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.
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.
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.
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.
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.
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.
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.
Two kinds of packing materials, molecular sieve (MS) and polyurethane foam (PUF), were loaded into two identical biotrickling filters respectively to compare the microbial removal efficiency of waste gas containing toluene by seeding with same bacteria. The affecting parameters of the removal performance, such as gas flow rates, inlet toluene concentrations, periods of starvation, were investigated in detail in biotrickling filters. The results demonstrated that both of the packing materials exhibited high toluene degradation efficiency when the gas flow rates ranged from 100 L h(-1) to 600 L h(-1). For MS, the total maximum removal efficiency (RE) of toluene maintained 100% when the gas flow rates increased from 100 L h(-1) to 200 L h(-1) accompanied with the decrease of empty bed residence time (EBRT) from 266s to 133s. However, as for PUF, merely 97.64% RE was obtained at the gas flow rate of 100 L h(-1) and the EBRT of 266s. With further increasing the gas flow rates (to 600 L h(-1)) and decreasing the EBRTs (to 44s), both the total REs of toluene for MS and PUF decreased to 70.68% and 63.18%, respectively. When varying the inlet toluene concentrations, the REs for MS are able to maintain nearly 100% at the inlet concentration of 9.19 mg L(-1) or below, and with the maximum elimination capacity (EC) of 373.24 gm(-3)h(-1) (RE=100%) at the inlet concentration of 9.19 mg L(-1). Contrastively, the maximum EC of PUF was only 119.41 gm(-3)h(-1) (RE=56.66%) at the inlet concentration of 5.19 mg L(-1). As illustrated by different starvation period (2, 10 and 60 days), MS possessed shorter recovery time (9h for 2 days, 17 h for 10 days and 324 h for 60 days starvation, respectively) than PUF (14 h for 2 days, 24h for 10 days and 324 h for 60 days starvation, respectively). Based on its higher removal capacity of toluene and shorter recovery time, MS would be a better choice than PUF for packing material used for biotrickling filter.
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