Tuning of halobenzenes uptake in montmorillonite from gas phase through a functionalization process involving Cu(II)-phenanthroline and heptanethiol

In this paper, montmorillonite functionalized with a Cu(II)-phenanthroline complex (Mt-CuPhen) and then exposed to heptanethiol vapors (Mt-CuPhen-HPT) was tested for the capture of halobenzenes in gas phase. The treatment of Mt-CuPhen with heptanethiol vapors produced important compositional changes involving Cu(II) reduction, oxidation of thiol to disulfide and dehydration of the mineral interlayer space. Entrapping experiments were carried out on fluorobenzene, chlorobenzene and bromobenzene at 25 and 45°C. The hybrid material proved to be very efficient for all halobenzenes and especially for fluorobenzene. Observed performances are slightly affected by temperature. Halobenzene desorption occurred even at 100°C, a temperature quite lower than that required for decomposition of Mt-CuPhen-HPT. The Mt-CuPhen-HPT hybrid material, therefore, can be reused several times and requires low energy costs for regeneration. An alternative regeneration procedure based on disulfide removal has been proposed as well. Mt-CuPhen-HPT was extensively characterized before and after halobenzenes immobilization through elemental analysis, UV-Vis measurements, thermogravimetric analyses, FTIR, NMR and X-ray absorption spectroscopies.