Sulfur containing ethene bridged PMOs as adsorbent and catalyst

Periodic Mesoporous Organosilicas (PMOs) are very promising materials and research in this area has expanded during the lastest decade. They are ordered materials with high specific surface areas, large pore volumes and narrow pore size distributions. They combine inorganic rigidity with organic chemical flexibility resulting in a stable material with many modification opportunities. In this study, the use of PMOs as adsorbents and as acid catalysts has been investigated. Starting from a pure trans ethene bridged PMO, an adsorbent is created by the incorporation of a thiol group. This group can be easily converted in a sulfonic acid group, transforming the PMO in a catalyst. The adsorbent has been compared with several other thiol containing silica materials for the adsorption of mercury(II) ions. Their chemical and structural stability and adsorption behaviour has been investigated. Whereas the silica grafted or cocondensed adsorbents lose their structure or functionalities during several mercury(II) adsorption and desorption cycles in aqueous media, the thiol functionalized PMO completely maintains its structure and amount of functionalities. The solid acid catalyst has been succesfully synthesized and investigated for an esterification reaction where the influence of the chain length of the acidic functionality on the catalytic activity will be discussed

Verwijdering van kwik uit waterige oplossingen : vergelijking van een nieuw ultrastabiel mesoporeus adsorbens met een commercieel ionenwisselaarshars

The performance of a new ultra stable, regenerable adsorbent SH-ePMO for the removal of mercury from aqueous solutions was compared with that of a commercial ion exchange resin TP-214. The operating variables studied were initial mercury concentration and contact time. The adsorption isotherms showed favourable adsorption. The adsorption isotherms were analyzed using Langmuir and Freundlich models. The Langmuir model yielded the best fit for the SH-ePMO, whereas the Freundlich model fitted best the adsorption on TP-214. The maximum adsorption capacities were 66, resp. 456 mg/g for SH-ePMO, resp. TP-214. TP-214 is capable of purifying water to ppt-levels. The adsorption kinetics showed a fast adsorption for both adsorbents. The kinetics were analyzed using Lagergren’s pseudo-first-order and pseudo-second-order kinetic models. The pseudo-first-order kinetic model showed a good agreement of the experimental data of both adsorbents. This study clearly shows the potential of the ultra stable, regenerable SH-ePMO for removing mercury from aqueous solutions and confirms the performance of the ion exchanger resin TP-214