Carbon Species Research Articles

Source apportionment of water-soluble oxidative potential of PM2.5 in a port city of Xiamen, Southeast China

The main objective of this study was the source attribution of the water-soluble oxidative potential of PM2.5 in Xiamen, China. Mean concentrations of individual water-soluble trace elements varied within a wide range from <1 ng m−3 to >100 ng m−3 between November 2015 and May 2018. Their fractional solubility ranged from <5% to >70%, depending mainly on the origin, followed by meteorological conditions and atmospheric aging. The annual mean value of the volume-normalized dithiothreitol activity (DTTv) in PM2.5 between January 2017 and May 2018 in the urban area (0.632 ± 0.299 nmol min−1 m−3) was higher than in the suburban area (0.562 ± 0.247 nmol min−1 m−3) (p < 0.05), which was consistent with the spatial difference of transition metals and carbon species. DTTv were lower in summer than in winter (p < 0.05), consistent with the variations in Cu and Mn, which accounted for more than 94% of the reconstructed DTTv. DTTv could not be predicted well by lifetime cancer risk (LCR) and hazard index (HI), because the main contributors to HI (V, Ni, and Mn) and LCR (Cr(VI) and V) were different from those of DTTv. Based on the positive matrix factorization (PMF) and the multiple linear regression (MLR) models, the identified sources of DTTv at the urban/suburban sites were as follows: vehicle exhaust + biomass burning (39.9%/24.2%), primary organic aerosol (19.5%/23.9%), secondary nitrate/chlorine (10.5%/18.4%), secondary sulfate + ship emissions (18.2%/7.8%), mineral dust (2.3%/20.0%), and coal combustion (9.7%/5.6%). The results differed from those for PM2.5, LCR and HI, which had larger contributions from coal combustion and secondary sulfate + ship emission.

Quantification of carboxylic binding sites on functionalized silicon nitride surface through X-ray photoelectron signal and fluorescence labelling

The wet-chemical functionalization of inorganic surfaces by organic bifunctional interlayers is a viable method towards the realization of optical (bio-)sensing devices. A detailed description of the organic-inorganic interface and a quantification of the surface functional group density is desirable, as they will determine the interaction of the transducer surface with the bioreceptor, thus final sensor efficiency. By characterizing surfaces at different sample preparation stages, we demonstrate that X-ray photoelectron spectroscopy (XPS) can be used to identify different coexisting carbon species at the interface as well as to quantify the packing density of the bifunctional interlayer. As a model system for proof-of-concept, the silicon nitride surface was functionalized with a dodecanoic acid molecule bearing a carboxylic end group, and the molecular packing density was quantified both via standard fluorescence-based labelling and XPS attenuation. Our combined approach identifies the fraction of bioreceptor-accessible and -inaccessible binding sites on the functionalized surface. This information will help to optimize the formation of dense layers of immobilized bioreceptors at the transducer surface.

Plastic residues alter soil microbial community compositions and metabolite profiles under realistic conditions

Wide usage of plastic coupled with mismanagement has created a humongous environmental hazard threatening entire ecosystems. To date, the potential effects of plastic debris-induced soil nutrition substance changes and the relevant microbial metabolic behavior remain unclear. Here, we studied the effect of plastic films polyethylene and polylactic acid in differential soil environments (farmland, woodland, and wetland) for 120 days. Soil enzyme activities (urease, neutral phosphatase, and catalase) and nutrition substance (NH4+-N, available P, available K, and soil organic matter) present obvious variations in polylactic acid groups compared to polyethylene-treated samples. 16S rRNA gene sequencing indicates that several bacteria abundance such as Bacteroidales, Actinobacteriota, Nitrososphaeraceae, Pyrinomonadalcs, Muribaculaceae, exhibited obvious up-regulation or down-regulation, and simultaneously, the carbon, nitrogen, and phosphorus cycling relevant species Bryobacter, Bradyrhizobium, and Sphingomonas, expressed wider margin of down-regulation in abundance in plastic treatment soil samples. As a result, the abundance of metabolites including sugar, amino acid, and fatty acids, which may associated with nutrition substance metabolic pathways, were significantly altered in the stress of plastic. These findings provide valuable information on the environmental effects of plastics, and the relationships of subsequent nutrition substance changes and microbial metabolic behavior.

