rocio carmona | Universidad Autónoma Metropolitana-Iztapalapa (original) (raw)
Papers by rocio carmona
Microporous and Mesoporous Materials, 2014
The sol-gel polymerization of resorcinol/formaldehyde mixtures to obtain porous gels is typically... more The sol-gel polymerization of resorcinol/formaldehyde mixtures to obtain porous gels is typically a long process performed throughout several days. In this work, we have explored an experimental approach to reduce the time necessary to obtain porous gels based on mild polymerization conditions and direct drying. We have analyzed the effects of the temperature and time of the gelation/aging step on the porosity of the gels, as well as the impact on the overall energetic cost of the process. Data have shown that welldeveloped micro-mesoporous architectures can be obtained within less than a day. The temperature of the gelation/aging step mainly affects the mesopore network, whereas the microporosity is determined by the composition of the precursor's mixture. The exclusion of the solvent exchange step yields soft mechanically fragile porous gels with structural limitations upon carbonization at high temperature in inert atmosphere, due to the surface tensions applied to the backbone during the evolution of volatiles. The mesopore structure lost during carbonization is not recovered upon activation in CO 2 atmosphere, but it is preserved upon chemical activation in K 2 CO 3 and the resulting gel exhibits a bimodal micromesoporous distribution. Furthermore, the energy savings of this route are similar to those obtained using microwave-heating in terms of grams of xerogel per kilowatt hour of energy consumed for similar textural properties. The correlation between the energy power consumed and the textural parameters is a useful tool to optimize the synthesis.
Carbon, 2014
The photocatalytic performance of titania/Cu-carbon composites was investigated towards phenol de... more The photocatalytic performance of titania/Cu-carbon composites was investigated towards phenol degradation under visible light. The approach consisted on the incorporation of the transition metal on the carbon component of the hybrid composite via impregnation of the carbon precursor with a metal salt followed by activation. Data showed a homogeneous dispersion of copper particles within the carbonaceous matrix, predominantly as copper (II) species. The synthesized carbons displayed a well developed nanoporous texture, although comparatively the impregnation of copper caused a marked inhibition of the textural development of the carbon precursor. The phenol photooxidation tests carried out on 1:1 titania/carbon composites showed the outstanding role of copper under visible light, with an increased efficiency in terms of phenol conversion, mineralization degree and degradation rate. This is important, since similar overall conversions were obtained with half of the amount of the photoactive semiconductor (1:1 composites). The beneficial effect of copper loading was also observed in the marked regioselectivity towards the preferential formation of catechol. Furthermore, the copper-loaded photocatalyst was found to be stable with no lixiviation or photorreduction of the copper species after illumination.
Journal of colloid and interface science, Jan 13, 2014
This work investigates the competitive adsorption under dynamic and equilibrium conditions of ibu... more This work investigates the competitive adsorption under dynamic and equilibrium conditions of ibuprofen (IBU) and amoxicillin (AMX), two widely consumed pharmaceuticals, on nanoporous carbons of different characteristics. Batch adsorption experiments of pure components in water and their binary mixtures were carried out to measure both adsorption equilibrium and kinetics, and dynamic tests were performed to validate the simultaneous removal of the mixtures in breakthrough experiments. The equilibrium adsorption capacities evaluated from pure component solutions were higher than those measured in dynamic conditions, and were found to depend on the porous features of the adsorbent and the nature of the specific/dispersive interactions that are controlled by the solution pH, density of surface change on the carbon and ionization of the pollutant. A marked roll-up effect was observed for AMX retention on the hydrophobic carbons, not seen for the functionalized adsorbent likely due to th...
Carbon, 2014
The long term performance of semiconductor-free activated carbons showing photochemical activity ... more The long term performance of semiconductor-free activated carbons showing photochemical activity was explored by monitoring the photodegradation of phenol from aqueous solution along 20 hours of illumination in consecutive photocatalytic cycles. The efficiency of the process was evaluated in terms of phenol conversion, mineralization degree and evaluation of degradation intermediates upon cycling. Data showed a strong dependence of the photooxidation efficiency on the hydrophobic/hydrophilic nature of the carbons. The outstanding role of dissolved oxygen as a promoter of phenol photodegradation through the formation of O-radicals upon illumination of the carbons was also demonstrated. The excess of oxygen not only improved phenol conversion and mineralization, but delayed the clogging of the carbon's porosity upon cycling. This is important since a fraction of the photooxidation reaction also takes place inside the porous network of the carbon materials. Overall, the performance of the activated carbons, especially in conditions of excess of oxygen, is comparable to that of commercial titania. *Corresponding author. Tel./Fax: +34 985 118846/ +34 985 297662.
