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Hydrogen sulphide is a part of well known environmental problem. It can be found in
natural gases and it is also produced by different human industrial activities such as natural
gas extraction and processing, chemical industries, skin processing, municipal engineering,
cattle farms. Emission control of hydrogen sulphide is required for reasons of health, odour
problems, safety and corrosivity problems. The means of removing of hydrogen sulphide
mainly depend on its concentration and kind of purified medium. When hydrogen sulphide
concentration is very low, techniques such as thermal and catalytic combustion, oxidative
scrubbing and biofiltration might be preferable to attain deodorization. However, combustion
converts sulphur into SO2, while oxidative scrubbing gives rise to sulphate containing
solutions.
In the present paper removal of low concentration of hydrogen sulphide by its
selective catalytic oxidation with Fe(III)-EDTA catalyst carried on fibrous ion exchangers has
been described. The complex of trivalent iron converts hydrogen sulphide to elemental
sulphur. Bivalent iron formed in the reaction is oxidized by the atmospheric oxygen, so
complex of trivalent iron is continuously regenerated and the overall process can be accounted
as pseudo-catalytic. Iron(III) chelates are well known and widely applied catalysts in many
methods of hydrogen sulphide abatement. The main disadvantage of the methods is the fact
that the catalyst is active only in strong alkali environment which causes serious operational
problems. The problems could be solved with help of Fiban fibrous ion exchangers as carriers
of the catalyst. The base of these materials is fibrous ion exchanger with Fe(III)-EDTA
complex immobilized on their functional groups. The role of fibrous package is improving the
mass-transfer between the gas and liquid, buffering the pH of absorbing solution and,
probably, catalyzing the reactions of oxidation of sulphur and iron ions. It was proved that the
filtering layers with anion exchange package are much more active in the catalytic processes
of hydrogen sulphide removal than cation exchanger and inert materials. In the addition to the
nature of the fibre–solution carrier the process of catalytic oxidation depends on concentration
of hydrogen sulphide in the air, relative air humidity, the process time and the content of Fe-
EDTA complex in the fibres. Among them relative humidity of the purified air seems to be a
critical factor determining efficiency of the material in the air purification from H2S. It was
shown that the efficiency of the ion exchanger as a gas absorber was controlled (alongside
with the other factors) by the amount of “free” water, not bound in strong hydrates and thus
able to dissolve the gaseous component. It has been established that application of the Fe(III)-
EDTA/Fiban catalytic system, under appropriate conditions, leaded to nearly complete
conversion of H2S to elemental sulphur.
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