Solid-liquid Interface Adsorption And Fire Evidence Identification Of New Analytical Methods

This dissertation consists of three parts. In the first part, chemometrics methods were applied in surfactants adsorption in solid/liquid interface and solution equilibrium of the mixture of surfactants. In the second part, the adsorption of protein and surfactants was in situ monitored by a piezoelectric sensor and density wave effect was investigated. In the last part, a computer assistant analysis method was developed 'for the gas chromatographic data in samples of arson residues. The details were given below.1) Adsorption of surfactants at solid-liquid interfaces plays a crucial role in many industrial applications, including detergents, enhanced oil recovery, surface wetting modification, emulsification, corrosion inhibition, foaming control, dispersion of solids, surfactant-based separation processes and flotation. Surfactants have the characteristic to adsorb at solid/liquid interface in orientation, which modifies significantly the properties of the interface. In practical applications, a mixture of surface active homologues are used rather than isomerically pure surfactants, since the latter are more expensive to produce and generally have only a small potential advantage in performance over the surfactant mixture. To improve the measuring method for adsorption amounts, chemometrics method was added in the study for surface adsorption. One of the reasons why poor reproducibility in adsorption amounts in references was given. By using multiple linear regression or Kalman filter method, the influence of the variational scattering background caused by non-separated residual particles in each supernatant on spectrometric measurements can be corrected efficiently. The concentration of surfactants in the mixture were determined simultaneously. Two model adsorption systems, the mixture of an anionic surfactant, sodium dodecyl benzenesulfonate (SDBS) and a nonionic surfactant, Triton X-100, on alumina, and the mixture of a cationic surfactant, cetylpyridinium chloride (CPC), and a nonionic surfactant, Triton X-100, on silica, were tested. It was shown that false "negative" adsorption amounts for alumina from single Triton X-100 solutions were given without correcting the influence of light scattering from residualalumina particles. The chemometrics method offers a simple and efficient way to eliminate the variational scattering background. The practicability of the two methods was demonstrated. The adsorption process for mixture surfactant was monitored by a piezoelectric sensor, the thermodynamic and kinetic parameters for adsorption were obtained.2) The strong interaction between anionic and cationic surfactants results in complicated solution equilibrium in their mixture. A primary component analysis method was applied to investigate the mixture of dodecyl benzenesulfonate and cetylpyridinium chloride. A new method for data treatment was reported. From the measurements of spectra data in the mixture, the number/of components, Ksp value for precipitation, equilibrium constant and solubility for the complex, as well as the absorbance spectrum of the complex can be obtained. The absorbance spectrum of the complex can not be measured directly in spectrometric method. This example shows the good practicability for chemometrics methods in solution equilibrium.3) Piezoelectric sensors are very sensitive to mass change at the sensing surface. For a piezoelectric quartz crystal operated in liquid phase, its response is also related to the properties. Hence, cell design is an important aspect in the experiment for piezoelectric sensor. The longitudinal wave effected originated from the variation in liquid density is reported for the first time. The influence of the density wave on the response of the sensor was investigated by an impedance analyzer method. The fine structure of the response of the sensor was observed. Based on the detailed investigation, an equivalent circuit model was proposed. The relationships for the impedance parameters were derived for the density waves. The phase difference between the impedance p...