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A state-of-the-art review on capture and separation of hazardous hydrogen sulfide (H2S): Recent advances, challenges and outlook
Abstract
Hydrogen sulfide (H2S) is a flammable, corrosive and lethal gas even at low concentrations (ppm levels). Hence, the capture and removal of H2S from various emitting sources (such as oil gas processing facilities, natural emissions, sewage treatment plants, landfills and other industrial plants) is necessary to prevent and mitigate its adverse effects on human (causing respiratory failure and asphyxiation), environment (creating highly flammable and explosive environment), and facilities (resulting in corrosion of industrial equipment and pipelines). In this review, the state-of-the-art technologies for H2S capture and removal are reviewed and discussed. In particular, the recent technologies for H2S removal such as membrane, adsorption, absorption and membrane contactor are extensively reviewed. To date, adsorption using metal oxide-based sorbents is by far the most established technology in commercial scale for the fine removal of H2S, while solvent absorption is also industrially matured for bulk removal of CO2 and H2S simultaneously. In addition, the strengths, limitations, technological gaps and way forward for each technology are also outlined. Furthermore, the comparison of established carbon capture technologies in simultaneous and selective removal of H2S–CO2 is also comprehensively discussed and presented. It was found that the existing carbon capture technologies are not adequate for the selective removal of H2S from CO2 due to their similar characteristics, and thus extensive research is still needed in this area.
... One of the primary sources of H 2 S emissions is the oil and natural gas industry, through processes such as exploration, extraction, refining, and transportation [19]. In each of these processes, H 2 S can be released as a by-product, particularly during petroleum refining and desulfurization, and in the processing of natural gas, where chemical and thermal separations are employed [20]. ...
... Its presence in industries such as oil and gas requires highly specialized methods to reduce concentrations to safe levels [256]. These methods, ranging from physical and chemical processes to biological treatments, have been significantly developed to address the hazardous nature of H 2 S [19]. The industry has made considerable progress in its removal, prioritizing efficient solutions such as converting gas into less harmful compounds or capturing it using liquid and solid absorbents, while optimizing separation technologies [19]. ...
... These methods, ranging from physical and chemical processes to biological treatments, have been significantly developed to address the hazardous nature of H 2 S [19]. The industry has made considerable progress in its removal, prioritizing efficient solutions such as converting gas into less harmful compounds or capturing it using liquid and solid absorbents, while optimizing separation technologies [19]. ...
Malodorous gases—particularly hydrogen sulfide (H2S), ammonia (NH3), and volatile sulfur compounds (VSCs)—significantly degrade water quality, threaten public health, and disrupt ecosystems. Their production stems from microbial activity, nutrient overload, and industrial discharges, often magnified by low dissolved oxygen. This review integrates current insights into the microbial sulfur and nitrogen cycles to elucidate how these gases form, and surveys advances in detection technologies such as gas chromatography and laser-based sensors. We also assess diverse mitigation methods—including biotechnological approaches (e.g., biofilters, biopercolators), physicochemical treatments, and chemical conversion (Claus Process)—within relevant regulatory contexts in Colombia and worldwide. A case study of the Bogotá River exemplifies how unmanaged effluents and eutrophication perpetuate odor issues, underscoring the need for integrated strategies that reduce pollution at its source, restore ecological balance, and employ targeted interventions. Overall, this review highlights innovative, policy-driven solutions and collaborative efforts as pivotal for safeguarding aquatic environments and surrounding communities from the impacts of odorous emissions.
... One of the ways of interpreting the effect of hydrogen sulfide in contact with humans is shown in Figure 1 [21,22]. Considering the undesirable effects both on industrial installations and on humans, researchers have focused on the elimination of hydrogen sulfide or its derivatives (mercaptans, thiophene, etc.) from various gaseous or liquid environments [23][24][25]. ...
... The applications of membranes and membrane techniques are in continuous development, being applied both in the separation processes of dispersed systems and gas mixtures [49][50][51][52][53][54]. In the last decade, biopolymers such as chitosan or cellulosic derivatives Considering the undesirable effects both on industrial installations and on humans, researchers have focused on the elimination of hydrogen sulfide or its derivatives (mercaptans, thiophene, etc.) from various gaseous or liquid environments [23][24][25]. ...
Hydrogen sulfide is present in active or extinct volcanic areas (mofettas). The habitable premises in these areas are affected by the presence of hydrogen sulfide, which, even in low concentrations, gives off a bad to unbearable smell. If the living spaces considered are closed enclosures, then a system can be designed to reduce the concentration of hydrogen sulfide. This paper presents a membrane-based way to reduce the hydrogen sulfide concentration to acceptable limits using a cellulosic derivative–propylene hollow fiber-based composite membrane module. The cellulosic derivatives considered were: carboxymethyl–cellulose (NaCMC), P1; cellulose acetate (CA), P2; methyl 2–hydroxyethyl–cellulose (MHEC), P3; and hydroxyethyl–cellulose (HEC), P4. In the permeation module, hydrogen sulfide is captured with a solution of cadmium that forms cadmium sulfide, usable as a luminescent substance. The composite membranes were characterized by SEM, EDAX, FTIR, FTIR 2D maps, thermal analysis (TG and DSC), and from the perspective of hydrogen sulfide air removal performance. To determine the process performances, the variables were as follows: the nature of the cellulosic derivative–polypropylene hollow fiber composite membrane, the concentration of hydrogen sulfide in the polluted air, the flow rate of polluted air, and the pH of the cadmium nitrate solution. The pertraction efficiency was highest for the sodium carboxymethyl–cellulose (NaCMC)–polypropylene hollow fiber membrane, with a hydrogen sulfide concentration in the polluted air of 20 ppm, a polluted air flow rate (QH2S) of 50 L/min, and a pH of 2 and 4. The hydrogen sulfide flux rates, for membrane P1, fall between 0.25 × 10⁻⁷ mol·m²·s⁻¹ for the values of QH2S = 150 L/min, CH2S = 20 ppm, and pH = 2 and 0.67 × 10⁻⁷ mol·m⁻²·s⁻¹ for the values of QH2S = 50 L/min, CH2S = 60 ppm, and pH = 2. The paper proposes a simple air purification system containing hydrogen sulfide, using a module with composite cellulosic derivative–polypropylene hollow fiber membranes.
... Among these techniques, adsorption is an effective method to remove H 2 S from natural gas. Therefore, commercially available and advanced technology for H 2 S adsorption leads to high removal capacity [6]. Highly porous adsorbents include zeolites [7], activated carbon [8], silica gel [9], and metal-organic frameworks (MOFs) [10]. ...
Hydrogen sulfide (H2S) removal from natural gas is critical due to its toxicity and corrosive nature. Adsorption is one of the most effective methods, but polymeric hydrogels often exhibit limited H2S adsorption capacity. To overcome this, an amine‐functionalized fly ash (FA)‐grafted polyacrylic acid (PAA) hydrogel (FA‐g‐PAA) was synthesized using 5 wt.% FA via solution polymerization and functionalized with 30 wt.% monoethanolamine (MEA) to enhance H2S removal. Physiochemical properties and H2S adsorption performance were evaluated using Fourier‐transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, thermogravimetric analysis (TGA), and X‐ray diffraction (XRD). The results confirmed the successful grafting of FA and MEA into the PAA matrix. Due to the grafting of FA, the morphology and surface area of the FA‐g‐PAA hydrogel enhanced from 0.04 m²/g (pure hydrogel) to 0.8m ²/g. The breakthrough analysis showed the 30 wt.% MEA‐functionalized FA‐g‐PAA hydrogel demonstrated a superior H2S adsorption capacity of (2.0 mmol/g), significantly outperforming the nonfunctionalized FA‐g‐PAA (1.6 mmol/g) and pure PAA hydrogel (0.08 mmol/g) at room temperature. Molecular dynamics (MD) simulations confirmed the hydrogel model and revealed the synergistic role of FA and MEA in enhancing H2S adsorption. Overall, the MEA‐functionalized FA‐g‐PAA hydrogel shows efficient H2S adsorbent for industrial gas purification applications.
