Effluent Gas Research Articles

Effects of the surface properties and particle size of hydrated lime on desulfurization

In the gas treatment center in smelters, hydrogen fluoride (HF) is separated from the outlet gases of electrolysis cells, which are used to produce aluminum from alumina. However, SO2 largely remains in the effluent gas. Another method has to be developed to separate this gas which is harmful to the environment. In this study, semi-dry desulfurization of a SO2 containing gas was performed at low SO2 concentrations using hydrated lime [Ca(OH)2] as a catalytic desulfurizer under specific humidity conditions. The low reaction temperature of 100 °C and minimal use of the Ca-based desulfurizer under 17 % relative humidity achieved more than 95 % removal of SO2. The morphological changes and presence of sulfur in different lime samples were analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Brunauer–Emmett–Teller (BET) analysis showed changes in the surface properties of hydrated lime after desulfurization. X-ray photoelectron spectroscopy (XPS) analysis provided the phase and composition identification of the sulfur species on hydrated lime and the CaSO3/CaSO4 product ratio. Based on the experimental results, the optimum catalyst surface area with a specific particle size is critical to the effective conversion of Ca(OH)2 into CaSO3 and CaSO4. The practicality of a Ca-based desulfurizer and its ability to convert into the required product may be the key to reducing the overall cost of desulfurization in aluminum industry.

A deformation-diffusion interactive model to study crack-tip behaviour and predict crack growth rate under fatigue and hydrogen-embrittlement conditions

Hydrogen is accepted as a cleaner and more sustainable energy source, since it carries abundant energy and does not produce any effluent gas from burning when compared to fossil fuels. However, long-term degradation in mechanical properties, attributed to hydrogen embrittlement, is reported for metallic materials exposed to gaseous hydrogen, leading to accelerated crack growth behaviour under fatigue. In this paper, a visco-plastic deformation-diffusion interactive model is developed to study fatigue crack growth behaviour in a nickel-based superalloy under hydrogen-embrittlement condition. In the model, cyclic deformation is described by visco-plasticity constitutive model, while hydrogen diffusion is simulated by a modified form of Fick’s first law of diffusion which can address hydrogen diffusion driven by the hydrostatic stress gradient. In particular, trapped hydrogen, expressed as dependent on both diffusible hydrogen concentration and inelastic strain, is considered in the modelling of hydrogen diffusion. The model also describes the effects of hydrogen concentration on mechanical deformation by considering its influence on the evolution of isotropic hardening as well as on the strain state. Interaction between cyclic deformation and hydrogen diffusion is therefore studied for a crack tip in a compact tension specimen subjected to fatigue and hydrogen attack, showing a strong dependency on both loading frequency and stress intensity factor range. Subsequently, a two-parameter criterion is proposed for fatigue crack growth prediction, which accounts for the contributions of both cyclic deformation and hydrogen diffusion. The predictions show a good agreement with experimental data in terms of crack growth rate under fatigue and hydrogen-embrittlement conditions.

Comparative Study of Mesophilic Biomethane Production in Ex Situ Trickling Bed and Bubble Reactors

Biomethane production via biogas upgrading is regarded as a future renewable gas, further boosting the biogas economy. Moreover, when upgrading is realized by the biogas CO2 conversion to CH4 using surplus renewable energy, the process of upgrading becomes a renewable energy storage method. This conversion can be carried out via microorganisms, and has attracted scientific attention, especially under thermophilic conditions. In this study, mesophilic conditions were imposed using a previously developed enriched culture. The enriched culture consisted of the hydrogenotrophic Methanobrevibacter (97% of the Archaea species and 60% of the overall population). Biogas upgrading took place in three lab-scale bioreactors: (a) a 1.2 L bubble reactor (BR), (b) a 2 L trickling bed reactor (TBR) filled with plastic supporting material (TBR-P), and (c) a 1.2 L TBR filled with sintered glass balls (TBR-S). The gas fed into the reactors was a mixture of synthetic biogas and hydrogen, with the H2 to biogas CO2 ratio being 3.7:1, lower than the stoichiometric ratio (4:1). Therefore, the feeding gas mixture did not make it possible for the CH4 content in the biomethane to be more than 97%. The results showed that the BR produced biomethane with a CH4 content of 91.15 ± 1.01% under a gas retention time (GRT) of 12.7 h, while the TBR-P operation resulted in a CH4 content of 90.92 ± 2.15% under a GRT of 6 h. The TBR-S operated at a lower GRT (4 h), yielding an effluent gas richer in CH4 (93.08 ± 0.39%). Lowering the GRT further deteriorated the efficiency but did not influence the metabolic pathway, since no trace of volatile fatty acids was detected. These findings are essential indicators of the process stability under mesophilic conditions.

