Lincheng Zhou

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.

Use of microorganisms immobilized on composite polyurethane foam to remove Cu(II) from aqueous solution

Composite polyurethane (PU) foams were made via the polymerization of toluene diisocyanate (TDI) and polyether polyol with activated carbon fiber, and immobilized microorganisms on polyurethane (IPU) foam were prepared by cultivating the microbe B350 in a mixture of culture medium and PU. We used batch adsorption techniques to study the removal of Cu(II) ions from aqueous solutions via PU and IPU. Moreover, the effects of pH, temperature, carrier amount, and biosorption time on the removal rate of Cu(II), adsorption equilibrium, and adsorption kinetics were investigated in detail. The IPU showed an excellent removal rate for Cu(II). The adsorption kinetics data were in good agreement with the pseudo-second-order rate model, and the adsorption isotherms could be adequately described by the Langmuir equation. For synthetic wastewater containing Cu(II), the removal rates for Cu(II) and COD after 4h treatment were 85% and 80%, respectively.

Enhancement of phenol degradation using immobilized microorganisms and organic modified montmorillonite in a two-phase partitioning bioreactor.

A study was conducted to determine the potential of a two-phase partitioning bioreactor (TPPB) for enhancing the treatment of phenol at high initial concentrations. TPPBs are characterized by a cell-containing aqueous phase and an immiscible and biocompatible organic phase that partitions toxic substrates to the biocatalyst on the basis of their metabolic demand and the thermodynamic equilibrium of the system. In the present work, in order to enhance the degradation of phenol in TPPB, the polysulfone capsule containing organic modified montmorillonite (OMMT-PSF capsule) was used as organic phase, and polyurethane foam immobilized microorganism (PUF-immobilized microorganism) was used as biocatalyst. Experiments showed that OMMT-PSF capsules offered improved sorption capacity (30.2mg phenol/g OMMT-PSF capsules at the fixed initial phenol concentration of 2030.2mg/L) and a greater sorption rates (the equilibriums were reached at about 6h). The characters of vast sorption capacity and rapid sorption rates are in accordance with the desire of delivery agent in TPPB, further testing demonstrated that OMMT-PSF capsules using as a reservoir in TPPB played a significant role. The phenol biodegradation rates of batch fermentation were examined, the maximum volumetric consumption rate of phenol decreased in the order: immobilized microorganisms with OMMT-PSF capsules in a TPPB (342.4 mg/(Lh))>immobilized microorganisms without OMMT-PSF capsules (300 mg/(Lh))>free microorganisms with OMMT-PSF capsules in a TPPB (208.4 mg/(Lh))>free microorganisms without OMMT-PSF capsules (125.8 mg/(Lh)). This work demonstrates that the use of immobilized microorganisms and OMMT-PSF capsules in TPPB offers improved degradation of phenol.

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.

Selective removal for Pb2+ in aqueous environment by using novel macroreticular PVA beads

Batch sorption experiments were conducted using macroreticular poly(vinyl alcohol) (MR-PVA) beads as a adsorbent to adsorb Pb(II) from both single component system and multi-metal solution in which experimental parameters were studied including solution pH, contact time, adsorbent dose, initial concentration of metal ions and ionic strength. The equilibrium isotherms were determined at pH 6 under constant ionic strength and at different temperatures. The results showed that the maximum adsorption capacity of Pb(II) (213.98 mg g(-1)) with 1 g L(-1) of adsorbent was observed at 300 mg L(-1) at an initial pH value of 6.0 under temperature of 288 K. Removals of about 60% occurred in 30 min, and equilibrium was attained at around 150 min. The equilibrium data for the adsorption of Pb(II) on MR-PVA beads was tested with various adsorption isotherm models among which three models were found to be suitable for the Pb(II) adsorption. In addition, the kinetic adsorption fitted well to the pseudo-second-order model and the corresponding rate constants were obtained. Thermodynamic aspects of the adsorption process were also investigated.

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.

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 of copper doped magnetic porous carbon for removal of methylene blue by a heterogeneous Fenton-like reaction

High-specific-surface-area copper doped magnetic porous carbon (CuFe2O4/Cu@C) was fabricated by annealing iron, copper and 1,3,5-benzenetricarboxylic ([Cu/Fe]-BTC) metal–organic coordination polymers, which were prepared via a one-pot solvothermal method. The novel CuFe2O4/Cu@C catalyst consists of Cu (3.80%), CuFe2O4 (64.84%), and C (31.36%). Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, elemental analysis, inductively coupled plasma, Brunauer–Emmett–Teller surface area measurement, and vibrating sample magnetometer analysis were used to characterize the materials. The as-prepared materials were employed as a heterogeneous Fenton’s reagent with the addition of H2O2 for degradation of methylene blue (MB). The results showed that the materials effectively catalyzed H2O2 to generate hydroxyl radicals (˙OH). And due to their magnetism, the materials can be easily separated from wastewater to achieve repeatability. It also turned out that CuFe2O4/Cu@C had a higher catalytic activity than Fe3O4@C, which proved the importance of copper doped into the catalyst. This work indicated that porous carbon composites provide good support for the development of a highly efficient heterogeneous Fenton catalyst, which is useful for environmental pollution cleanup.

Fe3O4/MWCNT as a heterogeneous Fenton catalyst: degradation pathways of tetrabromobisphenol A

Tetrabromobisphenol A (TBBPA) is the most widely used brominated flame retardant around the world. In this study, we report that iron oxide decorated on a magnetic nanocomposite (Fe3O4/MWCNT) was used as a heterogeneous Fenton catalyst for the degradation of TBBPA in the presence of H2O2. Fe3O4/MWCNT was prepared by a simple solvothermal method, whereby an iron source (Fe(acac)3) and a reductant (n-octylamine) were allowed to react in n-octanol solvent. Monodisperse Fe3O4 nanoparticles of consistent shape were uniformly dispersed on the nanotubes. Samples were characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller surface area measurement, and vibrating sample magnetometry. The samples effectively catalyzed the generation of hydroxyl radicals (·OH) from H2O2, which degraded and subsequently mineralized the TBBPA. The whole process took four hours at near neutral pH. A degradation pathway for the system was proposed following analysis of intermediate products by gas chromatography-mass spectrometry. The quantification of Fe2+ and Fe3+ distribution before and after the recycling test of the composite were explored by X-ray photoelectron spectroscopy, in order to explain the stability and recyclability of the composite. Analysis of the results indicated that the magnetic nanocomposite is a potentially useful and environmentally compatible heterogeneous Fentons reagent with promising applications related to pollution control.