Operando ME-DRIFTS study of reaction intermediates during toluene oxidation on CeO2 nanoparticles supported on MgO hexagonal plates

Operando DRIFT spectroscopy was employed to investigate the intermediates involved in the oxidation of toluene on highly dispersed ceria nanoparticles supported on magnesium oxide hexagonal nanoplates. Small CeO2 nanoparticles dispersed on magnesium oxide hexagonal nanoplates showed enhanced catalytic performance to total toluene combustion compared to a high surface area polycrystalline CeO2. Selective identification of active surface species was carried out by combining concentration-modulation excitation spectroscopy (c-MES) experiments with phase-sensitive detection (PSD) spectral analysis and a chemometric multivariate curve resolution alternating least squares (MCR-ALS) method. The results revealed a stepwise reaction pathway for toluene oxidation on the catalyst surface. Initially, toluene is molecularly adsorbed and reacts with surface oxygen species to produce intermediate benzyl (C6H5CH2-). Next, benzyl is stepwise oxidized to benzyloxy/benzyl alcohol, benzaldehyde, and benzoate. Further oxidation of benzoate and the aromatic ring produces formate and carbonate species. On pure CeO2, formates accumulate on the ceria surface, and only a minor part of them reacts to produce CO2 (and CO). Instead, formates species are rapidly oxidized to CO2 on the CeO2/MgO catalyst and do not accumulate on the surface, due to the enhanced redox capacity and higher presence of oxygen vacancies of the supported nanoparticles.

4D Printable Salicylic Acid Photopolymers for Sustained Drug Releasing, Shape Memory, Soft Tissue Scaffolds.

3D printing of pharmaceuticals offers a unique opportunity for long-term, sustained drug release profiles for an array of treatment options. Unfortunately, this approach is often limited by physical compounding or processing limitations. Modification of the active drug into a prodrug compound allows for seamless incorporation with advanced manufacturing methods that open the door to production of complex tissue scaffold drug depots. Here we demonstrate this concept using salicylic acids with varied prodrug structures for control of physical and chemical properties. The role of different salicylic acid derivatives (salicylic acid, bromosalicylic allyl ester, iodosalicylic allyl ester) and linker species (allyl salicylate, allyl 2-(allyloxy)benzoate, allyl 2-(((allyloxy)carbonyl)oxy)benzoate) were investigated using thiol-ene cross-linking in digital light processing (DLP) 3D printing to produce porous prodrug tissue scaffolds containing more than 50% salicylic acid by mass. Salicylic acid photopolymer resins were all found to be highly reactive (solidification within 5 s of irradiation at λ = 405 nm), while the cross-linked solids display tunable thermomechanical behaviors with low glass transition temperatures (Tgs) and elastomeric behaviors, with the carbonate species displaying an elastic modulus matching that of adipose tissue (approximately 65 kPa). Drug release profiles were found to be zero order, sustained release based upon hydrolytic degradation of multilayered scaffolds incorporating fluorescent modeling compounds, with release rates tuned through selection of the linker species. Cytocompatibility in 2D and 3D was further demonstrated for all species compared to polycarbonate controls, as well as salicylic acid-containing composites (physical incorporation), over a 2-week period using murine fibroblasts. The use of drugs as the matrix material for solid prodrug tissue scaffolds opens the door to novel therapeutic strategies, longer sustained release profiles, and even reduced complications for advanced medicine.

Enhanced synthesis of C2+ alcohols from syngas over a Co-Co2C catalyst supported on mesoporous carbon–silica composites

Higher alcohol synthesis (HAS) from syngas is a promising route for converting non-petroleum fossil energy resources into useful fuels or chemicals, while the design and preparation of highly efficient catalysts remain challenging. Herein, a series of Co0-Co2C catalysts supported on mesoporous carbon–silica composites were prepared for HAS. The composites were derived from carbon-silica nanocages, consisting of uniformly distributed carbon and silica species, which significantly affected the particle dispersion, phase evolution and catalytic performance. With increasing the carbon content, the initial carburization of cobalt was promoted, and some obtained Co2C tended to convert to hexagonal closest packed cobalt (hcp-Co, a highly active site for Fischer-Tropsch), boosting the CO dissociation and catalyst activity. While as the silica content increased, more Co2C phases can be stabilized, leading to enhanced Co2C/Co0 ratio and ROH selectivity. As a result, the optimal 15Co/22Si@C catalyst achieved a ROH selectivity of 40.1% where 96.0 wt% was higher alcohols (HA), and a space time yield (STY) towards HA of 26.5 mmol·gcat−1·h−1, which remarkably outperformed most of the reported Co-based catalysts in HAS. Moreover, the superior stability of over 250 h reaction was obtained, owing to the confinement effect and strong metal-support interaction provided by the mesoporous carbon–silica composites. This work may provide guidance for designing high-performance monometallic cobalt catalyst in HAS.