... This indicates the need for careful selection of the method depending on the required product quality. Y.H. Chan et al. (2022) also conducted a study, the results of which showed that when comparing purification methods by the degree of reduction of sulphur content in a fraction, different technologies may demonstrate different levels of efficiency in removing hydrogen sulphide. For example, chemical purification and absorption can provide higher performance than adsorption, depending on the selected reagents and process conditions. ...
The study was conducted to determine the most effective and economically substantiated desulphurisation method for oil and gas deposits, ensuring a minimum content of sulphur compounds in the propane-propylene fraction. In this study, the methods of absorption, adsorption, and chemical purification, including catalytic, were compared in terms of hydrogen sulphide removal efficiency, economic feasibility, and impact on the final quality of the propane-propylene fraction. As a result of the analysis, it was found that the effectiveness of various methods of desulphurisation of the propane-propylene fraction depends on the initial concentration of hydrogen sulphide, the technical characteristics of the equipment, and the economic operating conditions. Absorption methods using amine solutions showed the highest degree of purification, reducing the hydrogen sulphide content to less than 5 ppm for large volumes of gas. However, the significant costs of absorbent regeneration reduce their economic attractiveness. Adsorption using zeolites and activated carbon has demonstrated high efficiency in processing small and medium volumes of gas. However, a reduction in the hydrogen sulphide content to 10 ppm is achieved, and adsorbent regeneration is possible without significant costs, which makes the method preferable for small installations. Catalytic purification using oxidising agents proved to be less effective at high concentrations of hydrogen sulphide, but ensures stable operation at low levels of impurities. This method requires significant capital investments, but it allows obtaining a fraction with a sulphur content of less than 8 ppm. Based on the data obtained, it was established that the choice of the optimal desulphurisation method is determined by the scale of production and the acceptable economic costs. Absorption is preferable for large enterprises, while the adsorption method is optimal for small installations
... Hydrogen sulfide is a highly aggressive gas that forms a weak acid, hydrogen sulfide acid, upon contact with an aqueous medium [29][30]. This acid contributes to H₂S-induced corrosion, accelerating the degradation of materials, particularly iron and steel. ...
Corrosion detection is essential for maintaining infrastructure safety, reliability, and longevity, particularly in industries such as oil and gas, where harsh environmental conditions accelerate material degradation. Corrosion in this industry affects the structural integrity of pipelines and increases life cycle costs. Carbon steel, a commonly used material, is highly susceptible to corrosion due to extreme operational conditions like high pressure, temperature fluctuations, and exposure to corrosive elements such as CO₂, H₂S, and chlorides. The extensive network of pipelines and remote locations make real-time corrosion detection challenging, as traditional inspection methods often prove insufficient, particularly for internal monitoring. Deep gas wells add another layer of difficulty, requiring reliable wireless communication for data acquisition. However, challenges persist in effectively detecting corrosion, especially in large, complex systems such as pipelines and offshore rigs, where traditional methods may not be sufficient. Additionally, advanced monitoring techniques using artificial intelligence (AI), and machine learning (ML), based solutions offer promising advancements, but they introduce new challenges related to cybersecurity, data management, and the need for specialized personnel. This review paper explores the different types of corrosion, detection techniques, their respective limitations, and the potential solutions to address these issues to ensure the long-term sustainability of the oil and gas industry.
... Guoqiang Li gqli@nankai.edu.cn due to its extremely low odor threshold (approximately 1.83 µg·m − 3 ) and high toxicity [4,5]. ...
Background
Hydrogen sulfide (H2S) gas, characterized by its low odor threshold and toxicity, poses significant challenges in non-point source odor management. Traditional biotechnologies are effective in removing malodorous gases from point sources but they are limited for non-point source odor control.
Results
In this study, the sqr and pdo genes from Cupriavidus pinatubonensis JMP134 were introduced into the bacterial cellulose-producing strain Kosakonia oryzendophytica FY-07. This genetic modification enhanced the strain’s sulfur oxidation capacity, which increased over time, with an average transformation capacity of approximately 275 mg·L− 1·day− 1. By incorporating 1% activated carbon, an efficient, naturally degradable bio-composite membrane was developed, achieving a maximum H2S adsorption capacity of 7.3 g·m− 3·day− 1. FY-07 remained stable in soil and improved the microbial community for H2S treatment.
Conclusion
The resulting bio-composite membrane is environment-friendly and efficient, making it suitable for emergency odor control in landfills. This study offers recommendations for using membrane materials in managing non-point hydrogen sulfide emissions.
... High levels of these contaminants can deplete dissolved oxygen, suffocating aquatic organisms and promoting excessive algal growth, which further reduces oxygen levels as the algae decompose [99]. High amounts of nitrate and phosphate lead to eutrophication, causing an imbalance in the aquatic ecosystem [100], while sulfur and hydrogen may combine to produce an unpleasant H 2 S that harms marine life [101]. The results of this research indicate that copper nanoparticles have considerable potential for a range of industrial uses, especially in cleaning wastewater, where they can effectively eliminate the biochemical oxygen demand (BOD), chemical oxygen demand (COD), phosphates, and nitrates. ...
Nanotechnology offers effective solutions for removing contaminants and harmful bacteria from polluted water. This study synthesized copper nanoparticles using a carbohydrate-based bioflocculant derived from Proteus mirabilis AB 932526.1. The bioflocculant is a natural polymer that facilitates the aggregation of particles, enhancing the efficiency of the nanoparticle synthesis process. Characterization of the bioflocculant and copper nanoparticles was conducted using Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Energy-Dispersive X-ray Spectroscopy, Ultraviolet-Visible Spectroscopy, X-ray Diffraction, and Transmission Electron Microscopy techniques to assess their properties, flocculation efficiency, and antibacterial characteristics. The optimal flocculation efficiency of 80% was achieved at a copper nanoparticle concentration of 0.4 mg/mL, while a concentration of 1 mg/mL resulted in a lower efficiency of 60%. The effects of biosynthesized copper nanoparticles on human-derived embryonic renal cell cultures were also investigated, demonstrating that they are safe at lower concentrations. The copper nanoparticles effectively removed staining dyes such as safranin (90%), carbol fuchsine (88%), methylene blue (91%), methyl orange (93%), and Congo red (94%), compared to a blank showing only 39% removal. Furthermore, when compared to both chemical flocculants and bioflocculants, the biosynthesized copper nanoparticles exhibited significant nutrient removal efficiencies for nitrogen, sulfur, phosphate, and total nitrates in coal mine and Vulindlela domestic wastewater. Notably, these biosynthesized copper nanoparticles demonstrated exceptional antibacterial activity against both Gram-positive and Gram-negative bacteria.
... Hydrogen sulfide promotes corrosion in oil and gas equipment that may cause cracking of pipes [11]. For SSC to occur, hard material, stress, hydrogen sulfide, and water must simultaneously exist [12]. ...
Low-carbon steels are usually surfaced with surface-modified electrodes to improve their wear and corrosion resistance. In carbon steel, the maximum hardness levels of 235 BHN (250 HV) are beneficial to avoid SCC (NACE). This research work aims at the improvement of the wear resistance of the low carbon steel by deposition of different layers using SMAW electrodes. These electrodes have different microstructures including austenitic stainless steel (AWS A5.4 E312 – 16 electrode), martensitic stainless steel (AWS A5.4 E410 – 16 electrode) with and without post-weld heat treatment (PWHT), and martensitic steel (JIS DF 2B – 500 – B electrode) without PWHT. Moreover, the susceptibility of the hard-faced layer to sulphide stress corrosion cracking (SSC) was studied. It was found that the weld metal hardness values greatly affect the sulphide stress corrosion cracking susceptibility. The weld metal deposited using JIS DF 2B – 500 – B electrode without PWHT gave hardness values higher than 300 HV (about 334 HV) that showed an SSC cracking tendency. However, the other specimens give a hardness value lower than 250 HV (about 210 HV) without any SSC cracking. The hard-faced layer deposited using JIS DF 2B – 500 – B electrodes showed the least wear index (maximum wear resistance). The austenitic stainless steel (AWS A5.4 E312 – 16) gave a higher wear index value but was still lower than that of the base metal.
