Entropy and enthalpy of adsorption of gaseous metal chlorides and oxychlorides on quartz glass as functions of adsorbate composition
- Joint Inst. of Nuclear Research, Dubna (Russian Federation); and others
Microamounts of radionuclides have been used for studying adsorption of chlorides of Cs, Au, Tb, Tm, Pb, Zr, Hf, Sb, Bi, and Nb, as well as of oxychlorides of some of these elements, in a quartz thermochromatographic column with SOCl{sub 2} as chlorinating component of the carrier gas. Based on the temperature dependence of the bulk-to-surface concentration ratio, enthalpy and enthropy changes in the course of adsorption (for a certain standard state) have been determined for a number of compounds. The {Delta}S{sub a}{sup o}values fall within a fairly narrow range and correlate with the number of atoms m in the sorbate molecule: {Delta}S{sub a}{sup o}[J mol{sup -1}K{sup -1}] = -(184{plus_minus}3) + (8.5{plus_minus}0.2)m. Thus, a simplified equation has been derived for estimating {Delta}H{sub a}{sup o}based on the adsorption constant measured for only one temperature: {Delta}H{sub a}{sup o}[kJ mol{sup -1}]= [(8.5 {plus_minus} 0.2)m - (184 {plus_minus}3) - R ln K{sub a}{sup o}]T. Reproducible {Delta}H{sub a}{sup o}values have been obtained only in the case when the inert component of the carrier gas was thoroughly predried and the column was pretreated with SOCl{sub 2}vapor for a long time, i.e., in the case of the high degree of Cl{sup -} modification of the quartz surface. The parameter {vert_bar}{Delta}H{sub a}{sup o}{vert_bar} usually approximates the enthalpy of vaporization of the adsorbate substance.
- OSTI ID:
- 224065
- Journal Information:
- Radiochemistry, Vol. 37, Issue 6; Other Information: PBD: Nov-Dec 1995; TN: Translated from Radiokhimiya; 37: No. 6, 528-536(1995)
- Country of Publication:
- United States
- Language:
- English
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