Baoling Yuan

Synthesis of porous magnetic ferrite nanowires containing Mn and their application in water treatment

Two kinds of porous magnetic ferrite nanowires containing manganese (MnFe2O4 and Mn doped Fe3O4) have been successfully synthesized by thermal decomposition of organometallic compounds, using nitrilotriacetic acid (NA) as a chelating agent to coordinate with various ratios of Fe(II) and Mn(II) ions. The resultant MnFe2O4 and Mn doped Fe3O4 nanostructures are superparamagnetic, and have magnetization saturation values of about 45.9 and 48.7 emu g−1 for MnFe2O4 and Mn doped Fe3O4, respectively. The Brunauer–Emmett–Teller specific surface areas of the MnFe2O4 and Mn doped Fe3O4 are 37.8 and 45.4 m2 g−1, respectively. The as-prepared porous MnFe2O4 and Mn doped Fe3O4 nanowires exhibit excellent ability to remove heavy metal ions and organic pollutant in waste water. In addition, these porous magnetic ferrites may be useful in other fields such as biomedicine and Li-ion batteries.

Fabrication of magnetic porous Fe–Mn binary oxide nanowires with superior capability for removal of As(III) from water

Magnetic porous Fe-Mn binary oxide nanowires were successfully fabricated to efficient removal of As(III) from water. The adsorption capacity of the porous nanowires for As(III) obviously increased with increasing of manganese oxide in the composite, accompanying decrease of the saturation magnetization of the adsorbents. Magnetic porous Fe-Mn binary oxide nanowires with an initial Fe:Mn molar ratio of 1:3 exhibited the highest absorption capacity for As(III) and enable magnetic separation from water. The maximal adsorption capacity value is 171mgg(-1) at pH 7.0. In the initial pH range from 3 to 9, 200μgL(-1) of As(III) could be easily decreased to below 10μgL(-1) by the magnetic porous Fe-Mn binary oxide nanowires (0.05gL(-1)) within 75min, and the corresponding residual As was completely oxidized to less toxic As(V). The coexisting chloride, nitrate and sulfate had no significant effect on arsenic removal, whereas, phosphate and humic acid reduced the removal of As(III) by competing with arsenic species for adsorption sites. The resulting magnetic porous Fe-Mn binary oxide nanowires could be a promising adsorbent for As(III) removal from water.

Intercalation and adsorption of ciprofloxacin by layered chalcogenides and kinetics study.

The hydrothermally synthesized layered chalcogenide, K(2x)Mn(x)Sn(3-x)S6 (x=0.5-0.95) (KMS-1), was applied to remove ciprofloxacin from aqueous solution. Kinetic data showed the removal reaction followed a pseudo-second-order kinetic model and the rate controlling step was both through external film and intraparticle diffusion. The adsorption of CIP by KMS-1 is endothermic and the maximum adsorption capacity of KMS-1 was 199.6, 230.9 and 269.5 mg/g at temperature of 10, 25 and 40°C, respectively. The heavy metal ions had great effect on the removal efficiency of CIP and the degree of inhibition followed the order: Pb(2+)>Zn(2+)>Cd(2+)>Ni(2+). The shift of Bragg peaks from XRD at various pH accompanying CIP removal and FE-SEM images confirmed that cation exchange is the major mechanism for the adsorption of CIP by KMS-1. In the pH range of 4.0-7.0, the intercalation of cationic CIP adopted a titled orientation of di-molecular CIP in KMS-1 with the titling angle of 68° and 42°, respectively. A vertical arrangement of the zwitterionic CIP adsorbed on the surface of KMS-1 was also confirmed. These results suggested that KMS-1 is an effective adsorbent to remove CIP from water.

Toward NIR driven photocatalyst: Fabrication, characterization, and photocatalytic activity of β-NaYF4:Yb(3+),Tm(3+)/g-C3N4 nanocomposite.

