Effect Of Clay On The Transport And Retention Of Nanoparticles In Saturated Porous Media

The wide application of industrial nanomaterials is unavoidably released to the natural environment,which poses a potential threat to human beings.The influence of clay,ionic strength and organic matter on the transport of nanomaterial makes the threat more complex and serious,so effect of environmental factors on the transport of nanomaterials should be studied systematically.The object of this paper are the nano titanium dioxide?nTiO₂?and the nano zero valent iron?nZVI?.The transport and mechanism are studied by the experiments of column transport in the presence of clay,the measurement of zeta potential and the hydraulic radius under different conditions,and two-site kinetic attachment model?TSKAM?.?1?Aggregation and transport of rutile nTiO₂ with montmorillonite and diatomite in the presence of phosphate in porous sand:the transportability of nTiO₂ are inhibited by the presence of montmorillonite and diatomite.The improvement of nTiO₂ retention in sand was more pronounced by diatomite than montmorillonite.Compression of nTiO₂ transport with diatomite and montmorillonite was disappeared by the addition of P.?2?Transport and retention behaviors of titanium dioxide nanoparticles in iron oxide-coated quartz sand in the presence of organic acid:the transport of nTiO₂ was inhibited due to the existence of iron oxide-coated sand in the absence of organic acid.The study demonstrates that transport of nTiO₂ was promoted due to in the presence of organic acid.Facilitated the transport of nTiO₂ in NH₄Cl ionic concentration follows the order:Gallic acid>Tannic acid>Oxalic acid.When CaCl₂ is used as background,the order of promoting nTiO₂ is the following order:Gallic acid>Tannic acid>Oxalic acid>Humic acid>Fulvic acid.The promoting effect of humic acid and fulvic acid was greatly reduced under high CaCl₂ concentration.This is because oxalic acid,humic acid and fulvic acid react with calcium ions,and calcium ions have stronger shielding effect on the negative charge of fulvic acid molecules.?3?The transport behaviors of nZVI loaded with clay in quartz sand column:Clay loading nZVI promotes the transport of nZVI in quartz sand column,and nZVI loaded with montmorillonite or diatomite is higher than that nZVI loaded with zeolite in the background of NaCl and CaCl₂.The transport curves of nZVI loaded with attapulgite are irregular,which may be related to the characteristic of attapulgite.?4?The transport behaviors of nZVI loaded with clay in the Presence of Lead chloride in quartz sand column:Compared with zeolite and attapulgite,the effect of nZVI loaded with montmorillonite and diatomite on lead adsorption isotherm is better.In the experiment of transport in column,the transport of nZVI loaded on montmorillonite and diatomite decreased with the increase of lead chloride concentration,but the content of total lead in the effluent increased gradually.It is indicated that quartz sand and nZVI trapped in columns adsorbed part of lead,and more lead transport along with the solution of nZVI.