Combustion behavior and effluent liquid properties in extra-heavy crude oil reservoirs developed by steam huff and puff

In recent years, interest in in-situ combustion (ISC) as an alternative technique for extra-heavy crude oil reservoirs subjected to steam huff and puff has grown significantly; however, the ISC behavior and effluent liquid properties in such oil reservoirs remain under-explored. In this work, the combustion tube (CT) was used to investigate the combustion behavior of extra-heavy crude oil. Also, the effluent liquid properties during ISC were analyzed comprehensively. The results revealed that when the secondary water bodies (SWB) were present at the injection end of CT, a stable combustion front advanced, causing a gradual temperature rise and a CO2 concentration above 12 % in the effluent gas. This suggested that steam injection wells in these reservoirs were suitable candidates for subsequent air injection after steam huff and puff. Conversely, when the SWB was located at the production end of CT, the peak temperature of combustion decreased, indicating a transition to medium-temperature combustion and unstable combustion front advancement, making steam injection wells unsuitable for ISC as production ones. Three key criteria for evaluating ISC effectiveness in extra-heavy crude oil were: (1) the intensity of –CH2 and –CH3 peaks, (2) the C-O absorption peak between 1100 and 1000 cm−1, and (3) the distribution of characteristic peaks around 750 cm−1. A significant decrease in these peaks indicated high-temperature combustion and substantial oil upgrading. Also, the presence of alkynes suggested extensive thermal cracking and a stable combustion front. The anion concentration of effluent water increased compared to crude water, but the relationship between water ion concentration and combustion state was weak, without a discernible pattern.

Experimental investigation of explosion hazard from lithium-ion battery thermal runaway effluent gas

Fire and explosion hazards present a serious concern to the widespread adoption of battery technology. This work experimentally investigates the explosion hazards associated with synthesized lithium-ion battery thermal runaway effluent gases (TREG) in an enclosed garage space typical of modern construction in North America. Pressure rise inside the compartment is examined using high-frequency piezoelectric pressure transducers. Data on overpressure and impulse is compared with known ranges for structural damage and bodily injury thresholds and calculation methods for maximum overpressure. Data on time-resolved overpressure are compared with a vented explosion model from literature. These comparisons support that existing models for maximum overpressure and time-resolved pressure rise remain valid for the examined synthesized TREG. Correlations are developed between gas volume and measured impulse and overpressure. An extension of this analysis with values of TREG production from literature supports that pressures measured in these experiments can be generated from ignition of gases released from batteries sized in the range of 3300W⋅h to 80 500W⋅h.

Comparison of thermogravimetry response of alkali-activated slag and Portland cement pastes after stopping their hydration using solvent exchange method

AbstractThe critical step for any subsequent instrumental analysis of cementitious binders is to stop their hydration reactions, i.e., to remove free water. One of the most available techniques is a solvent exchange method. However, the solvents are known to be strongly bound in ordinary Portland cement (OPC) paste and alter the results of thermogravimetric analysis (TGA) and sensitive hydrates, while their effect on TGA response of alkali-activated slag (AAS) has not been comprehensively investigated. Therefore, the objective of this paper is to track the effects of fundamental aspects of the solvent exchange on the TGA response of AAS with different sodium activators (hydroxide, carbonate, waterglass) and to support these results by X-ray diffraction and effluent gas analysis. All solvents used (acetone, diethyl ether, isopropyl alcohol, ethanol, and methanol) affected the TGA response of all tested pastes, and their effect was enhanced by prolonged immersion time. All solvents induced an additional mass loss at around 800 °C and, especially for OPC paste, increased in situ carbonation, even in an inert atmosphere. Methanol and ethanol had a detrimental effect on ettringite and decreased the basal distance of the C–(A)–S–H gel, while they only marginally affected gaylussite. For AAS, hydration stoppage by washing out the alkali-rich pore solution with water was also investigated and can usually be recommended (except for its detrimental effect on gaylussite), as it is more efficient than organic solvents, which lack solubility for activators. Methanol and ethanol are the most suitable alternatives, particularly for NaOH.

