ABSTRACT
A class of heterogeneous catalysts based on commercial bentonite from natural origin, containing at least 80 wt% of montmorillonite clay, was designed to transform selectively and under mild conditions toxic organosulfur and organophosphorus chemical warfare agents into non-noxious products with a reduced impact on health and environment. The bentonite from the natural origin was modified by introducing iron species and acid sites in the interlayer space, aiming to obtain a sorbent with strong catalytic oxidising and hydrolytic properties. The catalytic performance of these materials was evaluated in the oxidative abatement of (2-chloroethyl)ethyl sulfide (CEES), a simulant of sulfur mustard, in the presence of aqueous hydrogen peroxide as an oxidant. A new decontamination formulation was, moreover, proposed and obtained by mixing sodium perborate, as a solid oxidant, to iron-bentonite catalysts. Solid-phase decontamination tests, performed on a cotton textile support contaminated with organosulfide and organophosphonate simulant agents revealed the good activity of the solid formulation, especially in the in situ detoxification of blistering agents. Tests carried out on the real blistering warfare agent, sulfur mustard (HD agent), showed that, thanks to the co-presence of the iron-based clay together with the solid oxidant component, a good decontamination of the test surface from the real warfare agent could be achieved (80% contaminant degradation, under ambient conditions, in 24 h).
ABSTRACT
The CO2 adsorption properties of hybrid organic-inorganic MCM-41 silicas with different particle sizes are described here. Micrometric to nanometric MCM-41 silicas are functionalized by introducing amino groups via grafting of 3-[2-(2-aminoethyl)aminoethyl]aminopropyltrimethoxysilane (PAPTS). A combination of FTIR and SS-NMR spectroscopies is adopted to distinguish between physisorbed and chemisorbed CO2. A higher amount of CO2 is physisorbed in the nanometric sample because of a higher pore volume, whereas chemisorbed (carbamate and acid carbamic) species are more abundant in the micrometric sample. The adsorption process is also quantitatively studied using three different techniques (i.e. volumetric measurements, Thermo-Gravimetric Analysis (TGA) and Zero Length Column (ZLC) analysis), especially focusing on the reversibility of the reactions between CO2 and amino groups. The three techniques show a higher CO2 adsorption capacity for MCM-41 with nanometric size compared to the micrometric one. Finally, the process is studied at different temperatures (i.e. from 35 to 90 °C) in order to find the best operating conditions.
ABSTRACT
Hybrid organic-inorganic SBA-15 silicas functionalized with increasing amounts of amino groups were studied in this work aiming to evaluate the effects of their physico-chemical properties on CO2 capture ability. Three different amino-silane species were used: 3-aminopropyltriethoxysilane (APTS), 3-(2-aminoethyl)aminopropyltrimethoxysilane (EAPTS) and 3-[2-(2-aminoethyl)aminoethyl] aminopropyltrimethoxysilane (PAPTS). More specifically, samples were prepared by using two methods, following a post-synthesis grafting procedure and a one-pot preparation method. Experimental and computational techniques were used to study the structural and textural properties of the obtained samples and their surface species in relation to the adopted preparation method. For the most reactive samples, additional hints on the interactions of organosilane species with the silica surface were obtained by a combination of IR and SS-NMR spectroscopy, with particular emphasis on the effects of the silane chain length on the mobility of the organic species. Advanced complementary solid-state NMR techniques provided deeper information on the interactions of organosilane species with the silica surface. Finally, the amount of CO2 adsorbed was estimated by comparing the classical microcalorimetric analysis method with a new type of screening test, the Zero Length Column analysis, which is able to evaluate small amounts of samples in a very short time and the adsorption properties of the adsorbents. The reactivity of the amino-modified silica samples is deeply influenced by both the preparation route and by the type of organosilane used for the functionalization of the materials. In particular, samples prepared by the post-synthesis grafting procedure and containing higher amount of amino groups in the chain are more reactive, following the order PAPTS > EAPTS > APTS.