Defect control and optical performance of yttrium orthovanadate nanocrystals via a facile pH-sensitive synthesis

Nanocrystalline YVO4 powders have been synthesized via a facile co-precipitation method, which has been investigated over the wide pH range from 4 to 13. XRD patterns indicated that the phase structure purity of the precipitation is influenced by the pH value. The reaction mechanism of YVO4 crystal was suggested to illustrate the development stages beginning with precipitates to form impure amorphous phase structures such as amorphous yttrium polyvanadate and hydrous Y(OH)3. SEM and TEM techniques were performed to observe the changes of the morphology and size by adjusting the pH conditions after YVO4 nanocrystals were sintered under ambient conditions at 600 °C for 2 h. Luminescence properties showed that the self-activated emission of YVO4 matrix material shows an obvious peak at 486 nm in the 400–650 nm wavelength range, attributing to the charge transfer in the vanadate groups. With decreasing the pH value, the diffuse reflectance spectra of YVO4 nanocrystals demonstrated that the energy gap Eg showed a red-shift trend mainly ascribed to the oxygen vacancies. Moreover, the luminescence emission intensity of YVO4 nanocrystals increases obviously after sintering treatment, which can be explained by the sintering-induced grain growth and improved surface band bending due to the dehydration or the removal of carbonate species. The findings of this study could provide new insights into the understanding of the reaction mechanism of YVO4 crystal with variable optical band gap and offer an opportunity for realizing tunable optical performance by defect structure regulation for laser and optoelectronics applications.

Plasma functionalization mechanism to modify isocyanate groups on multiwalled carbon nanotubes

This article reports a possible functionalization mechanism of isocyanate (NCO) groups on multiwalled carbon nanotubes (CNTs) with low-temperature plasma. The mechanism was clarified according to the analysis with two plasmas generated with the gas mixture of (1) nitrogen and carbon dioxide and (2) nitrogen and oxygen. We analyzed the mechanism through optical emission spectroscopy from these plasmas and the NCO functionalization ratio measured with the fluorescent method after plasma exposure over CNTs. The optical emission gave us information on the quantitative analysis of the gas species of atomic nitrogen (N), atomic oxygen (O), and carbon monoxide (CO) and the qualitative analysis of carbon nitride (CN) species in the plasma. Compared with our results from the gas species in the plasma and the NCO functionalization ratio on CNTs, CO and CN species in the gas phase in plasma are less likely to contribute to forming NCO groups on CNTs. Rather, the equal densities of atomic nitrogen and oxygen species in the plasma could be effective in forming NCO groups on the CNT surface: the NCO groups should form by N, O, and carbon (C) species on the CNT surface. The groups likely build up gradually by N, O, and C individually reaching a CNT surface, or the NCO radicals form in the gas phase and then attach to the CNT surface.

Stability of Iridium Single Atoms on Fe3O4(001) in the mbar Pressure Range.

Stable single metal adatoms on oxide surfaces are of great interest for future applications in the field of catalysis. We studied iridium single atoms (Ir1) supported on a Fe3O4(001) single crystal, a model system previously only studied in ultra-high vacuum, to explore their behavior upon exposure to several gases in the millibar range (up to 20 mbar) utilizing ambient-pressure X-ray photoelectron spectroscopy. The Ir1 single adatoms appear stable upon exposure to a variety of common gases at room temperature, including oxygen (O2), hydrogen (H2), nitrogen (N2), carbon monoxide (CO), argon (Ar), and water vapor. Changes in the Ir 4f binding energy suggest that Ir1 interacts not only with adsorbed and dissociated molecules but also with water/OH groups and adventitious carbon species deposited inevitably under these pressure conditions. At higher temperatures (473 K), iridium adatom encapsulation takes place in an oxidizing environment (a partial O2 pressure of 0.1 mbar). We attribute this phenomenon to magnetite growth caused by the enhanced diffusion of iron cations near the surface. These findings provide an initial understanding of the behavior of single atoms on metal oxides outside the UHV regime.