... One of the ways of interpreting the effect of hydrogen sulfide in contact with humans is shown in Figure 1 [21,22]. Considering the undesirable action both on industrial installations and on humans, researchers have focused on the elimination of hydrogen sulfide or its derivatives (mercaptans, thiophene etc.) from various gaseous or liquid environments [23][24][25]. ...
Hydrogen sulfide is present in active or extinct volcanic areas (mofettas). The habitable premises in these areas are affected by the presence of hydrogen sulfide, which, even in low concentrations, gives off a bad to unbearable smell. If the living spaces considered are closed enclosures, then a system can be designed to reduce the concentration of hydrogen sulfide. This paper presents a membrane way to reduce the hydrogen sulfide concentration to acceptable limits using a cellulosic derivative-propylene hollow fiber based composite membrane module. The cellulosic derivatives considered were carboxymethyl–cellulose (NaCMC), cellulose acetate (CA), methyl 2–hydroxyethyl–cellulose (MHEC), and 2–hydroxyethyl–cellulose (HEC). In the permeation module, hydrogen sulfide is captured with a solution of cadmium that forms cadmium sulfide, usable as a luminescent substance. The composite membranes were characterized by SEM, EDAX, FTIR, FTIR 2D maps, thermal analysis (TG and DSC) and from the perspective of hydrogen sulfide air removal performance. To determine the process performances, the variables were: the nature of the cellulosic derivative–polypropylene hollow fiber composite membrane, the concentration of hydrogen sulfide in the polluted air, the flow rate of polluted air, and the pH of the cadmium nitrate solution. Pertraction efficiency was maximum for the sodium carboxymethyl–cellulose (NaCMC)-polypropylene hollow fiber membrane, a hydrogen sulfide concentration in the polluted air of 20 ppm, polluted air flow rate of 50 L/min, and a pH of 2 and 4.
... According to the study, the LCOE and COA of solar-assisted power plants were roughly $73/MWh and $39/tonCO 2 , respectively [227]. Fig. 11 Cost breakdown of the VSA technology using zeolite 13x, taking into account expenses for drying and cooling [226] Fig. 12 Prices of adsorbents have an impact on Zeolite 13X's minimum CO 2 collection cost, which includes VSA drying and chilling expenses. Indicators 1 × , 2 × ,…, 10 × denote the multiplier that has been applied to the cost [226] Vol:.(1234567890) ...
This review was carried out on removal of flue gases (CO2, SO2, and H2S) that are emitted from various sources. Burning solid fuels for heat, such as natural gas, gasoline, and coal or biomass, results in the production of flue gas. Adsorption of flue gases by utilizing Zeolites was properly explained, including the zeolite synthesis technique, characteristics, zeolite sensitivity, variables that influence the adsorption process, zeolite efficiency, and cost-effectiveness. Zeolites have a notable adsorption capability for CO2, SO2, and H2S, despite their major disadvantage of being poor long-term durability and stability. Remarkable advancements are being made in present-day CO2 capture methods, especially concerning the use of zeolites. Zeolites are unique materials with great potential for CO2 collection because of their tiny holes, high porosity, structural variety, and recyclability. Since atmospheric CO2 concentrations are already more than 415 parts per million, it is imperative to limit future releases of this gas and keep it out of the carbon cycle. The elimination of SO2 by the majority of zeolites was shown to rise with temperatures up to 200 °C and subsequently decrease at higher temperatures. It was also shown that SO2 uptake and breakthrough time are significantly affected by drying zeolite using microwave and traditional heating methods. The sorption capacity and sorbent regenerability of SO2 are sensitive to the presence of other gases in the flue gas, such as O2, CO2, NOx, and water vapor, as well as the reaction temperature. Zeolites must possess strong sulfur loading capacity, good regenerability, and a stable structure to be an effective adsorbent for the removal of H2S. Regarding the utilization of zeolites as adsorbents for the flue gases, new developments, and continuing difficulties have been concluded in this review work.
The valorization of hydrogen sulfide (H₂S) through its dissociation into hydrogen and elemental sulfur presents a promising route for converting hazardous waste into valuable commodities. Here, we report a novel...
To advance the utilization of high-concentration CO2 produced in biogas upgrading, it is essential to remove associated hydrogen sulfide (H2S). This study presents a series of bimetallic Fe-Cu oxieds supported...
This paper presents a literature review focusing on the separation of hydrogen sulfide (H2S) from biogas using activated carbon (AC), compared with other materials such as biochars, zeolites, metal–organic frameworks (MOFs) and metal-based adsorbents in terms of H2S separation capacity. The evaluation is carried out on different biogas compositions used to achieve breakthrough curves, including mixtures containing, in addition to H2S, methane (CH4) and carbon dioxide (CO2), air and inert gases. H2S adsorption mechanisms are presented and discussed. The article also includes a review of simulation studies on room-temperature H2S separation by adsorption columns. In addition, sorbent regeneration is addressed through a comparison in terms of degradation of separation performance. The results reveal that ACs, particularly when impregnated, outperform other sorbents in terms of H2S separation efficiency at room temperature. This research presents important information for optimizing the H2S removal process in biogas purification, thus contributing to the development of environmentally sustainable energy solutions.
Solid-state batteries have garnered global attention due to their high energy density and safety, holding the potential to replace traditional lithium-ion batteries in the electric vehicle, alleviating “range anxiety”. However, a comprehensive solid-state battery management system to complement these batteries has not yet been systematically proposed. We attempt to construct a management system for solid-state batteries based on various characteristics, considering both the demand- and supply-side. This review first introduces the advantages and disadvantages of polymer-based, oxide-based, and sulfide-based solid electrolytes, as well as anode and cathode materials with higher specific capacities and promising applications. It lists the cycling performance and safety demonstrated by assembled solid-state pouch cells. Then, we systematically analyzes the differences between all-solid-state batteries and traditional lithium-ion batteries, proposing the demands and development directions for all-solid-state battery management from multiple dimensions. Finally, we build an all-solid-state battery management system from aspects such as signal monitoring, model building, aging, and early warning of failure, which includes three parts: the electric management system, the thermal management system, and the pressure management system. This review aims to provide researchers with new insights and ideas, promoting the efficient development and industrial upgrading of battery management technology.
In this study, chitosan was first used as the raw material for filmmaking, and the film-forming conditions were optimized to prepare six kinds of chitosan-based membranes, and then charcoal composite membrane materials were prepared by adding different amounts of lignin charcoal to fill in the base membranes; the adsorption performance of the composite membrane was analyzed using H 2 S as the target, and the mechanical properties and structure of the composite membrane were explored using various testing techniques. The experimental results showed that the chitosan-based membrane could adsorb a certain amount of H 2 S due to its hydroxyl-rich surface. When lignin carbon was added to it, and with the increase of the content of lignin carbon, the performance of the membrane adsorption of H 2 S was improved, but the mechanical properties decreased, and in a comprehensive comparison of the adsorption performance and mechanical properties of the composite membrane, which had a better adsorption length of H 2 S adsorption of 84 min and the tensile strength of 1.65 MPa. The pore structure in the composite membrane due to microphase separation and the exposure of oxygen-containing functional groups on the surface of the base membrane and charcoal were the main reasons for the effective retention of H 2 S.
