Synthesis And Characterization Of Solid Phase Extractant Based On Silica Gel And Their Application To Solid Phase Extraction Of Heavy Metal Ions From Aqueous Solutions

In the past twenty years,the use of solid phase extraction techniques has become increasingly popular for separation and preconcentration of trace elemens in environmental samples. The choice of solid-phase extractant is the decisive factor that affects analytical sensitivity and selectivity. This dissertation consists of the following four chapters. In the first chapter, the recent development of solid phase extractant and its principle on separation and preconcentration of trace elements were reviewed, in addition, its future development was also discussed. In chapter two, a new chelating matrix TASG was prepared with thioacetamide anchored in silica gel modified withγ-aminopropyltriethoxysilane. By diffuse reflectance UV-VIS spectroscopy, raman spectroscopy,elemental analysis, its characteristics was investigated,and used for the separation and preconcentration of Pb(II),Cu(II) and Cd(II) through batch method and column method prior to their determination by flame atomic absorption spectrometry(FAAS). The optimum pH ranges for quantitative sorption are 4.0～8.0,2.0～7.0 and 5.0～10.0 for Pb(II),Cu(II) and Cd(II), respectively. Pb(II) and Cd(II) can be desorbed with 3mol.L－1 and 0.1mol.L-1 HCl/HNO3 ,and Cu(II) can be desorbed with 2.5% thiourea. The sorption capacity of the matrix has been found to be 19.76 ,16.35 and 12.50 mg.g-1 for Pb(II),Cu(II) and Cd(II), respectively, with the preconcentration factor of ~300 for Pb(II) and ~200 for Cu(II) and Cd(II).The FAAS was used to determine these metal ions in water sampls after their enrichment with the present matrix. In chapter three, a new chelating matrix GASG has been prepared by immobilizing 3,4,5-trihydroxybenzoic acid(gallic acid) on silica gel.After characterizing the matrix with diffuse reflectance UV-VIS spectroscopy,diffuse reflectance infrared fourier transformation (DRIFT) and elemental analysis,it has been used to separation and preconcentration of Pb(II),Cu(II),Cd(II) and Ni(II) through batch method and column method prior to their determination by flame atomic absorption spectrometry. The optimum pH ranges for quantitative sorption are 3.0～7.0,6.0～10.0,4.0～10.0 and 6.0～10.0 for Pb(II), Cd(II),Cu(II) and Ni(II), respectively. All the heavy meatals can be desorbed with 0.05mol.L-1HCl/HNO3 but 0.1mol.L-1HCl/HNO3 for Ni(II). The sorption capacity for these heavy metal ions is in range of 4.50-15.30mg.g-1 of the present chelating matrix.Preconcentrtion factors of 200,200,200 and 100 for Pb(II),Cu(II), Ni(II) and Cd(II),respectively. In water samples all these heavy metal ions were enriched with GASG and determinated with FAAS. The satisified results were obtained.In chapter four, a new solid phase extractor which was composed of a 5ml single-use syringe, an interface and a micro-colume was designed for separation and concentration of Pb(II). The flow rates of samples were controlled manually by a single-use syringe. 5ml sample solution (pH=3.30) was injected into the micro-column filled with SDG and through the micro-column in 30 seconds, and then the adsorbed Pb(II) was eluted by 5ml 2mol/LHCl at the same flow rate.The average recovery of Pb(II) up to 96.95% ,RSD＝3.33％(n＝22), pre-concentration factor of 200 for Pb(II) was obtained.It can be applied to separation and concentration of a large volume of sample solution contained trace amount of Pb(II) . It was satisfied to be applied to separate and enrich trace amount of Pb(II) in vegetables prior to its determination by FAAS.