Preparation Of Supported Ionic Liquid Materials And Their Application For Selective Adsorption Of Trace Level Of Heavy Metal Ions

Heavy metal ions are persistance in environment and hardly biodegradable.They are harmful for humen beings even with low concentration due to their bioconcentration in water solutions.Therefore,it is of great importance to sensitively determine and remove trace level of heavy metal ions from aqueous solutions.Ionic liquids?ILs?are a kind of materials with special properties,which have received widely concerned in recent years.Owing to their unique properties,such as negligible vapor pressure,high dissolvability,high extraction ability,high thermal stability and the structure can be designed,ILs have replaced traditional organic solvents for liquid/liquid extraction metal ions from aqueous solutions.However,the high cost,the large amount requirements of ILs and easy loss into water significantly weakened the practical applications of ILs.In addition,ILs are hardly separated from aqueous solution.Supported ionic liquid materials combined the characteristics of ionic liquids and the solid supports,reduced the consumption of ionic liquids and prevent their loss into water.Meanwhile,the material can be easily separated from water and reused.These properties were beneficial for metal ion separation and preconcentration from water.Therefore,the solid supported ionic liquid materials as new adsorbents for heavy metal ions removal,has become one of the frontiers in the research of new materials for ionic liquids.Based on the above reasons,three kind of solid supported ionic liquid materials were prepared in this work and have been used for selectively adsorption of Cr???,Hg???and Cd???from aqueous solutions.The factors affecting the metal ions adsorption were systematically investigated,the relationship between adsorption mechanism and the structure of the material were discussed,and these materials were used for solid phase extraction or removal of heavy metal ions from water solutions.The main contributions and conclusions of these works were list as following:1.1-hydroxyethyl-2,3-methyl imidazolium chlorine ionic liquid chemically functionalized magnetic carbon nanotubes was prepared,and structure,morphology of the material and the functional groups on the surface of the material were characterized by X-ray diffraction?XRD?,FT-IR spectroscopy,transmission electron microscopy?TEM?and thermogravimetric analysis?TGA?.The adsorption performances for Cr???were studied,including adsorption selectivity,adsorption capacity and equilibrium time,the factors affecting Cr???adsorption process such as pH,temperature and the concentration of Cr???were investigated.Adsorption kinetics and adsorption isotherms were also studied and the adsorption mechanism was proposed.In addition,the recoverable and the reusability of the material were investigated,then a new method for selectively adsorption of Cr???from aqueous solution was established.In was found that concentration of Cr???as low as 0.028 mg L^-1 could be efficiently removed,and the adsorption capacity was as high as 55.4 mg g^-1,other ions such as Hg²⁺,Cd²⁺,Cu²⁺,NO^3-,SO₄^2-and Cl-did not interfere with the adsorption process.Based on the analysis of the experimental data,the ion exchange mechanism of Cr???adsorption was proposed.After adsorption,the material can separate easily from solution in 20 s by an external magnet and the Cr???adsorbed on the material can be eluted.The material can reused at least 4 cycles and the Cr???removal percentage was still higher than 95 %.Based on the above analysis,the as-prepared material was an excellent adsorbent for Cr???removal,it can be used for selectively and sensitively solid phase extraction and adsorption of Cr???from water solutions.2.A new solid phase extractant material was prepared by chemically functionalized neutral red on the surface of core-shell magnetic silica gel?Fe₃O₄@SiO₂-NR?.The material was characterized by X-ray diffraction?XRD?,transmission electron microscopy?TEM?and FT-IR spectroscopy.Then,factors influence the extraction process was investigated,and a new method for solid phase extraction coupled with inductively coupled plasma-mass spectrometry was established for Hg???determination from environmental water samples.It is found that concentrations of Hg???as low as 2 ?g L^-1 can be efficiently extracted,and the enrichment factor is as high as 100,the adsorption capacity is 83.7 mg g^-1,other ions did not interfere with the extraction of Hg???.After extraction,the material can separate from water solution by an external magnet and the Hg???adsorbed on the material can be eluted by 1 mol L^-1 of HNO3.The material can reuse at least 10 cycles and shows good regenerability.The possible coordination and electrostatic attraction mechanism for Hg???extraction was proposed based on the adsorption data.At last,the new method was applied to determine Hg???from different environmental water samples,recoveries of 94.7-110.9 % were obtained.The material prepared in this work was an excellent magnetic solid phase extractant for Hg???and has potential application for separation and preconcentration of Hg???from water samples.3.The preparation of nano-SiO₂ supported task specific ionic liquid material by liquid-liquid phase homogenous reaction was designed.The method can effectively improve the adsorption site of new material and improve its adsorption performance.The material was characterized by X-ray diffraction?XRD?,transmission electron microscopy?TEM?and FT-IR spectroscopy.The effects of 14 ions and humic acid on the adsorption selectivity of the materials were investigated.The effects of solution pH,system temperature,concentration of Cd???and the amount of material on the adsorption properties were also studied.Based on the adsorption thermodynamics and adsorption kinetics,the adsorption mechanism was discussed,and the regeneration and recycling of the materials were investigated.It is found that the as-prepared material exhibits excellent adsorption sensitivity,selectivity and adsorption capacity towards Cd???.Under optimum conditions,0.3 mg L^-1 of Cd???in water could be removed effectively by a single step extraction,and the residual concentration was lower than the permitted concentration of Cd???in drinking water advised by USEPA.The adsorption capacity was 112.13 mg g^-1.Other ions such as Cu²⁺,Zn²⁺,Pb²⁺,Co²⁺,Ni²⁺,Hg²⁺,NO^3-,Cl-and SO₄^2-did not interfere with the extraction of Cd???.Mechanism study suggests that the strong coordination of Cd???with the ionic liquid is responsible for such an efficient and selective removal of Cd???.After extraction,the material can be collected and the Cd???on the surface of the material can be eluted by 0.5 mol L^-1of HCl.The material can be reused at least 10 cycles and shows excellent regenerability.Overall,the material prepared in this work was an excellent adsorbent for Cd???and can be used for separation and preconcentration or deep adsorption trace level of Cd???from water solutions.