Mechanism of hydrogen sulphide fixation on impregnated activated carbon fibres

摘要

In spite of their huge specific area (1400 m2/g), activated carbon fibres exhibit very small adsorption capacities for hydrogen sulphide. These capacities can be greatly increased by impregnation of the activated fibres in aqueous solutions of potassium hydroxide. The basic functions installed by the treatment favour acid – base reactions between H2S, which is an acidic gas, and the impregnating agent. The study of the hydrogen sulphide fixation on impregnated activated fibres is carried out at room temperature, in a reactor containing a given quantity of fibres in contact with a gas mixture made of H2S, water vapour and a vector gas. A gas detector connected to the outlet of the reactor records the volumic fraction of H2S coming out of it. From the data collected, H2S breakthrough curves are built. Fixation capacities of H2S on the fibres can be deduced from these curves. The thermodynamical aspects and the kinetics of H2S fixation on impregnated fibres have been studied in detail. The reaction mechanism is now mainly clarified and a model for H2S fixation on impregnated fibres has been written. Several steps occur : first, water vapour is adsorbed on the surface of the fibres, the multilayer sorbed water forms a superficial solution. Then, hydrogen sulphide dissolves and reacts in the solution with the impregnating agent. H2S is entirely retained on the fibres until the solution gets saturated. From this moment, the H2S starts breaking through the fibres and the reactor.