Preparation And Adsorption Properties Of Fe₃O₄/HA Composite Adsorbent

With the rapid development of China's economy,the problem of industrial and domestic water pollution is also becoming increasingly serious.The search for cheap and efficient water treatment methods has become a hot and difficult issue in the current study.As a sponge-like organic macromolecule,humic acid has the characteristics of large specific surface area,high porosity,and abundant active groups in the molecular structure.At the same time,humic acid has a wide range of sources,therefore it can be used as a material for adsorption in water treatment..In this experiment,Gansu Tianzhu lignite was used as raw material,humic acid?HA?was extracted by acid precipitation alkali dissolution method,and then Fe₃O₄ was used to modify it,and Fe₃O₄/HA composite adsorbents with different ratios were prepared.Scanning electron microscopy?SEM?,specific surface area measurement?BET?,fourier transform infrared spectroscopy?FT-IR?,and powder diffraction?XRD?were used to characterize the morphological and structural changes before and after humic acid modification.The results show that the modified humic acid particles are smaller,more porous,and the specific surface area increases.Through single-factor experiments,the adsorption of P?V?,methylene blue,Ni?II?and Mn?II?on modified humic acid adsorbents was studied by factors such as pH,temperature,adsorbent dosage,adsorption time,and initial concentration of adsorbates the effect of adsorption performance.Based on the results of single-factor experiments,an orthogonal experiment was designed for adsorption of P?V?by Fe₃O₄/HA composite adsorbent.The optimal experimental conditions were as follows:P?V?solution with a concentration of 100 mg/L.adding the adsorbent of 0.8g,adsorption for 4h,the adsorption rate can reach 95.04%and the adsorption amount is 5.94mg/g when the temperature is 20?and pH=9;the Fe₃O₄/HA composite adsorbent absorbs methylene blue by orthogonal experiments.The best experimental conditions are:the concentration of 300mg/L methylene blue solution,adding the adsorbent of 0.3g,adsorption 6h,at a temperature of 40?,pH=9 adsorption rate of up to 99.70%,adsorption capacity of 49.85mg/L.Fe₃O₄/HA composite adsorbent Adsorption of Ni?II?by orthogonal experiments,the best experimental conditions are as follows:Ni?II?solution with concentration of 100 mg/L,adding the adsorbent of 0.6 g,adsorption for 6 h,adsorption at a temperature of 30?,pH=3 The rate is up to 87.78%,the adsorption capacity is 7.315mg/g;the Fe₃O₄/HA composite adsorbs Mn?II?by orthogonal experiments.The best experimental conditions are as follows:the concentration of Mn?II?solution is 100mg/L.adding the adsorbent of 0.6g,adsorption for 1h,at the temperature of 40?and pH=6,the adsorption rate of up to 91.93%,the adsorption capacity of 7.66mg/g.The cyclic adsorption and desorption experiments show that the Fe₃O₄/HA composite adsorbent exhibits good desorption and regeneration performance.After 10 times of adsorption and desorption,the adsorption rate of methylene blue and Mn?II?by the adsorbent still reached 60%,the adsorption rate of P?V?reached 58%,and the adsorption rate of Ni?II?reached 57%.The adsorption thermodynamics,adsorption kinetics and shell growth model of P?V?,methylene blue,Ni?II?and Mn?II?adsorbed on Fe₃O₄/HA composite adsorbent were fitted and analyzed.The conclusion was drawn that the adsorption process was satisfactory.Quasi-secondary equations indicate that the adsorption process is dominated by chemical adsorption;the adsorption type is in accordance with the Freundlich adsorption model,and the adsorption is dominated by multi-layer adsorption;whereas the study of the adsorption control mechanism shows that Fe₃O₄/HA composite adsorbent is effective for P?V?.The adsorption process is controlled by liquid film diffusion?FDC?.The adsorption process of methylene blue and Ni?II?is controlled by chemical reaction?CRD?.The adsorption process of Mn?II?cannot be fitted to the shell growth model.