Bo Ruan,Pingxiao Wu,Xiaolin Lai,Huimin Wang,Liping Li,Liya Chen,Chunxi Kang,Nengwu Zhu,Zhi Dang,Guining Lu
The objective of this study was to investigate the interaction between stearic acid-modified montmorillonite (SA-Mt) and Sphingomonas sp. GY2B and its effect on the physical and chemical properties of montmorillonite in the 2 days' biodegradation of phenanthrene . Due to bacterial activities , surface and colloidal properties of the bacteria-treated sample evidently changed in comparison with the untreated SA-Mt. Changes in surface morphology and the agglomerate state of SA-Mt were clearly observed by scanning electron microscopy (SEM) after interaction with GY2B for 2 days. Although the interlayer space of SA-Mt structure remained basically unchanged, the decrease of the structural order and the appearance and shift of several absorbance bands in the Fourier transform infrared (FTIR) spectra verified the structural changes of SA-Mt after bacterial treatment . Besides, the second derivative infrared spectra indicated that bacterial growth and metabolism largely affected the microstructure in SA-Mt. Dissolution rates of major elements were obtained by inductively coupled plasma optical emission spectroscopy (ICP-OES) in the solution, which revealed that bacterial activities enhanced the release of major elements and brought about a significant higher dissolution of Si preferentially from the tetrahedral sheet edges of SA-Mt than Al. The improvement of elemental dissolution in the biotic experiment was attributed to the combined action of pH effect and ligand-promoted process. These results substantiated that microorganisms have a considerable influence on the physicochemical properties and structure in the clay-modulated biodegradation of organic compounds. This study has profound impacts on the clay-modulated biodegradation of hydrophobic organic contaminants in the environment.
Bo Ruan,Pingxiao Wu,Meiqing Chen,Xiaolin Lai,Liya Chen,Langfeng Yu,Beini Gong,Chunxi Kang,Zhi Dang,Zhenqing Shi,Zehua Liu
In this study, batch experiments were carried out to evaluate the biodegradation of phenol by Sphingomonas sp. GY2B, which were immobilized in polyvinyl alcohol (PVA) – sodium alginate – kaolin beads under different conditions. The optimal degradation performance was achieved by GY2B immobilized in beads containing 1.0% (w/v) of kaolin, 10% (w/v) of PVA, 0.3% (w/v) of sodium alginate, 10% (v/v) of biomass dosage, and exposed to an initial phenol concentration of 100 mg/L. The experimental results indicated that PVA-sodium alginate-kaolin beads can accelerate the degradation rate of phenol by reducing the degradation time and also improve degradation rate. The biodegradation rate of phenol by immobilized cells (16.79 ± 0.81 mg/(L·h)) was significantly higher than that of free cells (11.49 ± 1.29 mg/(L·h)) under the above optimal conditions. GY2B immobilized on beads was more competent than free GY2B in degradation under conditions with high phenol concentrations (up to 300 mg/L) and in strong acidic (pH = 1) and alkaline (pH = 12) environments. Higher phenol concentrations inhibit the biomass and reduce the biodegradation rate, while the lower biodegradation rate at low initial phenol concentrations is attributed to mass transfer limitations. The Haldane inhibitory model was in agreement with the experimental data well, revealing that phenol showed a considerable inhibitory effect on the biodegradation by Sphingomonas sp. GY2B, especially at concentrations higher than 90 mg/L. Intra-particle diffusion model analysis suggests that adsorption of phenol by immobilized beads was controlled by both rapid surface adsorption as well as pore diffusion mechanism. It's worth noting that the presence of 1 mg/L Cr(VI) enhanced the biodegradation of phenol by free cells, while Cr(VI) showed no obvious impact on the removal of phenol by immobilized cells. In addition, immobilized cells were reused 16 times and removed 99.5% phenol, and when stored at 4 °C for 90 days, more than 99% phenol was removed. These results showed that immobilized cells can significantly improve the microbial degradation performance, and protect microorganisms against unfavorable environment. It is implied that PVA -sodium alginate-kaolin beads have great potential to be applied in a practical and economical phenolic wastewater treatment system.
危险品化学品经营许可证（带存储）