier B.V.)

In this work, self-assembled gels were prepared with exfoliated montmorillonite and chitosan (EMCG) as the adsorbent for removing methyl orange (MO) from water in absence and presence of methylene blue (MB). Several techniques including scanning electron microscope (SEM), zeta potential, fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used for the characterization of the EMCG before and after removal of MO. The EMCG performed well in the removal of MO attributing to the electrostatic attraction, cation exchange and hydrogen bond. The adsorption behaviors were followed pseudo-second-order and Langmuir isotherm. More surprisingly, the maximum adsorption capacity of MO was obviously enhanced in the presence of MB that it increased from 545 mg g -1 (absence of MB) to 1060 mg g -1 with the shielding effect of MB on EMCG which allowed MO and MB to alternately arrange at the adsorption sites. This finding of the synergistic effect between the two dyes on the proposed composite opens up new vistas to imagine the enhanced purification of the wastewater with multiple dyes co-existed using the multifunctional adsorbents., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

TiO 2 loaded 2D montmorillonite (2DMMT)-chitosan-poly (acrylic acid) hydrogel with 3D network structure as a novel adsorbent for methylene blue (MB) removal was investigated. The hydrogel was formed via the polymerization and molecular forces between 2DMMT and polysaccharide. Physicochemical analysis and factor experiments were implemented on hydrogel. The results implied that hydrogel possessed a porous structure and high surface area, facilitating the access and removal of MB. A completely removal of MB could be achieved in a small hydrogel dose of 0.2 g/L within 120 min even after 5 regeneration cycles, which could lower costs and enhance efficiency dramatically. MB adsorption onto hydrogel was reasonably correlated with pseudo-second-order kinetic model and Redlich-Peterson isotherm model. MB adsorption mechanism onto hydrogel was analyzed by FTIR, EDS and XPS. It was found MB molecules reacted with carboxyl groups as well as substituted cation from 2DMMT. Such hydrogel could not only realize the green/sustainable application in water treatment, but also guide the preparation for polymer materials from polyelectrolyte and nanoclay., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Based on the strong activation activity and affinity of Co and MoS 2 for peroxymonosulfate (PMS), respectively, in this study, a CoS 2 /MoS 2 @chitosan (CoS 2 /MoS 2 @CS) gel with favorable photo responsive behavior was synthetically synthesized for more potent degradation of tetracycline (TC). It was found that CoS 2 /MoS 2 @CS had excellent catalytic active for the degradation of TC under visible light irradiation. The presence of CoS 2 /MoS 2 interfacial structure improve the electron transfer ability of the MoS 2 interface, and the degradation rate of TC was increased from 0.0106 min−1 to 0.0463 min−1, with a high degradation rate of 97.4 %. CoS 2 /MoS 2 can effectively degrade TC within 5 cycles, demonstrating superior cycling stability. In addition, the system degraded different organic pollutants (tetracycline (TC), tetracycline hydrochloride (TCH), crystal violet (CV), and methylene blue (MB)) with a degradation rate higher than 96 %, which supports the ability of the CoS 2 /MoS 2 @CS-PMS system to degrade various chemical contaminants. Quenching analysis indicates that SO 4 •− is the primary reactive chemical free radical for the degradation of TC in the CoS 2 /MoS 2 @CS-PMS system. It provides an approach of combining the synergistic action of Co (II) and photogenerated carriers for more efficient activation of PMS that some inspirations of heterojunction catalysts for AOP applications. • Construction of CoS 2 /MoS 2 heterojunction catalysts as PMS catalysts for TC degradation. • Catalytic activity and cycling stability of TC degradation by CoS 2 /MoS 2 @CS. • Ability of CoS 2 /MoS 2 @CS-PMS system to degrade a variety of organic pollutants. • Synergistic effect of Co(Ⅱ) and photogenerated carriers on TC degradation. [ABSTRACT FROM AUTHOR]

