Marta Andrade

Activated carbons from sisal waste by chemical activation with K2CO3: Kinetics of paracetamol and ibuprofen removal from aqueous solution

Sisal waste was used as precursor to prepare carbons by chemical activation. The influence of the K(2)CO(3) amount and activation temperature on the materials textural properties were studied through N(2) and CO(2) adsorption assays. As the severity of the treatment increases there is a development of supermicropores, and the micropore size distribution changes from mono to bimodal. A carbon with an apparent surface area of 1,038 m(2)g(-1) and pore volume of 0.49 cm(3)g(-1) was obtained. TPD results showed the incidence in acidic type groups although the pH(PZC) reveals an almost neutral character of the surface. Adsorption kinetic data of ibuprofen and paracetamol show that the processes obey to a pseudo-second order kinetic equation. Regarding the removal efficiency the prepared samples attained values comparable to a commercial carbon (>65%), revealing that chemical activation of sisal wastes with K(2)CO(3) allows obtaining samples suitable for pharmaceutical compounds removal from liquid phase.

Physicochemical characterization of silylated functionalized materials

Silylation of several materials where the surface area arises from the internal pores (MCM-41 and FSM-16) or is essentially external (silica gel, and clays) was performed using three organosilanes: (3-aminopropyl)triethoxysilane (APTES), 4-(triethoxysilyl)aniline (TESA) and (3-mercaptopropyl)trimethoxysilane (MPTS). The materials were characterized by nitrogen adsorption-desorption at -196 degrees C, powder XRD, XPS, bulk chemical analysis, FTIR and (29)Si and (13)C MAS NMR. For MCM-41 and FSM-16 the highest amounts of organosilane are obtained for APTES, while for the remaining materials the highest amounts are for MPTS; TESA always anchored with the lowest percentage. In terms of surface chemical analysis, TESA anchored with the highest contents irrespectively of the material, and the opposite is registered for MPTS. Comparison of bulk vs surface contents indicate that TESA is mainly anchored at the material external surface. Moreover, with N or S (surface and bulk) contents expressed per unit of surface area, MCM-41 and FSM-16 (internal porosity) show the lowest amounts of silane; the highest amounts of silane per unit of surface area are obtained for the clays. Grafting of the organosilanes to the surface hydroxyl groups was corroborated by FTIR and (29)Si and (13)C MAS NMR. Furthermore, NMR data suggested that TESA and APTES grafted mostly through a bidentate approach, whereas MPTS grafted by a monodentate mechanism.

Sustainable activated carbons prepared from a sucrose-derived hydrochar: remarkable adsorbents for pharmaceutical compounds

We present a two-step methodology for the preparation of highly activated carbons with tailored morphologies and micropore size distributions (MPSD) through the hydrothermal carbonization (HTC) of renewable biomass (i.e. sucrose) and further activation. Depending on the activation agent, activated carbons with spherical (K2CO3 or steam activation) or sponge-like morphologies (KOH activation) were obtained. The control of the activation variables allows tailoring the MPSD of the materials with K2CO3 activation at 700–800 °C originating porous materials with molecular sieve properties, and KOH activation giving porous carbon materials with wider MPSD. The highly developed porous structures of the activated carbons give them remarkable adsorption capacities for the removal of pharmaceutical compounds of distinct therapeutical classes (i.e. ibuprofen, paracetamol, clofibric acid, caffeine and iopamidol). Although the superactivated carbon obtained by the KOH activation at 800 °C has very high adsorption capacities for all the pharmaceutical compounds assayed, the material obtained by the K2CO3 activation at 800 °C has a similar adsorption capacity for all pharmaceuticals but iopamidol, the most voluminous compound. The distinct performance of the porous carbon materials for the removal of the pharmaceutical compounds is mainly related to their MPSD. The high performance of some of the synthetized carbons combined with the possibility of controlling the size of the particles in the HTC step allows not only their possible use as filter media but also coupling to other advanced water treatment technologies (e.g. membrane systems). Moreover, the abovementioned properties associated with the acidic surface chemistry of the developed activated carbons open new possibilities for the synthesis of functional carbon-based materials.

Novel Chemotherapeutic Agents - The Contribution of Scorpionates

The development of safe and effective chemotherapeutic agents is one of the uppermost priorities and challenges of medicinal chemistry and new transition metal complexes are being continuously designed and tested as anticancer agents. Scorpionate ligands have played a great role in coordination chemistry, since their discovery by Trofimenko in the late 1960s, with significant contributions in the fields of catalysis and bioinorganic chemistry. Scorpionate metal complexes have also shown interesting anticancer properties, and herein, the most recent (last decade) and relevant scorpionate complexes reported for application in medicinal chemistry as chemotherapeutic agents are reviewed. The current progress on the anticancer properties of transition metal complexes bearing homo- or hetero- scorpionate ligands, derived from bis- or tris-(pyrazol-1-yl)-borate or -methane moieties is highlighted.