Effect Of Tire Wear Particles On The Migration Of Cd/Ni In Saturated Porous Media

In this paper,the migration characteristics of tire wear particles（TWPs）in saturated porous media and its effect on the migration of Cd/Ni under the aging effects of acid,UV and ozone were studied by artificial simulated aging experiment,column migration and adsorption desorption experiment.The findings suggest that aging effects can significantly alter the physicochemical properties of TWPs,On the endogenous heavy metal release from TWPs,the release behavior of heavy metals is more likely to occur after aging;The aging effect significantly improves the migration ability of TWPs in the porous media of quartz sand（The maximum breakthrough of as-received TWPs（i.e.,C/C₀）only reached 36.52%,whereas those of the aged ones were 52.48%,54.40%and 68.29%for H⁺-TWPs,UV-TWPs and O₃-TWPs,respectively.）;Aging causes an increase in the surface aerobic functional groups of TWPs as well as the absolute value of the surface Zeta potential,It is speculated that the aging effect enhances the hydrophilicity of TWPs,Thus promoting the migration of TWPs in quartz sand,the minimum breakthrough of as-received TWPs（i.e.,C/C₀）only reached 34.28-34.82%,whereas those of the aged ones were 50.65-50.83%,53.42-52.68%and 66.37-66.86%for H⁺-TWPs,UV-TWPs and O₃-TWPs,respectively;The decrease in mobility of both TWPs and Cd/Ni in cotransport experiments showed,which may be due to the interaction.In addition to its altered migration capacity,the ability of Cd/Ni migration of TWPs after aging also depends on the irreversible adsorption or adsorption-desorption retardation of TWPs.The adsorption results show that UV-TWPs are slightly stronger than as-received TWPs,while H⁺/O₃-TWPs are significantly reduced,which may be due to different proportions of carbon black to rubber matrix and different changes of physical and chemical properties,and the adsorption capacity of TWPs to Ni is much higher than Cd,which may be related to different ion radius（Hofmeister Sequence）and electric potential（HASB Theory）.The decorption experiment results showed that TWPs are highly prone to Cd/Ni desorption,and the as-received TWPs are more prone to desorption（The desorption of TWPs for Cd decreased from 1650.30 mg/kg to 351.01 mg/kg and from 2469.28 mg/kg to 931.54 mg/kg for Ni）.Combined with characterization and experimental analysis:it shows that the adsorption of Cd/Ni on the surface of TWPs is mainly by electrostatic interaction and physical adsorption.In summary,aging will accelerate the release of endogenous heavy metals by TWPs,The enhanced electrostatic repulsion between TWPs and quartz sand leads to the enhanced migration ability of TWPs in saturated porous media after aging;At the same time,the interaction may be one of the reasons for the decreased mobility of both TWPs and Cd/Ni in cotransport experiments,The TWPs provide more adsorption sites for the adsorption of Cd/Ni,Leading in altered adsorption capacity of aging TWPs to Cd/Ni,more Cd/Ni is trapped in porous media due to adsorption effect,and the migration ability of TWPs to Cd/Ni changed with aging effects.