A new adsorbing material for crystal violet (CV) and methylene blue (MB) dye removal, fly ash and bentonite-supported microscale zero-valent iron (FB-mZVI), was synthesized by using iron-ore tailings (IOT) as the iron source. Palm kernel shells (PKSs) were used to reduce the iron oxide of the IOT to Feo. A statistical orthogonal method was used to evaluate the factors determining the adsorbent synthesis. It was found that the important factors were the mass ratio of the fly ash, bentonite, IOT, and PKSs as well as the synthesis time, temperature, and heating rate. Optimum mass ratio of the fly ash, bentonite, PKSs, and IOT was found to be 2:2:1:1, and optimum synthesis temperature, time, and heating rate were found to be 800°C, 10 min, and 10°C/min, respectively. An FB-mZVI adsorbent was used to remove the CV and MB from aqueous solutions. Removal efficiency for CV was much higher than that for MB. UV, XRD, and FTIR analyses revealed that the adsorption mechanisms for removal of CV were different from those for MB. Adsorption process was well described by the pseudo-second-order kinetic model, and Langmuir isotherm model better represented the adsorption isotherm data. [ABSTRACT FROM AUTHOR]

New microscale zero-valent iron adsorbent on fly ash and bentonite matrix for removal of crystal violet (CV) and methylene blue (MB) was synthesized through direct reduction of iron oxide using coke and palm kernel shell. The adsorbent was prepared as cylindrical shaped pellets to remove the CV and MB from the aqueous solution. Nitrogen adsorption-desorption isotherm and scanning electron microscopy (SEM) studies showed that the adsorbent is highly porous, and the iron particles are finely dispersed on the supporting material surfaces. FTIR and UV studies indicated that the C=C bonds in CV and C=N(CH) bonds in MB were affected in the adsorption process. MB switched to the reduced MBH species while CV was reduced to two small-size molecular compounds, explaining the higher CV adsorption in comparison to that of MB. The reduction of these compounds was coupled to the oxidation of Fe to FeO as revealed by XRD characterization of the adsorbent after adsorption. CV and MB adsorption isotherms fitted well with the Langmuir adsorption model. Different adsorption and reduction kinetic models were examined for the MB and CV removal processes. A better fit of the experimental data with the pseudo-second-order model was observed. CV and MB adsorption increased with temperature in the 30-50 °C range. At 50 °C, adsorption capacities of CV and MB reached to 89.9 and 42.8 mg/g, respectively. This new adsorbent showed a superior adsorption capacity for CV and MB when compared to other adsorbents. [ABSTRACT FROM AUTHOR]

The graphene oxides (GOs) with various content of metallic ions impurities were prepared, and the adsorption performance of the GO before and after elution was evaluated. The prepared GOs were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, inductively coupled plasma and atomic force microscopy. The results indicated that the metallic ion impurities hardly affected the interlayer distance, microstructure and thickness of the prepared GOs. The adsorption isotherm and adsorption kinetic results showed that the metallic ions adsorbed on the GO surface had a negative influence on both the adsorption capacity and rate. After eluted by HNO3 or HCl, most of the metallic ions adsorbed on the GO-91 surface were ion-exchanged by the protons of the acid eluents, and the purified GO showed enhanced equilibrium capacities and improved adsorption rate. The elution efficiency of HCl was better than that of HNO3, and the adsorption capacity and rate of the GO eluted by HCl approximately reached to those of the GO prepared from the graphite with high purity. It indicated that HCl could efficiently remove the metallic ions adsorbed on the GO surface. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The preparation and characterization of nanoscale zero-valent iron-loaded porous sepiolite, as well as its application in the decolorization of methylene blue in aqueous solution, have been studied in this work through the measurements of field emission scanning electron microscope with energy dispersive spectrometry, x-ray photoelectron spectrometry, Fourier transform infrared spectroscopy and specific surface area. The results showed that nanoscale zero-valent iron particles were successfully loaded on the surface and interior pores of sepiolite through physical adsorption. It was revealed that the decoloration capacity of methylene blue on nanoscale zero-valent iron-loaded porous sepiolite in water was comparable to that of nanoscale zero-valent iron, and nine times higher than that of natural sepiolite. This indicates that porous sepiolite was a good supporter for the loading of nanoscale zero-valent iron and nanoscale zero-valent iron-loaded sepiolite was a good decolorant because of its high decoloration efficiency and easy separation. [ABSTRACT FROM AUTHOR]