Community-driven research and capacity building to address environmental justice concerns with industrial air pollution in Curtis Bay, South Baltimore.

Curtis Bay (CB) is an environmental justice (EJ) community in South Baltimore. With a high concentration of industrial polluters and compounding non-chemical stressors, CB has experienced socioeconomic, quality of life, and health burdens for over 100 years. Today, these polluters include the open-air CSX Coal Terminal, waste-to-energy incinerators, and heavy diesel traffic through residential areas. The Community of Curtis Bay Association, Free Your Voice, and South Baltimore Community Land Trust are local organizations enacting a vision for equitable, healthy, and community-led development without industrial encroachment. In response to community-identified EJ concerns and an explosion at the CSX Coal Terminal, CB community groups partnered with academic researchers to develop a community-driven hyperlocal air monitoring and capacity building approach. This paper describes this approach to characterizing hyperlocal air quality in CB, building bridges between community residents and regulatory agencies, and nurturing a cohesive and effective community-academic partnership toward EJ. Using hyperlocal air monitoring, we are collecting real-time air pollution (particulate matter, black carbon, and ground-level gas species) and meteorological data from 15 low-cost sensors in residential and industrial areas of CB. We also use trail cameras to record activities at the CSX Coal Terminal. We merge air pollution and industrial activity data to evaluate the following: overall air quality in CB, multi-air pollutant profiles of elevated events, spatiotemporal changes in air quality in the community, patterns of industrial activity, and potential correlations between air quality and observed industrial activity. Members of our partnership also lead a high school course educating students about the history and ongoing efforts of the EJ movement in their community. Students in this course learn how to employ qualitative and quantitative data collection and analysis methods to bring scientific support to community EJ concerns. Our hyperlocal air monitoring network and community-academic partnership are continuing to evolve and have already demonstrated the ability to respond to community-identified EJ issues with real-time data while developing future EJ leaders. Our reflections can assist other community and academic groups in developing strong and fruitful partnerships to address similar EJ issues.

CO2 -Mediated Photocatalytic Chlorine Production Over Bismuth Oxychloride in Chloride Solution.

As one of the most commonly bulky chemicals, chlorine is conventionally manufactured by electrolysis of NaCl solution in the chlor-alkali process, which requires a huge supply of electrical energy. The photocatalytic route to produce chlorine by using solar energy and NaCl solution offers a promising strategy to reduce energy consumption and bring economic benefits. Herein, it was found that the introduction of CO2 would enhance the productivity of Cl2 from 8.24 μmol⋅h-1 to 39.6 μmol⋅h-1 in NaCl solution over BiOCl. Experimental studies reveal that the CO2 species (CO3 2- ) entered into the crystal texture of BiOCl and the interlayer space between [Bi2 O2 ]2+ slabs were increased and distorted, accelerating the cycle of Cl species. Besides, the cycle of carbonate species also existed and accelerated the reaction efficiency of Cl- oxidation to Cl2 . This work provides a new feasible method of using abundant CO2 resources to accelerate the process of chlorine production via photocatalysis.

Submarine Groundwater Discharge Strengthens Acidification in the Coastal Semi‐Closed Bays

AbstractCoastal ocean acidification is a worldwide problem associated with anthropogenic activity and climate change. In this study, a close relationship between submarine groundwater discharge (SGD) and coastal ocean acidification in Hong Kong's coastal waters is discovered. We for the first time evaluated the direct influence of SGD on seawater pH decline. Results show that SGD can contribute to up to 48% of seawater pH variation among terrestrial water input, air‐sea CO2 exchange, photosynthesis/respiration, and bay‐open water exchange in semi‐closed bays through direct input of carbonate species. Local air‐sea CO2 exchange has negligible influences on the seawater pH. In the semi‐closed bay areas, SGD and aerobic respiration are major contributors to seawater pH variation but in areas with open space, the exchange process with open waters is more important. In addition to the direct input of carbonate species (total alkalinity and dissolved inorganic carbon), SGD also influences the seawater pH via considerable nutrient loadings. The findings highlight the importance of the investigation and management of groundwater to alleviate the fast coastal ocean acidification.

