Experimental and Theoretical Estimations of Atrazine's Adsorption in Mangosteen-Peel-Derived Nanoporous Carbons.

Nanoporous carbons were prepared via chemical and physical activation from mangosteen-peel-derived chars. The removal of atrazine was studied due to the bifunctionality of the N groups. Pseudo-first-order, pseudo-second-order, and intraparticle pore diffusion kinetic models were analyzed. Adsorption isotherms were also analyzed according to the Langmuir and Freundlich models. The obtained results were compared against two commercially activated carbons with comparable surface chemistry and porosimetry. The highest uptake was found for carbons with higher content of basic surface groups. The role of the oxygen-containing groups in the removal of atrazine was estimated experimentally using the surface density. The results were compared with the adsorption energy of atrazine theoretically estimated on pristine and functionalized graphene with different oxygen groups using periodic DFT methods. The energy of adsorption followed the same trend observed experimentally, namely the more basic the pH, the more favored the adsorption of atrazine. Micropores played an important role in the uptake of atrazine at low concentrations, but the presence of mesoporous was also required to inhibit the pore mass diffusion limitations. The present work contributes to the understanding of the interactions between triazine-based pollutants and the surface functional groups on nanoporous carbons in the liquid-solid interface.

C-doped anatase TiO2: Adsorption kinetics and photocatalytic degradation of methylene blue and phenol, and correlations with DFT estimations.

This work shows an easy and eco-friendly methodology to obtain almost pristine anatase phase of TiO2 by using furfural, a biomass-derived molecule, as a bio-template. The photocatalytic activity was studied following the degradation of methylene blue and phenol under artificial solar irradiation. Results were compared against those obtained on a commercial pristine anatase TiO2. The pseudo first-order, the second-order and the intraparticle diffusion kinetic models were verified. The textural and surface chemistry properties of the materials were correlated with the surface density of molecules adsorbed in equilibrium. The reaction-rate showed an almost perfect quadratic regression as a function of the surface density. Theoretical estimations of the density of states by DFT + U were performed showing that the total electron charge in the oxygen bonded to anatase TiO2 increased due to carbon doping in agreement with the prediction of appearance of atomic orbitals 2p from carbon atom in the hybrid material. C-doping is responsible of the red-shift from 3.14 to 2.94 eV observed for a Ti15O32C super-cell than pristine anatase Ti16O32. The increase in the activity of the C-doped TiO2 photocatalyst was due to the decrease in the energy band-gap promoting a higher absorption of photons from the visible light.