Preparation Of Amino-modified Fe₃O₄@mC Composite And Its Adsorption Properties For Pb²⁺ In Solution

As one of the most common and toxic heavy metal pollutants,Pb has caused serious harm to human health and the ecological environment.In recent years,the adsorption method has been widely concerned and applied because of its excellent removal effect in the field of advanced treatment of heavy metal wastewater.In this paper,two adsorbent materials,Fe₃O₄@mC-NH₂ and Fe₃O₄@mC/NH₂-MIL-125?Ti?,were prepared to remove Pb²⁺in water,and the adsorption mechanism of the materials were investigated,which also provides a theoretical basis for their practical application.The main conclusions are as follows:?1?The Fe₃O₄@mC-NH₂ adsorbent was prepared by silane coupling method,and the prepared Fe₃O₄@mC-NH₂ material was characterized by means of BET,VSM,TEM,XRD,FTIR,etc.The results proved that the amino group was grafted to the surface of the carrier with good magnetic properties,the material was successfully prepared.The static adsorption test shows that Fe₃O₄@mC-NH₂ has a high adsorption capacity and stability for Pb²⁺,and its adsorption capacity is 96.99 mg/g.In a certain p H range,the removal rate of Pb²⁺is positively related to the p H of the solution.The best effect is achieved at p H=6.0,and the change trend of the adsorption amount is to increase first and then tend to balance.In addition,increasing the temperature can effectively enhance the adsorption performance of the adsorbent.Studies on the effects of common interfering ions in water indicate that Mg²⁺has a strong adsorption interference to lead ions and PO₄^3-has a weak interference level.The material can be regenerated using dilute nitric acid.After four cycles,the removal rate of low concentration Pb²⁺can still reach 96.86%.Thermodynamic analysis shows that the adsorption of Fe₃O₄@mC-NH₂ to Pb²⁺is a spontaneous and endothermic process.Kinetic analysis shows that the adsorption process of Pb²⁺by Fe₃O₄@mC-NH₂ is consistent with Langmuir and quasi-second-order kinetic equations.?2?In order to improve the adsorption performance of the material and increase its adsorption capacity,Fe₃O₄@mC/NH₂-MIL-125?Ti?was prepared by solvothermal method.The prepared composite materials were characterized by means of TEM,XRD,FTIR,etc.The crystal diffraction peaks of Fe₃O₄@mC and NH₂-MIL-125?Ti?were simultaneously observed in the XRD spectrum of the composite material,which proved the material successful preparation.The static adsorption test shows that the adsorption capacity of the material is 130.04 mg/g and the optimal p H value is 5.The quasi-second-order kinetic model and Langmuir isotherm Line model.The intra-particle diffusion model shows that the reaction rate of the material adsorption process is mainly dominated by the internal diffusion stage;the adsorption of Fe₃O₄@mC/NH₂-MIL-125?Ti?to Pb²⁺can be spontaneous and is an endothermic process,and increasing the temperature is not conducive to the adsorption of Pb²⁺.After reusing 5 times,the removal rate of 5 mg/L Pb²⁺solution could still reach88.12%.In addition,when investigating the effect of coexisting ions in the solution on the adsorption of Pb²⁺.The adsorption mechanism shows that the complexation of amino groups is the main reason for the removal of Pb²⁺;the hydroxyl group?-OH?on Fe₃O₄@mC/NH₂-MIL-125?Ti?is also involved in the removal of Pb²⁺.