Plasma-catalytic pyrolysis of polypropylene for hydrogen and carbon nanotubes: Understanding the influence of plasma on volatiles

Plasma-catalytic pyrolysis was developed for upgrading polypropylene (PP) pyrolysis volatiles to co-produce carbon nanotubes (CNTs) and hydrogen. To uncover the role of plasma on the plastic catalytic pyrolysis process, the pyrolysis of polypropylene (PP) over Fe/γ-Al2O3 was carried out in a two-stage pyrolysis system with a coaxial dielectric barrier discharge (DBD) plasma reactor. The results showed that the plastic pyrolysis volatiles were further cleaved and activated with plasma, resulting in more active carbon species for the growth of CNTs. Compared to conventional catalytic pyrolysis, plasma addition shifted the initial formation temperature of CNTs to a lower ambient temperature by ∼100 °C, and significantly promoted the conversion of liquid and gaseous products to CNTs and hydrogen, with higher carbon and hydrogen yields of ∼322 mg/gplastic and 30 mmol/gplastic, respectively. In addition, the degree of graphitization of the CNTs in the presence of the plasma was significantly enhanced with less defectivity. The influence of catalytic temperature variation caused by plasma on CNTs growth was also discussed from the perspective of volatile evolution. This work highlights the potential of plasma-catalytic pyrolysis for the production of hydrogen and high-value carbon materials from plastic waste.

The 14C dose assessment model chain – 14C source term definition and uncertainty quantification

Abstract. Carbon-14 (14C) is an important, dose-determining contributing radionuclide in a deep geological repository for low and intermediate level radioactive waste (L/ILW). 14C is relevant for safety assessments as it can be present both as dissolved and gaseous species in the disposal facility and the host rock, and 14C-organic compounds migrate in the near field and the geosphere due to weak interaction with mineral surfaces in alkaline to near-neutral conditions. Thus, the chemical form of the 14C-bearing carbon species dictates the routes of 14C migration in the engineered barrier system of a deep geological repository and the surrounding host rock and therefore determines the long-term contribution of 14C to dose release from a repository for radioactive waste. Furthermore, 14C released from a deep repository would be subject to a certain accumulation in the biosphere, given the role of carbon as main building block of any life form on earth. The contribution will illustrate Nagra's recent progress within the 14C dose assessment model chain for a L/ILW deep geological repository to address the quantification of uncertainties. The systematic approach began by incorporating a realistic best-estimate plus uncertainty description of 14C activities within the Swiss model inventory of radioactive materials assembled specifically for the purpose of the general licence application. In this context state-of-the-art activation calculations for expected reactor and decommissioning wastes as well as extensive inquiries into origin and use of 14C within medicine, research, and industry played a key role. Uncertainties were screened for relevance and main contributing factors taken into account, differentiating between the characterisation methods of the relevant waste streams. Based on detailed knowledge of the expected activity and material inventory, release rates for the release pathways through congruent and instantaneous release processes as well as resulting chemical species could be defined with confidence. Key findings and characteristics of the 14C source term will be highlighted and discussed.

Aluminum-Boron Bond Formation by Boron Ester Oxidative Addition at an Alumanyl Anion.

The potassium diamidoalumanyl, [K{Al(SiNDipp)}]2 (SiNDipp = {CH2SiMe2NDipp}2), reacts with the terminal B-O bonds of pinacolato boron esters, ROBpin (R = Me, i-Pr), and B(OMe)3 to provide potsassium (alkoxy)borylaluminate derivatives, [K{Al(SiNDipp)(OR)(Bpin)}]n (R = Me, n = 2; R = i-Pr, n = ∞) and [K{Al(SiNDipp)(OMe)(B(OMe)2)}]∞, comprising Al-B σ bonds. An initial assay of the reactivity of these species with the heteroallene molecules, N,N'-diisopropylcarbodiimide and CO2, highlights the kinetic inaccessibility of their Al-B bonds; only decomposition at high temperature is observed with the carbodiimide, whereas CO2 preferentially inserts into the Al-O bond of [K{Al(SiNDipp)(OMe)(Bpin)}]2 to provide a dimeric methyl carbonate species. Treatment of the acyclic dimethoxyboryl species, however, successfully liberates a terminal alumaboronic ester featuring trigonal N2Al-BO2 coordination environments at both boron and aluminum.

