Study On Preparation Of Functionalized Magnetic Fe₃O₄ Nanoparticles And Adsorption Properties Of Heavy Metal Ions In Sewage

The over-exploitation of nature by human beings has caused the problem of water pollution becoming increasingly serious,especially the pollution of heavy metals such as lead,chromium,cadmium,arsenic,and mercury.In order to reduce the threat of heavy metals to humans and the environment,it is urgent to develop or improve wastewater treatment technology.In recent years,magnetic Fe₃O₄ nanoparticles(Fe₃O₄MNPs)have attracted widespread attention from researchers due to their advantages of high efficiency,low cost,and recyclability.However,with the in-depth study of Fe₃O₄MNPs by researchers,its shortcomings have also been exposed,such as:Fe₃O₄ MNPs are easy to agglomerate,and are easily corroded in air or acid and alkali.Therefore,it is necessary to improve the performance of Fe₃O₄ MNPs by surface functionalization.At present,functionalized Fe₃O₄ MNPs are widely used in the adsorption of refractory organics and heavy metal ions.However,with the continuous improvement of national environmental protection requirements,the development of environmentally-friendly materials may become the focus of future development.Therefore,in this paper,two kinds of functional Fe₃O₄ MNPs with good biocompatibility were synthesized and applied to the removal of heavy metal ions in sewage.The main research contents and results are as follows:(1)Fe₃O₄ MNPs were modified with dopamine hydrochloride(DA)as a functional reagent to prepare a core-shell Fe₃O₄@PDA composite material,which was used to adsorb cadmium ions in aqueous solution.The results showed that the adsorption of Cd²⁺by Fe₃O₄@PDA reached equilibrium within 120 min,and the kinetics conforms to the pseudo-second-order kinetic model(R²>0.999).The adsorption isotherm of Fe₃O₄@PDA for Cd²⁺conforms to the Freundlich adsorption isotherm model.The theoretical maximum adsorption capacity(q_m)was 21.58 mg/g,which was obtained by Langmuir adsorption isotherm model.The parameters of thermodynamic and D–R adsorption isotherm model showed that the adsorption of Cd²⁺on Fe₃O₄@PDA is mainly electrical adsorption,and the adsorption behavior was significantly affected by the ionic strength of the system.The selected interfering ions HCO₃^–,CO₃^2–,and SiO₃^2–promoted adsorption,while Mg²⁺,Ca²⁺,and SO₄^2–inhibited adsorption.The results of the adsorption-desorption cycle experiments showed that Fe₃O₄@PDA had good stability and reusability,and the presence of Fe₃O₄ magnetic core facilitated the separation of the loaded Cd²⁺phase from the solution.(2)Fe₃O₄@PDA–DMSA nanoparticles were prepared by mixing Fe₃O₄,DA and 2,3–dimercaptosuccinic acid(DMSA)by a one-pot method.This material is used to remove Pb²⁺,Cu²⁺,and Cd²⁺from water.The kinetic results showed that the adsorption of Pb²⁺on adsorbent reached equilibrium at 180 min,and the adsorption equilibrium of Cu²⁺and Cd²⁺on adsorbent at 240 min.And the adsorption kinetics of these three heavy metal ions on adsorbent all were in accordance with the pseudo-second-order kinetic model,indicating that the rate control step of adsorption reactions were chemical adsorption.The adsorption of Pb²⁺and Cu²⁺on Fe₃O₄@PDA–DMSA conformed to Langmuir model,while the adsorption of Cd²⁺on adsorbent conformed to Freundlich model.The q_m of Fe₃O₄@PDA–DMSA for Pb²⁺,Cu²⁺,and Cd²⁺were 187.62,63.01 and49.46 mg/g,respectively.The results of D–R isotherm model further proved that the adsorptions were mainly chemical adsorption,and the adsorption behaviors were little affected by the system ionic strength.The selected interfering ions HCO₃^–,CO₃^2–,and SiO₃^2–mainly promoted the adsorption,while Mg²⁺,Ca²⁺,and SO₄^2–acted as inhibitors.In the application of multi-component simulated wastewater,Fe₃O₄@PDA–DMSA showed the best adsorption effect for Pb²⁺,with adsorption capacity up to 52.91 mg/g,followed by Cu²⁺and Cd²⁺,which is consistent with the results of single-component adsorption experiments.Therefore,Fe₃O₄@PDA–DMSA is expected to become a new material for treating lead-containing wastewater.