Studies Of Separation And Preconcentration Of Trace Silver And Palladium In Environmental Water Samples With Modified Nanometer SiO₂ And Determination By Atomic Absorption Spectrometry

With the development of the society, the atomic adsorption spectrometry (AAS),which has the merits of low cost and good precision and accuracy, has been widelyapplied. However, it is difficult to deteminate trace elements. Therefore, forimprovement of analytical sensitivity and selectivity, the preliminary separation andpreconcentration is much essential in the analysis of actual samples.AAS with solid-phase extraction (SPE) is widely applied in the separation andpreconcentration of trace elements. The analytical sensitivity of this analytical methodcould be efficiently improved, and the matrix interfere could been reduced andremoved. In addition, the choice of adsorb materials is the decisive factor whichaffects analytical sensitivity and selectivity. Therefore, it is a reseach hotspot to searchnew and good performance adsorbs materials.In this dissertation, on the base of reading a lot of literature, the self-madenanometer SiO₂ using sol-gel method and the modified nanometer SiO₂ materialswere used as adsorption materials. Moreover, the separation and concentrationbehavior of Pd and Ag ions had been studied in detail. It has established a newmethod for determination of trace precious elements, which with high efficiency, aswell as high sensitivity and selectivity. These methods made the application ofnanometer material more widen in the filed of separation/preconcentration .The major contents were described as follows:1. The methods of separation/preconcentration of precious elements and kinds ofadsorption materials in SPE were reviewed. The characteristics and application inseparation/preconcentration of new adsorption material-nanometer material wereintroduced in detail.2. Nanometer SiO₂ was prepared by Sol-Gel method. Then, the products werecharacterized by AFM and IR. The adsorption characteristics of trace Ag+ onnanometer SiO₂ under static condition were studied, and the factors affectingadsorption and desorption were optimized. The linear range for silver was 0.005¹.5μg/mL, detection limit (3σ, n=11) of this method was 0.77 ng/mL. In addition, therelative standard deviation was 3.6% and the recovery was in the range of 94.0% to101.5%. The proposed method has been applied to the determination of trace Ag inwater samples with satisfactory results.3. Nanometer SiO₂ was modified with 4-(2-pyridylazo)-resorcinol (PAR). The adsorption behaviors of Pd on PAR modified Nanometer SiO₂ was studied. Theresults showed that the adsorbing capacities for Pd were 31.2 mg/g. The detectionlimit (3σ, n=11) of this method was 2.97 ng/mL. The relative standard deviation was2.5% (c=0.5μg/mL, n=7), the recoveries of Pd were 98.0% 102.0%. The proposedmethod was applied to determinate trace Pd in actual samples with satisfactoryresults.4. 3-Aminopropylmethyldime-thoxysilane modified nanometer SiO₂ was used asadsorption materials in separation/preconcentration of trace Pd which determined byFAAS. The adsorption characteristics of trace Pd on modified nanometer SiO₂ werestudied in detail, and the conditions for preconcentration of this element wereoptimized. The detection limit (3σ, n=11) of this method was 2.48 ng/mL and therelative standard deviation was 2.6%. This method was succesfully used for thedetermination of trace Pd in environmental samples.