Research On The Adsorption Of Cu²⁺、 Pb²⁺、Cd²⁺ Ions Onto Magnetical Modified Sepiolite And Their Adsorption Mechanisms

Sepiolite has a great potential in heavy metal wastewater treatment because of itstheoretical estimation surface area value of900m²·g^-1 and containing a large numberof Si-O-Mg-O-Si groups in the crystal. But actual determination of specific surfacearea is smaller. Si-O-Mg-O-Si groups don’t play their maximizational role in theadsorption. In the adsorption systems, sepiolite and Solution are not easily separated.So utilization of sepiolite resource was limited in heavy metal wastewater treatmentapplications.Magnetically modified sepiolite （MMS） was prepared as heavy metal wastewater treatment adsorbent. On the basis of characterizing of MMS and determining ofsurface point of zero charge, focus on adsorption characteristics of Cu²⁺, Pb²⁺, Cd²⁺ byMMS was centered on studying in single and composite heavy metal systems. Theadsorption mechanism was discussed at last. The conclusions were got as follows:（1） After that sepiolite was magnetically modified, the zero point of charge（pHzpc） of sepiolite was elevated to8.5±0.1, the surface of sepiolite has obvious porestructure, surface area of sepiolite was increased to57.008m²·g^-1, pore volume ofsepiolite was increased to0.204cc·g^-1, hydroxyl groups and zeolite water of thestretching vibration strength were enhanced, Fe3O4crystal diffraction peaks werepresented in XRD mapping, sepiolite has a good magnetical properties andsuperparamagnetic.（2） In a single heavy metal system, optimal adsorption conditions: temperaturewas35C, initial pH value was3.5, dosage of MMS was2g·L^-1, adsorption time was180minutes, initial concentration of the adsorbate was50mg·L^-1. MMS on Cu²⁺, Pb²⁺,Cd²⁺ adsorption capacity increased with the temperature increasing. MMS on Cu²⁺,Pb²⁺, Cd²⁺ adsorption capacity decreased with ionic strength increasing. MMS onCu²⁺, Pb²⁺, Cd²⁺ the equilibrium adsorption amount respectively was18.46mg·g^-1,32.06mg·g^-1,16.44mg·g^-1.（3） In the composite heavy metal system, MMS on Cu²⁺, Pb²⁺, Cd²⁺ maximumadsorption quantity respectively was16.77mg·g^-1,24.69mg·g^-1,16.92mg·g^-1, thecomparison with the single system, adsorption quantity were respectively reduced by10.12%,27.31%,15.23%. （4） In the single and compound heavy metal systems, MMS on Cu²⁺, Pb²⁺, Cd²⁺ adsorption kinetics were consistent with Lagergren quasi two level dynamic model,adsorption thermodynamics process were consistent with Langmuir adsorptionisotherm model.（5） In the process of MMS adsorption of Cu²⁺, Pb²⁺, Cd²⁺, the crystal structurewas not changed and H-O-H bending deformation of the flexible vibration intensity indifferent degree weaken, Cu²⁺ and Pb²⁺ weakening degree was higher than Cd²⁺ in asingle heavy metal system.（6） MMS on Cu²⁺, Pb²⁺, Cd²⁺ adsorptional mechanisms including physicaladsorption,ion exchange adsorption,surface complexation adsorption and surfaceprecipitation reaction.