To investigate the co-influence of the pore size of adsorbents and the structure of adsorbates on adsorption capacity and rate, the adsorption of basic dyes, methylene blue (MB), and crystal violet (CV) onto a granular adsorbent based on fly ash (GAF) and a granular activated carbon (GAC) were conducted. MB and CV were selected as the target adsorbates due to their similar molecular weights (MB: 319.85 g/mol and CV: 407.98 g/mol) but different molecular structures (MB is line-shaped and CV is fork-shaped). Two different kinds of adsorbents, GAF and GAC, were used here: GAF, a mesoporous adsorbent (average pore diameter ≈ 4.28 nm) with small surface area (21.94 m2/g), and GAC, a microporous adsorbent (average pore diameter ≈ 0.45 nm) with high surface area (1,306 m2/g). Although the surface area of GAC was almost 60 times of GAF, the results of adsorption showed the adsorption capacity of GAC for MB was only 1.5 times of GAF (354.59 mg/g of GAC and 262.58 mg/g of GAF), whereas the adsorption capacity of GAC for CV was even less than that of GAC (327.77 mg/g of GAC and 430.73 mg/g of GAF). Moreover, thekpvalues obtained from intra-particle diffusion theory showed that the adsorption rate of both MB and CV in GAF were far bigger than in GAC. Thus, when choosing an adsorbent, surface area is not only the parameter should be considered, the pore size of adsorbents and the structure of adsorbates should also be considered. [ABSTRACT FROM AUTHOR]

The beneficiation of montmorillonite fines from ores has been studied with the dispersion-sedimentation process by using sodium phosphates as the dispersant in this work. This study was performed on a Ca-montmorillonite ore from China through the measurements of MB (methylene blue) adsorption and X-ray diffraction. Several parameters in the dispersing step, such as type and dosage of dispersant, solid concentration, and slurry stirring time, were tested to understand their effects on beneficiation. It was shown that the beneficiation process was very effective in upgrading montmorillonite, producing a high-grade montmorillonite concentrate. Simultaneously, the Ca-montmorillonite was transformed to Na-montmorillonite. It has been found that sodium pyrophosphate was the best phosphate dispersant for achieving a good beneficiation of montmorillonite from the ore, which might be due to the fact that pyrophosphate ions adsorbed on montmorillonite surfaces lead to a smaller swelling capacity of the mineral particles than other phosphate ions. [ABSTRACT FROM AUTHOR]

