Preparation Of Lanthanum-Modified Magnetic Nanocomposite And Study On Adsorption Of Phosphorus Removal Performance

Phosphorus is one of the essential nutrients in biological life activities.However,with the rapid development of industrialization and urbanization,a large number of phosphorus-containing substances enter lakes and reservoirs,resulting in water eutrophication,affecting the water ecological balance.Therefore,reducing and controlling the concentration of phosphate in water is an important problem that needs to be solved urgently in today’s society.Among the commonly used methods for phosphorus removal from wastewater,the adsorption method has proved to be one of the most promising methods for phosphorus removal,because of its simple process,relatively low cost,good selectivity and renewable utilization.However,natural adsorbents have some problems,such as unstable adsorption effect and low adsorption capacity.Therefore,it is particularly important to develop adsorbents with high adsorption efficiency and good adsorption selectivity.In this paper,lanthanum modified magnetic nanocomposites were prepared for the treatment low concentration Phosphorus Wastewater,and the adsorption experiments of the materials were studied.this paper prepared a new type of lanthanum-modified magnetic nanocomposite Fe₃O₄@C@CS-La.The Optimization of the preparation process of Fe₃O₄@C@CS-La magnetic nanocomposites were realized by changing the mass ratio of CS to Fe₃O₄@C,the volume fraction of N-[3-（Trimethoxysilyl）propyl]ethylenediamine and the concentration of La³⁺.And the optimization results showed that the mass ratio of CS to Fe₃O₄@C is 1:2,the volume fraction of N-[3-（Trimethoxysilyl）propyl]ethylenediamine is 1.67%,and the concentration of La³⁺is The Fe₃O₄@C@CS-La magnetic composite prepared at 0.15 mol/L can achieve a higher phosphate removal rate.The characterization results showed that lanthanum was successfully grafted doped on the surface of Fe₃O₄@C@CS.And the prepared Fe₃O₄@C,Fe₃O₄@C@CS and Fe₃O₄@C@CS-La are nano-sized mesoporous microspheres with good superparamagnetism（saturation magnetizations are 47.04 emu/g,37.56 emu/g and33.79 emu/g,respectively）and high BET specific surface area（65.78m²/g,75.11m²/g and 77.25 m²/g respectively）.Single factor experiments showed that the removal rate of phosphate for Fe3O4@C@CS-La magnetic composites was 98.99%when the reaction time was 150 min,pH=4.5 and dosage was 0.1 g/L.Adsorption kinetics,adsorption isotherms and adsorption thermodynamics studies showed that the adsorption data could be best fitted with the pseudo-second-order kinetic model and Langmuir adsorption isotherm model.The maximum adsorption capacity was 58.36 mg/g,61.60 mg/g,63.65mg/g and 67.78 mg/g at initial pH of 4.5 and the temperature of 288 K,298 K,308 K and 318 K,respectively.And the adsorption was a process of spontaneous and endothermic,so increasing the temperature was beneficial to the progress of the reaction.In addition,a certain concentration of Cl^-,SO₄^2-,NO₃^-,Ca²⁺,Mg²⁺ions in the solution was beneficial to improve the phosphate removal rate of Fe₃O₄@C@CS-La magnetic composites,while the presence of HCO₃^-inhibited the phosphate adsorption of Fe₃O₄@C@CS-La,which was not favorable for the process of phosphate adsorption.Finally,the reusability of Fe₃O₄@C@CS-La was evaluated by desorption experiments.The desorption results show that Fe₃O₄@C@CS-La after phosphate adsorption can realize the desorption and regeneration through 3mol/L NaOH solution.After five successive adsorption-desorption experiments,Fe₃O₄@C@CS-La still has higher Phosphate removal rate.Zeta potential,FTIR and X-ray photoelectron spectroscopy（XPS）test results confirmed that the main adsorption mechanism of phosphate on the surface of Fe₃O₄@CS-La magnetic composites is mainly electrostatic interaction and ligand exchange.