Metal–organic framework derivative NiWO4–NiO heterojunction was fabricated for high-performance H2S sensors. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy were used to systematically characterize and analyze the NiWO4–NiO composites. The H2S gas sensitivity performances of NiO, NiWO4(5%)–NiO, and NiWO4(10%)–NiO sensors were tested under different temperatures. The NiWO4(5%)–NiO sensor yielded the best response performance to hydrogen sulfide gas at 120 °C. The metal–organic framework derivative NiWO4–NiO has a large specific surface area and porosity. Meanwhile, the heterojunction can improve the carrier migration rate. In addition, first-principles calculations further revealed the improved H2S gas-sensitizing properties of NiWO4–NiO. Therefore, the sensor has gas-sensitive properties, such as low detection limit, good reproducibility, excellent humidity resistance, and fast response/recovery time in the detection of hydrogen sulfide gas. The NiWO4(5%)–NiO-based sensor is of practical significance for hydrogen sulfide sensing.
Hydrogen sulfide (H2S) is toxic and corrosive at high concentrations and pressures. Adsorption methods are suitable due to their low energy consumption, low cost, and high efficiency. Synthesis and optimization of structural and operational parameters of specific molecularly imprinted polymers (MIPs) Nano adsorbents for H2S gas adsorption carried out using response surface design methodology. The optimal polymerization conditions of MIPs included 16 experiments. The amounts of template molecules (1–5 mmol), cross-linker (5–20 mmol), functional monomer (2–12mmol), porogen solution (acetonitrile/ethyl acetate v/v 1–9%), elution solution (acetic acid/methanol 20/80) and initiator (25–100 mg) were optimized using Taguchi method of experimental design. We used the SRK equation of state for the molar mass of the gas on a fixed bed with a height of 400 mm and an inner diameter of 10 mm. Finally, physical properties were determined using FTIR, XRD, FE-SEM, and BET. Statistical analysis showed that the signal-to-noise ratio between the template molecule, cross-linker, and functional monomer was 2:15:2.5, and the optimal adsorption value occurred at a volume ratio of acetonitrile/ethyl acetate of 1:9 and initiator of 75. In this study, the surface is MIPs@H2S. Variance analysis showed that all Nano-adsorbents followed a second-order model, temperature and adsorbent dosage were the most critical variables in the process, and the equilibrium adsorption of all Nano-adsorbents followed the Langmuir isotherm and second-order synthesis model. The regeneration study highlighted that the Nano-adsorbent is a promising adsorbent with high reversibility and stability for H2S gas. Finally, the selectivity results of specific adsorption of H2S gas by CO2/H2S/CH4 gas mixture of MIPs@H2S were significantly higher than that of Non-imprinted polymers (NIPs) Nano adsorbent.
Sulfur plays a pivotal role in interactions within the atmosphere, lithosphere, pedosphere, hydrosphere and biosphere, and the functioning of living organisms. In the Earth's crust, mantle, and atmosphere, sulfur undergoes geochemical transformations due to natural and anthropogenic factors. In the biosphere, sulfur participates in the formation of amino acids, proteins, coenzymes and vitamins. Microorganisms in the biosphere are crucial for cycling sulfur compounds through oxidation, reduction and disproportionation reactions, facilitating their bioassimilation and energy generation. Microbial sulfur metabolism is abundant in both aerobic and anaerobic environments and is interconnected with biogeochemical cycles of important elements such as carbon, nitrogen and iron. Through metabolism, competition or cooperation, microorganisms metabolizing sulfur can drive the consumption of organic carbon, loss of fixed nitrogen and production of climate-active gases. Given the increasing significance of sulfur metabolism in environmental alteration and the intricate involvement of microorganisms in sulfur dynamics, a timely re-evaluation of the sulfur cycle is imperative. This Review explores our understanding of microbial sulfur metabolism, primarily focusing on the transformations of inorganic sulfur. We comprehensively overview the sulfur cycle in the face of rapidly changing ecosystems on Earth, highlighting the importance of microbially-mediated sulfur transformation reactions across different environments, ecosystems and microbiomes.
Biogas contains significant quantities of undesirable and toxic compounds, such as hydrogen sulfide (H2S), posing severe concerns when used in energy production-related applications. Therefore, biogas needs to be upgraded by removing H2S to increase their bioenergy application attractiveness and lower negative environmental impacts. Commercially available biogas upgradation processes can be expensive for small and medium-scale biogas production plants, such as wastewater treatment facilities via anaerobic digestion process. In addition, an all-inclusive review detailing a comparison of biochar and hydrochar for H2S removal is currently unavailable. Therefore, the current study aimed to critically and systematically review the application of biochar/hydrochar for H2S removal from biogas. To achieve this, the first part of the review critically discussed the production technologies and properties of biochar vs. hydrochar. In addition, exisiting technologies for H2S removal and adsorption mechanisms, namely physical adsorption, reactive adsorption, and chemisorption, responsible for H2S removal with char materials were discussed. Also, the factors, including feedstock type, activation strategies, reaction temperature, moisture content, and other process parameters that could influence the adsorption behaviour are critically summarised. Finally, synergy and trade-offs between char and biogas production sectors and the techno-economic feasibility of using char for the adsorption of H2S are presented. Biochar’s excellent structural properties coupled with alkaline pH and high metal content, facilitate physisorption and chemisorption as pathways for H2S removal. In the case of hydrochar, H2S removal occurs mainly via chemisorption, which can be attributed to well-preserved surface functional groups. Challenges of using biochar/hydrochar as commercial adsorbents for H2S removal from biogas stream were highlighted and perspectives for future research were provided.
Graphical abstract
The process of harmless treatment of livestock manure produces a large amount of odor, which poses a potential threat to human and livestock health. A vertical fermentation tank system is commonly used for the environmentally sound treatment of chicken manure in China, but the composition and concentration of the odor produced and the factors affecting odor emissions remain unclear. In this study, we investigated the types and concentrations of odors produced in the mixing room (MR), vertical fermenter (VF), and aging room (AR) of the system, and analyzed the effects of bacterial communities and metabolic genes on odor production. The results revealed that 34, 26 and 26 odors were detected in the VF, MR and AR, respectively. The total odor concentration in the VF was 66613 ± 10097, which was significantly greater than that in the MR (1157 ± 675) and AR (1143 ± 1005) (P < 0.001), suggesting that the VF was the main source of odor in the vertical fermentation tank system. Methyl mercaptan had the greatest contribution to the odor produced by VF, reaching 47.82%, and the concentration was 0.6145 ± 0.2164 mg/m3. The abundance of metabolic genes did not correlate significantly with odor production, but PICRUSt analysis showed that cysteine and methionine metabolism involved in methyl mercaptan production was significantly more enriched in MR and VF than in AR. Bacillus was the most abundant genus in the VF, with a relative abundance significantly greater than that in the MR (P < 0.05). The RDA results revealed that Bacillus was significantly and positively correlated with methyl mercaptan. The use of large-scale aerobic fermentation systems to treat chicken manure needs to focused on the production of methyl mercaptan.
Natural gas generates varying concentrations of H2S during natural formation and extraction, and H2S leak accidents are frequent, posing a significant threat to the safety of human life and the environment. Conventional treatment technology equipment is large and does not meet the emergency requirements of the complex topographical gas field. This study aimed to design a pilot-scale method coupling the venturi and bubbling reactors to reduce equipment size and improve emergency capabilities for the absorption of leaked H2S. It found that the ring system self-priming venturi reactor, which was suitable only for the coarse treatment of toxic gases, maintained an absorption efficiency of around 50% under most operating conditions, with substantial variations due to changes in process parameters, but that redundancy of the bubbling reactor was high. With the synergistic effect of venturi and bubbling, the coupling process had an extremely high absorption efficiency, basically more than 95%. The experiments also showed that the H2S concentration at the outlet of the venturi–bubbling reactor increased with increasing inlet gas concentration and gas volume. The absorption performance improved significantly on increasing Fe³⁺ concentration; it increased first and then remained constant, and the optimum Fe³⁺ concentration for the absorption of leaked H2S was 21 000 mg/m³. The absorption performance decreased with increasing submergence height and then remained stable after the size of the inlet approached 600 mm, whereas the overall absorption efficiency of the venturi–bubbling reactor remained constant. The optimum operating temperature range was 10 °C–50 °C. The experimental system kept the outlet concentration below the emergency discharge standard for a continuous period of 48 h following practical use in the gas field and resulting in significant enhancement in mass transfer performance, fully satisfying the emergency requirements.