High-performance two-dimensional montmorillonite supported-poly (acrylamide-co-acrylic acid) hydrogel for dye removal was investigated. Montmorillonite cooperated with acrylamide and acrylic acid via polymerization, hydrogen-bond, amidation and electrostatic interactions to form the three-dimensional reticular-structured hydrogel with the free entrance for macromolecules. Adsorption tests revealed that the efficient removal (97%) for methylene blue at high concentration (200 mg/L) could be achieved via a small dose of hydrogel (0.5 g/L) within a short time (20 min). The excellent adsorption performance was profited from the electronegative surface and fully exposed reaction sites of two-dimensional montmorillonite, which could save the treatment cost and promote the removal effect compared with the conventional adsorbents. The adsorption process of methylene blue onto hydrogel could be fitted by both the pseudo-first-order and pseudo-second-order kinetics models, and the adsorption isotherm corresponded to the Sips model. The mechanism analysis based on Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy measurements illustrated that the reaction between carboxyl groups and methylene blue molecules as well as the cation-exchange enabled the hydrogel performing extraordinary adsorption efficiency. Image 1 • 3D reticular-structured hydrogel formed via polymerization, hydrogen-bond, amidation and electrostatic interactions. • 2DMMT supports and maintains the framework in hydrogel to make the free entrance for MB molecules. • Efficient removal for MB at high concentration is achieved via small dose of hydrogel within a short time. Two-dimensional montmorillonite with high surface area and fully-exposed active sites formed the reticular-structured hydrogel, showing excellent dye removal performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3D reticular-structured MMT nanosheets-based hydrogel beads were prepared. • High exfoliation degree of MMT nanosheets improve adsorption performance of hydrogel beads. • Hydrogel beads have high mechanical strength and adsorption capacity for methylene blue of 543.1 mg/g. • Hydrogel beads also shows excellent dynamic adsorption performance and recycling performance. In this work, hydrogel beads with 3D network structure were successfully prepared using montmorillonite nanosheets (MMTNS) combined with macromolecule polymers. Batch adsorption tests revealed that the increase in exfoliation degree of MMTNS was beneficial to improve the methylene blue (MB) adsorption on hydrogel beads (HB). In addition, the HB with 25 % MMTNS-3 dosage achieved high mechanical strength and reached the maximum adsorption capacity of 543.1 mg/g. Effects of MB concentration (40–120 mg/L), adsorbent dosage (1–1.5 g) and flow rate (5–15 mL/min) on fixed-bed column adsorption indicated that the HB column exhibited an excellent dynamic adsorption performance and recycling performance, much better than the D113 resin. The good fits of Pseudo-first-order model and Pseudo-second-order model and a better Langmuir model fitting result implied a monolayer chemical adsorption and physical adsorption nature of MB on HB. Moreover, scanning electron microscope combined with the energy dispersive spectrometer, fourier transform infrared spectroscope and X-ray photoelectron spectroscopy measurements indicated that the adsorption mechanism was mainly attributed to Ca ion-exchange and chemical bonding of –COOH and –OH groups with MB. Such hydrogel beads showed a good potential in the application of practical wastewater treatment. [ABSTRACT FROM AUTHOR]

Poly(vinyl alcohol)-sodium alginate-chitosan-montmorillonite nanosheets (MMTNS) hydrogel beads with porous and steady structure were fabricated via hydrogen-bond and electrostatic interactions, and were characterized by FTIR, TG, SEM and effecting tests. The results suggested MMTNS could support and maintain the porous structure, making an open excess for MB molecules. The increasing proportion of MMTNS in hydrogel beads enhanced the MB removal. Hydrogel beads possessed higher affinity to MB at high pHs due to the stronger electronegativity triggered by deprotonation of hydroxyls. Moreover, hydrogel beads had a good stability and reusability. The adsorption process was correlated with Elovich kinetics model, and fitted well with Freundlich, Redlich-Peterson and Sips isotherm models. The adsorption of MB on hydrogel beads was a disorderliness, endothermic and spontaneous process detected by the thrmodynamic. MB molecules reacted with the oxygen atoms in hydroxyl and substitute the Na + in MMTNS were proved by EDS, XPS and Na + concentration variation. [ABSTRACT FROM AUTHOR]

In this work, self-assembled hydrogels were prepared with exfoliated montmorillonite nanosheets (MMTNS) and chitosan (CS) as the adsorbent for removing methylene blue (MB) from water. Adsorption properties were determined by studying the kinetics and thermodynamic of MB adsorption onto the hydrogels from aqueous solutions, and AFM, FTIR, SEM, and XPS were used for the characterization of the MMTNS and hydrogels. The experimental results have shown that the montmorillonite nanosheets/chitosan hydrogels were superb adsorbents for removing MB from water, reaching the maximum adsorption capacity of 530 mg/g. The adsorption well followed the pseudo-second-order kinetics and Langmuir isotherm, and was spontaneous endothermic. The adsorption of MB on the hydrogels could be easily realized through cation exchange and hydrogen binding. It was also found that the hydrogels prepared with lower solid concentration of MMTNS had a looser stratified structure and thus a greater adsorption capacity for MB in aqueous solutions. [ABSTRACT FROM AUTHOR]

