Transport Of Nanopollutant And The Effect Of Nanpollutant On The Transport Of Cu²⁺ In Saturated Porous Media

With the rapid development of nanotechnologies and the wide applacation of nanomaterials,nanomaterials will be released through various means into the natural environment inevitablely.With the unique particle sizes and surface characters,nanomaterials are likely to be a serious threat to human health and ecological environment.Additionally,nano pollutants as one kind of emerging contaminants,in addition to its own environmental behavior is worthy of study,its impact on the migration behavior of other pollutants is also worth attention because of the scale effect and high adsorption efficiency.Aiming at the two aspects,in this research,a new carbonaceous nanomaterial — Graphene oxide?GO?was chosen as the study object which had wide range of application value prospects,the influence of hydrochemical condition on the transport of GO in saturated porous media had been studied.At the same time,the adsorption characteristics of GO for Cu²⁺had been discussed.And based on this,the effect of GO on the transport of Cu²⁺ in saturated porious media at different GO concentrations and hydrochemical conditions was investigated as well.To analyze the migration deposition mechanism of GO/Cu²⁺,the deposition kinetics curve was determined by mathematical model and interface chemistry theory.The main research conclusions are as following:?1?With graphite,potassium permanganate and sulfuric acid as raw materials,GO was prepared with pressurized oxidation method and we observed the characterization of morphology and structure of GO by SEM,Raman spectra,XRD,FTIR and Zeta potential method.The results indicated that GO presents transparent mesh structure and possesses obvious fold,the C/O atomic ratio of is 1.63 and the oxidation degree is high enough.And it contains C=C,C=O,-OH and C-O-C functional groups.These oxygen-containing functional groups make GO have a good dispersion in aqueous environment,and can be taken place adsorption with metal ions and organics.?2?The influence of cation composition in mixed Na-Ca electrolyte systems on the transport of GO particles in saturated porous media showed that the retention of GO in sand column is strongly dependent on divalent iron of Ca2+.The effect of molar ratios of Ca2+/Na+?RCa:Na?on the transport behavior of GO in saturated porous media was different at varied ionic strength?IS?: at the lower IS of 1 m M,there was no obvious difference in GO retention in three groups of different RCa:Na solution conditions,the?C/C0?max approached 0.800?0.736 and 0.676 at RCa:Na =0?1 and ?,respectively.It was supposed that the compression of diffuse double layers mainly controlled GO deposition under lower IS of 1 mM.However,the deposition amount of GO of the six groups of different RCa:Na solution conditions were significantly different under higher IS?10m M?.The?C/C0?max decreased from 0.750 to 0.018 when the RCa:Na increased from 0 to ?.The charge neutrality and metal?Ca2+?bridging with functional groups such as carboxyl and hydroxyl groups on the surface of the GO played a significant role at the higher IS of 10 mM.Derjaguin-Landau-Verwey-Overbeek?DLVO?interaction energy calculations were also performed to better understand the mechanisms of GO mobility.A numerical advection-dispersion-retention model was successfully developed to simulate the transport process of GO through the sand column,and R2 ? 0.85.Knowledge from this study can help us understand the behavior of GO in soil and ground water systems well,especially when there were complicated hydrogeochemical reactions that can change the cation composition.And it is significant to evaluate the environmental risk of GO comprehensively and exactly.?3?The cotransport of GO and Cu²⁺ in porous media showed that GO could enhance the transport of the adsorbed metal iron Cu²⁺significantly.The adsorption ability of GO for Cu²⁺was higher than the natural sand and the maximum adsorption of GO and natural sand for Cu²⁺ were 132.2 and 0.107 mg/g,respectively.At lower IS of 1 mM,Cu²⁺ exhibited low mobility and all of the Cu²⁺ were removed completely by the natural sand during transport without GO involved.However,in the presence of GO,Cu²⁺was detected in the outflow,and the?C/C0?max increased from 0.121 to 0.573 when the GO concentration increased from 40 to120 mg/L.This was due to the adsorption ability of GO for Cu²⁺ was much higher than the natural sand,as a result,the cotransport ability of GO-facilitated Cu²⁺ could enhance accordingly.However,GO exhibited high mobility and 100% breakthrough?C/C0?max was reached regardless of the concentrations in the presence of Cu²⁺.Furthermore,due to the diffuse double layers of GO particles were compressed and weaked the electrostatic repulsion,when IS increased from 1 mM to 1000 mM but of constant GO concentration of 120 mg/L,the?C/C0?max of Cu-bearing GO decreased from 0.988 to 0.Accordingly,since the penetration of Cu²⁺ is mainly because the GO adsorption and thus carrying it outflow sand column by cotransporting,therefore,when the Cu-bearing GO retained by sand column,it will inevitably lead to the adsorption of Cu²⁺ by GO were also retained by natural sand,that is the?C/C0?max of Cu²⁺significantly decreased from 0.573 to 0.Derjaguin–Landau–Verwey–Overbeek?DLVO?interaction energy calculation was also performed to understand the mechanisms of GO mobility well.A numerical advection–dispersion–retention model was successfully developed to simulate the transport process of Cu-bearing GO and GO-F Cu through the sand column.The results showed that in the assessment the environmental risk of nanomaterials,we must also consider its impact on other pollutants and combained pollution by various pollutants.