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•High organic load and phenolic content difficult OMW treatment and management.•Fenton-like process efficiency is dependent on pH readjustments along the reaction.•Fe3+/H2O2 mass ...ratio is a key parameter affecting the process efficiency.•The catalyst also acts as a coagulant/flocculant agent after the oxidation step.•COD and TPh global reductions of 77% and 96% were achieved, with toxicity reduction.
The efficiency of Fenton/Fenton-like processes on the oxidation of organic matter from real olive mill wastewater (OMW) is described. Tests were performed in lab-scale batch reactors and the influence of different operational parameters was evaluated, namely: type of iron salt, effect of pH readjustments during the reaction, reactants addition method and Fe/H2O2 mass ratio. For the Fenton-like system (Fe3+/H2O2) it was found that H2O2 consumption and consequently total organic carbon (TOC) degradation rate are significantly affected by the reagents addition method, especially in earlier stages of the reaction, although the overall extent of TOC removal is not. Results showed that the gradual addition of H2O2 along with pH readjustments during the process led to better chemical oxygen demand (COD) and total phenolic content (TPh) reduction. Operating at pH0 = 3.0, T0 = 25 °C, Fe3+ = 1.0 g·L−1 and Fe/H2O2 = 0.04, 34.9% of TOC, 55.7% of COD and 81.4% of TPh were removed after 180 min. The same conditions were applied with the assistance of artificial radiation (photo-Fenton-like process) with slight organic matter degradation improvement (41.8% of TOC, 63.2% of COD and 83.8% of TPh removals). The catalyst’s (ferric chloride salt) ability to act as a coagulant/flocculant after the oxidative process was also checked, being reached a global reduction of 76.7% for COD and 96.4% for TPh after 1 h of sedimentation and no further pH adjustments. Moreover, the effluent’s biodegradability (BOD5:COD ratio) after the combined process improved from the initial value of 0.11 to 0.33, and toxicity against the bioluminescent Vibrio fischeri bacteria decreased from 53% to 4%, putting into evidence the possibility of coupling downstream a biological unit so that the final effluent meets legal discharge limits.
Active nickel phase dispersed in a carbon dioxide sorbent is used together with a zinc oxide promoter in the BRM. The 13X zeolite structure of the support used disappears at elevated temperatures, ...inducing moderate Ni crystal sizes and thus disfavoring reaction activity. However, the high-loaded catalyst with larger Ni particle sizes seems to be compensated by the presence of a ZnO promoter. Results show that the Ni-ZnO-13X based catalyst is adequate to perform the BRM reaction.
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•13XZnO20Ni17-u shows promising results for syngas production via BRM reaction.•Higher temperature increases catalyst activity.•Molar ratios of hydrogen-to-carbon monoxide are close to two at high temperatures.•Absence of inert gas in the feed did not influence catalyst activity and selectivity.•50–60% CO2 conversion was achieved at a maximum operating temperature of 800 °C.
Ennoblement of carbon dioxide, particularly the one produced by anaerobic digestion or by biomass combustion, is a motivation to develop novel or improving already existing processes. In this context, an interesting idea is to use carbon dioxide combined together with methane and water. Therefore, bi-reforming of methane (BRM) for syngas production appears to be a good choice. In this work, BRM was studied over a Ni-catalyst supported on a ZnO-doped zeolite 13X in the temperature range 300 to 900 °C. This material was deeply characterized by different techniques. The pure zeolite 13X shows relative good sorption capacity for CO2 at low temperatures (<100 °C). The ZnO phase introduced on zeolite 13X did not show a significant improvement for BRM, while 13X zeolite material impregnated with Ni and ZnO showed promising activities, achieving CO2 conversions in the range of 50–60% at a maximum operating temperature of 800 °C and atmospheric pressure. The results obtained suggest that ZnO acts as an oxygen supplier when methane is activated by surface nickel, thus destabilizing the feed in the following order: methane, water and carbon dioxide. The influence of the operating conditions in the reactants conversion and products distribution was also analyzed, and it can be concluded that the molar ratios of hydrogen-to-carbon monoxide are close to two at high temperatures.
