Synthesis And Antibacterial Effect Of Novel Biochar Nanocomposites Loaded With Silver And Titanium Dioxide Nanoparticles

Excess of bacteria in the water may lead to various human diseases,causing great damage to human body.causing great damage to human body.Therefore,disinfection methods are absolutely necessary in the water treatment process.Deep water treatment of parts of the waterworks in China is not enough,and long water pipe may lead the growth and reproduction of bacteria in the pipe.In order to access safe drinking water,some families choose to use water purifier to treat the water.At present,home-used water purifiers have three common water treatment devices,PP filtration and two AC adsorption devices.More advanced devices include softening device,reverse osmosis unit and nanofiltration device.Common AC devices can't kill bacteria,and life of the devices is short,which request regular change.Besides,people of parts of the rural places in China may drink untreated water,and the bacteria in the water might cause different diseases.Therefore,it is urgent to increase the life of adsorption materials,lengthen the period of replacement and enhance the treatment effect.Silver and Ti O₂nanoparticles are harmful to bacteria protein and structure,causing the death of bacteria,and have been applied to environmental areas.This study consider using silver and Ti O₂nanoparticles as antibacterial agents and biochar as nanoparticle carrier,to make nanocomposites with inexpensive price,robust antibacterial effect and simple synthesis process,and investigate the antimicrobial effect and mechanism of the nanocomposites.This study used corncob and crayfish shell as raw stocks,and produced corncob biochar and crayfish shell biochar pyrolyzed at 300?and 450?,respectively.Yields analysis was conducted towards the biochars.SEM and BET were applied to characterize different biochars.With biggest specific area and optimal hardness,crayfish shell biochar pyrolized at 450?was chosen to be the carrier of nano particles.Then tetrabutyl titanate and silver nitrate were used as the precursor of Ti O₂and Ag to load the nanoparticles on the surface of biochar with sol-gel methods.Simultaneous loading method,sequential loading method and multiple loading method were used to make Ti O₂-biochar(Ti-CFS),T-Ag-Ti-CFS,S-Ag-Ti-CFS-1?5.Different biochar nanocomposites were characterized with elemental analysis,TEM,XRD and Uv-Vis methods.After this,the loading effect and antibacterial effect of the nano materials were explored and the basic antibacterial mechanism was analyzed.According to the results,crayfish shell biochar had greater specific area than corncob biochar,and there were more micropores on the surface of crayfish shell biochar for the loading of Ag and Ti O₂ nano particles.Sequential loading method is better than simultaneous loading method.In single loading process,Ag loading amount of sequential loading method is more than sequential loading method by 13.75%.In multiple loading process,the loading amount of Ag nano particles increased by the third loading process,reaching 2.03 mg with loading rate of 10.15%,then it decreased.And the loading amount of Ti O₂ nano particles kept increasing during the loading process,reaching 2.72 mg with loading rate of 13.60%after the fifth loading process.The loading stability of Ag nano particles was worse than Ti O₂ nano particles,and it was possibly caused by the loss during sonication process.The order of antibacterial effect of the biochar nanocomposites is,sequentially loading Ag-Ti O₂-biochar>simultaneously loading Ag-Ti O₂-biochar>Ti O₂-biochar>crayfish shell biochar(with no antibacterial effect).During the short antibacterial experiment,sequentially loading Ag-Ti O₂-biochar could kill 99%bacterium in the solution with the bacterium concentration of 10⁵ CFU/m L.Ag nano particles and the silver ion released by Ag nano particles both possessed robust antibacterial effect,which could destroy the structure of the E.coli cell and kill it.Ti O₂ nano particles could produce different free radicals with great oxidative property,and they could kill the bacterium in the solution.According to the results of Uv-Vis,the best light wavelength was 250 nm and absorbance of the nanocomposites reached the highest point.