Tri-modified ferric alginate gel with high regenerative properties catalysts for efficient degradation of rhodamine B.

Water pollution caused by dyes has become a focal point of attention. Among them, the heterogeneous Fenton reaction has emerged as an effective solution to this problem. In this study, we designed a ferric alginate gel (PAGM) tri-modified with poly(vinyl alcohol), graphene oxide, and MoS2 as a heterogeneous Fenton catalyst for organic dye degradation. PAGM addresses the drawbacks of alginate gel, such as poor mechanical properties and gel chain dissolution, thereby significantly extending the catalyst's lifespan. The removal rate of rhodamine B by PAGM reached 95.5 % within 15 min, which was 5.9 times higher than that of unmodified ferric alginate gel. Furthermore, due to the π-π interactions, PAGM exhibits unique adsorption properties for pollutants containing benzene rings. Additionally, PAGM can be regenerated multiple times through a simple soaking procedure without any performance degradation. Finally, the reaction column constructed with PAGM maintained an 83.5 % removal rate even after 319 h of continuous wastewater treatment. This work introduces a novel concept for the study of alginate-based gel catalysts in heterogeneous Fenton reactions.

Preparation of EDTA-modified magnetic attapulgite chitosan gel bead adsorbent for the removal of Cu(II), Pb(II), and Ni(II).

Attapulgite (ATP) has a unique porous layered chain structure and is an excellent environment-friendly decolorizer. However, its high viscosity makes it difficult to separate. First, it was combined with magnetic Fe3O4 nanoparticles to obtain Fe3O4-ATP that is easy to recycle and reuse. Then, Fe3O4-ATP nanoparticles were embedded in chitosan (CS) gel beads, and glutaraldehyde was used for cross-linking and curing. Lastly, ethylenediaminetetraacetic acid (EDTA) was successfully connected to Fe3O4-ATP/CS gel beads through amidation reaction, which further increased the capability of the adsorbent to adsorb heavy metal ions. The prepared magnetic composite adsorbent is a sphere with a rough surface and porous structure. The maximum adsorption capacity of the prepared Fe3O4-ATP/EDTA/CS adsorbent for Pb(II), Cu(II), and Ni(II) is 368.32, 267.94, and 220.31 mg g-1, respectively. After 5 times of repeated use, Fe3O4-ATP/EDTA/CS still showed good adsorption capacity for Cu(II), Pb(II), and Ni(II). Fe3O4-ATP/EDTA/CS has a large adsorption capacity for heavy metal ions, a wide pH applicability, good reuse, and rapid magnetic separation. In addition, Cu(II) loaded Fe3O4-ATP/EDTA/CS also showed good catalytic degradation performance for bisphenol A. This study prepared a new type of adsorbent with good adsorption performance and provided a promising method for the treatment of wastewater.

Three-dimensional heterogeneous Electro-Fenton system with a novel catalytic particle electrode for Bisphenol A removal.

Herein, a novel three-dimensional (3D) heterogeneous Electro-Fenton (EF) system with improved gas diffusion electrode (GDE) as cathode and magnetic nitrogen doped/reduced graphene oxide (Fe3O4/N-rGO) as catalytic particle electrodes (CPEs) was built for Bisphenol A (BPA) removal. The Fe3O4/N-rGO served as both particle electrodes and heterogeneous catalyst. The study concluded that BPA could be effectively removed via this hybrid system. The synergistic effect between the 3D electrode and EF system was discussed by comparing the performance of different functional particle electrodes. The 3D electrode system exhibited a larger specific surface area electrode, which improved the mass transfer of pollutants to electrode, and also accelerated the regeneration of FeⅡ due to faster electron transfer, thereby enhancing the efficiency of EF catalysis. The EF process promotes the regeneration rate of particle electrodes and thus accelerates the 3D electrode reaction course. The parameters affecting degradation behavior of BPA were optimized. As a result, optimal removal rate of BPA and TOC was 93% and 60.5%, respectively within 90 min. The CPEs showed high catalytic performance (86.5% for BPA and 50.3% for TOC) and low catalyst loss (less than 9.5%) after 5 cycles, indicating its excellent stability and reusability. The possible mechanism of 3D heterogeneous EF was investigated by comparing the catalytic activity and •OH production capacity of homogeneous EF and Fenton-like. Built on the analysis of intermediates, a possible decomposition pathway of BPA was proposed.

