TiO2 and TiO2-SiO2 coated cement: Comparison of mechanic and photocatalytic properties

peer reviewedAn increasingly known application of nanomaterials in the construction industry is related to the photoactivity ability of semiconductors, where nano-anatase TiO2 is perhaps the most well-known photocatalytic semiconductor and one which possesses a strong oxidizing capability. To analyze the photo-efficiency of four TiO2 coatings and the effect of SiO2 interlayer on the mechanic and photocatalytic activity in Rhodamine B (RhB) and NOx photodegradation, two photocatalytic cement series have been prepared. First, cement mortar was coated with three commercial TiO2 suspensions (GG1, GC7 and CG13) and a home-made titania sol-gel (TEA), and secondly an insertion of a SiO2 layer was applied on cement surface before spraying the TiO2 layer.All studied TiO2-cements exhibited a significant RhB and NOx photodegradation, arising almost total RhB molar conversions, and upper 53% for NOx photo-oxidation respectively. Nevertheless, although SiO2 layer deposited in between mortar and TiO2-cement did not stabilize the commercial TiO2 coatings, a good adhesion was observed when silica was applied joint to the home-made titania gel (TEA), probably as a consequence of the interactions encountered between SiO2 and TiO2 gels. CG7-Si-Cem exhibited high rate at shorter irradiation times, but TEA-Cem and TEA-Si-Cem can be considered as very interesting and potential photocatalytic mortars due to useful mechanical properties, with a very good coatings adhesion that provides promising outdoor use, and good photo-efficiencies in RhB and NOx photo-oxidation

Sulfided NiMo/<em>Clinoptilolite</em> Catalysts for Selective Sulfur Removal from Naphtha Stream without Olefin Hydrogenation

The natural clinoptilolite zeolite has been modified by acid leaching with HNO3 in order to obtain economic material for supporting NiMoS hydrotreating catalysts. The most optimized zeolite material was obtained by leaching with HNO3 at 80°C during 24 h. The bimetallic NiMo catalysts prepared by wet impregnation of a zeolite support, followed by calcination and sulfidation, were characterized by several physico-chemical techniques and tested in the hydrodesulfurization (HDS) of 3-methyl-thiophene (3-MT) model feed at atmospheric H2 pressure and T = 280°C. For all catalysts, the 3-MT transformation mainly occurs via direct desulfurization reaction route being diminished the catalyst hydrogenation function. This was linked with the formation of highly stacked layers of MoS2 particles having a low amount of “brim sites,” as demonstrated by HRTEM. The cause of the best performance of Ni-Mo(H)/Z-1 sulfide catalyst in the HDS of 3-MT can be the presence of K+ impurities on the support surface which forces the formation of highly stacked layers of MoS2 particles

Eco-friendly mechanochemical synthesis of titania-graphene nanocomposites for pesticide photodegradation

Titania graphene hybrid nanocomposites (TiO2-FLG) synthesized from graphite and TiO2 precursors, in a simple and sustainable approach via a three-step method, including the mechanochemical treatment of pre-synthesized FLG and TiO2 NPs are efficient has led to the preparation of titania graphene hybrid nanocomposites (TiO2-FLG) as efficient nano-catalysts for photocatalytic degradation of a complex mixing of pesticides (isoproturon, pyrimethanil, alachlor and methomyl). The effect of few layer graphene (FLG) loading (0-1.0%) was analyzed to define the optimal ratio of FLG to TiO2 and compared with the corresponding physical mixtures. X-ray Powder Diffraction (XRD) patterns of all these hybrid photocatalysts have presented the same crystal structure, with anatase as the main crystalline phase and brookite as secondary phase. An interaction between the graphene structure and the TiO2 nanoparticles has been observed from Energy Dispersive X-Ray (EDX), X-ray photoelectron (XPS) and Raman spectroscopy studies, indicating that FLG is mainly deposited on the surface wrapping the TiO2 nanoparticles. The presence of FLG in low concentrations and the mechanochemical activation are the key steps to improve the photocatalytic activity of TiO2 nanoparticles on these hybrid nanocomposites. The TiO2-FLG-0.5% hybrid nanocomposite, with circa 1.9 % content of graphitic carbon in surface, has showed the best photocatalytic performance in the degradation of pesticides. Pesticides were completely removed at 350 minutes, and around 82 % of total organic carbon (TOC) conversion was achieved at 540 minutes of irradiation time

