Search

Six carbon materials were obtained from the carbonisation of resorcinol/formaldehyde xerogels. All carbon xerogels (CXs) showed essentially the same microporosity but differed in their meso- or macroporosity, covering a wide interval of average meso- or macropore sizes from 10 nm to 3000 nm. The graphitisation of the CXs was heterogeneous, as detected by X-ray diffraction. The relative amount of the amorphous, turbostratic and graphitic carbon phases on the graphitised xerogels was different depending on the pore size of the CXs. Crystalline parameters such as interlayer spacings (d002) and crystallite sizes along the c-axis (Lc) were calculated from the different contributions and were also found to depend on the pore size of the parent CXs. Transmission electron microscopy and Raman spectroscopy analyses helped to identify nanostructures that could be assigned to the three carbon components of the graphitic xerogels. The occurrence of most of these nanostructures was compatible with a solid-phase transformation of the amorphous precursor. The electrical conductivity of the graphitised xerogels also depended on their original pore size, with values ranging from 2 S cm−1 for the materials with a 10 nm pore size to 18 S cm−1 for the materials with bigger pore sizes.

The presence of moderate concentrations of impurities in the nickel-plating baths generates failures on the coated pieces. This situation entails the necessity of replacing the electroplating bath, which implies the generation of large volumes of wastewater with metallic species and high quantity of sludge. For this reason, the adsorption of the principal impurities of nickel-plating baths of an industry was analyzed in this work. Particularly, the removal of Zn2+ was studied in more detail since the presence of this metal in the baths generates black spots on the coated pieces. Different commercial materials were used as adsorbents and Zn2+ adsorption studies were carried out using both standard solutions and industrial water from the nickel-plating baths. All the adsorption tests were performed in batch systems under constant agitation and the quantification of the impurities was made by ICP-MS analysis. The bone char (BC) was an efficient adsorbent for the removal of the principal impurities of nickel-plating baths. The use of molecular simulation tools helped to understand the preferences of the hydroxyapatite (the principal component of bone char) for different metallic ions present in the industrial waters. According to both the experimental adsorption and molecular simulation results, hydroxyl and phosphate groups of bone char are responsible of the adsorption of impurities of nickel-plating baths., This work was supported by TECNM (7949.20-P), Ministerio de Economía, Industria y Competitividad, Spain (CTQ 2017-87820-R) and PCTI-Asturias/ FEDER, Spain, EU (IDI/2018/000118) projects. MC. Pérez-Jiménez acknowledges the grant (857757) received from CONACyT. L.A. Ramírez-Montoya thanks CONACyT for a post-doctoral grant (CVU No 330625, 2017).

Extensive studies on the correlation between synthesis variables and the final properties of resorcinol-formaldehyde carbon gels have been performed. This knowledge allows us to obtain carbon gels with analogous mean pore sizes and porosity from different combinations of synthesis variables. However, although the materials exhibit these similar characteristics, their behaviors may be very different in certain applications. Since the distribution and connectivity of the polymeric clusters are strongly affected by variables such as the amount of water and methanol in the precursor solution, it seems that the pore tortuosity and thus the permeability of the materials are also dependent on these factors. Further analysis of a series of carbon gels with the apparent same porosity shows how an increase in the amount of water or a suitable combination of methanol content and the pH of the precursor solution used for the polymerization process generate less tortuous pore structures. This allows us to attain even finer tuning of the porous structure of RF carbon gels either to reduce pressure drop or to increase the residence time of solutes in separation processes., Authors are grateful for the financial support received from the Ministerio de Economia, Industria y Competitividad from Spain (CTQ2017-87820-R) and Principado de Asturias–FICYT-FEDER(IDI/2018/000118). SFL is grateful to the Administración del Principado de Asturias for her research training grant awarded through the “Severo Ochoa” program. LARM thanks CONACYT, Mexico for a post-doctoral grant (CVU No 330625, 2017).

The simultaneous removal of phosphate and aluminum from water was studied on iron-modified activated carbons. Methods such as oxidation with HNO3, impregnation and co-precipitation of iron were used to modify a commercial coconut activated carbon and to obtain seven different modified carbons. The physicochemical properties of selected samples were studied by different analytic methods such as FT-IR spectroscopy, SEM/EDX analysis and X-ray diffraction. Adsorption studies of phosphate and aluminum from water in single and binary systems were performed in bath systems with constant agitation at 30 °C and different values of pH. Particularly, the sample obtained by Oxidation-Impregnation-Drying procedure (CCOFeTB) contains 3.80% of iron in amorphous phase according to the EDX and XRD analysis, respectively. Additionally, this sample showed the best adsorption performance achieving an adsorbed amount of phosphates of 23.33 mg/g at pH 2 in single system. In binary systems, it was observed a synergistic effect in the adsorption of both species (phosphate and aluminum) and the principal adsorption mechanism is related to electrostatic interactions according with the results of molecular simulation., This work was supported by TECNM (7949.20-P), Ministerio de Economía, Industria y Competitividad, Spain (CTQ2017-87820-R) and PCTI-Asturias/FEDER, Spain, EU (IDI/2018/000118) projects. MC. Delgadillo-Velasco acknowledges the grant (467325) received from CONACyT. L.A. Ramírez-Montoya thanks CONACyT for a post-doctoral grant (CVU No 330625, 2017).

A series of xerogels with a properly designed porous structure and surface chemistry have been synthesized and evaluated as a host structure to promote the nucleation and growth of methane hydrates. Organic xerogels (OGs) have been synthesized from resorcinol-formaldehyde mixtures using a sol-gel approach and microwave heating. These xerogels are hydrophilic in nature and possess designed meso/macrocavities in the pore size range 5–55 nm. Carbon xerogels (CGs) have been synthesized from their organic counterparts after a carbonization treatment at high temperature. Interestingly, the carbonization process does not alter/modify substantially the porous network of the parent xerogels, while developing new micropores. Under water-supplying conditions, the two types of xerogels exhibit a large improvement in the methane adsorption capacity compared to the pure physisorption process taking place in dry conditions (up to 200% improvement), and associated with a significant hysteresis loop. These excellent values must be associated with the promoting effect of these xerogels in the water-to-hydrate conversion process. The comparison of OGs and CGs as a host structure anticipates that surface chemistry, total pore volume and pore size are critical parameters defining the extent and yield of the methane hydrate formation process., Authors would like to acknowledge financial support from the MINECO (projects MAT2016-80285-p and CTQ2017-87820-R). Principado de Asturias-FICYT-FEDER (Project PCTI-Asturias IDI/2018/000118) is also acknowledged. L.A. Ramírez-Montoya thanks CONACyT, México, for a post-doctoral grant (CVU No 330625, 2017).