Direct Non-Oxidative Methane Conversion and Hydrogen Co-Production in a Proton Conducting Membrane Reactor

Direct Non-oxidation Methane Conversion (DMNC) has been recognized a promising technology for the upgrading of cheap and abundant methane to higher hydrocarbons (C2+) and H2, but this technology has not been commercialized yet because of the low methane equilibrium conversion and severe carbon deposition.1-3 Here, we present our effort to develop a proton conducting membrane reactor (SrCe0.7Zr0.2Eu0.1O3- ⴃ) combined with the catalysts (Fe©SiO2) to circumvent the equilibrium limitations of the DMNC reaction and solve the coking (i.e., solid carbon deposition) problem. By coupling the Fe©SiO2 catalysts with H2 permeable membrane reactor, part of produced H2 during the catalytic conversion can be extracted from the effluent gas, which not only provides a one-step hydrogen production without additional separation process, but also shifts the equilibrium of the reaction to the product side and achieves an improved methane conversion and higher C2+ yield when compared to the traditional fixed-bed reactor. In addition, an air sweep outside the reactor results in O-permeation into catalyst to oxidize any deposited carbon to CO thus preventing coking.The membranes were fabricated using tape casting of the support layer followed by dip coating process to form the dense membrane layer. Using this method, we obtained 25 µm for the thickness of the dense layer and around 700 µm for the thickness of the support layer (see Fig. 1a and 1b). The catalyst was synthesized by a simple sol-gel method followed by fusing process, and then was crushed into 40-80 mesh and loaded inside of membrane reactor to test.The performance metrics include methane conversion, selectivity, and product yield. Our membrane reactor achieved single-pass methane conversion of 17.5%, and a C2+ yield of 15% (see Fig. 1c) at 1323K.Finally, our membrane reactors were stable for over 350 hours, which, along with the aforementioned performance metrics, constitutes a major advance in the development of commercial DMNC technology. References Guo, X.; Fang, G.; Li, G.; Ma, H.; Fan, H.; Yu, L.; Ma, C.; Wu, X.; Deng, D.; Wei, M.; Tan, D.; Si, R.; Zhang, S.; Li, J.; Sun, L.; Tang, Z.; Pan, X.; Bao, X., Direct Nonoxidative Conversion of Methane to Ethylene, Aromatics, and Hydrogen. Science 2014, 344 (6184), 616-619.Thyssen, V. V.; Vilela, V. B.; de Florio, D. Z.; Ferlauto, A. S.; Fonseca, F. C., Direct Conversion of Methane to C2 Hydrocarbons in Solid-State Membrane Reactors at High Temperatures. Chemical Reviews 2022, 122 (3), 3966-3995.Sakbodin, M.; Schulman, E.; Cheng, S.; Huang, Y.-L.; Pan, Y.; Albertus, P.; Wachsman, E. D.; Liu, D., Direct Nonoxidative Methane Conversion in an Autothermal Hydrogen-Permeable Membrane Reactor. Advanced Energy Materials 2021, 11 (46), 2102782. Figure 1

