| Biofilm treatment is an efficient biochemistry method for wastewater treatment, and the choice of suitable biofim-carrier is one of the most important steps in biofilm treatment technology. For the late start of bilfim application and lack of technical experience in our courtry, related studies are minority and incomplete, and research about immobilization mechanisms of microorganisms on carrier in wastewater is expecailly little, which limits the choice of carrier and the development of biofilm treatment technology. Considering that carbon kind materials generally have outstanding biocompatibility, carbon-based materials have highly possibility to be biofilm-carriers with good microbial affinity and immobilization ability. Carbon Fiber (CF) has stable surface physicochemical properties and good anti-corrosion ability, so CF may have very broad development prospects as biofim-carrier. In this pater, PAN-based CF was treated by different surface modifications to prepare biofilm-carrier with good microbial affinity, CF surface nature such as chemistry, function groups, hydropilicity, roughness and charge were characterized, and the biocompatibility of CF was discussed based on macroscopic immonbilization and microscopic adhesion, thereby analyze the surface nature effects on microorganisms immobilization and study immobilization mechanism synthetically.PAN-based CF biofilm-carrier was treated by time-gradient nitric acid modification. The CF surface morphology and nature were characterized by laser confocal microscopy (LCM), Fourier transfor infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and degree of moisture (DM). In addition, the biocompatibility of CF was discussed based on the immobilization behavior of microorganisms. The outcomes indicated that the nitic acid oxidation treatment could be regarded as a favorable surface treatment for CF carrier, which can make biofilm fully developed in 2 h, and the immobilization ratio can reach to 227.0% in 24 h when DM is 6.13%. Immobilization capacity of microorganisms could be improved if the CF surface was modified to a better hydrophilicity state by producing oxygen-based function groups, among which the O-C=O group had a great effect on microorganisms adhesion. Besides that, microorganisms showed a preference of adhering onto carrier surfaces with moderate wettability and oxygen content for the corporating surface effects of hydrophilicity and electronegativithy.CF was modified by anodic oxidation and electropolymeriztion using sulfuric acid and maleic anhydride (MA) respectively before surface nature and biocompatibility were characterized. The result indicated that the two kinds of electrochemistry modifications could be regarded as favorable surface treatments to improve biocompatibility of CF carrier by the increase of surface oxygen content, and the anodic oxidation has higher superiority then the other. During the microorganism immonilization process, the IRM increased first, then getting stable when the development and subduction of biofilm got balance. Besids that, acetone is more suitable to wipe off the sizing agent on CF surface than ethanol.CF was modified by hypochlorous oxidation and urea graft before surface nature and biocompatibility were characterized. The result shows that the modification composed of hypochlorous oxidation and urea graft could be regarded as a favorable surface treatment for CF carrier, which can make biofilm fully developed in 2 h, especially suitable for short-term and rapid immobilization of microorganism on CF surface. When hydrofilicity is poor, the increase of oxygen or nitrogen functional groups and wettability on CF carrier could be helpful to enhance the immobilization ability of microorganism of CF. The improvement of CF surface smoothness would limit the performace of biocompability on CF. In addition, LCM is mor suitable to abserve CF surface morphology then SEM for the superior depth resolution.CF was treated by a multiple-modification composed of mixed acid oxidation, MA graft and metalion adsorption before surface nature and biocompatibility were characterized. The result shows that the multiple-modification could be regarded as a favorable surface treatment for CF carrier, which could make biofilm fully developed in 1 h and be suitable for short-term and rapid immobilization of microorganism on CF surface. After metalion-adsorption, the metalion could improve immobilization ability of microorganisms by connecting both electronegative oxygen groups on CF surface and extracellular polymeric substance on microorganism cells. In addition, both KBr-pellet and reflex FTIR detection methods could be used to analyze organo-functional groups on CF surface, but KBr-pellet is more resultful.In order to study the influence of carrier’s biocompability on wastewater treatment result, modified and unmodified CF was choosen to be biofilm-carrier for comparition, and the treatment result was evaluated by remove1 rate of Chemical Oxygen Demand (COD). The outcome shows that both traditional acticated sludge process and biofilm treatment can reduce the organic matter content in wastewater, but the COD removel rate of biofilm treatment is much higher. Besides that, the quantity of immobilized biofilm is positively correlated with wastewater treatment ability, and COD removel rate would be higher if the biofilm-carrier has better biocompability.Ultrasonic oscillator was used to exfoliate biofilm by applying force on microorganism adhered on CF carrier, and micro-biocompability of CF was characterized by the quantity of remant biofilm on CF surface. The result shows that microorganism exfoliation would appear inside bibfilm, and inner microorganism would still be immobilized if the carrier has good biocompability, otherwise the exfoliation woud appear at the interface between CF surface and biofilm. Besides that, immobilization strength of microorganism is positively correlated with biocompability of carrier. |
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