Deep eutectic solvent (DES) was applied as the solvent of iron/alcohol amine system, and the prepared iron/ethanolamine/DES system was found to be a good desulfurizer for H2S removal. The absorbents were characterized by Fourier transform infrared spectroscopy. The iron/ethanolamine/DES system showed a significantly enhanced desulfurization performance compared with DES solution of iron or alcohol amine separately. Besides, the absorbents showed relatively stable desulfurization performance, which could keep a high H2S removal efficiency in a wide temperature range from 30–90°C. The iron/ethanolamine/DES system could be recycled for at least three times. The desulfurization product was analyzed by energy dispersive spectrum and X-ray diffraction, and the desulfurization product was identified as sulfur element.
The coal to ethylene glycol (CTEG) process has drawn much attention due to the serious conflict between supply and demand of ethylene glycol in China. However, it is inevitably accompanied by the problem of high CO2 emissions. Carbon capture is one of the most promising potential effective ways to address this issue. However, the CTEG process, integrated with carbon capture technology, will lead to energy and economic penalties. Thus, a comprehensive evaluation of CTEG process with different CO2 capture technologies is urgently needed. This study analyzed the technoeconomic performance of four CO2 capture alternatives for the CTEG process: Rectisol, mono-ethanol amine (MEA), chilled ammonia process (CAP) and dimethyl carbonate (DMC) technologies. Results show the energy consumption of CO2 capture of the Rectisol process is the lowest, 1.88 GJ/tCO2, followed by the DMC process, 2.10 GJ/tCO2, the CAP process, 3.64 GJ/tCO2, and the MEA process, 5.20 GJ/tCO2. The CO2 capture cost of the Rectisol process is lowest, CNY 169.5/tCO2, followed by the DMC process, CNY 193.2/tCO2, the CAP process CNY 232.6/tCO2, and the MEA process CNY 250.5/tCO2. As the Rectisol technology has the best comprehensive performance, it is the best option for CTEG industry in comparison with the MEA, CAP, and DMC technologies.
With fossil fuel being the major source of energy, CO 2 emission levels need to be reduced to a minimal amount namely from anthropogenic sources. Energy consumption is expected to rise by 48% in the next 30 years, and global warming is becoming an alarming issue which needs to be addressed on a thorough technical basis. Nonetheless, exploring CO 2 capture using membrane contactor technology has shown great potential to be applied and utilised by industry to deal with post- and pre-combustion of CO 2 . A systematic review of the literature has been conducted to analyse and assess CO 2 removal using membrane contactors for capturing techniques in industrial processes. The review began with a total of 2650 papers, which were obtained from three major databases, and then were excluded down to a final number of 525 papers following a defined set of criteria. The results showed that the use of hollow fibre membranes have demonstrated popularity, as well as the use of amine solvents for CO 2 removal. This current systematic review in CO 2 removal and capture is an important milestone in the synthesis of up to date research with the potential to serve as a benchmark databank for further research in similar areas of work. This study provides the first systematic enquiry in the evidence to research further sustainable methods to capture and separate CO 2 .
The efficient screening of solvents for CO2 capture requires a reliable and robust equation of state to characterize and compare their thermophysical behavior for the desired application. In this work, the potentiality of 14 ionic liquids (ILs) and 7 deep eutectic solvents (DESs) for CO2 capture was examined using soft-SAFT as a modeling tool for the screening of these solvents based on key process indicators, namely, cyclic working capacity, enthalpy of desorption, and CO2 diffusion coefficient. Once the models were assessed versus experimental data, soft-SAFT was used as a predictive tool to calculate the thermophysical properties needed for evaluating their performance. Results demonstrate that under the same operating conditions, ILs have a far superior performance than DESs primarily in terms of amount of CO2 captured, being at least two-folds more than that captured using DESs. The screening tool revealed that among all the examined solvents and conditions, [C4 py][NTf2] is the most promising solvent for physical CO2 capture. The collection of the acquired results confirms the reliability of the soft-SAFT EoS as an attractive and valuable screening tool for CO2 capture and process modeling.
In this study, hollow fibers of commercial polyimide were arranged into membrane modules to test their capacity and performance towards natural gas processing. Particularly, the membranes were characterized for CO2/CH4 separation with and without exposure to some naturally occurring contaminants of natural gases, namely hydrogen sulfide, dodecane, and the mixture of aromatic hydrocarbons (benzene, toluene, xylene), referred to as BTX. Gas permeation experiments were conducted to assess the changes in the permeability of CO2 and CH4 and related separation selectivity. Compared to the properties determined for the pristine polyimide membranes, all the above pollutants (depending on their concentrations and the ensured contact time with the membrane) affected the permeability of gases, while the impact of various exposures on CO2/CH4 selectivity seemed to be complex and case-specific. Overall, it was found that the minor impurities in the natural gas could have a notable influence and should therefore be considered from an operational stability viewpoint of the membrane separation process.
To high efficiently remove H2S from low partial pressure coke oven gas (COG), a novel activator (tetramethylammonium arginine, [N1111][Arg]) was used to blend with N-methyldiethanolamine (MDEA) for the absorption of H2S. High concentrated [N1111][Arg]-MDEA aqueous solution was used as absorbent. Thermodynamic properties including absorption amount and H2S loading values were measured, then the kinetic apparent absorption rate was calculated based on the change of absorption amount with time. The removal efficiency of H2S in simulated COG was verified in tray towers. Compared with monoethanolamine (MEA)-MDEA and tetramethylammonium glycinate ([N1111][Gly])-MDEA aqueous solutions, [N1111][Arg]-MDEA aqueous solution takes advantages of higher absorption capacity, absorption rate and removal efficiency. Our results showed that the proposed absorbent has good industrial application prospect in coke oven gas desulfurization, because it achieved 100% removal of H2S in the tray tower containing only 4 sieve plates under high concentrated condition (water content < 45%), which may significantly decrease the energy consumption.
Biological desulfurization of biogas from a field-scale anaerobic digester in Peru was tested using air injection (microaeration) in separate duplicate vessels and chemical desulfurization using duplicate iron filters to compare hydrogen sulfide (H2S) reduction, feasibility, and cost. Microaeration was tested after biogas retention times of 2 and 4 h after a single injection of ambient air at 2 L/min. The microaeration vessels contained digester sludge to seed sulfur-oxidizing bacteria and facilitate H2S removal. The average H2S removal efficiency using iron filters was 32.91%, with a maximum of 70.21%. The average H2S removal efficiency by iron filters was significantly lower than microaeration after 2 and 4 h retention times (91.5% and 99.8%, respectively). The longer retention time (4 h) resulted in a higher average removal efficiency (99.8%) compared to 2 h (91.5%). The sulfur concentration in the microaeration treatment vessel was 493% higher after 50 days of treatments, indicating that the bacterial community present in the liquid phase of the vessels effectively sequestered the sulfur compounds from the biogas. The H2S removal cost for microaeration (2 h: 27/m³ H2S removed) was an order of magnitude lower than for the iron filter ($382/m³ H2S removed). In the small-scale anaerobic digestion system in Peru, microaeration was more efficient and cost effective for desulfurizing the biogas than the use of iron filters.
