Study On The Adsorption Behavior Of Metal Ions On Nanometer Titanium Dioxide And Its Application

Sensitive, rapid, reproducible, simple and accurate analytical methods are required for the determination of trace elements in geological, biological and environmental samples. The direct determination of extremely low concentrations of trace elements by mode.m atomic spectroscopic methods, such as atomic absorption spectrometry (AAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) is often difficult. The limitations are associated not only with the insufficient sensitivity of these techniques but also with matrix interference. For this reason, the separation and preconcentration of trace elements is often required.Solid-phase extraction (SPE) technique has become increasingly popular in recent years because it is experienced with several major advantages: (i) the fast, simple and direct sample application in very small size (micro liter volume) without any sample loss; (ii) higher preconcentration factor; (iii) rapid phase separation; (iv) the ability of combination with different detection techniques in the form of on-line or off-line mode; (v) time and cost saving. SPE separation/preconcentration followed by atomic spectroscopy detection gains more and more important position in trace analysis, and the choice of solid-phase adsorbents is the decisive factor that affects analytical sensitivity and selectivity.Nanometer material is a new solid material that gained importance due to its special properties. The regime of nanoparticle is from 1 nm to almost 100 nm, falls between the classic fields of chemistry and solid-state physics. One of its properties is that most of the atoms of the nanoparticle are on the surface .The surface atoms are unsaturated and can therefore bind with other atoms, possess highly chemical activity. Consequently, nanometer material can adsorb metal ions selectively, and has a high adsorption capacity. According to our knowledge, up to now, a few systematic data on the adsorption characteristics of nanometer material and its application in trace analysis have been reported.The major contents are described as follows:1. The adsorption characteristics of some metal ions (Zn, Cd, Co) on nanometer TiO2i under static condition was studied, and the conditions for preconcentration of trace elements were optimized. A new method of nanometer TiO2 separation/preconcentration coupled with ICP-AES for simultaneous determination of these elements in real samples was proposed.2. The adsorption characteristics of metal ion Pb on nanometer TiO2 under static condition was studied, and the conditions for preconcentration of this element were optimized. A new method of nanometer TiO2 separation/preconcentration coupled with GFAAS for the determination of trace Pb in real water samples was proposed.3. A PTFE microcolumn packed with nanometer TiO2 was used in a FI-ICP-AES system for the speciation of chromium. Based on the difference of adsorption behavior of Cr(III) and Cr(VI) in nanometer TiO2, a simple and convenient method was developed for the speciation of chromium by selective adsorption of Cr(III) and Cr(VI) on nanometer TiO2 at different pH. The proposed method was applied to the analysis of real water samples.