Influence of water matrix on the photocatalytic degradation of pesticides

Trabajo presentado en el ANQUE.ICCE.BIOTEC - Congress on Chemistry, Chemical Engineering and Biotechnology, celebrado en Madrid del 01 al 04 de julio de 2014.In the beginning of the 21st century, mankind must face the problem of the availability water as an important threat given that demand of water has increased with population growth, industrialization, and expansion of irrigated agriculture in recent years. Therefore, the increasingly stringent wastewater regulations and the growing demand for water recycling have generated a need for more efficient technologies to remove pollutants from aqueous effluents. So, there is a growing interest in developing cheaper and improved technologies that make industrial development and environmental protection compatible, such as AOPs which are emerging as promising solutions. Among them, one of the most frequently investigated in recent years is the photocatalytic heterogeneous technology which is especially attractive when polluted effluents are characterized by low or moderate organic charges and when solar irradiation can be used as the primary source of energy. Heterogeneous photocatalytic oxidation process, employing semiconductors such as TiO2 and UV light, has proved to be a promising technology for the degradation of persistent organic pollutants such as pesticides, producing more biodegradable by-products. Actually, in the last decades the exponential increase of intensive agriculture in the Mediterranean area has caused an important pollution of water resources with pesticides. Therefore, the present work analyses the photocatalytic activity of some commercial TiO2 catalysts in the photodegradation of four pesticides classified by the EU as priority pollutants: Diuron, Alachlor, Isoproturon and Atrazine, and the effect of two water matrix compositions on the final photoefficiency.Peer Reviewe

Bone Diagenesis at Azokh Caves

Bone diagenesis is a set of processes by which the organic and mineral phases and the structure of bone are transformed during fossilization. To understand how these processes have affected skeletal material recovered from Azokh caves (particularly the organic preservation), we measured ‘diagenetic parameters’ of skeletal material from Holocene, Late Pleistocene and Middle Pleistocene deposits from Azokh caves. Additionally, we used this study to further test the application of both nitrogen adsorption isotherm analysis and mercury intrusion porosimetry for measuring the porosity of fossil bone. The skeletal material from the Pleistocene layers of Azokh caves can be characterized as generally poorly preserved (especially collagen preservation). Porosity values of the bones are lower than might be expected as many bones show evidence of extensive infilling of the pores with secondary minerals. The pore infilling in the Middle Pleistocene layers is most extensive and this type of preservation has not previously been described in archaeological material.Peer Reviewe

Solar Assisted Photodegradation of Isoproturon: Recovery and Reuse of Titania Catalysts

Trabajo presentado en el 8th European Meeting on Solar Chemistry and Photocatalysis, celebrado en Salónica (Grecia) del 25 al 28 de Junio de 2014.Heterogeneous Photocatalysis, using TiO2 is one of the most successful applications to degrade moderate charges of recalcitrant pollutants, such as pesticides, in ambient conditions. However, catalyst efficiency and recovery after the photocatalytic processes are key challenges that have limited the practical deployment of TiO2 catalysts in wastewater applications. In this context, the present work analyzes the photo-efficiency of two titania catalysts in the solar light assisted photodegradation of isoproturon, and their reuse in two consecutive cycles, where titania catalysts were easily recovery by sedimentation and no catalyst deactivation was observed.This work have been supported by the Spanish Plan Nacional I +D+I throught the projet CTM2010-14883/TECNO.Peer Reviewe

TiO2 and SiO2-TiO2 coated cement: comparison of mechanical and photocatalytic properties

Trabajo presentado en el 8th European Meeting on Solar Chemistry and Photocatalysis, celebrado en Salónica (Grecia) del 25 al 28 de Junio de 2014.Despite regulation straightening, air pollutants concentration is one of the biggest problems that modern society faces, increasingly aware of the danger associated. Solar assisted heterogeneous photocatalysis has become an interesting alternative to degradate NOx and VOCs. In this context, the photoefficiency of four TiO2 coated cements (TiO2-Cem) in Rhodamine B (RhB) and NOx photodegradation tests and the effect of a SiO2 interlayer (SiO2-TiO2-Cem) on the mechanical and photocatalytic properties has been analyzed. Although a good photodegradation was always achieved, the home-made titania (TEA) showed the best global behavior in both series.This work have been supported by the Spanish Plan Nacional I +D+I throught the projet CTM2010-14883/TECNO.Peer Reviewe

Photocatalytic degradation of phenol and isoproturon: Effect of adding an activated carbon to titania catalyst

