Various Carbon Fiber Surface Modification Methods To Study The Effects And Mechanism Of Bacterial Immobilization

Biofilm water treatment technology is a new type of sewage treatment technology,which mainly uses microorganisms attached to the surface of carrier materials to degrade organic substances in sewage,thereby purifying water quality.During the preparation of biofilm materials,the surface properties of the carrier material play a crucial role in the immobilization of microbial cells.As a new carrier material,carbon fiber has been widely used in the sewage treatment industry.However,the inertia of the surface of the carbon fiber is relatively large,which has a certain restriction on the immobilization of the microbial cells.Therefore,the surface modification of the carbon fiber is required to improve the bio-compatibility to promote the sewage treatment capacity of the biofilm material.In this thesis,three kinds of carbon fiber carriers were prepared by the combination of nitric acid oxidation and calcium ion adsorption,electrochemical deposition of polyamic acid film and anodic oxidation and manganese ion adsorption.Scanning electron microscopy was used to observe the surface morphology of carbon fiber carriers.EDS and Fourier infrared spectroscopy were used to analyze the surface of the material.The microbial cell immobilization assays evaluated the ability of carbon fiber carriers to immobilize microbial cells,and the ability of microbial cells was analyzed and explained from the theoretical point of view by using DLVO theory.Finally,the immobilization ability of the three carbon fiber carriers was comprehensively compared by the biofilm colonization experiment in simulated organic water.The main conclusions can be summarized as follows:(1)Surface oxidation can enhance the ability of carbon fibers to immobilize microbial cells.The adsorption of metal ions can immobilize more microbial cells to the oxidized carbon fibers,and the greater the metal ion content,the stronger the immobilization ability.Surface oxidation can reduce the diiodomethane contact angle of the surface,thereby reducing the van der Waals potential.However,the introduction of oxygen-containing groups will increase the electrostatic potential energy.Metal ions adsorbed by the oxidizedcarbon fiber carrier could reduce the absolute value of the zeta potential due to the positive charge,resulting in a decrease in the electrostatic potential energy.Therefore,the total potential energy is reduced,and the larger the metal ion content,the lower the total potential energy and the stronger the immobilizing ability.(2)The polyamic acid film deposited on the surface of carbon fiber can effectively enhance its ability to immobilize microbial cells.When the molar ratio of carboxyl group is2.0 and the electrodeposition time is 10 minutes,the carbon fiber composite material can immobilize the most microbial cells.It is the carbon fiber carrier under this condition that has a small diiodomethane contact angle and small absolute zeta potential.In fact,the polyamic acid film leads to an increase in the electrostatic potential energy of the carrier materials.But since the electrostatic potential energy increase is small,the total potential energy after the integrated superposition is still reduced.(3)The immobilization ability of three carbon fiber carriers for microbial cells is arranged from small to large as CF-Ca,CF-Mn and CF-PAA.Thus CF-PAA is the most bio-affinitive biofilm carrier,for the smallest diiodomethane contact angle,resulting in the lowest van der Waals potential.