Functionalized graphene derivatives including graphene oxide (GO), reduced graphene oxide (rGO), and heteroatom (nitrogen/sulphur (N/S) or boron (B))-doped graphene were used to synthesize composites ...with TiO2 (T). The photocatalytic performance of composites was assessed for the degradation of Orange G dye (OG) under simulated solar light. All the prepared graphene derivatives—TiO2 composites showed better photocatalytic performance than bare TiO2. A higher photocatalytic activity was found for the composites containing GO and N/S co-doped rGO (kapp = 109.2 × 10−3 and 48.4 × 10−3 min−1, for GO-T and rGONS-T, respectively). The influence of both initial solution pH and the reactive species involved in the OG degradation pathway were studied. The photocatalytic activity of the samples decreased with the increase of the initial pH (from 3.0 to 10.0) due to the occurrence of electrostatic repulsive forces between the photocatalysts surface and the molecules of OG, both negatively charged. The use of selective scavengers showed that although the photogenerated holes dominate the degradation mechanism, radicals and singlet oxygen also participate in the OG degradation pathway. In addition, reutilization experiments indicated that the samples were stable under the reaction conditions used.
Graphitic carbon nitride (g-C3N4) was used to enhance the photocatalytic activity of ZnO nanoparticles for the degradation of 5-fluorouracil (5-FU) cytostatic drug under UV-LED irradiation. CN/ZnO ...composites were synthetized by an easy one-pot thermal method, varying the g-C3N4 loading, i.e., from 10 to 67 wt% and a post-thermal exfoliation in air. The physicochemical and optical properties of the materials were analyzed by several techniques. CN/ZnO composites showed a coral-like structure of spherical ZnO wurtzite particles on the g-C3N4 structure. In general, the synergism and heterojunction interface between both phases allowed the enhancement of the mesoporosity, light absorption ability, and the aromaticity of the corresponding composites. Moreover, the photocatalytic activity of the CN/ZnO composites was increased with the addition of g-C3N4 in comparison with pristine ZnO. The highest activity was found for the composite containing 25 wt% of g-C3N4 (i.e., CN25/ZnO), reaching the total degradation of 5-FU and a mineralization of 48% at 180 min, as well as a good photostability during four reuse cycles. Experiments with different pH solutions and scavengers allowed for the assessment of the reactive oxygen species (ROS) involved in the 5-FU degradation pathway, with radicals and non-radical species as the main responsible active species. Furthermore, a tentative photocatalytic mechanism was proposed for CN/ZnO composites.
A series of biochars and activated carbons (ACs) was prepared combining carbonization and physical or chemical activation of cheap and abundant residues of the olive oil industry. These materials ...were used as Fe-support to develop low-cost catalysts for the heterogeneous Fenton-like oxidation of simulated olive mill wastewater (OMW), the highly pollutant effluent generated by this agroindustry. Commercial ACs were also used as reference. All catalysts prepared were extensively characterized and results related with their performances in the catalytic wet peroxide oxidation (CWPO). Results showed a linear relationship of the textural properties of the catalysts with the adsorptive and catalytic performance, as well as the preferential adsorption and degradation of some phenolic compounds (caffeic and gallic acids) by specific interactions with the catalysts' surface. Despite the best performance of catalysts developed using commercial supports, those prepared from agro-industrial residues present some advantages, including a smaller catalyst deactivation by iron leaching. CWPO results show that catalysts from physically activated olive stones are the most promising materials, reaching total organic carbon and toxicity reductions of 35% and 60%, respectively, as well an efficient use of H
O
, comparable with those obtained using commercial supports. This approach showed that the optimized treatment of this type of residues will allow their integration in the circular economic process of the olive oil production.
A supported gold nanoparticle-catalyzed strategy has been utilized to promote a click chemistry reaction for the synthesis of 1,2,3-triazoles via the azide-alkyne cycloaddition (AAC) reaction. While ...the advent of effective non-copper catalysts (i.e., Ru, Ag, Ir) has demonstrated the catalysis of the AAC reaction, additional robust catalytic systems complementary to the copper catalyzed AAC remain in high demand. Herein, Au nanoparticles supported on Al2O3, Fe2O3, TiO2 and ZnO, along with gold reference catalysts (gold on carbon and gold on titania supplied by the World Gold Council) were used as catalysts for the AAC reaction. The supported Au nanoparticles with metal loadings of 0.7–1.6% (w/w relative to support) were able to selectively obtain 1,4-disubstituted-1,2,3-triazoles in moderate yields up to 79% after 15 min, under microwave irradiation at 150 °C using a 0.5–1.0 mol% catalyst loading through a one-pot three-component (terminal alkyne, organohalide and sodium azide) procedure according to the “click” rules. Among the supported Au catalysts, Au/TiO2 gave the best results.
