Preparation Of Mno₂-based Composite Material For Adsorption Of TBBPA,Heavy Metal Ions And Dyes From Aqueous Solution

Pollutants such as TBBPA,heavy metal,dyes and so on,one of factors which caused the global water crisis,have negative effects on water quality and the public health.In today's study the focus is on how to remove the contaminants from water efficiently.Adsorption method has many advantages including simple design,easy operation and no secondary pollution.However,the difficult design and preparation of high-performance absorbents limited the further application of adsorption.Thus,to remove organic and inorganic pollutants from water is a significant research direction.This dissertation surveys the dangers of polluted water and the relevant methods treating with those pollutants and discusses the applications of all kinds of low-cost adsorbents,especially metallic oxide composites in sewage treatment.In this study,four kinds of MnO₂-based novel nano-adsorbents have been prepared.The prepared adsorbents have been characterized by scanning electron microscope?SEM?and Fourier transform infrared spectroscopy?FT-IR?.The adsorption properties of the nano-adsorbents also have been investigated to remove TBBPA,heavy metal ions and dyes in aqueous solutions under static conditions.The optimum factors on the adsorption properties were studied including the concentration of the pollutants,pH,adsorbent amount,concentration of NaCl,reaction time and temperature.The optimal adsorption conditions and the maximum adsorption capacity were put forward.Several adsorption isotherm models,kinetics and thermodynamics have been fitted to describe the absorption process.The influence factors of the adsorption properties and the mechanism of the adsorption were analyzed,the reusability of the adsorbents was studied.The main conclusions were listed as follow.1.Fly ash?FA?modified by?-MnO₂?FA@nM?were prepared by oxidization of MnSO₄with?NH₄?₂S₂O₈.The study focuses on the absorbent properties of TBBPA in water by FA@nM.The results showed that when the contact time was 40 min,pH was 7.1 and the adsorbent amounts were 1.0 g/L,the adsorption capacity reached the maximum value?39.15 mg/g?.When the concentrations of TBBPA varied from 10 to 40 mg/L,the removal rate of TBBPA in water was all above 98%.However,the removal rate decreased with the increase of ionic strength under an alkaline condition.Because the adsorption process was spontaneous and exothermic,it was unfavorable for the reaction under higher temperature.Pseudo-first order reaction kinetics could describe the adsorption process well.2.A mesoporous composite nano-adsorbent?ACs-?-MnO₂?with the large special surface area?813.09 m²/g?and average particle size of 4.06 nm was prepared by a one-step synthesis.The optimal pH for removing TBBPA from water was 7.0.The maximum adsorption capacity was65.79 mg/g when the added amount of ACs-?-MnO₂ was 1.5g/L and the contact time was 90 min.When the concentrations of TBBPA was 100 mg/L,the removal rate of TBBPA in water was98.85%.The experimental results showed that the adsorption processes included both physical and chemical process,and chemical reaction was the rate-controlling step.The adsorption was a spontaneous,exothermic process and the ionic strength had nearly no effect on the adsorption of TBBPA by ACs-?-MnO₂.The suitable model for this adsorption process was Langmuir isotherm model.The kinetic data of ACs-?-MnO₂ for adsorbing TBBPA from sewage were best described by the pseudo-second order model.After 5 circles of adsorption-desorption process,the adsorbent maintained>90%adsorption capacity.3.A mixture of Fe₃O₄ aqueous solution?100 mg/L?,2-?N-morpholino?ethanesulfonic acid?MES?buffer,0.5 g of kaolin and certain amount of KMnO₄ solution?10 mmol/L?was sonicated for 40 min at room temperature to form black precipitate.Then the black precipitate was separated from the reaction system by an extra magnet and washed repeatedly with distilled water and ethanol until the solution became neutral.The magnetic spheres?Fe₃O₄-MnO₂-kaolin?C#?and Fe₃O₄-MnO₂-kaolin?3#??which possessed good adsorption properties for methylene blue and Pb²⁺from aqueous solution were obtained.The specific surface area of Fe₃O₄-MnO₂-kaolin?C#?was 73.35 m²/g,which was higher than the original kaolin?48.89 m²/g?and the specific saturation magnetization of the prepared adsorbent was 3.67 emu/g.The suitable model for this adsorption process was Freundlich isotherm model.That implied that the adsorption reaction has taken place on the heterogeneous surface.The pseudo-second order model was suitable to describe the adsorbing of methylene blue from sewage.The chemical adsorption process was the control step and the process was spontaneous and exothermic.Moreover,the specific surface area of Fe₃O₄-MnO₂-kaolin?3#?was 86.99 m²/g,which was higher than the original kaolin;the specific saturation magnetization of the prepared adsorbent was 3.81 emu/g.When the optimal adsorption conditions were pH=5.0⁶.0 and 2.0 g/L added amount of adsorbent,the maximum adsorption capacity was 185.45 mg/g.The suitable model for the adsorption of Pb²⁺was Langmuir isotherm model and this indicated it was monolayer chemical adsorption.The desorption efficiency of methyl blue with ethanol and Pb²⁺with 0.1M HCl were researched.Also,the reusabilities of Fe₃O₄-MnO₂-kaolin?C#?and Fe₃O₄-MnO₂-kaolin?3#?were investigated.4.PS-EDTA@?-MnO₂ was prepared by a one-step hydrothermal method,in which the surface of PS-EDTA was modified by?-MnO₂.The specific surface area of the composite sphere was 70.88 m²/g,this increased 23.96 m²/g when compared to PS-EDTA.The analysis of adsorption isotherm showed that the adsorption happened on the homogeneous surface.The adsorption thermodynamics indicated that the adsorption was an endothermic reaction.The pseudo-second order model was suitable for the adsorbing of Hg²⁺from sewage and the chemical adsorption process was the control step.The compound PS-EDTA@?-MnO₂ particles presented better selective adsorption of Hg²⁺while the Pb²⁺,Hg²⁺and Cu²⁺were coexisted in the solution.When the optimal pH for adsorption of Hg²⁺were 5.0⁶.0,the amount of adsorbent was added with 1.0 g/L,the concentration of Hg²⁺was under 50 mg/L,the removal rates were higher than97%.The maximum adsorption amount was 187.63 mg/g.The maximum adsorption capacity for Hg²⁺of compound PS-EDTA@?-MnO₂ particles was compared with the reported adsorption capacity of other adsorbents.