Construction of magnetic bifunctional ß-cyclodextrin nanocomposites for adsorption and degradation of persistent organic pollutants.

Herein, we report a novel magnetic bifunctional ß-cyclodextrin nanocomposite (Fe3O4@ß-CD-CDI) based on metal coordination, which may be used for adsorption and degradation of persistent organic pollutants in aqueous solution. More importantly, N,N'-carbonyldiimidazole (CDI) functionalized ß-CD ligand (ß-CD-CDI) was assembled on the surface of Fe3O4 by Zn-N interaction. The results of kinetic and isothermal adsorption model investigation indicated that the adsorption rate and capacity of Fe3O4@ß-CD-CDI were better than other materials, suggesting the effective accessibility of adsorption sites. We further confirmed that Fe3O4@ß-CD-CDI can be used as heterogeneous catalyst to remove BPA through Fenton-like reaction in the presence of hydrogen peroxide (H2O2). Moreover, the material effectively alleviated the secondary pollution owing to the existence of ß-CD inner cavity. This study indicated that the magnetic Fe3O4@ß-CD-CDI material has great potential applications in wastewater purification containing persistent organic pollutants.

Novel porous magnetic nanospheres functionalized by ß-cyclodextrin polymer and its application in organic pollutants from aqueous solution.

Magnetic ß-cyclodextrin (ß-CD) porous polymer nanospheres (P-MCD) was fabricated by one-pot solvent thermal method using ß-CD immobilized Fe3O4 magnetic nanoparticles with tetrafluoroterephthalonitrile as the monomer. Compared with the ß-CD polymerization method reported in the literature,_ENREF_1 the synthetic route is effective and simple, thereby overcoming the harsh conditions that require nitrogen protection and always maintain anhydrous and oxygen-free. Moreover, the immobilization of ß-CD on magnetic nanoparticles is combined with the cross-linking polymerization of the cross-linker, leading to a good synergistic effect on the removal of contaminants. Meanwhile, the dispersibility of the magnetic carrier enhances the dispersion of the ß-CD porous polymer in the aqueous phase, and improves the inclusion adsorption performance and the adsorption process. P-MCD exhibited superior adsorption capacity and fast kinetics to MB. The maximum adsorption capacity of MB for P-MCD was 305.8 mg g -1, which is more than ß-CD modified Fe3O4 magnetic nanoparticles (Fe3O4@ß-CD). Moreover, the material had a short equilibrium time (5 min) for MB, high recovery and good recyclability (the adsorption efficiency was still above 86% after five repeated uses).

Efficient electrochemical degradation of tetrabromobisphenol A using MnO2/MWCNT composites modified Ni foam as cathode: Kinetic analysis, mechanism and degradation pathway.

In this study, MnO2/MWCNT hybrids, prepared using a solvothermal method, were coated onto Ni foam and then used as a cathode for tetrabromobisphenol A (TBBPA) degradation. The reaction was confirmed to exhibit the pseudo first-order kinetics. Compared with the original Ni foam cathode, the fabricated electrode exhibited higher catalytic activity, attributed to its strong cross-linking and ability to produce catalytic free radicals. Radical scavenger experiments revealed that O2- and OH were involved in the decomposition of TBBPA. The effects of current density, pH, catalyst dosage, and initial TBBPA concentration on removal efficiency were further studied. An optimal removal rate of 98.3% was achieved while the rate constant reached values up to 0.07293 min-1 and the debromination rate was more than 75.4% within 60 min. The electrode showed high catalytic performance and low catalyst loss after 10 cycles, indicating its excellent stability and reusability. The probable mechanism and pathway of TBBPA degradation were suggested based on the analysis of intermediate products. It could be inferred that the decomposition of TBBPA involved CC bond breaks (oxidation) and debromination (reduction). The MnO2/MWCNT-Ni foam could be a promising cathode material for electrochemical degradation of halogenated organic compounds.

