Migration-deposition Of Nano-hydroxyapatite And Induced Removal Of Manganese In Ground Water

Nano-hydroxyapatite is a kind of active material with good biocompatibility,which has been widely applied in the remediation of heavy metals of contaminatedsoil and sewage, such as Cd²⁺、Cu²⁺、Pb²⁺、Zn²⁺etc.. As one of the most commonheavy mental pollutants in groundwater, manganese hasn’t seen the application ofremoval of nano-hydroxyapatite in groundwater.Quartz sand is used as porous medium, and fulvic acid as main natural organicmatter, which exists in the experimental conditions. In controlling of differentenvironmental factors （hydrodynamic, chemical conditions and pollutants）, underdifferent conditions a series experiments of nano-hydroxyapatite migration anddeposition in groundwater are conducted, the ζ potential of nano-hydroxyapatitecolloidal particles and quartz sand colloidal part and the colloidal particle’s flow ratiois measured. On the basis of these experiments, the study of nano-hydroxyapatite inadsorption of manganese has also been conducted. The main conclusion is as follows:（1） Through electrostatic interaction and specific adsorption, the fulvic acidbinds with colloidal particles, results in the increase of surface electrostatic charge ofelectrostatic repulsion force between colloidal particles. Finally the zeta potential ofnano-hydroxyapatite increases and the stability is enhanced, which is favorable for thetransport of colloidal particles in porous media. And in subsequent experiments,10mg/L fulvic acid is determined as the stabilizer of nano-hydroxyapatite colloidalparticles.（2） The gravity has an important influence on the migration and deposition ofnHAP. The ability of colloidal particle migration is stronger under horizontal flowthan under vertical flow condition. Colloidal particles are easier to deposit at theentrance section of quartz sand columns. At different velocities, with the increase ofvelocity, transport of the colloidal particles will be enhanced.（3） The transport of colloidal particles will decrease with the increase of ionicstrength of the solution. In terms of Na+and K+, the bigger the ionic radius is, theweaker stability and migration of the colloidal particles are. The higher cation valenceis, the lower stabilization and migration of nano-hydroxyapatite is.（4） Different kinds of pollutants in groundwater have different effects on the deposition of nano-hydroxyapatite. The result shows that nitrate has little effect on thenegatively charged colloidal particles, which can be neglected. The heavy metalmanganese has great influence on the stability of nano-hydroxyapatite, withincreasing the content of manganese ions, the stability of colloidal particles issignificantly reduced and the relative migration ability also decreases.（5） The adsorption experiment of manganese on nano-hydroxyapatite shows thatnano-hydroxyapatite has stronger adsorption capacity of heavy metal manganese.While adding the stabilizer fulvic acid, it will compete for the adsorption site ofnano-hydroxyapatite with manganese ions, then makes the adsorption of colloidalparticles decreased slightly.