Effects of organic matter and alkalinity on the ozonation of antiviral purine derivatives as exemplary micropollutant motif.

Ozonation of micropollutants strongly depends on the water matrix. Natural organic matter is known to highly affect the hydroxyl radical exposure due to radical promoting and inhibiting effects. Other important matrix components in ozonation are carbonate species which scavenge hydroxyl radicals. However, additional factors such as the formation of other radicals might also play a role but are generally not covered in research or considered in modelling of micropollutant degradation. Hence, the ozonation of purine derivatives, the basic structure of various antiviral micropollutants, in different artificial water matrices is investigated in this study with focus on the impact of natural organic matter and increasing alkalinity on the degradation and product formation. The degradation of purine and adenine is inhibited by bicarbonate in the water matrix due to the anion's scavenging of hydroxyl radicals. This effect is already observed for low bicarbonate concentrations of 0.3mM. However, formed carbonate radicals contribute to the compounds' degradation and also affect the stability of transformation products. This effect gains in relevance with increasing alkalinity and needs consideration in evaluating ozonation of very hard waters. Three ozonation products are evaluated in detail, which are affected by the matrix due to impacts on ozone stability, hydroxyl radical yield and carbonate radical formation. One product of adenine with the mass 147 was reported for the first time and only occurs in presence of matrix components. Under typical water treatment conditions rough predictions of pollutants' degradation are possible by the Rct concept using ozone and hydroxyl radical exposures. However, other reactive species such as carbonate radicals are not considered leading to deviations between modelled and experimental data at extreme conditions such as industrial wastewater. A general correlation between the Rct and the fraction f of hydroxyl radicals scavenged by bicarbonate (ln(Rct)=-5.9×f-16.3) calculated from the concentration of organic matter and alkalinity was observed for various water samples allowing the estimation of micropollutant degradation during ozone treatment at moderate conditions by simple organic and inorganic carbon measurements.

Construction of high-capacitance carbonate-rich bimetallic layered (hydr)oxides onto ZIF-67–derived Co/CoO-N-carbon hybrid cubes for high-performance symmetric supercapacitors

Herein, we fabricated carbonate-rich bimetallic layered hydr(oxides) (CoMnOx), which are primarily used as active materials for supercapacitors, using a simple hydrothermal method. CoMnOx was deposited onto cobalt oxide (CoO), which was produced by pyrolyzing ZIF-67 at 800 °C under N2 atmosphere. The Co/CoO cubes synthesized using carbonized ZIF-67 (ZIFC) were covered with CoMnOx shells with high reduction efficiency and abundant Co active sites and surface O species. The effects of the carbonate species present between the CoMnOx layers and at the surface of the hybrid CoMnOx@ZIFC materials were evaluated using PXRD and XPS. The peaks at the binding energies of 290 and 400 eV in the C 1s and N 1s XPS profiles of CoMnOx@ZIFC, respectively, indicate the presence of carbonate species and coordination of CoO and Co with the N-rich carbon materials, respectively. The FE-SEM images of CoMnOx@ZIFC revealed the partial decomposition of the cubic structure of ZIFC, which agreed with previously reported data. Moreover, the elemental composition of CoMnOx@ZIFC was confirmed using EDS mapping and point analysis. The CoMnOx@ZIFC electrodes exhibited a remarkable specific capacitance/capacitor of 963 F g−1/588 C g−1 at 1 A g−1 and excellent cycling stability over 1000 cycles, which was superior to those of previously reported MOF-derived carbonate-based materials in alkaline electrolytes. The CoMnOx@ZIFC||CoMnOx@ZIFC symmetric supercapacitor exhibited an energy density of 60.75 W h kg−1 with a power density of 5947 W kg−1 and an exceptional cycling stability (>99.5 %) after 3000 cycles.

