We report the first direct observation of an interfacial charge-transfer complex using second-harmonic spectroscopy. The second-harmonic spectrum of catechol adsorbed on 0.4 micron-sized TiO2 (anatase) colloidal particles in aqueous suspension reveals a charge-transfer band centered at 2.72 eV (456 nm). In addition, the adsorption isotherm of catechol on the colloidal TiO2 suspension was obtain...

It is well known that adsorption density of a multivalent metal ions (M) on a variety of substrates increases sharply only at pHs where the concentration of the singly-charged hydroxo complex (M(OH)(z-1)) is appreciable (1-4). In Chapter 4, a new mechanism was proposed to explain why adsorption of these hydroxo-complexes may be thermodynamically more favorable than that of the unhydrolyzed meta...

The perturbed-chain statistical associating fluid theory (PC-SAFT) density functional theory developed in our previous work was extended to the description of inhomogeneous confined behavior in nanopores for mixtures. In the developed model, the modified fundamental measure theory and the weighted density approximation were used to represent the hard-sphere and dispersion free energy functional...

In the present study, we investigated the ability of an immobilized phospholipase A1 (PLA1) in degumming of soybean oil. The enzyme was immobilized by simple adsorption on bentonite without any further modification. The free and immobilized PLA1 were characterized by Fourier Transform InfraRed (FT-IR) spectroscopy and X-Ray Diffraction (XRD). The immobilizat...

Monovalent and divalent aqueous electrolytes confined in negatively charged porous silica are studied by means of molecular simulations including free energy calculations. Owing to the strong cation adsorption at the surface, surface charge overcompensation (overscreening) occurs which leads to an effective positive surface next to the Stern layer, followed by a negatively charged diffuse layer...

Different types of surface forces, acting in the films of pentane, hexane, and heptane on water are discussed. It is shown that an important contribution to the surface forces originates from the solubility of water in alkanes. The equations for the distribution of electric potential inside the film are derived within the Debye-Hückel approximation, taking into account the polarization of the f...

The interface between a fluid and a static wall is a useful model for a chemically heterogeneous solid-liquid interface. In this work, we outline the calculation of the wall-fluid interfacial free energy (gamma(wf)) for such systems using molecular simulation combined with adsorption equations based on Cahn's extension of the surface thermodynamics of Gibbs. As an example, we integrate such an ...

The thermodynamic parameters viz. the standard free energy (∆Gº), Standard enthalpy change (∆Hº) and standard entropy change (∆Sº) were determined using the obtained values of distribution coefficient (kd) of U (VI) in two different types of soils (agricultural and undisturbed) by conducting a batch equilibrium experiment with aqueous media (groundwater and deionised water) at two different tem...

We apply density functional theory to study adsorption of ions, treated in the framework of the restricted primitive model (RPM), on surfaces modified by tethered polyampholytes. The residual electrostatic contribution to the free energy functional is approximated by using the approach proposed by Wang et al. [J. Phys.: Condens. Matter 23, 175002 (2011)] for simple nonuniform RPMs systems. Our ...

This study investigated the feasibility of Date-palm) Phoenix dactylifera (Leaf Ash (DLA) (an inexpensive agricultural-byproduct) as an application to adsorb Pb(II) ions. An adsorption process was carried out to evaluate initial concentration Pb(II) ions, adsorbent dose, contact time, pH and temperature on the systematic removal of Pb(II). The effects were examined and results showed that remov...