Comparison of different regeneration options for direct air capture (DAC) has usually been limited to only consider pure CO2 production, limiting the process options to e.g. temperature-vacuum swing adsorption (TVSA) or steam-stripping. In this work, detailed experimental comparison is conducted of temperature swing adsorption (TSA/TCSA) and TVSA for DAC. Particularly, TVSA is assessed with air or inert gas purge flow (TVCSA) and without purge flow. The working capacity, regeneration specific energy requirement (SER) and adsorbent regenerability of these processes was compared. For all other studied regeneration options except TVSA without purge flow, over 85% regeneration was obtained already at 60 °C. Isobaric TSA at 60 °C had the lowest regeneration SER of 4.2 MJ/kgCO2. Coupling TSA with mild vacuum improved desorption rate and increased working capacity from 0.47 to 0.51 mmolCO2/gsorbent, requiring 7.5 MJ/kgCO2 for regeneration. Without purge flow, TVSA resulted in only 0.39 mmolCO2/gsorbent with the SER of 8.6 MJ/kgCO2 at 100 °C. Due to lower allowable regeneration temperature of 60 °C, mild vacuum TVSA with air flow also had a lower cyclic capacity decrease rate of 0.26 %/cycle compared to 0.38 %/cycle with TVSA without purge flow at 100 °C. However, using 100 °C with air flow in the TVSA process lead to a significant capacity decrease of 0.6 %/cycle. Therefore, using either air or inert purge flow below 100 °C coupled with mild vacuum has benefits over the TVSA process with no inflow in terms of CO2 productivity, specific energy requirement and adsorbent regenerability. For utilization purposes that require low-concentration CO2, TVSA with purge flow should thus be considered as a viable regeneration option for direct air capture along with isobaric TSA.
Four deep eutectic solvents (DESs) were synthesized, and 5–30% polyethylenimine (PEI) was added to make functional DESs (FDESs) for dynamic absorption experiments of hydrogen sulfide. The synthesized FDESs were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and nuclear magnetic resonance. The results demonstrated the successful synthesis of FDESs. The interaction between H2S and the FDESs was discussed at a molecular level via the quantum chemical calculations. It was noticed that FDESs prefer chemisorption on H2S. In this work, the 25% PEI/[email protected] showed the highest desulfurization performance. The effects of H2S concentration and temperature on the desulfurization performance were investigated. It was found that a relatively low temperature (30 °C) was favorable for the absorption of H2S. The 25% PEI/[email protected] could remove H2S efficiently over a low H2S concentration. Moisture played an important role in the FDES desulfurization system. The absorption/desorption cycle experiment indicated that the FDESs retain their good regeneration performance for at least five times.
The separation of hydrogen sulfide (H2S) from gas streams has significant economic and environmental repercussions for the oil and gas industries. The present work reviews H2S separation via nonreactive and reactive adsorption from various industrial gases, focusing on the most commonly used materials i.e., natural or synthetic zeolites, activated carbons, and metal oxides. In respect to cation-exchanged zeolites, attention should also be paid to parameters such as structural and performance regenerability, low adsorption temperatures, and thermal conductivities, in order to create more efficient materials in terms of H2S adsorption. Although in the literature it is reported that activated carbons can generally achieve higher adsorption capacities than zeolites and metal oxides, they exhibit poor regeneration potential. Future work should mainly focus on finding the optimum temperature, solvent concentration, and regeneration time in order to increase regeneration efficiency. Metal oxides have also been extensively used as adsorbents for hydrogen sulfide capture. Among these materials, ZnO and Cu–Zn–O have been studied the most, as they seem to offer improved H2S adsorption capacities. However, there is a clear lack of understanding in relation to the basic sulfidation mechanisms. The elucidation of these reaction mechanisms will be a toilsome but necessary undertaking in order to design materials with high regenerative capacity and structural reversibility.
Subsea natural gas processing attracts increased interest due to the smaller environmental footprint. Natural gas (NG) dehydration and sweetening are the main processing steps to avoid pipeline plugging and corrosion caused by the presence of water and CO2. Triethylene glycol (TEG) and amine absorption are the commercial technologies for these applications. However, membrane technology is considered as promising solutions for alternative subsea gas processing technologies, which provides unmanned operations without the requirements for rapidly periodical maintenance. In this work, a hybrid membrane process was designed for integrated dehydration and sweetening of a saturated natural gas containing 10 mol.% CO2, and the process operating parameters such as inter-stage feed and permeate pressures are investigated. The simulation results indicated that the optimal permeate pressure in the 2nd -stage unit is 4 bar, and the optimal 3rd-stage feed and permeate pressures are15bar and 2bar, respectively. The minimum specific cost of <2.71×10⁻³ $/m³ sweet natural gas was estimated to achieve the separation requirement of <2.5 mol% CO2 in purified NG together with captured high purity CO2 (>95 mol%) for enhanced gas recovery. However, due to the relatively low water selectivity of the dehydration membranes at high pressure of 60 bar used in the simulation, the hydrocarbon loss is still quite higher. Thus, advanced membranes with high H2O/CH4 selectivity at high pressure should be pursued to promote the application of the designed membrane system for subsea natural gas dehydration and sweetening.
PurposeBiogas cleaning is a fundamental step before its exploitation to take off potential pollutants, particularly hydrogen sulfide (H2S), from the gas and therefore to protect downstream facilities while reducing toxic emissions in the atmosphere. The aim of the presented work is to compare H2S adsorption efficiencies between different types of thermal treatment residues: a biochar, two biomass ashes and an incinerated sewage sludge.MethodsH2S-adsorption experiments were realized with a real landfill biogas. All materials were characterized before and after adsorption in order to evaluate their physicochemical properties related to their reactivity.ResultsThe results showed that biochar and biomass ashes can both remove H2S from biogas, despite these materials have very different features. Biomass ashes are basic, humid and mineral materials, whereas biochar is dry, mainly organic and very porous. On the contrary, incinerated sewage sludge could adsorb only a small amount of H2S under tested experimental conditions, underlining the importance of the porosity of materials for sufficient H2S adsorption.Conclusions
The use of thermal treatment residues for biogas cleaning has a positive impact on the environment with the reuse of waste material and can also reduce the costs of biogas as an energy vector and enable its development.Graphic Abstract
Recently, the selective removal of H2S and CO2 has been highly desired in natural gas sweetening. Herein, four novel azole‐based protic ionic liquids (PILs) were designed and prepared through one‐step neutralization reaction. The solubility of H2S (0–1.0 bar), CO2 (0–1.0 bar), and CH4 (0–5.0 bar) was systematically measured at temperatures from 298.2 to 333.2 K. NMR and theoretical calculation were used to investigate the reaction mechanism between these PILs and H2S. Reaction equilibrium thermodynamic model (RETM) was screened to correlate the H2S solubility. Impressively, 1,5‐diazabicyclo[4,3,0] non‐5‐ene 1,2,4‐1H‐imidazolide ([DBNH][1,2,4‐triaz]) shows the highest H2S solubility (1.4 mol/mol or 7.3 mol/kg at 298.2 K and 1.0 bar) and superior H2S/CH4 (831) and CO2/CH4 (199) selectivities compared with literature results. Considering the excellent absorption capacity of H2S, high H2S/CH4, and CO2/CH4 selectivity, acceptable reversibility, as well as facile preparation process, it is believed that azole‐based PILs provide an attractive alternative in natural gas upgrading process.