The β-NaYF4:Yb(3+),Tm(3+)/g-C3N4 (NYT/C3N4) photocatalyst has been successfully fabricated by a stepwise method. Firstly, the advanced near-infrared (NIR) driven photocatalyst was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV-Vis-NIR diffuse reflectance spectroscopy. It was found that NYT/C3N4 photocatalyst consisted of uniform hexagonal phase NaYF4 nanocrystals with about 20nm diameter distributed on surface of g-C3N4 sheets, and the NYT/C3N4 composite exhibited strong near-infrared light absorption and the energy transfer from β-NaYF4:Yb(3+),Tm(3+) to g-C3N4 was confirmed. Secondly, the photocatalytic activities of the catalysts were evaluated by the degradation of methyl blue dye and colorless phenol under the irradiation of 980nm laser. The results suggested that NYT/C3N4 nanocomposite is an advanced NIR-driven photocatalyst. Moreover the NYT/C3N4 photocatalyst showed good stability for photocatalytic decoloration of dye in the recycled tests. This study suggested a promising system to utilize the NIR energy of sunlight for photochemical and photoelectrical applications based on g-C3N4, which will contribute to the utilization of solar energy in the future.

One step solvothermal synthesis of functional hybrid γ-Fe2O3/carbon hollow spheres with superior capacities for heavy metal removal.

One-step hydrothermal method was developed to prepare hybrid γ-Fe2O3/carbon hollow spheres with a predominant orientation (111) plane of γ-Fe2O3 and rich oxygen-containing functional groups on carbon. The resulting functional hybrid exhibited extremely high adsorption capacities for toxic Pb(II) and Cr(VI) ions in solutions with easy magnetic separation. The ease of synthesis and low cost, coupled with the efficient and rapid removal of toxic heavy metal ions, make hybrid γ-Fe2O3/carbon hollow spheres an attractive adsorbent for the purification of waste and contaminated water.

Decolorization of RhB dye by manganese oxides: effect of crystal type and solution pH

AbstractBackgroundOrganic dye pollution in water has become a major source of environmental pollution. Mn(III/IV) oxides have attracted a great deal of attention to remove organic dye pollutants due to their unique structures and physicochemical properties. Numerous studies have reported the removal of dye by various Mn(III/IV) oxides through catalytic degradation and adsorption. The crystalline structures of manganese oxides and solution pH may exert substantial impact on the removal of dyes. However, few studies have focused on the oxidative degradation of RhB dye using Mn(III/IV) oxides with different crystal structures during a spontaneous reaction. In the present study, three manganese oxides with different crystal type (α-MnO2, β-MnO2, and δ-MnO2) were prepared by refluxing process to decolorize RhB dye in various pH solutions.ResultsThe results showed that the decolorization efficiencies of RhB for the three manganese oxides all increase with decrease solution pH. α-MnO2 exhibited highest activity and could efficiently degrade RhB at pH 2–6. The degradation of RhB by β-MnO2 and δ-MnO2 could be observed at pH 2–3, and only little adsorption RhB on manganese oxides could be found at pH 4–6. The UPLC/MS analysis suggests that the decolorization of RhB by manganese oxides consists of three main stages: (1) cleavage of the ethyl groups from RhB molecular to form Rh; (2) further destruction of –COOH and –CNH2 from Rh to form the small molecular substances; (3) mineralization of the small molecular substances into CO2, H2O, NO3− and NH4+.ConclusionsOverall, these results indicate that α-MnO2 may be envisaged as efficient oxidants for the treatment of organic dye-containing wastewater under acid conditions.

Laboratory-scale column study for remediation of TCE-contaminated aquifers using three-section controlled-release potassium permanganate barriers.

