Preparation Of Modified Diatomite Composite And Its Application In Water Treatment

Due to the physicochemical properties of diatomite(DE),it can be used as a water source treatment material.As an adsorbent,DE has poor adsorption performance and needs to be modified to enhance its adsorption performance.As a filter material,DE itself has no bactericidal properties,and microorganisms will multiply on the surface.DE is modified by graphene oxide(GO)and silver nanoparticles(AgNPs)to improve its adsorption and antibacterial properties.In this paper,GO/DE and AgNPs/GO/DE were prepared,and the adsorption behavior of GO/DE for methylene blue(MB)was studied.Antibacterial properties of AgNPs/GO/DE against Gram-negative bacteria,E.coli and Gram-positive bacteria,S.aureus were studied.The prepared AgNPs/GO/DE composite material was loaded into the filter column to make a simple filter device and filter the Fenhe River water.The chromium ions and total phosphorus in the filtered water were measured,and the zebrafish were cultured with the filtered water to determine the biochemical indicators of the zebrafish.The main findings are as follows:(1)GO/DE composites were prepared from DE and GO.A series of structural characterization and morphology tests were carried out on the GO/DE composites,indicating that GO covers the surface of DE by non-covalent bond and the structure of DE is not changed.(2)The GO/DE composite was used for adsorption of MB in an aqueous solution.The experimental results showed that the highest adsorption efficiency can reach 99% at 0.025g/mL dosage of GO/DE(GO content 0.3%),time of 120 min and pH=8.0.Under the same conditions,when the dosage of the DE was also 0.025 g/mL,the adsorption rate of MB can reached 63.3%.It can be seen that GO improved the adsorption performance of DE on MB.Itcan be seen that GO improves the adsorption performance of DE on MB,and also solves the problem that GO is difficult to separate from water.Pseudo second-order kinetics equation can describe the adsorption process appropriately.Particle film diffusion and intraparticle diffusion occur simultaneously by fitting the intraparticle diffusion model.Intraparticle diffusion is not the only rate control step for the entire process.The equilibrium datas were excellent correlation with the Freundlich isotherm model and the adsorption behavior was spontaneous and exothermic.In addition,GO/DE composites have good desorption and recyclability.(3)AgNPs/GO/DE composites were prepared from AgNPs,DE and GO.A series of structural characterization and morphology tests were carried out on AgNPs/GO/DE composites,indicating that GO can firmly immobilize AgNPs with a particle size of about20-40 nm on DE,and the silver content is 2340 ppm.And GO covers the surface of DE by non-covalent bond,and AgNPs and GO did not change the structure of DE through characterization.(4)The AgNPs/GO/DE composite was tested for antimicrobial activity.The as-prepared AgNPs/GO/DE demonstrated excellent antibacterial properties to E.coli and S.aureus,evaluated by measuring the minimum bactericidal concentration(MBC)using twofold serial dilutions in a lysogeny broth medium.The MBC of AgNPs/GO/DE against E.coli and S.aureus were 5 and 10 mg/mL,respectively.The amount of silver released into the water was38-46 ppb,which is lower than the amount specified in the World Health Organization standards(<100 ppb).The composite adsorbs bacteria to its surface and then kills the bacteria,which is observed by Fluorescence staining and SEM.(5)The prepared AgNPs/GO/DE composite material was loaded into the filter column to make a simple filter device and filter the Fenhe River water.The filtered water was measured for chromium ions and total phosphorus content,and zebrafish was cultured with filtered water.The experimental results show that AgNPs/GO/DE composites have remarkable effect in treating chromium ions and total phosphorus in water.Through the study of protein content and POD,CAT enzyme activity in zebrafish,it was found that there was no significantdifference between filtered water treated with AgNPs/GO/DE composite and Fenhe water and tap-water on zebrafish culture to a certain extent.It was demonstrated that filtered water treated with AgNPs/GO/DE composite have no effect on the safety of zebrafish.