Study Of The Biological Affinity Of The Surface Of Modified Polyethylene Based On Oyster Shell

Biological membrane method is one of the most common wastewater treatment technologies, whose key part is biological carrier, the performance of biological carrier has a direct impact on the effect of wastewater treatment. However, the existing biological carriers have some disadvantages, such as poor biological compatibility, biological membrane grow slowly and can't adhere tightly. In this paper,we using a kind of natural biological mineral material—oyster shell to improve the polyethylene material's biological affinity.The composition, microstructure and thermal stability of oyster shell were studied by means of XRD, FT-IR, TG, and SEM. The experimental results showed that the internal structure of oyster shell is porous and layered, the pores diameter are5~60nm. Its main component is calcium carbonate, about 96% of the total quality, the rest are organic matters include glycine, valine, phenylalanine, et al. as well as some trace elements such as Mg, Ni, Co, Zn, etc. The TG results show that the thermal stability of oyster shell is good, and the weight loss rate is only 0.4% at 200 ?. The contact angle results show that oyster shell powder has good hydrophilicity, and the contact angle is 15 degree.The release rule and influence factors of the organic matter and trace elements were tested by three-dimensional fluorescence photometer and ICP-OES, we found that the oyster shell particles were easy to be wrapped by polyethylene film in the preparation process, it will affect the release of organic matter and trace elements. The rate of organic matter released by the composite was significantly increased after the surface treatment of the simulated fluidized bed, and most of the oyster shell particles are exposed to the surface of the material.Aiming at the problem that the surface of polymer material is smooth, the effectof oyster shell powder on the surface roughness and contact angle of polyethylene is studied. We found that with the increase of the proportion of the oyster shell powder,the surface roughness of the polyethylene increased gradually, and the contact angle decreased gradually. When the proportion of the oyster shell powder is more than 6%,the contact angle decreases gradually, the contact angle of the composite material reduced from 93°to 70°, the hydrophilicity was improved obviously.The physical and chemical properties of the modified polyethylene materials were tested by universal testing machine, density measuring instrument and melting index measuring instrument. We found that there is a positive correlation between the density of the polyethylene and the proportion of the oyster shell powder, the density of the material can be accurately controlled by adjusting the proportion of the oyster shell powder. When the proportion of the oyster shell powder is about 5%, the density of the polyethylene material can reach 0.975g/cm3, which accordance with the requirements of the biological carrier density. When the oyster shell powder filling ratio is 6% and 5%, the impact strength and tensile strength reached the maximum40.06kJ/m2 and 25.87 MPa, which increased 26.6% and 28.5%,respectively.Biofilm performance of oyster shell powder modified polyethylene was investigated using a biofilm reactor, it was found that when the ratio of oyster shell powder was 5%, the membrane of modified polyethylene reached 0.0211g/g, which increased by 124%, and the biological affinity was greatly improved.