Preparation Of Natural Biomass Straw Carbon-loaded Silver Antibacterial Composite And Its Application In Drinking Water

Microbial contamination in drinking water is being concerned by more and more people.Therefore,bacteriostatic treatment of water has become the most important step.Currently,the filtration materials on the market are mainly activated carbon,resin and zeolite.However,there is greater focus on the ability of the filtering material to absorb,while ignoring its ability to inhibit bacteria.Water is a breeding ground for common microbial pathogens,and in a wet environment,it is easy for bacteria to breed on the surface of some materials.If the sterilization is incomplete at the terminal drinking water device,it could lead to the growth of some pathogenic microorganisms.These pathogenic microorganisms may cause intestinal infections in humans.In this paper,three antibacterial composites（CTS/C-Ag、PVA/C-Ag、PVA/BC/C-Ag）were prepared and used in the terminal drinking water treatment device.The inhibition of the common microorganisms（E.coli and S.aureus）in water was studied.The possible antibacterial mechanism of composites was discussed.The main contents of this paper are summarized as follows:（1）Firstly,silver-loaded biochar（C-Ag）was prepared by impregnating silver nitrate with high-temperature carbonization and reduction under nitrogen atmosphere with corn stalks commonly used in Shaanxi as a carrier.The effects of different carbonization temperatures on the antibacterial effect of silver-loaded biochar were studied.The prepared silver-loaded biochar（C-Ag）was characterized by Fourier transform infrared spectroscopy（FT-IR）and X-ray diffraction（XRD）,and the prepared silver-loaded biochar was also analyzed by scanning electron microscopy（SEM）.（2）Chitosan/silver-loaded biochar（CTS/C-Ag）antibacterial composite was prepa-red by sol-gel method.The antibacterial effect of the composite（CTS/C-Ag）on common microorganisms（E.coli）in drinking water was studied.The results showed that the CTS/C-Ag composite showed good antibacterial activity in the actual water.The surface morphology,structure and stability of CTS/C-Ag were characterized by Scanning electron microscopy（SEM）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）,thermogravimetry and differential thermal analysis（TG-DSC）,and specific surface area analysis（BET）.The results showed that chitosan coated a thin layer on the surface of C-Ag,the particle size of silver particles was about50 nm,and it was uniformly dispersed in CTS/C-Ag composite.CTS/C-Ag composite had good stability in water.The BET analysis test showed that the total pore volume of the adsorption decreased,mainly because the surface of the biochar was coated with chitosan,which resulted in a decrease in specific surface area and a decrease in adsorption capacity,further indicating that CTS/C-Ag composite has been synthesized.（3）Polyvinyl alcohol/silver-loaded biochar（PVA/C-Ag）particle composite was prepared by sol-gel method.The effect of the mass fraction of cross-linking agent（boric acid and sodium carbonate）on the ball-forming properties was investigated.The optimal dose and time,antibacterial durability and reusability of the composite were studied,and it was found that the polyvinyl alcohol/silver-loaded biochar composite（PVA/C-Ag）had good antibacterial durability and reusability.SEM,XRD,FT-IR,and TG-DSC were used for characterization.The results show that PVA/C-Ag microsphere composite has good stability,and there exist a large number of pores in the cross section,and the pore size is about micron,which further indicates that the internal structure of the pellets has been improved after the pore formation of calcium carbonate.Through the practical application of bacteriostasis test,it was shown that PVA/C-Ag microsphere composite has a good bacteriostasis effect,and could effectively remove the common microorganisms（E.coli）in water.It has a certain adsorption capacity for some common metal ions(Pb²⁺and Cu²⁺)in water.（4）Polyvinyl alcohol/bacterial cellulose/silver-loaded biochar（PVA/BC/C-Ag）composite was prepared by sol-gel method.The addition of bacterial cellulose improves the mechanical properties of the polyvinyl alcohol film.The swelling ratio of the composite under different ratios was studied,and the water flux of PVA/BC/C-Ag was tested.The antibacterial properties of the composite film were tested.Scanning electron microscopy（SEM）,X-ray diffraction（XRD）,Fourier infrared spectroscopy（FT-IR）,and thermogravimetric and differential thermal analysis（TG-DSC）were used for characterization.The results show that the silver-loaded biochar（C-Ag）is embedded in the inner or surface of the film evenly,and PVA/BC/C-Ag composite has a high stability in water.