In this work, we report a novel urea-modified copper-based material ([email protected]) obtained by directly calcinating a mixture of urea and copper nitrate. This material enables the efficient purification of H2S under dry and anaerobic conditions. The performance test results showed that the H2S capacity of the optimal adsorbent ([email protected]) could reach 364.2 mg(H2S)∙gsorbent⁻¹, which is much superior to those of other adsorbents in the literature. Further study demonstrates that the ultra-desulfurization performance of [email protected] is mainly attributed to the extensive alkaline site, the high concentrations of active oxygen, and the abundance of oxygen vacancy; which are quite effective for capturing H2S (acidic and strong reducibility). Interestingly, the deactivation adsorbent ([email protected]) is mainly composed of high-purity CuS, which means that the [email protected] adsorbent can simultaneously achieve efficient purification of H2S and recovery of sulfur resources since CuS is a valuable product. In addition, in-situ FT-IR and theoretical calculation results indicate that H2S molecules dissociate on the CuO(111) surface by stepwise dehydrogenation, while S combines with adjacent Cu to form CuS. The consumption of active components (CuO) and the accumulation of reaction products (CuS) are the primary reasons for the deactivation of adsorbents. Considering the simple preparation process, low cost, and excellent H2S adsorption activity, these urea-modified copper-based materials are very promising H2S adsorbents.
Carbon materials for the room-temperature selective oxidation of H2S have attracted growing attention in recent years. The recent development of carbon-based desulfurization catalysts is reviewed, including activated carbon modified by alkalis, porous carbon doped with nitrogen or modified with functional groups, and carbon composites with other species such as alkaline metal oxides. The oxidation mechanisms for H2S on the various catalysts are discussed, and the important function of carbon in desulfurization are emphasized, including its large specific area, porous structure and adjustable surface chemistry. In addition to the catalytic oxidation of H2S, the extended use of the spent catalysts, sulfur/carbon composites, as sulfur cathode materials for high-performance lithium-sulfur batteries, is discussed as a way to add extra value to the sulfur-containing pollutants. Finally, the outlook for using carbon-based materials for room-temperature desulfurization and the key challenges to its large-scale use are explored.
The present study investigated the odor emission potential of activated sludge through comprehensive assessment for physicochemical properties and bacterial profile of sludge. Three types of sludges from wastewater treatment plants treating slaughterhouse (SWTP), meat processing (MWTP) and domestic wastewater (DWTP) were used based on distinct morphological features which were speculated to impact odor generation. Total element S in the SWTP sludge with relatively more disintegrated cellular debris exhibited higher level than that in the MWTP and DWTP sludge, while the emitted odorants (hydrogen sulfide and methyl mercaptan) showed the opposite patterns (i.e., the lowest level for the SWTP sludge). Nitrifying bacteria was only detected in the SWTP sludge, which was well in line with abundant nitrate in the corresponding aeration tank. Principal component analysis indicated that the potential of the odor emission from the sludge had strong correlations with dehydrogenase activity, and nitrate, which implies that these parameters may serve as referring indices for evaluating the potential of odor emission of sludge or treated product.
The permeability of poly(dimethylsiloxane) [PDMS] to H2, O2, N2, CO2, CH4, C2H6, C3H8, CF4, C2F6, and C3F8, and solubility of these penetrants were determined as a function of pressure at 35 °C. Permeability coefficients of perfluorinated penetrants (CF4, C2F6, and C3F8) are approximately an order of magnitude lower than those of their hydrocarbon analogs (CH4, C2H6, and C3H8), and the perfluorocarbon permeabilities are significantly lower than even permanent gas permeability coefficients. This result is ascribed to very low perfluorocarbon solubilities in hydrocarbon-based PDMS coupled with low diffusion coefficients relative to those of their hydrocarbon analogs. The perfluorocarbons are sparingly soluble in PDMS and exhibit linear sorption isotherms. The Flory–Huggins interaction parameters for perfluorocarbon penetrants are substantially greater than those of their hydrocarbon analogs, indicating less favorable energetics of mixing perfluorocarbons with PDMS. Based on the sorption results and conventional lattice solution theory with a coordination number of 10, the formation of a single C3F8/PDMS segment pair requires 460 J/mol more energy than the formation of a C3H8/PDMS pair. A breakdown in the geometric mean approximation of the interaction energy between fluorocarbons and hydrocarbons was observed. These results are consistent with the solubility behavior of hydrocarbon–fluorocarbon liquid mixtures and hydrocarbon and fluorocarbon gas solubility in hydrocarbon liquids. From the permeability and sorption data, diffusion coefficients were determined as a function of penetrant concentration. Perfluorocarbon diffusion coefficients are lower than those of their hydrocarbon analogs, consistent with the larger size of the fluorocarbons. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 415–434, 2000
The desulfurization and regeneration performance of nanofluids composed of oxidizing ionic liquids and four inert nanoparticles are investigated. The addition of different nanoparticles has been proved to have enhancement effect on the H2S removal performance of oxidizing ionic liquids. The nanofluids with SiO2 nanoparticles showed the most significant strengthening desulfurization performance as well as regeneration performance. The optimal weight ratio of SiO2 nanoparticles in nanofluids was confirmed as 0.5%. The regeneration efficiency of the optimal nanofluid system can exceed 88%, which is far higher than that before the addition of SiO2 nanoparticles. The mass transfer coefficient increased significantly after the addition of nanoparticles. The nanoparticles and nanofluids before and after absorption were characterized by Fourier transform infrared spectra, nuclear magnetic resonance, scanning electron microscope, transmission electron microscope, energy dispersive spectrum and X-ray photoelectron spectroscopy. It was found that the structure and morphology of SiO2 nanoparticles remained basically unchanged in the absorption-regeneration process. The main final desulfurization product was identified as sulfate.
Natural gas purification is a challenging task due to the existing number of contaminants in the mixture. Sour natural gas, in particular, presents an even higher challenge due to the presence of the highly toxic hydrogen sulfide (H2S) gas. These contaminants level must be reduced to meet the sales gas specifications. In this paper, three DAM-based random copolymers were prepared for simultaneous improvement of the acid gases (CO2 and H2S) separation properties of their corresponding membranes. While the developed membranes exhibit high CO2/CH4 selectivity in a non-sour mixed-gas, their unconventional behavior during sour gas separation is difficult to predict. Therefore, their membranes were subjected to sour mixed-gas separation tests a quinary gas mixture including 20 vol.% H2S at different upstream pressures up to 34.5 bar. Each membrane demonstrated one or more improved properties in terms of acid gases permeability and selectivity coefficients. Taking into consideration the overall performance, membranes prepared from 6FDA-DAM/6FpDA (1:3) exhibited the most attractive separation properties among the series prepared. However, based on the relatively high H2S/CH4 selectivity obtained of 6FDA-DAM/CARDO (1:3) membranes, a block 6FDA-DAM/6FDA-CARDO (1:1) copolyimide was prepared, and the sour mixed-gas separation properties were evaluated. The overall block copolymer membrane demonstrated very attractive productivity and efficiency, compared to the standard industrially used glassy polymer, cellulose acetate, thereby rendering it a potential candidate for sour natural gas purification.
Poisonous gases, such as H2S and PH3, produced by industrial production harm humans and damage the environment. In this study, H2S and PH3 were simultaneously removed at low temperature by modified activated carbon fiber (ACF) catalysts. We have considered the active metal type, content, precursor, calcination, and reaction temperature. Experimental results exhibited that ACF could best perform by loading 15% Cu from nitrate. The optimized calcination temperature and reaction temperature separately were 550°C and 90°C. Under these conditions, the most removal capacity could reach 69.7 mg/g and 132.1 mg/g, respectively. Characterization results showed that moderate calcination temperature (550°C) is suitable for the formation of the copper element on the surface of ACF, lower or higher temperature will generate more cuprous oxide. Although both can exhibit catalytic activity, the role of the copper element is significantly greater. Due to the exceptional dispersibility of copper (oxide), the ACF can still maintain the advantages of larger specific surface area and pore volume after loading copper, which is the main reason for better performance of related catalysts. Finally, increasing the copper loading amount can significantly increase the crystallinity and particle size of copper (oxide) on the ACF, thereby improving its catalytic performance. In situ IR found that the reason for the deactivation of the catalyst should be the accumulation of generated H2PO4 and SO
2−4
(H2O)6 which could poison the catalyst.
