Dejun Bian

A novel conversion of the groundwater treatment sludge to magnetic particles for the adsorption of methylene blue.

Iron sludge, produced from filtration and backwash of groundwater treatment plant, has long been considered as a waste for landfill. In this study, iron sludge was reused to synthesize Fe3O4 magnetic particles (MPs) by using a novel solvothermal process. Iron sludge contained abundant amounts of silicon, iron, and aluminum and did not exhibit magnetic properties. After treatment for 4h, the amorphous Fe in iron sludge was transformed into magnetite Fe3O4, which could be easily separated from aqueous solution with a magnet. The prepared particles demonstrated the intrinsic properties of soft magnetic materials and could aggregate into a size of 1 μm. MPs treated for 10h exhibited excellent magnetic properties and a saturation magnetization value of 9 emu/g. The obtained particles presented the optimal adsorption of methylene blue under mild conditions, and the maximum adsorption capacity was 99.4 mg/g, which was higher than that of granular active carbon. The simple solvothermal method can be used to prepare Fe3O4 MPs from iron sludge, and the products could be applied to treatment of dyeing wastewater.

Novel Porous Polyethersulfone Beads as Matrix to Immobilize Comamonas testosteroni sp. bdq06 in Quinoline Biodegradation

Novel matrix beads for the immobilization of strain Comamonas testosteroni sp. bdq06 to degrade quinoline were fabricated from polyethersulfone(PES). The beads have an average size of 3 mm and a surface dense layer of 20 microns. To help adhesion and proliferation of bacterial cells, the surfaces of the PES beads were etched, and numerous holes about 1.5 micrometers in diameter were generated as tunnels for cell colonizing in the larger internal cavities of about 5 micrometers in diameter. The quinoline degradation was remarkably enhanced by the cells immobilized in PES beads compared with that by the free cells at pH 5.0 or 10.0 and a temperature of 40 °C. The enhanced degradation of quinoline was contributed to the biofilm on the surface of PES beads, resulting in the significant reduction of retention time from 9 h to 2 h. Furthermore, the beads remain intact after the ultrasonic treatment of them for 30 min or recycling 50 times, indicating that they have excellent mechanical strength, flexibility and swelling capacity. Thus, PES beads have great potential to be matrix for the cell immobilization in bioaugmentation.

Synthesis and characterization of a magnetic adsorbent from negatively-valued iron mud for methylene blue adsorption

With increasing awareness of reduction of energy and CO2 footprint, more waste is considered recyclable for generating value-added products. Here we reported the negatively-valued iron mud, a waste from groundwater treatment plant, was successfully converted into magnetic adsorbent. Comparing with the conventional calcination method under the high temperature and pressure, the synthesis of the magnetic particles (MPs) by Fe2+/Fe3+ coprecipitation was conducted at environment-friendly condition using ascorbic acid (H2A) as reduction reagent and nitric acid (or acid wastewater) as leaching solution. The MPs with major component of Fe3O4 were synthesized at the molar ratio (called ratio subsequently) of H2A to Fe3+ of iron mud ≥ 0.1; while amorphous ferrihydrite phase was formed at the ratio ≤ 0.05, which were confirmed by vibrating sample magnetometer (VSM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). With the ratio increased, the crystalline size and the crystallization degree of MPs increased, and thus the Brunauer-Emmett-Teller (BET) surface and the cation-exchange capacity (CEC) decreased. MPs-3 prepared with H2A to Fe3+ ratio of 0.1 demonstrated the highest methylene blue (MB) adsorption of 87.3 mg/g and good magnetic response. The adsorption of MB onto MPs agreed well with the non-linear Langmuir isotherm model and the pseudo-second-order model. Pilot-scale experiment showed that 99% of MB was removed by adding 10 g/L of MPs-3. After five adsorption-desorption cycles, MPs-3 still showed 62% removal efficiency for MB adsorption. When nitric acid was replaced by acid wastewater from a propylene plant, the synthesized MPs-3w showed 3.7 emu/g of saturation magnetization (Ms) and 56.7 mg/g of MB adsorption capacity, 2.8 times of the widely used commercial adsorbent of granular active carbon (GAC). The major mechanism of MPs adsorption for MB was electrostatic attraction and cation exchange. This study synthesized a magnetic adsorbent from the negatively-valued iron mud waste by using an environment-friendly coprecipitation method, which had a potential for treatment of dye wastewater.

Comparing polyethersulfone and polyurethane-immobilized cells of Comamonas testosteroni QYY in treatment of an accidental dye wastewater

Well-channeled porous polyethersulfone(PES) beads were synthesized and used for the immobilization of Comamonas testosteroni QYY cells for an aerobic reactor to remove quinoline, phenol, and other refractory com-pounds in accidentally-released dye wastewater supplemented with domestic wastewater. The pore size in PES beads mainly depended on the dripping time through the water vapor cylinder. When the cylinder was 2.5 m in length, the pore size in the obtained beads was enlarged to 3 μm, which provided an ideal surface for cells to pass through and grow inside. The reactor with the immobilized C. testosteroni QYY on PES beads resisted organic loading shock and enhanced total organic carbon(TOC) removal, which had 100% removal efficiencies of both quinoline and phenol when the volume ratio of the accidental wastewater to domestic wastewater was increased from 1:2 to 1:1, as compared with the 100% and 34.7% removal efficiencies by the reactor with immobilized C. testosteroni QYY on polyurethane(PU) cube or the 82% and 2.4% removal efficiencies by the reactor with only the suspended C. testosteroni QYY cells, respectively. The PES beads had a specific surface area of 1843 cm2/cm3, which had immobilized (0.024±0.003) g of C. testosteroni QYY cell dry mass/cm3, compared with the specific surface area of 564 cm2/cm3 of the PU cube with (0.018±0.002) g of cell dry mass/cm3. The kinetic study revealed that the quinoline and phenol degradation followed zero-order reactions for all the three reactors. The PES reactor demonstrated the highest quinoline and phenol removal efficiencies. The immobilized C. testosteroni QYY on the low-cost inert PES beads demonstrated good shock resistance and was able to completely remove the toxic compounds, including phenyl carbamate, 2-nitrotoluene, and dioctyl phthalate. Therefore, the beads were ideal for large-scale accidental wastewater treatment.