Conclusions

From the results described above, activated carbon can be envisaged as alternative adsorbents for the removal of propanethiol from liquid-phase effluents. Both, the porous structure and the surface chemistry of the activated carbons affect the removal process. Interestingly, the adsorption of propane-thiol is accompanied by surface assisted oxidation processes of propanethiol to dipropyl disulfide. In fact, whereas the porous structure is the main parameter in defining the removal kinetics, the surface chemistry has a strong influence in the oxidation reaction and consequently, in the total removal capacity. Selective modifications of the surface chemistry show that the oxidation reaction is mainly promoted by the more stable oxygen surface groups, i.e. those evolved as CO, most probably quinone groups. The limited amount of these oxygen groups on the carbon surface constitutes a limiting factor in defining the extent of the oxidation reaction, as observed on fix-bed adsorption/breakthrough experiments.

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