Heterogeneous Fenton degradation of bisphenol A using Fe3O4@ß-CD/rGO composite: Synergistic effect, principle and way of degradation.

In this study, a multi-component catalyst, ß-cyclodextrin (ß-CD) and reduced graphene oxide (rGO) co-modified Fe3O4, was fabricated via one-pot solvothermal method and used as a synergistic catalyzer for Bisphenol A (BPA) removal. The study found that catalytic reactions of BPA followed the pseudo-first-order kinetics model, and the correlation rate constants (kobs) were calculated. Compared with Fe3O4@ß-CD (0.02173 min-1), Fe3O4/rGO (0.09735 min-1) and Fe3O4 (0.01666 min-1), the composite (0.15733 min-1) exhibited stronger catalytic ability to remove BPA from aqueous solution under the same conditions, which were attributed to the synergistic enhancement effect among the components. The introduction of rGO in the composites was beneficial to the generation of •OH, and the role of ß-CD might enhance the utilization of •OH. A possible three-element catalytic schematic diagram was described. The effects of pH, dosage of the catalyst, initial H2O2 and NH2OH concentrations on the removal efficiency were further investigated. The removal of BPA and TOC retained 78.2 ±â€¯2.4% and 52.9 ±â€¯2.5% after five cycles, indicating its excellent stability and reusability. Furthermore, a probable reaction pathway of BPA removal was suggested by analyzing the intermediate products. All results indicated that the composite had high and stable catalytic performance, which made it have potential application on the industrial treatment of wastewater.

Simple Urea Immersion Enhanced Removal of Tetracycline from Water by Polystyrene Microspheres.

Antibiotics pose potential ecological risks in the water environment, necessitating their effective removal by reliable technologies. Adsorption is a conventional process to remove such chemicals from water without byproducts. However, finding cheap adsorbents with satisfactory performance is still a challenge. In this study, polystyrene microspheres (PSM) were enhanced to adsorb tetracycline by surface modification. Simple urea immersion was used to prepare urea-immersed PSM (UPSM), of which surface groups were characterized by instruments to confirm the effect of immersion. Tetracycline hydrochloride (TC) and doxycycline (DC) were used as typical adsorbates. The adsorptive isotherms were interpreted by Langmuir, Freundlich, and Tempkin models. After urea immersion, the maximum adsorption capacity of UPSM at 293 K and pH 6.8 increased about 30% and 60%, achieving 460 mg/g for TC and 430 mg/g for DC. The kinetic data were fitted by first-order and second-order kinetics and Weber⁻Morris models. The first-order rate constant for TC adsorption on UPSM was 0.41 /h, and for DC was 0.33 /h. The cyclic urea immersion enabled multilayer adsorption, which increased the adsorption capacities of TC on UPSM by two to three times. The adsorption mechanism was possibly determined by the molecular interaction including π⁻π forces, cation-π bonding, and hydrogen bonding. The simple surface modification was helpful in enhancing the removal of antibiotics from wastewater with similar structures.

Preparation of novel magnetic molecular imprinted polymers nanospheres via reversible addition - fragmentation chain transfer polymerization for selective and efficient determination of tetrabromobisphenol A.

A well-defined molecularly imprinted polymer nanospheres with excellent specific recognition ability was prepared on Fe3O4 nanoparticles via the combination of click chemistry and surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization and using Tetrabromobisphenol A as template. Concretely, Fe3O4 nanoparticles were prepared by solvothermal method and then modified by 4-vinylbenylchloride through distillation-precipitation, which makes azide groups easily introduced on the surface of magnetic nanoparticles to form the relatively large amount of benzyl chloride groups. With high efficiency, alkyne terminated RAFT chain transfer agent were then immobilized onto the surface of Fe3O4 by means of click chemistry, which is Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The highly uniform imprinted thin film was finally fabricated on the surface of RAFT agent modified Fe3O4 nanoparticles. The binding results demonstrated that as-prepared imprinted beads exhibited remarkable molecular imprinting effects to the template molecule, fast rebinding kinetics and an excellent selectivity to compounds with similar configuration.