Microporous and Mesoporous Materials, 2014
The sol-gel polymerization of resorcinol/formaldehyde mixtures to obtain porous gels is typically... more The sol-gel polymerization of resorcinol/formaldehyde mixtures to obtain porous gels is typically a long process performed throughout several days. In this work, we have explored an experimental approach to reduce the time necessary to obtain porous gels based on mild polymerization conditions and direct drying. We have analyzed the effects of the temperature and time of the gelation/aging step on the porosity of the gels, as well as the impact on the overall energetic cost of the process. Data have shown that welldeveloped micro-mesoporous architectures can be obtained within less than a day. The temperature of the gelation/aging step mainly affects the mesopore network, whereas the microporosity is determined by the composition of the precursor's mixture. The exclusion of the solvent exchange step yields soft mechanically fragile porous gels with structural limitations upon carbonization at high temperature in inert atmosphere, due to the surface tensions applied to the backbone during the evolution of volatiles. The mesopore structure lost during carbonization is not recovered upon activation in CO 2 atmosphere, but it is preserved upon chemical activation in K 2 CO 3 and the resulting gel exhibits a bimodal micromesoporous distribution. Furthermore, the energy savings of this route are similar to those obtained using microwave-heating in terms of grams of xerogel per kilowatt hour of energy consumed for similar textural properties. The correlation between the energy power consumed and the textural parameters is a useful tool to optimize the synthesis.
Carbon, 2014
The photocatalytic performance of titania/Cu-carbon composites was investigated towards phenol de... more The photocatalytic performance of titania/Cu-carbon composites was investigated towards phenol degradation under visible light. The approach consisted on the incorporation of the transition metal on the carbon component of the hybrid composite via impregnation of the carbon precursor with a metal salt followed by activation. Data showed a homogeneous dispersion of copper particles within the carbonaceous matrix, predominantly as copper (II) species. The synthesized carbons displayed a well developed nanoporous texture, although comparatively the impregnation of copper caused a marked inhibition of the textural development of the carbon precursor. The phenol photooxidation tests carried out on 1:1 titania/carbon composites showed the outstanding role of copper under visible light, with an increased efficiency in terms of phenol conversion, mineralization degree and degradation rate. This is important, since similar overall conversions were obtained with half of the amount of the photoactive semiconductor (1:1 composites). The beneficial effect of copper loading was also observed in the marked regioselectivity towards the preferential formation of catechol. Furthermore, the copper-loaded photocatalyst was found to be stable with no lixiviation or photorreduction of the copper species after illumination.
Journal of colloid and interface science, Jan 13, 2014
This work investigates the competitive adsorption under dynamic and equilibrium conditions of ibu... more This work investigates the competitive adsorption under dynamic and equilibrium conditions of ibuprofen (IBU) and amoxicillin (AMX), two widely consumed pharmaceuticals, on nanoporous carbons of different characteristics. Batch adsorption experiments of pure components in water and their binary mixtures were carried out to measure both adsorption equilibrium and kinetics, and dynamic tests were performed to validate the simultaneous removal of the mixtures in breakthrough experiments. The equilibrium adsorption capacities evaluated from pure component solutions were higher than those measured in dynamic conditions, and were found to depend on the porous features of the adsorbent and the nature of the specific/dispersive interactions that are controlled by the solution pH, density of surface change on the carbon and ionization of the pollutant. A marked roll-up effect was observed for AMX retention on the hydrophobic carbons, not seen for the functionalized adsorbent likely due to th...
Carbon, 2014
The long term performance of semiconductor-free activated carbons showing photochemical activity ... more The long term performance of semiconductor-free activated carbons showing photochemical activity was explored by monitoring the photodegradation of phenol from aqueous solution along 20 hours of illumination in consecutive photocatalytic cycles. The efficiency of the process was evaluated in terms of phenol conversion, mineralization degree and evaluation of degradation intermediates upon cycling. Data showed a strong dependence of the photooxidation efficiency on the hydrophobic/hydrophilic nature of the carbons. The outstanding role of dissolved oxygen as a promoter of phenol photodegradation through the formation of O-radicals upon illumination of the carbons was also demonstrated. The excess of oxygen not only improved phenol conversion and mineralization, but delayed the clogging of the carbon's porosity upon cycling. This is important since a fraction of the photooxidation reaction also takes place inside the porous network of the carbon materials. Overall, the performance of the activated carbons, especially in conditions of excess of oxygen, is comparable to that of commercial titania. *Corresponding author. Tel./Fax: +34 985 118846/ +34 985 297662.