The Preparation And Adsorption Performance Of Magnetic Cr(?) Imprinted Nano-adsorbent

Cr(?)is one of the most common heavy metal pollutants in the world.It is highly toxic and will transfer with rivers or groundwater to pollute the water and soil resources in the earth's environment,thereby affecting human health.Ion imprinting technology is the development and upgrading of molecular imprinting technology.In this paper,magnetic imprinted nano-adsorbents with high adsorption selectivity and easy recovery and separation for Cr(?)were prepared by ion imprinting technology,and their adsorption properties for Cr(?)were systematically investigated.Firstly,magnetic imprinted nano-adsorbent(M-MIPs)was prepared by using chitosan as carrier coated on nano-Fe3O4 particles:nano-Fe3O4 magnetic powder as core,Cr(?)as template molecule,chitosan as functional monomer,sodium oleate as dispersant,epichlorohydrin as cross-linking agent,which is easy to separate and recover,has high stability and strong acid-alkali tolerance.Through various characterizations,the obtained materials have uniform particle size distribution and good magnetic properties,and it can be proved that chitosan is uniformly coated on nano-Fe3O4 particles.Secondly,using M-MIPs to adsorb simulated Cr(?)polluted wastewater,the adsorption conditions were optimized with the adsorption capacity as the index.Under the optimal conditions(pH 7.0,25 ?,adsorption equilibrium time 60 min),the initial concentration of Cr(?)was 50 mg/L,the adsorption capacity could reach 16.7 mg/g,the removal rate was 67%,and the adsorption capacity was higher than that of magnetic non-imprinted particles under the same conditions.It has been proved that the adsorption process is endothermic.When the temperature of the reaction system rises to 45 ?,the adsorption capacity of M-MIPs particles to Cr(?)can be increased to 25.6 mg/g.By comparing the XRD and infrared spectra of M-MIPs before and after adsorption of Cr(?)ions,it is inferred that the adsorption mechanism of M-MIPs for Cr(?)ions in aqueous solution is as follows:the redox reaction of Cr(?)ions occurs on the surface of the adsorbent particles and Cr3+ ions are formed.In addition,the adsorption of Cr3+ ions on the surface of particles can be separated by physical methods,so that the adsorbent can be recycled again.After repeated recycling,M-MIPs can still maintain good superparamagnetic properties.The selective adsorption experiments show that the selectivity of M-MIPs for Cr(?)adsorption increases with the coexistence of mixed ions,while the selectivity of M-MIPs for Cr(?)is inhibited by anions.Finally,the adsorption and removal of Cr(VI)in soil by M-MIPs imprinting material was investigated.The results showed that after the pretreatment of contaminated soil by leaching,the waste liquid containing Cr(?)was taken as the research object,and M-MIPs were used as adsorbent to adsorb Cr(?).It was found that the removal rate of Cr(?)in the soil leachate with higher concentration of Cr(?)by M-MIPs was lower than that of the soil leachate with lower concentration of Cr(?).Therefore,in order to apply M-MIPs to the actual remediation of contaminated soil or groundwater,a lot of technical improvements and improvements are needed.