Performance of nitrogen-doped graphene aerogel particle electrodes for electro-catalytic oxidation of simulated Bisphenol A wastewaters.

The treatment of effluent containing Bisphenol A (BPA) was investigated experimentally using nitrogen-doped graphene aerogel (NGAs) as particle electrodes in a three-dimensional electrode reactor for the electrochemical treatment was studied. The effects of the cell voltage, pH, the ratio of NGAs mass to solution volume and repeated times on the removal efficiency were investigated. Compared with commercial carbon particle electrodes, the NGAs exhibited stronger activity to remove BPA simulated wastewater. For 15mgL-1 of BPA solution, the degradation rate of BPA exceeded 90% after treatment for only 30min under the optimum conditions. The CODCr removal rate of BPA was 85%. Moreover, in the process of reused 50 times, the degradation rate of BPA can be kept in more than 85%. The CODCr removal rate was stable at about 73%. The intermediate products of electrochemical degradation of BPA were identified by liquid chromatography-mass spectrometry liquid chromatography (LC-MS), and a probable BPA degradation pathway was proposed. It was considered that OH radicals by water electrolysis could constantly attack the aromatic ring to form various intermediates such as hydroxylated-BPA, isopropylphenol, hydroquinone, phenol and butantetraol, maleic acid, oxalic acid. These compounds were eventually mineralized by electrolysis into CO2 and H2O.

A novel structural Fenton-like nanocatalyst with highly improved catalytic performance for generalized preparation of iron oxide@organic dye polymer core-shell nanospheres.

FexOy@FexOy/C nanoparticles with a soap-bubble-like shell have been synthesized, and the materials exhibit excellent Fenton catalytic performance. More importantly, FexOy@FexOy/C nanoparticles as catalysts and precursors could catalyze organic dye molecules to form iron oxide@organic dye polymer core-shell nanospheres.

Mussel-inspired surface modification of magnetic@graphite nanosheets composite for efficient Candida rugosa lipase immobilization.

By the facile adhesion way, the novel composite complex by polydopamine (PDA) and magnetic graphite nanosheets (Fe3O4@GNSs) has been successfully synthesized. The resulting composite was characterized by means of scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectra, and Raman spectra, X-ray diffraction, X-ray photoelectron spectroscopy, and vibrating sample magnetometry. Meanwhile, the PDA functionalized Fe3O4@GNSs (Fe3O4@GNSs-PDA) was applied for Candida rugosa lipase (CRL) immobilization covalently without any toxic coupling agent. Combining the superior physical properties and chemical stability of Fe3O4@GNSs and the well biocompatibility, functional characteristics of PDA, the Fe3O4@GNSs-PDA composite displayed several advantages, including the high enzyme capacity, enzyme activity and stability and a decrease in enzyme loss. Our work demonstrated that the mussel-inspired Fe3O4@GNSs can be extended to many other applications such as biocatalytic, genetic and industrial.

Novel magnetic porous carbon spheres derived from chelating resin as a heterogeneous Fenton catalyst for the removal of methylene blue from aqueous solution.

Porous magnetic carbon spheres (MCS) were prepared from carbonized chelating resin composites derived from ethylenediaminetetraacetic acid-modified macroporous polystyrene (PS-EDTA) resin, and then loaded with iron composites via ion exchange. The resulting composites were characterized for this study using X-ray diffraction, MÖssbauer spectroscopy, and Raman spectroscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area method, scanning electron microscopy, and vibrating sample magnetometry. The porous magnetic carbon spheres were then used, in the existence of H2O2 and NH2OH, with a view to remove methylene blue from the aqueous solution by catalyze a heterogeneous Fenton reaction. Results indicated excellent removal rates and removal efficiency for this catalytic system. Optimal degradation was achieved (nearly 100% within 10 min) using initial concentrations of 5 mmol H2O2 L(-1), 2.5 mmol L(-1) NH2OH and 40 mg L(-1) methylene blue. The catalyst retained its activity after six reuses, indicating strong stability and reusability. Porosity of the catalyst contributed to its high activity, suggesting its potential application for the industrial treatment of wastewater.