An integrated process based on combination of adsorption, with a commercial activated carbon (AC), and heterogeneous photocatalysis, with a home-made titania catalyst (TiEt), has been studied in phenol and isoproturon removal. In this work, different physical mixtures of TiEt and AC catalysts were first studied in phenol photodegradation in order to optimize the TiEt/AC concentration ratio. In this sense, a higher degree of mineralization and an improvement of phenol photodegradation were reached with a 500/100 TiEt/AC mixture (500 mg L−1 TiO2: 100 mg L−1 AC) in the same photoassisted reactor in ambient conditions. The best photo-efficiency found with this TiEt/AC physical mixture can be well explained by means of a synergistic effect between both catalysts, where the activated carbon and titania particles interaction provides the formation of an active common contact interphase between both materials, and part of the adsorbed compounds on AC surface are photo-oxidized by the active species photogenerated in titania particles under irradiation conditions. Nevertheless, the higher photo-efficiency found during isoproturon photo-oxidation, when AC was combined with TiO2 in aqueous suspensions, is better related to an associative phenomena where an important adsorption step with the commercial AC is followed by photo-oxidation with the home-made titania catalyst, leading to a moderate improvement in TOC removal efficiency.This work has been supported by the Spanish Plan Nacional de I+D+i through the project CTM2010-14883/TECNO. Jaime Carbajo thanks to the Spanish Ministerio de Economía y Competitividad (MINECO) for his FPI grants, and Patricia Garcia-Muñoz thanks CSIC and SECAT for her initial research grants.Peer Reviewe

TiO2 and TiO2–SiO2 coated cement: Comparison of mechanic and photocatalytic properties

An increasingly known application of nanomaterials in the construction industry is related to the photoactivity ability of semiconductors, where nano-anatase TiO2 is perhaps the most well-known photocatalytic semiconductor and one which possesses a strong oxidizing capability. To analyze the photo-efficiency of four TiO2 coatings and the effect of SiO2 interlayer on the mechanic and photocatalytic activity in Rhodamine B (RhB) and NOx photodegradation, two photocatalytic cement series have been prepared. First, cement mortar was coated with three commercial TiO2 suspensions (GG1, GC7 and CG13) and a home-made titania sol–gel (TEA), and secondly an insertion of a SiO2 layer was applied on cement surface before spraying the TiO2 layer. All studied TiO2-cements exhibited a significant RhB and NOx photodegradation, arising almost total RhB molar conversions, and upper 53% for NOx photo-oxidation respectively. Nevertheless, although SiO2 layer deposited in between mortar and TiO2-cement did not stabilize the commercial TiO2 coatings, a good adhesion was observed when silica was applied joint to the home-made titania gel (TEA), probably as a consequence of the interactions encountered between SiO2 and TiO2 gels. CG7-Si-Cem exhibited high rate at shorter irradiation times, but TEA-Cem and TEA-Si-Cem can be considered as very interesting and potential photocatalytic mortars due to useful mechanical properties, with a very good coatings adhesion that provides promising outdoor use, and good photo-efficiencies in RhB and NOx photo-oxidation.This work has been supported by the Spanish Plan National I+D+I through the project CTM2010-14883/TECNO.Peer Reviewe

Performance of Iron-Functionalized Activated Carbon Catalysts (Fe/AC-<i>f</i>) on CWPO Wastewater Treatment

Two commercial activated carbon were functionalized with nitric acid, sulfuric acid, and ethylenediamine to induce the modification of their surface functional groups and facilitate the stability of corresponding AC-supported iron catalysts (Fe/AC-f). Synthetized Fe/AC-f catalysts were characterized to determine bulk and surface composition (elemental analysis, emission spectroscopy, XPS), textural (N2 isotherms), and structural characteristics (XRD). All the Fe/AC-f catalysts were evaluated in the degradation of phenol in ultrapure water matrix by catalytic wet peroxide oxidation (CWPO). Complete pollutant removal at short reaction times (30–60 min) and high TOC reduction (XTOC = 80 % at ≤ 120 min) were always achieved at the conditions tested (500 mg·L−1 catalyst loading, 100 mg·L−1 phenol concentration, stoichiometric H2O2 dose, pH 3, 50 °C and 200 rpm), improving the results found with bare activated carbon supports. The lability of the interactions of iron with functionalized carbon support jeopardizes the stability of some catalysts. This fact could be associated to modifications of the induced surface chemistry after functionalization as a consequence of the iron immobilization procedure. The reusability was demonstrated by four consecutive CWPO cycles where the activity decreased from 1st to 3rd, to become recovered in the 4th run. Fe/AC-f catalysts were applied to treat two real water matrices: the effluent of a wastewater treatment plant with a membrane biological reactor (WWTP-MBR) and a landfill leachate, opening the opportunity to extend the use of these Fe/AC-f catalysts for complex wastewater matrices remediation. The degradation of phenol spiked WWTP-MBR effluent by CWPO using Fe/AC-f catalysts revealed pH of the reaction medium as a critical parameter to obtain complete elimination of the pollutant, only reached at pH 3. On the contrary, significant TOC removal, naturally found in complex landfill leachate, was obtained at natural pH 9 and half stoichiometric H2O2 dose. This highlights the importance of the water matrix in the optimization of the CWPO operating conditions