Study On The Preparation And Application Of Iron-based Functionalized Materials For Removal Of Antimony And Lead From Water

In recent years,antimony（Sb）,lead（Pb）pollution in waters has attracted much attention worldwide.It is highly in demand to develop efficient and economical treatments to address those urgent issues.In addition,the coexistence of antimony and lead pollution has been rarely reported,and was difficult for remediation.This study focused on the pollution control of Sb and Pb in water,and further improved the removal performance of iron（hydro）oxide by functional modification,investigated the main factors affecting the removal process,and explored the possible mechanism.The main research contents are as follows:In view of the low removal efficiency and narrow application range of p H in the removal of Sb（V）from water by traditional iron（hydro）oxide,sulfide-modification was proposed to enhance the reactivity of ferrihydrite.The removal performance and mechanism of Sb（V）by sulfidated ferrihydrite were investigated.As the S:Fe molar ratio ranges from 0.00 to 1.48,the removal efficiency of Sb（V）by sulfidated ferrihydrite decreased first and then increased considerably.Sulfidated ferrihydrite showed the optimal removal capacity of 963.74 mg Sb/g,which was 3.20-fold higher than that of ferrihydrite.The adsorption affinity of sulfidated ferrihydrite increased from 95.65 mg^1-（1/n）L^1/ng^-1 to 194.99 mg^1-（1/n）L^1/ng^-1.Sulfidated ferrihydrite could efficiently remove Sb（V）over a comprehensive p H range of 3.00～11.00.The marginal impact was observed on Sb（V）removal of sulfidated ferrihydrite in the presence of NO₃^-,Cl^-,SO₄^2-,Si O₃^2-and CO₃^2-,while PO₄^3-displayed the greatest hindrance.According to the experimental results and material characterization analysis（XRD,TEM Mapping and XPS）before and after the reaction,it was found that sulfidation could facilitate the iron leaching of sulfidated ferrihydrite followed by the removal of Sb（V）in the form of Fe Sb O₄ precipitation.In addition,Sb（V）could be adsorbed on the surface of sulfidated ferrihydrite by forming complexes（≡Fe-O-Sb and≡S-O-Sb）.For the coexistence pollution of Pb（II）（cation）and Sb（V）（anion）,the co-precipitation method was proposed to prepare iron（hydro）oxide-phosphogypsum composite materials（FPG）,and the removal behavior and internal mechanisms were elucidated for a single system with Pb or Sb pollutant and a coexisting system with both.In a single system,iron（hydro）oxide-phosphogypsum composite material could significantly improve the removal performance of Pb（II）（<100 mg/L）with the removal efficiency more than 85.45%.This process not only involved ion exchange（Pb SO₄）but also the complexation of iron hydroxyl（≡Fe-O-Pb）.The removal efficiency of Sb（V）in a single system by composite material was 2.08～3.31 times higher than that of phosphogypsum,which mainly attributed to the complexation of iron hydroxyl（≡Fe-O-Sb/≡Fe-O-Ca-Sb/≡Fe-O-Sb-Ca）.Compared with the single systems,the coexistence greatly enhanced the Pb（II）and Sb（V）removal performance by FPG,and synergistic effects depended on the coexisting concentrations.The synergistic removal mechanisms mainly involved precipitation,bridging complexation and electrostatic attraction.This study provided a theoretical basis for understanding the migration and transformation behavior of Sb（Ⅴ）and Pb（Ⅱ）in the environment,enriching the related research on the removal of Sb（Ⅴ）and Pb（Ⅱ）pollution from water by iron-based functional materials.It also provided a new idea for the resource utilization of phosphogypsum.