Analysis of carbon‐14 discharges from Korean nuclear power plants

AbstractThe routine practice accompanying the operation of nuclear facilities involves the discharge of radioactive effluents from nuclear power plants (NPPs). Regulation of this discharge to the environment hinges on three criteria: radioactivity concentration, public dose, and radioactivity. Among these, radioactive carbon‐14 holds particular significance as it possesses an extensive half‐life of 5730 years, making it a primary source of radiation dose to communities residing around NPPs. In Korea, the monitoring of carbon‐14 discharges from pressurized water reactors (PWRs) in gaseous effluents has been ongoing since 2012, whereas before 2012, monitoring exclusively focused on carbon‐14 discharges from pressurized heavy water reactors (PHWRs). Analysis of carbon‐14 discharges from Korean PHWRs indicates that their emission constituted less than 1% of total radioactive effluents over the past two decades. In the context of Korean PWRs, carbon‐14 discharge monitoring was absent from 2002 to 2011, resulting in an absence of data regarding such discharges during that period. After introducing carbon‐14 discharge monitoring in gaseous effluents from Korean PWRs, emissions from 2012 to 2021 contributed 3% of the total gaseous effluents. These findings indicate that despite being the primary contributor to public dose, carbon‐14 discharges from NPPs constitute a minor portion of the radioactive effluent discharge.

Continuous CO2 capture and reduction to CO by circulating transition-metal-free dual-function material in fluidized-bed reactors

To mitigate global warming and achieve a sustainable society, innovative technologies for efficient CO2 utilization are required. Integrated CO2 capture and reduction (CCR) using dual-function materials (DFMs) is favorable owing to its potentially low energy consumption, capital investment, and processing costs. Although numerous studies have focused on catalytic science, continuous and steady-state CCR operations have not been sufficiently addressed from an engineering perspective. In this study, a circulating fluidized bed (CFB) system is investigated for continuous CCR to syngas (CO + H2). In the CFB system, transition-metal-free DFM (Na/Al2O3) particles are circulated between two bubbling fluidized-bed reactors. The DFM captures CO2 in one reactor (CO2 capture reactor) and reduces the captured CO2 to CO by the reaction with H2 in the other reactor (H2 reactor). The effluent gas concentrations from both reactors reach steady state and are maintained for over 8 h. For the product gas from the H2 reactor, the CO2 conversion and CO selectivity exceed 80 % and 99 %, respectively. However, the H2 conversion is <20 %, indicating a potential challenge for the CFB system for integrated CCR. Furthermore, this study confirms that the H2/CO ratio for syngas can be controlled by adjusting the experimental conditions (particularly, the H2 flow rate). Consequently, the CFB system can be modified to facilitate the interaction between H2 gas and the DFM particles.

Photocatalytic degradation properties

Photocatalysis, an innovative technology, holds promise for addressing industrial pollution issues across aqueous solutions, surfaces, and gaseous effluents. The efficiency of photodegradation is notably influenced by light intensity and duration, underscoring the importance of optimizing these parameters. Furthermore, temperature and pH have a significant impact on pollutant speciation, surface chemistry, and reaction kinetics; therefore, process optimization must consider these factors. Photocatalytic degradation is an effective method for treating water in environmental remediation, providing a flexible and eco-friendly way to eliminate organic contaminants from wastewater. Selectivity in photocatalytic degradation is achieved by a multidisciplinary approach that includes reaction optimization, catalyst design, and profound awareness of chemical processes. To create efficient and environmentally responsible methods for pollution removal and environmental remediation, researchers are working to improve these components.

Synthesis of calcium aluminate hydrates, their characterization and dehydration

This study is focused on the description of the dehydration of calcium aluminate hydrates (CAHs) and their identification. Four calcium aluminates (CA, C12A7, C3A, CA2) prepared by high temperature solid-state synthesis or modified Pechini synthesis served as precursors for CAHs. Hydration was carried out at the various temperatures in a range of 5–60 °C for 48 h. CAHs were identified by X-ray diffraction analysis (XRD) and their dehydration was characterized by Thermogravimetry and effluent gas analysis (TG/EGA) and high temperature XRD. Pure C3AH6 and CAH10 were successfully prepared, other CAHs (C2AH8, C4AH19, AH3, C4A C‾ H11) were present in the mixtures. The results indicate that dehydration of C3AH6 takes place at a temperature of about 300 °C, followed by the formation of a new product with a structure similar to C12A7. C2AH8 dehydration can be described in three steps. The dehydration is accompanied by the formation of crystalline intermediate products. CAH10 dehydration can be assigned to a broad peak on the DTG curve with a maximum at approximately 100 °C. The decomposition of C4A C‾ H11 takes place in two steps, with CO2 evolving in the temperature range 500–700 °C.