A series of Ni-doped carbon aerogels with different Ni loadings were prepared and extensively characterized from a textural, chemical and electro-chemical point of view. The formation of graphitic ...clusters on nickel particles was specially analysed by XPS and Raman spectroscopy. Electro-capacitive properties were studied by cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy in a three and two-electrode cell, and in acidic media and non-aqueous aprotic electrolyte.
The use of Ni as a polymerization catalyst slightly decreases the micropore volume of the carbon aerogels but on the contrary, a great increase in their mesopore volume was obtained. All samples present high gravimetric capacitances, ranging from 182 to 219 F g−1 in 1 M H2SO4, and from 49 to 63 F g−1 in 1 M tetraethylammonium tetrafluoroborate. Results show that the equivalent series resistances decrease as the Ni content increases and the capacitance increases in the same sense. This trend is directly related to the presence of a good developed mesopore network in Ni-doped carbon aerogels and a better electrical conductivity due to the formation of the graphitic clusters around the Ni particles. The stability of the charge-discharge cycles, studied by floating tests, showed a very good performance of the doped-carbon aerogels.
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Gradients in elevation impose changes in environmental conditions, which in turn modulate species distribution and abundance as well as the interactions they maintain. Along the gradient, interacting ...species (e.g., predators, parasitoids) can respond to changes in different ways. This study aims to investigate how egg parasitism of a forest pest, the pine processionary moth (PPM), Thaumetopoea pityocampa, vary along an elevational gradient (190–2000 m.a.s.l.) in a mountain range of SE Spain, including areas of recent elevational expansion, for a seven years period (2008–2014). We used generalized linear mixed models to ascertain the effect of both elevation and the winter North Atlantic Oscillation (NAO) index (a proxy of interannual climatic conditions) on the rate of parasitism, and the occurrence probabilities of two parasitoid species: a PPM specialist and a generalist species. Since four pine species are stratified along the elevational gradient, we repeated all the analyses separately for lowlands (190–1300 m. a.s.l.) and uplands (1350–2000 m. a.s.l.). Results showed a decrease in both parasitism rate and probability of occurrence of the two main parasitoid species with elevation, although decline was more severe for the specialist species. The effect of elevation was more conspicuous and intense in uplands than in lowlands. Positive NAO winter values, associated with cold and dry winters, reduced the rate of parasitism and the probability of occurrence of the two main parasitoid species—but particularly for the generalist species—as elevation increases. In a context of climate warming, it is crucial to mitigate PPM elevational and latitudinal expansion. Increasing tree diversity at the PPM expansion areas may favor the establishment of parasitoids, which could contribute to synchronizing host– parasitoid interactions and minimize the risk of PPM outbreaks.
In this study, co-precipitation and hydrothermal synthesis methods were employed to prepare two types of magnetite nanoparticles (MNPs). An activated carbon derived from olive stones (OSAC) was used ...as MNPs-support. The physicochemical properties of the resulting OSAC-MNPs catalysts were determined using various characterization techniques. A more homogeneous distribution of larger and well-defined MNPs was obtained by hydrothermal synthesis, resulting in a more extensive blockage of the microporous structure of the support. Both catalysts exhibited paramagnetic behavior, but with relatively low magnetization due to the small size and low crystallinity of the Fe3O4 nanoparticles obtained. The catalytic peroxidation performance of OSAC-MNPs was studied using tyrosol (TY) as a model compound, but also real samples of winery wastewater (WW) were used in the optimized operational conditions, including pH, temperature, and doses of catalyst and hydrogen peroxide. The MNPs-based catalyst prepared by co-precipitation performed better in the range of experimental conditions tested because of the higher surface concentration of active phase that is easily accessible to the pollutant and was less prone to deactivation during successive reaction runs. The combination of active materials and optimized process enables to remove up to 92 % TPh, 35 % COD, and 26 % TOC, while the high stability of the samples associated to a low Fe-leaching (0.07 mg L−1) permits the reuse of materials in consecutive cycles.
•An agricultural by-product – olive stone – is integrated in winery wastewater treatment•Co-precipitation and hydrothermal methods are employed for MNP-catalysts synthesis•Tyrosol oxidation is correlated with the chemical & morphological properties of the materials•Fe surface distribution and size is key for MNP-catalysts' peroxidation efficiency•Consistently low iron leaching obtained in real wastewater treatment experiments
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