Beatriz López Ruiz

Carbon dioxide/methane separation by adsorption on sepiolite

In this work, the use of sepiolite for the removal of carbon dioxide from a carbon dioxide/methane mixture by a pressure swing adsorption (PSA) process has been researched. Adsorption equilibrium and kinetics have been measured in a fixed-bed, and the adsorption equilibrium parameters of carbon dioxide and methane on sepiolite have been obtained. A model based on the LDF approximation has been employed to simulate the fixed-bed kinetics, using the Langmuir equation to describe the adsorption equilibrium isotherm. The functioning of a PSA cycle for separating carbon dioxide/methane mixtures using sepiolite as adsorbent has also been studied. The experimental results were compared with the ones predicted by the model adapted to a PSA system. Methane with purity higher than 97% can be obtained from feeds containing carbon dioxide with concentrations ranging from 34% to 56% with the proposed PSA cycle. These results suggest that sepiolite is an adsorbent with good properties for its employment in a PSA cycle for carbon dioxide removal from landfill gases.

Electrochemical behaviour of tizanidine at solid electrodes

The electrochemical behaviour of tizanidine [5-chloro(delta-2-imidazolinyl-2-amino)-4-benzothiadiazole-2,1,3], a centrally-active skeletal muscle relaxant has been investigated in aqueous media at the carbon paste electrode (CPE). Cyclic voltammetry at different pH values, controlled potential coulometry and comparative studies on three structurally related molecules have permitted identification of the oxidation site of tizanidine and suggest possible oxidation products in acidic media. The electrochemical reduction at the CPE occurred in one irreversible step and the reduction product (diamine derivative) was detected and characterized on the positive going scan in cyclic voltammetry. Quantitative measurements of tizanidine within the range 2 x 10(-5) M and 1 x 10(-4) M have been realized at the CPE using the differential pulse technique.