Organic additives enhance Fenton treatment of nitrobenzene at near-neutral pH.

Nitrobenzene (NB) is considered a toxic and potential carcinogen. Continuous contamination has resulted in an urgent need for remediation. Fenton reagent provides an advanced oxidation process that is capable of remediating recalcitrant nitroaromatic compounds, such as NB. However, one drawback of Fenton chemistry is that the reaction requires acidic pH to prevent precipitation of iron. Our studies have investigated Fenton conversion of NB at near-neutral pH with several organic additives: ß-cyclodextrin (ß-CD), hydroxypropyl-ß-cyclodextrin (HPCD), carboxymethyl-ß-cyclodextrin (CMCD), and polyethylene glycol (molecular weight (MW) = 200, 400, and 600) for developing a process for treating NB-contaminated waters. The main factors influencing NB conversion, such as iron concentration, hydroxyl radicals (·OH) scavengers, and kinds or concentration of organic additives, were examined. Meanwhile, the reactive mechanisms and kinetics were investigated for Fenton conversion of NB. The results show that organic additives for Fenton process should be a good alternative for the advanced treatment of NB at near-neutral pH.

Formulation of robust organic-inorganic hybrid magnetic microcapsules through hard-template mediated method for efficient enzyme immobilization.

A mild and facile method for the construction of robust organic-inorganic hybrid magnetic microcapsules was developed by a hard-template mediated method combined with polydopamine (PDA) and Fe3O4 nanoparticles onto a CaCO3 microparticle template. More specifically, negatively charged Fe3O4 nanoparticles were adsorbed on the surface or into the lumen of porous CaCO3 microparticles through electrostatic interaction and physical absorption. Then, the magnetic sacrificial templates were coated with PDA through the self-polymerization of dopamine to obtain the magnetic PDA-CaCO3 microparticles, which was followed by template removal using EDTA to construct organic-inorganic hybrid magnetic microcapsules. Characterization confirmed that the microcapsules possess a robust hollow structure such that the enzyme inside exists in a free state. The Fe3O4 nanoparticles acted as critical factors in the microcapsules for both recyclable component and tough scaffolds to sustain the microcapsules away from collapsing and folding. Combing the merits of the organic layer and the inorganic component, the microcapsules were applied for the encapsulation of Candida Rugosa Lipase (CRL). The encapsulated CRL was demonstrated to have several advantages, including increased encapsulation efficiency, enzyme activity and long-term storage stability. Hopefully, the as-prepared microbioreactor may provide a facile and generic approach for other biochemical applications.

Preparation and characterization of magnetic porous carbon microspheres for removal of methylene blue by a heterogeneous Fenton reaction.

High-specific-surface-area magnetic porous carbon microspheres (MPCMSs) were fabricated by annealing Fe(2+)-treated porous polystyrene (PS) microspheres, which were prepared using a two-step seed emulsion polymerization process. The resulting porous microspheres were then sulfonated, and Fe(2+) was loaded by ion exchange, followed by annealing at 250 °C for 1 h under an ambient atmosphere to obtain the PS-250 composite. The MPCMS-500 and MPCMS-800 composites were obtained by annealing PS-250 at 500 and 800 °C for 1 h, respectively. The iron oxide in MPCMS-500 mainly existed in the form of Fe3O4, which was concluded by characterization. The MPCMS-500 carbon microspheres were used as catalysts in heterogeneous Fenton reactions to remove methylene blue (MB) from wastewater with the help of H2O2 and NH2OH. The results indicated that this catalytic system has a good performance in terms of removal of MB; it could remove 40 mg L(-1) of MB within 40 min. After the reaction, the catalyst was conveniently separated from the media within several seconds using an external magnetic field, and the catalytic activity was still viable even after 10 removal cycles. The good catalytic performance of the composites could be attributed to synergy between the functions of the porous carbon support and the Fe3O4 nanoparticles embedded in the carrier. This work indicates that porous carbon spheres provide good support for the development of a highly efficient heterogeneous Fenton catalyst useful for environmental pollution cleanup.

