Effect Of Graphene Oxide On The Migration Of Lead And Cadmium In Porous Media

Nanoscience is considered as one of the three new technological fields in the 21st century.Graphene oxide is an artificial nanoparticle that has been studied in recent years.It may affect the environmental behaviors of pollutants such as migration,transformation,and sedimentation,thereby creating greater ecological risks due to its strong adsorption capacity for pollutants.In this paper,the effect of ionic strength and flow velocity on the transport of graphene oxide was studied through sand column experiment.The co-transport behavior of graphene oxide with lead and cadmium was also explored and explained the transport mechanism.Secondly,different modified media were used to simulate different soil conditions,and the effect of different soil components on the migration behavior of graphene oxide and the interaction between lead and cadmium were investigated.Next,the effect of functional group content on the migration and interaction of graphene oxide and lead in porous media was clarified.To further understand the migration characteristics and mechanisms of the graphene oxide in the environment,to elucidate the migration characteristics and mechanism of heavy metal adsorption of artificial nanoparticles in porous media,and to explore the effect of graphene oxide on the environmental behavior of pollutants,which is great significance for evaluating the environmental risk of graphene oxide.The main conclusions of this study are as follows:?1?As a result,the co-presence of GO and heavy metal ions significantly affects their transport in saturated porous media.Concurrent transport experimental results indicated that the sole presence of GO in porewater resulted in high mobility in the quartz sand column.However,this mobility decreased significantly when Pb²⁺and Cd²⁺ions were also present in the sand column.Conversely,the mobility of Pb²⁺and Cd²⁺ions was enhanced in the presence of GO in porewater.The recovery of GO in Pb²⁺-or Cd²⁺-spiked sand columns was less than that observed in unspiked quartz sand columns.Additionally,some of the Pb²⁺and Cd²⁺ions previously retained in the quartz sand column were remobilized and released from the column with the GO,at the same time,a small amount of graphene oxide was also retained in the quartz sand column.?2?The SEM images showed that about 60%to 90%of the quartz sand surface was covered with smectite,kaolinite,humic acid and ferrihydrite.Results from co-transport experiments indicated that the individual GO in the solution had high mobility in the coated sand column.However,the mobility of GO was significantly reduced when Pb²⁺and Cd²⁺ions were present in solution,and the mobility of Pb²⁺and Cd²⁺ions was also reduced in the presence of GO.The recovery of GO in Pb²⁺or Cd²⁺-spiked coated sand columns was less than that in un-spiked coated sand columns,except the ferrihydrite-coated sand column.Additionally,some of the Pb²⁺and Cd²⁺ions previously retained in the coated sand column were remobilized and released from the column.For smectite-coated sand columns,graphene oxide did not release Pb²⁺and Cd²⁺ions,and the migration ability of graphene oxide was also greatly reduced.?3?As the ionic strength increased,the mobility of graphene oxide decreased in porous media.When the ionic strength was 0.01 mol L^-1,the mobility of 18 kGy graphene oxide was lower than that of other graphene oxides under other radiation intensities.Under the other ionic strengths,the higher the radiation intensity,the higher the recovery of graphene oxide.As the flow rate increased,the outflow rate of graphene oxide decreased.The ability of irradiated graphene oxide to facilitate the migration of lead increased with increasing radiation intensity.The breakthrough curves of graphene oxide in Pb²⁺-contaminated sand columns showed that graphene oxides with different radiation intensities had different lead activation abilities.Graphene oxide with high radiation intensity had a relatively high release of lead.When the radiation intensity exceeded a certain range,the release ability of graphene oxide to lead began to weaken,and its recovery rate was significantly lower than graphene oxide with low radiation intensity.