A novel granular adsorbent material containing zero-valent iron (ZVI-GAM) was prepared with fly ash as skeletal material, bentonite as binder and Enteromorpha prolifera as pore former. ZVI was synthesized by direct reduction of iron ore tailings powder with the coke as reductant in high temperature reducing atmosphere and embedded in the fly ash-based porous adsorbent, which could reduce the agglomeration and oxidation of ZVI. The structure of ZVI-GAM was characterized by SEM, EDX, XRD, FTIR and BET. The removal amount of crystal violet (CV) and methylene blue (MB) was evaluated at different contact time, initial dye concentration, pH values and temperature. The adsorption isotherms of CV and MB fitted well to the Langmuir model. The maximum removal capacity of ZVI-GAM for CV and MB was found to be 172.41 mg/g and 151.52 mg/g, respectively. The adsorption processes of CV and MB could be described by a pseudo-second-order kinetic model. The reduction kinetics of CV by ZVI-GAM fitted to pseudo-first-order kinetics model. The results indicated that chemisorption and reduction controlled the removal process of CV while chemisorption only controlled the removal process of MB. The thermodynamic study indicated that the adsorption processes of CV and MB were found to be endothermic and spontaneous. Therefore, ZVI-GAM was an effective, low-cost and recyclable material for dye removal. [ABSTRACT FROM AUTHOR]

The adsorption of methylene blue (MB) on graphene oxide (GO) prepared from an economical and resourceful amorphous graphite (AG) was studied. The effects of pH, foreign ions and concentrations of KClO 4 on MB removal were also evaluated. XRD, FT-IR, XPS, AFM and an Analyzer were employed to characterize the prepared GO. The results indicated that the C/O mass ratio of GO reached 1.84 and that thin layers (thickness of which less than 2 nm) accounted for 83.76%. The results of batch experiments showed that the adsorption of MB in the presence of cations decreased in the sequence Li + ≈ Na + > K + , while it was reduced in the order ClO 4 − > NO 3 − > Cl − in the presence of anions. MB removal in ClO 4 − was independent of solution pH, which may be ascribed to the synergistic effect between GO and ClO 4 − . The adsorption process was well described by a pseudo-second-order kinetics model, and the adsorption isotherm agreed well with the Langmuir model. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxygen-incorporated MoS 2 is firstly researched as a Co-catalyst in Fenton system. • A complete MB degradation can be quickly achieved on oxygen-incorporated MoS 2 -Fe. • Faster conversion of Fe2+/Fe3+ was achieved after oxygen incorporation in MoS 2. MoS 2 could be used as co-catalysts to accelerate the conversion of Fe2+/Fe3+ in Fenton reaction. However, the basal plane of pristine MoS 2 was catalytically inert, which limited the promotion to Fenton process. Thus, improving the co-catalytic activity of MoS 2 via microstructural regulation is crucial to further enhance the Fenton performance. In this work, we incorporated oxygen into MoS 2 structure and fabricated oxygen-incorporated MoS 2 -Fe as a heterogeneous Fenton catalyst for the first time. After controllable oxygen incorporation engineering, MoS 2 showed optimized band structure, better optical response ability, superior electrons transformation and more catalytic sites for Fe3+ reduction through the synergetic effect of photocatalysis and redox, leading to an extraordinary performance for methylene blue (MB) degradation in H 2 O 2 + visible light system. According to the results of quenching experiments and EPR tests, ·O 2 – and HO· were confirmed as the direct species to decompose MB molecule during reaction. Other experimental conditions, such as pH effect, dosage influence and effectiveness of various organics, were also explored. This novel strategy of oxygen incorporation in MoS 2 -Fe was an efficient way to enhance Fenton activity and was meaningful for environmental remediation in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • Eliminating methyl orange (MO) from water with methylene blue (MB) as a photosensitizer. • Both Type Ⅰ and Type Ⅱ photosensitization exist in binary MB-MO system. • Efficient degradation of MO at a wide concentration range. • Synchronous removal of MO and MB. In this work, a novel method that homogeneous degrading methyl orange (MO) with methylene blue (MB) as a photosensitizer under visible-light irradiation is proposed. MO can be efficiently degraded at a wide concentration range, and its degradation rate is significantly promoted by increasing MB concentration. The result of EPR, LC-MSMS, TOC and ion chromatography reveals that the degradation mechanism of MO consists two parts: 1O 2 mediated Type II pathway and Type I photosensitization of involving direct electron transfer between 3MB* and MO. Furthermore, benefitting from the self-degradation of MB, synchronous removal of MO and MB in water can be realized by controlling the initial MB concentration in system, thus avoiding the problems faced by heterogeneous photocatalytic such as solid-liquid separation. Therefore, this cost-effective and easy method possesses great potential in the application of eliminating MO and MB from wastewater as well as provides a new strategy for sustainable water treatment. [ABSTRACT FROM AUTHOR]