A laboratory-scale study with a sand column was designed to simulate trichloroethylene (TCE) pollution in the aquifer environment with three-section controlled-release potassium permanganate (CRP) barriers. The main objective of this study was to evaluate the feasibility of CRP barriers in remediation of TCE in aquifers in a long-term and controlled manner. CRP particles with a 1:3 molar ratio of KMnO4 to stearic acid showed the best controlled-release properties in pure water, and the theoretical release time was 138.5 days. The results of TCE removal in the test column indicated that complete removal efficiency of TCE in a sand column by three-section CRP barriers could be reached within 15 days. The molar ratio of KMnO4 to TCE in the three-section CRP barriers was 16:1, which was much lower than 82:1 as required when KMnO4 solution is used directly to achieve complete destruction of TCE. This result revealed that the efficiency of CRP for remediation of TCE was highly improved after encapsulation.

Fabrication of 3D porous Mn doped α-Fe2O3 nanostructures for the removal of heavy metals from wastewater

Three-dimensional porous Mn doped α-Fe2O3 nanostructures are successfully fabricated by calcined carbon spheres containing Fe(II) and Mn(II) ions, which were obtained by hydrothermal treatment of glucose, Fe(II), and Mn(II) mixed solutions. The obtained nanostructures exhibit excellent abilities for the removal of Pb(II), Cr(VI), and As(III) ions from wastewater with easy magnetic separation.

Fabrication of resin supported Au–Pd bimetallic nanoparticle composite to efficiently remove chloramphenicol from water

The evolution of antibiotic resistance and the potential impact on human health of chloramphenicol (CAP) have made it an environmental pollutant requiring urgent action. In this study, Au–Pd bimetallic nanoparticles (BNPs) were first synthesized and then successfully loaded on Amberlite 717 to form an Amberlite 717 supported Au–Pd BNP catalytic system (717@Au–Pd) with the mass fraction of Au–Pd at about 4.5%. The as-synthesized catalytic system was used to degrade CAP in water under a H2 atmosphere at room temperature. When 0.5 g of 717@Au–Pd was added into the CAP solution (50 mg L−1, 50 mL, pH 7), about 60% of CAP was absorbed on the 717@Au–Pd in the first 10 h and then all of CAP can be completely removed in the following 3 h under a H2 atmosphere. The degradation process of the reaction can be fitted with a first-order kinetics equation with the kinetics constant of 4.3 h−1 ± 0.009. The degradation products and mechanism were studied using LC/MSD Trap-XCT. The results showed that CAP was removed by the 717@Au–Pd via cleaving the carbon–halogen bond of CAP while keeping the nitro-group unaffected and this made the degradation products less environmentally toxic. The recycled experiments showed that the removal rate of CAP can still be maintained at 99% even after 5 cycles. The study indicated that 717@Au–Pd is a promising catalyst for removing environmental pollutants such as CAP containing carbon–halogen bonds.

Evaluating the biosafety of conventional and O3-BAC process and its relationship with NOM characteristics

ABSTRACT It is the priority to guarantee biosafety for drinking water treatment. The objective of this study was to evaluate the impact of widely applied conventional and ozone-biological activated carbon (O3-BAC) advanced treatment technology on biosafety of drinking water. The items, including assimilable organic carbon (AOC), biodegradable dissolved organic carbon (BDOC), heterotrophic plate counts (HPCs) and the microorganism community structures, were used to evaluate the biosafety. Moreover, their relationships with molecular weights (MWs) and fluorescence intensity of dissolved organic matter were investigated. The results indicated that the technology provided a considerable gain in potable water quality by decreasing dissolved organic carbon (DOC, from 5.05 to 1.71 mg/L), AOC (from 298 to 131 μg/L), BDOC (from 1.39 to 0.24 mg/L) and HPCs (from 275 to 10 CFU/mL). Ozone brought an increase in DOC with low MW <1 kDa, which accompanies with an increase in AOC/BDOC concentration, which could be reduced effectively by subsequent BAC process. The formation of AOC/BDOC was closely related to DOC with low MWs and aromatic protein. Bacteria could be released from BAC filter, resulting in an increase in HPC and the presence of pathogenic bacteria in effluent, while the post sand filter could further guarantee the biosafety of finished water.