Preparation Of Magnetic Separation Material And Its Application In The Treatment Of Lead-copper Heavy Metal Wastewater

A large amount of wastewater including lead and copper heavy metal ion is generated from process of burning rate catalysts production,which will cause serious ecological risks if wastewater is not completely treated and migrated into water environmental.Chemical precipitation treatment for heavy metal wastewater has the advantages of simple technological process,lowly cost and mature technology.However,there are also common problems such as small particle size,small particles easily pass through the filter layer,high viscosity of precipitate and slowly solid-liquid separation rate.At present,magnetic separation materials have wide application prospects in the field of heavy metal wastewater treatment.In particular,magnetic adsorption and magnetic flocculation materials have the obvious advantages of fast solid-liquid separation,low separation energy consumption and complete removal of heavy metals,which becomes research hot-pots in the field of water treatment materials.In this paper,the amino-functionalization magnetic adsorption material Fe₃O₄/Si O₂/m Si O₂-NH₂was designed and constructed.The magnetic core was double-coated with silica.The inner dense silica layer can prevent the magnetic core from being eroded and the outer porous silica layer provides more anchor points for grafting amino groups,which is beneficial to connect more active sites.The magnetic adsorbent Fe₃O₄/Si O₂/m Si O₂-NH₂was characterized by TEM,SEM,N₂adsorption-desorption,VSM and XRD method.The particles were spherical with diameter of about 115 nm,its saturation magnetization was about 42.05emu/g,and its specific surface area was 82.46 m~2/g,pore volume was 0.21 cm~3/g.The adsorption performance evaluation showed that the optimum p H for the adsorption of Pb²⁺and Cu²⁺was 6,the equilibrium adsorption time was 80 min,and the saturated adsorption capacities were 65.25 mg/g and 40.34 mg/g respectively.Theoretical analysis shows that the adsorption process can be described by the Langmuir model,which belongs to the endothermic reaction and monolayer adsorption,and conforms to the second-order kinetic reaction model and chemical adsorption.The adsorption of Pb²⁺by Fe₃O₄/Si O₂/m Si O₂-NH₂mainly occurs by surface complexation and electrostatic attraction,in process the chemisorption was predomiant.The Fe₃O₄/CPAM magnetic flocculation material was designed and synthesized,the material with flocculation function was obtained through polymerization on the surface of magnetic core.The material is fluffy spherical particles with 110 nm in diameter,its saturation magnetization was 50.06 emu/g,the optimum p H for the treatment of simulated wastewater was about 9,the optimum dosage was 0.3 g/L,the optimum settling time was 20 min,and the removal of Pb²⁺and Cu²⁺were 92.46%and 94.91%.The isoelectric point of Fe₃O₄/CPAM was 7.68.When the p H is less than 7.68,the surface is positively charged,and the compressive electric double layer and adsorption bridging may exist.When the p H is more than 7.68,electric neutralization,net sweeping and adsorption bridging can also exist at the same time,which is helpful to further explore the flocculation mechanism.Two magnetic separation materials,Fe₃O₄/SiO₂/mSiO₂-NH₂and Fe₃O₄/CPAM,were used to treat the wastewater produced from burning rate catalysts.When the dosage of Fe₃O₄/Si O₂/m Si O₂-NH₂was 2.8 g/L,the maximum adsorption capacity of Cu²⁺was 40.38mg/g,the maximum adsorption capacity of Pb²⁺was 58.37 mg/g,and the removal of Pb²⁺and Cu²⁺could reach 99.81%and 99.65%.When the dosage of Fe₃O₄/CPAM was 0.8g/L,the optimum settling time was 30min,and the removal of Pb²⁺and Cu²⁺were 99.83%and 99.81%.The residual concentrations of heavy metals after treatment by the two magnetic separation materials Fe₃O₄/Si O₂/m Si O₂-NH₂and Fe₃O₄/CPAM were in the range of 0.1 mg/L～0.5 mg/L,meeting the national discharge standard Pollutant Discharge Standard for Urban Sewage Treatment Plant GB18918-2002 Standard values（Pb（Ⅱ）≤0.1 mg/L,Cu（Ⅱ）≤0.5 mg/L）.