Physical and reactive absorption of CO2 in capillaries: Mass transfer, modelling and produced chemical species

In a circular economy and sustainability context, CO2 utilization is key. For photochemical or electrochemical transformations, CO2 absorption in liquids has become crucial and even a limiting step. This work aimed to establish an average mass transport coefficient (k̅La) characteristic of the CO2 absorption in water and in alkaline solutions in capillary absorbers (2–4 mm) under Taylor flow and recirculation mode. A correlation among prevailing dimensionless numbers (Sh, Re, Ca and Sc) was also established. To achieve so, the absorption of CO2 was conducted in both, water and NaOH solutions (0.5 mol/dm3), and its concentration was monitored by measuring total inorganic carbon and pH. The gas and liquid flowrates used for the tests were 1.66×10−4 L/s and 2.5×10−4 L/s, respectively. The effect of temperature was investigated in the range of 283 and 308 K. The highest k̅La was found to be 12 × 10−2 and 2.1 × 10−2 s−1, for water and NaOH solutions, respectively. The modelling and simulation of the carbon species formation and production was also conducted and a determination coefficient (R2) of 0.99 was found.

High catalytic performance of CuCe/Ti for CO oxidation and the role of TiO2

CuCe/Ti-A and CuCe/Ti-R catalysts were prepared using anatase TiO2 (TiO2-A) and rutile TiO2 (TiO2-R) as supports using the incipient wetness impregnation method for the carbon monoxide (CO) oxidation reaction and were compared with a CuCe-C catalyst prepared using the co-precipitation method. The CuCe/Ti-A catalyst exhibited the highest activity, with complete CO conversion at 90 °C, when the gas hourly space velocity was 24000 ml·g−1·h−1 and the CO concentration was approximately 1% (vol). A series of characterizations of the catalysts revealed that the CuCe/Ti-A catalyst has a larger specific surface area, more Cu+ species and oxygen vacancies, and the Cu species of CuCe/Ti-A catalyst is more readily reduced. In situ FT-IR results indicate that the bicarbonate species generated on the CuCe/Ti-A catalyst have lower thermal stability than the carbonate species on CuCe/Ti-R, and will decompose more readily to form CO2. Therefore, CuCe/Ti-A has excellent catalytic activity for CO oxidation.

Carbon and biodiversity cobenefits of second-growth tropical forest: The role of leaf phenology

Second-growth tropical forests offer important carbon and biodiversity cobenefits, as well as different leaf functional types of tree species. Leaf deciduousness is an important functional trait that can contribute to seasonal and spatial changes in carbon balance. We investigated the distribution pattern of carbon stock, species richness, and functional dominance among trees with differing leaf phenology (evergreen, semideciduous and deciduous) as well as the carbon and biodiversity cobenefits of tree communities in contrasting topographical conditions in a second-growth tropical Atlantic forest. We tested the hypotheses that topographic conditions shape differences in species richness and aboveground carbon stock between leaf phenology groups, as well as the carbon-biodiversity cobenefits within the tree communities. We studied fourteen 20 m × 40 m plots established in the forest with contrasting topographical conditions. We selected the mean functional traits related to carbon stock capacity in tropical forest: wood density and maximum tree height and calculated community-weighted mean metrics based on these traits. Aboveground biomass of trees for each stem sampled was calculated from a combination of variables using the general allometric equation. We constructed linear mixed-effect models (LMMs, with random and fixed effects) to test the cobenefits between aboveground carbon stock and leaf phenology group (evergreen, semideciduous and deciduous species) on species richness at community level. Our results showed that evergreen species had a higher richness, while the deciduous species had a greater contribution to aboveground carbon stock. Thus, the leaf phenology groups can affect the relationships between species richness and aboveground carbon stock. The deciduous species are key to maintaining higher carbon stock with smaller numbers of species; meanwhile evergreen species are important to maintain a higher species richness. Leaf phenology groups could be responsible for important cobenefits (i.e. positive aboveground carbon stock and species richness relationship) in Atlantic forests. Therefore, this study showed a relevant result on the relative contribution of leaf phenology groups in the carbon and biodiversity cobenefits along topographic gradients. In addition, our results allow for the selection of key tree species to improve management, conservation and restoration practices in the Atlantic forest in order to protect threatened biodiversity as a cobenefit of maintaining forests and the carbon they store.