Isotope exchange of ND3 on Pt catalyst-loaded 13X molecular sieve

During D-T fusion operations the capture, purification, and recycling of unburned tritium will be crucial, as the formation of tritium containing molecules require additional processing. Removing the tritium can require costly processing to be unbound from the tritium-containing molecules and improvements to these processes will be necessary moving forward. Existing techniques using sorbent material beds to remove tritium-containing molecules from process gas streams undergo repeated high-heat cycling which leads to diminished bed lifespans, necessitating replacement and associated downtime. This work demonstrates the capture and isotopic exchange technique of deuterated ammonia (ND3), used as a surrogate for tritium, at ambient temperature using a Pt catalyst-loaded 13X molecular sieve. Unmodified 13X molecular sieve is capable of adsorbing and retaining the ND3 however, incorporation of a catalyst facilitates the isotopic exchange of the hydrogen isotopes. The effluent gas streams were analyzed in conjunction with desorbed ammonia isotopologues post-exchange to verify these results. Isotopically exchanging and removing heavier hydrogen isotopes using this technique provides an alternative to traditional removal methods.

Microalgae to biodiesel: A novel green conversion method for high-quality lipids recovery and in-situ transesterification to fatty acid methyl esters

Greenhouse gases (GHGs) emissions due to increasing energy demand have raised the need to identify effective solutions to produce clean and renewable energy.Biotechnologies are an effective platform to attain green transition objectives, especially when synergically integrated to promote health and environmental protection. In this context, microalgae-based biotechnologies are considered among the most effective tools for treating gaseous effluents and simultaneously capturing carbon sources for further biomass valorisation. The production of biodiesel is regarded as a promising avenue for harnessing value from residual algal biomass. Nonetheless, the existing techniques for extracting lipids still face certain limitations, primarily centred around the cost-effectiveness of the process.This study is dedicated to developing and optimising an innovative and cost-efficient technique for extracting lipids from algal biomass produced during gaseous emissions treatment based on algal-bacterial biotechnology. This integrated treatment technology combines a bio-scrubber for degrading gaseous contaminants and a photobioreactor for capturing the produced CO2 within valuable algal biomass. The cultivated biomass is then processed with the process newly designed to extract lipids simultaneously transesterificated in fatty acid methyl esters (FAME) via In Situ Transesterification (IST) with a Kumagawa-type extractor. The results of this study demonstrated the potential application of the optimised method to overcome the gap to green transition. Energy production was obtained from residuals produced during the necessary treatment of gaseous emissions. Using hexane-methanol (v/v = 19:1) mixture in the presence KOH in Kumagawa extractor lipids were extracted with extraction yield higher than 12% and converted in fatty acid methyl esters. The process showed the enhanced extraction of lipids converted in bio-sourced fuels with circular economy approach, broadening the applicability of biotechnologies as sustainable tools for energy source diversification.

Mathematical modelling of a semi-dry SO2 scrubber based on a Lagrangian-Eulerian approach

Semi-dry desulfurization is an efficient means of SO2 removal from the effluent gases from electrolysis cells in aluminum smelters. These gases are at low temperature and contain low concentrations of SO2, as opposed to thermal power plants. The removal is carried out by injecting powdered alkaline sorbent, hydrated lime (solid particles), into the SO2-containing gas (gas phase) in the presence of humidity. The reaction is controlled by the adsorption of SO2 onto the surface of lime. This study involves the mathematical modelling of a lab-scale scrubber using a Lagrangian-Eulerian approach in order to analyze the desulfurization efficiency. The model was validated based on experimental data. A parametric study was carried out to investigate the effects of particle size, sorbent amount, and relative humidity (RH) on the desulfurization efficiency. The results show that the particle size is the most important parameter; as the particle size decreases, the desulfurization efficiency increases. However, using finer particles may increase the process cost. The loss in SO2 capture efficiency due to the use of coarser particle size could be compensated by increasing the relative humidity (RH) of the gas, another key parameter of the process.