Development of carbon nanotubes/CoFe2O4 magnetic hybrid material for removal of tetrabromobisphenol A and Pb(II).

Multi-walled carbon nanotubes (MWCNTs) coated with magnetic amino-modified CoFe2O4 (CoFe2O4-NH2) nanoparticles (denoted as MNP) were prepared via a simple one-pot polyol method. The MNP composite was further modified with chitosan (CTS) to obtain a chitosan-functionalized MWCNT/CoFe2O4-NH2 hybrid material (MNP-CTS). The obtained hybrid materials were characterized by Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectrogram (FT-IR) Analysis and X-ray Photoelectron Spectroscopy (XPS) Analysis, Vibrating Sample Magnetometer (VSM) Analysis and the Brunauer-Emmett-Teller (BET) surface area method, respectively. The composites were tested as adsorbents for tetrabromobisphenol A (TBBPA) and Pb(II), and were investigated using a pseudo-second-order model. The adsorption of TBBPA was well represented by the Freundlich isotherm; the Langmuir model better described Pb(II) absorption. MNP-CTS adsorbed both TBBPA and Pb(II) (maximum adsorption capacities of 42.48 and 140.1mgg(-1), respectively) better than did MNP without CTS. Magnetic composite particles with adsorbed TBBPA and Pb(II) could be regenerated using 0.2M NaOH solution and were separable from liquid media using a magnetic field.

Treatment on low carbon-to-nitrogen micro-polluted water by layered biological aerated filter with floating and sunken media.

In order to improve the TN removal efficiency on low carbon-to-nitrogen micro-polluted water, in this study, a layered biological aerated filter (L-BAF) was built. The results showed that the removal efficiency for CODMn, NH3-N, and TN was 71.6-90.3%, 99.8-99.9%, and 57.8-65.7%, respectively, when the C/N ratio was kept at 3 and the volumetric flow rate was 0.072 m(3) d(-1). The L-BAF could improve the TN removal efficiency by about 20% compared to a traditional process. The L-BAF and traditional process removal efficiency for NH3-N and CODMn were similar. The kinetic performance of the L-BAF indicated that the relationship of CODMn removal efficiency with the influent CODMn concentration could be described by ln(C/C0) = -(0.0023/Q0C0(0.9398))H.

Novel chelating resin with cyanoguanidine group: useful recyclable materials for Hg(II) removal in aqueous environment.

A novel chelating resin containing cyanoguanidine moiety has been successfully prepared by the functionalizing reaction of a macroporous bead based on chloromethylated copolymer of styrene-divinylbenzene (CMPS) with dicyandiamide (DCDA) in the presence of phase transfer catalyst. The Fourier transform-infrared spectra (FT-IR) and scanning electron microscopy (SEM) were employed in the characterization of the resulting chelating resin, meanwhile, the adsorption properties of the resin for Hg(II) were investigated by batch and column methods. The results indicated that the resin displayed a marked advantage in Hg(II) binding capacity, and the saturated adsorption capacity estimated from the Langmuir model was dramatically up to 1077 mg g(-1) at 45 °C. Furthermore, it was found that the resin was able to selectively separate Hg(II) from multicomponent solutions with Zn(II), Cu(II), Pb(II) and Mg(II). The desorption process of Hg(II) was tested with different eluents and the ratio of the highest recovery reached to 96% under eluting condition of 1M HCl+10% thiourea. Consequently, the resulting chelating resin would provide a potential application for treatment process of Hg(II) containing wastewater.

Facile synthesis of amino-silane modified superparamagnetic Fe3O4 nanoparticles and application for lipase immobilization.

In present study, a facile prepared nano-sized magnetic support was successfully synthesized. Then this support was applied for lipase immobilization using glutaraldehyde as a coupling agent. Experimental data showed that the immobilized lipase exhibited good thermal stability and reusability. The lipase loading amount and activity recovery were found to be 43.6 mg/g support and 58.2%. Kinetic studies suggested it an acceptable degree of specificity retention for an immobilization process.