Co-transport Of Silver Nanoparticles And Escherichia Coli In Saturated Porous Media

With the in-depth study of Silver nanoparticles(AgNPs),we found AgNPs are widely applied in industrial production and people's life,silver nanoparticles are likely to be using and final disposal process such as agricultural waste water seepage and sludge into the groundwater environment,the possible hazard gradually attracted everybody's attention.A large number of microorganisms in the environment,they are likely to be damaged by silver nanoparticles toxicity,and maybe change the existence form of silver nanoparticles or transport way.There are a little study about the silver nanoparticles and Escherichia coli co-transport in porous medium in so far.In order to reduce the potential environmental risk of silver nanoparticles,in-depth development of silver nanoparticles in water migration mechanism and the research with the interaction of microorganisms in water has become very important.Research environment together with the transport behavior of Escherichia coli,silver nanoparticles for nano silver and typical microorganism in the groundwater migration mechanism and provides the theory basis for risk assessment,explain and explore the interaction between silver nanoparticles and microorganism in the environmental medium and for risk prevention and control of groundwater and management has very important significance.In this article,Escherichia coli K12 and Polyvinylpyrrolidone(PVP)coated silver nanoparticles(PVP-Ag NPs)were used as the research object.Use two typical colloid particle in three kinds of fillings:glass beads,iron-oxide coated glass beads,and natural sand to explore the transport of adsorption characteristic and related mechanisms.Through the static mixing experiment combined with dynamic column experiment,focus on investigating filling medium size distribution(large particles in homogeneous,heterogeneous,small particles in homogeneous),water flow rate(l mL/min and 2 mL/min),and the way of transport(co-transport and single-transport).Understanding of Escherichia coli K12 and silver nanoparticles settlement release process in saturated porous media,the main research results are as follows:(1)Silver nanoparticles in porous media release characteristic controlled by electrical,polymer coatings and Escherichia coli K12 extracellular secretion.In size large medium,silver nanoparticles transport is mainly controlled by adsorption sedimentation,and in small size medium,the transport process controlled by adsorption sedimentation and blocking subsidence mechanism at the same time.(2)Deposition of Escherichia coli K12 in saturated porous media mainly affected by the surface charge,the pure almost does not occur in the porous media adsorption sedimentation,and in iron-oxide coating and natural sand deposits to increase.(3)Flow velocity changes can also change the settling velocity and blocking rate,at the same time can change size exclusion effect,which changes the migration velocity of silver nanoparticles,velocity increases,the Silver nanoparticle migration quantity increase.(4)The smaller the particle size of porous media,the greater the amount of nano silver deposit.