Quantitative Assessment of Gaseous Effluents during Routine Operation: A Comparative Study of Planned Nuclear Power Plants at Lubiatowo-Kopalino and Pątnów Sites in Poland

On September 2021, Polish government declared that six pressurized water reactors with combined capacity of 6–9 GWe will be built by 2040 to reduce Poland’s reliance on coal. Due to the adopted schedule, construction of the first nuclear power plant will begin in 2026, with the first reactor capacity of 1–1.6 GWe to be operational in 2033. The Polish authorities announced in 2022 the selection of two locations and technologies for Poland’s first commercial nuclear power plants. Westinghouse AP1000 reactor was selected by Polish government to be built as the first plant in the location of Lubiatowo-Kopalino, on the coast of the country. In the meantime, Poland’s ZE PAK, Polska Grupa Energetyczna, and Korea Hydro &amp; Nuclear Power have signed the letter of intent to collaborate on the project that evaluates the feasibility of building South Korean APR1400 on Pątnów site in central Poland. The objective of this study was to acquire and examine the gaseous effluents released during the standard operation of the AP1000 and APR1400 reactor technologies, with the primary goal of focusing on estimating the potential exposure of the general public. The effluents were calculated by using the GALE code based on each nuclear reactor technical specification. The obtained results were compared with those included in the Design Control Document for each reactor. Subsequently, the HotSpot software was used to calculate the radiation risk for downwind areas by utilizing GALE code results as source terms together with specific meteorological data corresponding for each localization. The results for AP1000 at Lubiatowo-Kopalino site and for APR1400 at Pątnów site were analysed and compared in the study. As the study findings were evaluated with the Polish radiation limits for the general public, all doses remained below the legal thresholds. With no previous alike studies conducted, this research begins the analysis of radiation impacts associated with the planned nuclear power plant in Poland during normal operation.

Changes in Concurrent Meteorological Extremes of Rainfall and Heat under Divergent Climatic Trajectories in the Guangdong–Hong Kong–Macao Greater Bay Area

Concurrent meteorological extremes (CMEs) represent a class of pernicious climatic events characterized by the coexistence of two extreme weather phenomena. Specifically, the juxtaposition of Urban Extreme Rainfall (UER) and Urban Extreme Heat (UEH) can precipitate disproportionately deleterious impacts on both ecological systems and human well-being. In this investigation, we embarked on a meticulous risk appraisal of CMEs within China’s Greater Bay Area (GBA), harnessing the predictive capabilities of three shared socioeconomic pathways (SSPs) namely, SSP1-2.6, SSP3-7.0, and SSP5-8.5, in conjunction with the EC-Earth3-Veg-LR model from the CMIP6 suite. The findings evidence a pronounced augmentation in CME occurrences, most notably under the SSP1-2.6 trajectory. Intriguingly, the SSP5-8.5 pathway, typified by elevated levels of greenhouse gas effluents, prognosticated the most intense CMEs, albeit with a temperate surge upon occurrence. Additionally, an ascendant trend in the ratio of CMEs to the aggregate of UER and UEH portends an escalating susceptibility to these combined events in ensuing decades. A sensitivity analysis accentuated the pivotal interplay between UER and UEH as a catalyst for the proliferation of CMEs, modulated by alterations in their respective marginal distributions. Such revelations accentuate the imperative of assimilating intricate interdependencies among climatic anomalies into evaluative paradigms for devising efficacious climate change countermeasures. The risk assessment paradigm proffered herein furnishes a formidable instrument for gauging the calamitous potential of CMEs in a dynamically shifting climate, thereby refining the precision of prospective risk estimations.

Production of large quantity of plasma activated water using multiple plasma device setup

This study focuses on large-scale production of plasma-activated water (PAW) using batch processes with circulating and non-circulating modes. A multi-plasma device setup, powered by a self-developed high-voltage high-frequency supply. This plasma is electrically characterized and the produced radicals/species are identified using emission spectroscopy, with resulting effluent gases containing polluting species. The PAW setup utilizes these gases to create substantial quantities of PAW, decreasing environmental pollutants. The non-circulating mode produces highly reactive PAW (2L/batch) while the circulating mode yields larger volumes (20L/batch) with lower reactivity. Applications range from microbial inactivation to agriculture. Both batch setups are scalable for industrial PAW production.