The use of sediment wastes after water treatment, from traditional wastewater management to secondary resource recycling, has attracted increasing attention. In this work, the feasibility, catalytic effect and mechanism of using artificial copper-based precipitation as photo-Fenton-like catalysts were investaged. According to the XRD, SEM-EDS, XPS and various photoelectric characterizations, the copper-based precipitation showed the potential acting as a photo-Fenton-like catalyst due to its abundant copper ions and photoresponse characteristics. The 0.06 g L−1 copper-based precipitation decolors 97% of methylene blue with initial concentration of 20 mg L−1 within 20 min assisted by H 2 O 2 and light, which is superior to the commonly used catalysts in terms of decolorization rate and catalysts dosage. Excellent catalytic performance is by virtue of the enhanced reduction reaction from Cu(II) to Cu(I), resulting in an increasing utilization rate of hydrogen peroxide, and increasing ·OH for decoloration. In addition, the catalyst activity can be replicated in successive experiments without a significant decline, further suggesting the feasibility from wastes to materials. The research progress shows the potential value of secondary resources containing posnjakite based on its unique character. [Display omitted] • Novel use of posnjakite containing sludge as a photo-catalyst. • Higher decolorization rate and lower catalyst dosage than common catalysts. • Enhanced reduction from Cu(II) to Cu(I) assisted with photoelectron. [ABSTRACT FROM AUTHOR]

• Gel of Fe-chitosan/montmorillonite nanosheets efficiently degraded methylene blue. • Synergistic effect of adsorption and photo-Fenton reaction led to dye degradation. • Gel had effective reusability due to continuous reactivation of adsorption sites. • Gel was stable and worked efficiently under a wide range of pH conditions. • Methylene blue was decomposed by demethylation and oxidation reactions. Self-assembled gel of Fe-chitosan/montmorillonite nanosheets (Fe-CS/MMTNS) was prepared for elimination of methylene blue (MB) under visible light in the presence of H 2 O 2. The Fe-CS/MMTNS gel was characterized by FTIR, SEM-EDS, XPS and TG. The Fe-CS/MMTNS gel performed well in the removal of MB through the synergistic effect of adsorption and photo-Fenton reaction. Moreover, this gel worked efficiently under a wide range of pH conditions. This composite gel also showed effective reusability because the adsorption sites of the Fe-CS/MMTNS are continually reactivated through photo-Fenton degradation. Additionally, the Fe-CS/MMTNS gel was found to be stable and the iron ions were hardly leached out because of the complexation between iron and chitosan (CS). The MB degradation occurred by two pathways: a part of MB was directly attacked by reactive radicals and gradually converted into inorganic substances while another part of MB was firstly adsorbed by Fe-CS/MMTNS gel and then degraded by reactive radicals. [ABSTRACT FROM AUTHOR]