Recycling PVC Waste into CO2 Adsorbents: Optimizing Pyrolysis Valorization with Neuro-Fuzzy Models

Nowadays, the environmental challenges associated with plastics are becoming increasingly prominent, making the exploitation of alternatives to landfill disposal a pressing concern. Particularly, polyvinyl chloride (PVC), characterized by its high chlorine content, poses a major environmental risk during degradation. Furthermore, PVC recycling and recovery present considerable challenges. This study aims to optimize the PVC pyrolysis valorization process to produce effective adsorbents for removing contaminants from gaseous effluents, especially CO2. For this purpose, PVC waste was pyrolyzed under varied conditions, and the resulting solid fraction was subjected to a series of chemical and physical activations by means of hydroxides (NaOH and KOH) and nitrogen. Characterization of the PVC-based activated carbons was carried out using surface morphology (SEM), N2 adsorption/desorption, elemental analysis, and FTIR, and their capacity to capture CO2 was assessed. Finally, neuro-fuzzy models were developed for the optimization of the valorization technique. The resulting activated carbons exhibited excellent CO2 adsorption capabilities, particularly those activated with KOH. Optimal activation conditions include activations at 840 °C with NaOH at a ratio of 0.66 and at 760 °C using either NaOH or KOH with ratios below 0.4. Activations under these experimental conditions resulted in a significant increase in the adsorption capacity, of up to 25%, in the resulting samples.

New Trends for Hydrogen Sulfide Scavenging Using Natural Compounds as Biogenic Amines.

Hydrogen sulfide (H2S) mitigation through the use of additives in a laboratory-scale evaluation of steam injection in batch reactors was studied using extra heavy crude oil. For this purpose, additives based on biogenic amines from a fishing effluent were used with methanol and ethanol as solvents in a previous extraction of industrial fishmeal waste. The study of the extracts using high-performance liquid chromatography (HPLC) permitted the determination that the methanol-based extract with 48 h of decomposition had the highest biogenic amine content, totaling 1472 ppm. In addition, methanol extractions were more efficient, with an average biogenic amine content of 592 ppm. Subsequent evaluations were carried out for sand/oil/water/scavenging additive systems, where solutions of commercial organic compounds, analytical-grade histamine, and biogenic amine extracts were used. These evaluations were performed at a constant temperature of 247 °C and under an initial pressurization of methane gas of 215 psig, with a reaction time of 24 h. Characterization of gaseous effluents for each system allowed us to determine that the methods in which biogenic amine extracts were used with methanol were more effective in H2S scavenging because they had the lowest gas concentration at the end of the reaction time. Within this group, the most effective was the C1 extract, with a H2S reduction from 1700 to 150 ppm, representing 91% removal. The biogenic amine family produced by decomposition in conjunction with histamine has a synergistic effect in tests under vapor injection conditions when comparing the results with analytical-grade histamine solution-based additives and commercial additives. This study shows that using steam injection technology to use biogenic amines in H2S mitigation is feasible.

Selective photocatalytic and photoelectrocatalytic synthesis of valuable compounds in aqueous medium

In the past decades, photocatalytic and photoelectrocatalytic methods have been widely employed for the degradation of harmful compounds present both is gaseous and aqueous effluents. In the last years scientists have paid great attention to the synthesis of valuable compounds and hydrogen production. Organic syntheses are generally carried out in organic solvents, under high temperature/pressure, with toxic oxidants such as permanganate. On the other hand, photocatalysis and photoelectrocatalysis using water as solvent, air or water as oxidant, and sunlight as energy source, can be an efficient alternative to the traditional, non-environmentally friendly methods. This review summarizes the photocatalytic and photoelectrocatalytic transformations of organic molecules to commercially valuable products in water, sometimes evaluating also the contemporary H2 production. The reaction conditions, mechanisms and kinetics are presented and discussed. Future perspectives are also given.