Gasification has been increasingly seen as a method to convert solid fuel into combustible syngas. However, these applications require syngas with strict requirements and raw syngas often does not meet these requirements. Therefore, a form of syngas upgrading needs to be applied. One of the most common form of syngas upgrading is removal of CO2, which is often present in large concentrations in raw syngas. The currently existing CO2 removal technologies were either designed not with syngas in mind or for large scale industries, which makes them somewhat inefficient for application with gasification syngas. This calls for more research into efficient removal of CO2, from syngas. In this review, the application of deep eutectic solvent (DES) as one of the potential new absorbent for CO2 removal from gas stream and more specifically from syngas are discussed. DES has garnered attention due to its high CO2 absorption performance, process friendliness, and environmental friendliness. At present, most studies on DES are still limited to basic absorption behavior of the absorbent. This review aims to provide not just a clear picture of the current research situation for DES as CO2 removal absorbent, but also detail the possible research directions that might be taken for the development of DES as CO2 absorbent from syngas. To that end, this paper shall discuss the specific situation of gasification development, syngas utilization, and the current DES research situation including: its advantages compared to conventional absorbents, its current research situation, challenges, and possible future research directions.
Polymeric gas separation membranes have become a competent technology over the past few decades. This review focuses on the broad classifications of membrane materials and the criteria for the selection of membrane materials, describes the various synthesis routes adopted for membrane fabrication, and explains various gas transport mechanisms. A comparison of membrane-based separation technology with other conventional technologies has also been made. The review also discusses the current polymers used for gas separations, current commercially viable membrane-based gas separation processes, and various limitations associated with the development of membrane material and separation processes. Further, various new classes of membranes developed for gas separations, including thermally rearranged polymers, polymers of intrinsic microporosity, room temperature ionic liquids, perfluoro polymers, and mixed matrix membranes, that has high separation performance has also been discussed. Some of the emerging membrane-based gas separations are also reviewed.
The synthesis of a green product depends on a deep perception concerning its economic and environmental impacts. To attain this purpose, a life cycle assessment (LCA) coupled with life cycle cost (LCC) comparative study was conducted concerning two highly efficient synthesized carbon-based adsorbents i.e. activated carbon (AC) and modified AC (MAC) for 1 kg CO2 adsorption. A set of different analyses comprising CML baseline 2000, cumulative energy demand (CED), ecological footprint (EF), and greenhouse gas protocol (GGP) were explored. The most affected categories by the synthesized adsorbents were human toxicity (>2.63 %), marine (86 %), and freshwater aquatic ecotoxicity (7.46 %), resulting in CO2, SO2, and NO2 emission and metal release. The CED was 2.6 times more for MAC, dominantly supplied by fossil fuel (>91.45 %). The total economic costs were 2/kg for the AC and MAC, respectively. The H3PO4 and copper ion consumption exhibited the highest environmental impacts accounted for a 97 % contribution for AC and 61.48 % for MAC, while the most economic burden belonged to equipment and construction (>23 %). The marine aquatic toxicity (19.50 %) and human toxicity (16.09 %) were the most sensitive categories by a 95 % confidence limit through the uncertainty analysis. Accordingly, the LCA coupled LCC results elucidated that the MAC possessed more significant economic and environmental impacts, despite its higher CO2 adsorption.
Over the past decade, CO2 separation and capture have become the new bandwagon for polymer science and membrane research. This review presents the fundamentals of CO2/gas separation in polymeric membranes and discusses how these principles underpin opportunities and challenges for post-combustion carbon capture (CO2/N2), hydrogen purification (CO2/H2), and natural gas and biogas sweetening (CO2/CH4). Emerging polymeric membrane materials are discussed, including a few polymers containing a high content of polar functional groups (i.e., ether oxygen-rich polymers and polymeric ionic liquids), shape-persisting glassy polymers (i.e., perfluoropolymers, thermally rearranged polymers, iptycene-containing polymers), and reactive polymers featuring facilitated transport. Moreover, the promising candidates for each CO2 separation application are highlighted. Finally, the permeability-selectivity data reviewed were plotted against their 2008 and 2019 upper bounds.
In recent years, membrane technology has shown special advantages in the field of carbon capture from flue gas. However, the increase of mass transfer resistance caused by membrane wetting becomes a major obstacle to improve the CO2 removal efficiency. In this work, ceramic membrane contactor consisting of 16 commercial ceramic membranes is used to capture CO2 and a new system operation mode is proposed to avoid membrane wetting. The ceramic membrane is characterized by a series of instruments. In the CO2 capture process, Monoethanolamine (MEA) solution as the liquid absorbent is flowed in the tube side of the membrane and the gas is flowed counter-currently in the shell side. Furthermore, the effects of gas flow rate, absorbent flow rate, absorbent concentration and absorbent temperature on CO2 removal efficiency are investigated. In addition, under fixed gas-liquid ratio conditions, the effects of increasing gas-liquid flow rate on CO2 removal efficiency are investigated. Compared with other studies, the results indicate higher CO2 removal efficiency and mass transfer rate. Compared with self-prepared hydrophobic ceramic membranes, commercial ceramic membranes have more prospects for large-scale application because they are cheaper and easier to operate and maintain.
In the present study, a novel N-S rich nanoporous carbon based on jute thread waste (JW) as a prevalent cellulosic biomass in order to remove CO2 and H2S from gaseous stream has been successfully synthesized and fabricated. For this end , we synthesized a series of jute-derived nanoporous carbon (JW-NC) samples with different KOH/C ratios (i.e., 3, 4 and 5), synthesis temperatures (i.e., 700, 800 and 900 ˚C) and times (i.e., 60, 90 and 120 min).The results indicated that JW-NC nanoadsorbents have been mainly composed of carbon nanofibers, and provided high surface area (up to 2579.55 m²/g) with excellent pore volume (up to 1.50 cm³/g) . As experimentally investigated JW-NC nanoadsorbents displayed an extra-high CO2 and H2S adsorption capacity at 1 bar (8.05 mmol/g for CO2 and 17.19 mmol/g for H2S), 10 bar (20.53 mmol/g for CO2 and 29.26 mmol/g for H2S) and 35 bar (30.36 mmol/g for CO2 and 40.41 mmol/g for H2S). The results obtained by the density functional theory (DFT) method showed that the Pyrrolic-N atoms affect the pores significantly and play an important role for gas adsorption in all cases. However, the presence of S atoms around Pyrrolic-N atoms in the pores could change the adsorption mechanisms, from which the chemisorption of H2S (Ead = -336.28 kJ.mol⁻¹) changed interestingly to physisorption (Ead = -23.92 kJ.mol⁻¹) as increased S/N ratio of the adsorbent. To sum up , the high gas adsorption capacity, along with excellent cyclic performance and superior preferential gas adsorption, make JW-NC nanoadsorbents as a viable and cost-effective candidate for large-scale natural gas purification.
Polymers of intrinsic microporosity (PIMs) with high free volumes have been synthesized by incorporating contorted rigid moieties into polymers backbones. Despite their many appealing properties, membranes made of these polymers have not been used industrially because of their fast physical aging. The unprecedented CO2 permeability and satisfactory CO2/N2 and CO2/CH4 selectivity of PIMs have led to establishing the new 2019 upper bounds for the gas mixtures. This article reviews recent advances in the field of PIM-based membranes. It discusses polymer synthesis strategies to modify PIM structures such that the resulting membranes have improved CO2 separation performance and lower physical aging. The strategies include the use of monomers with suitable side chains, kinked moieties, and stable structures.
Recycling hazardous gas of H2S is one of the most important strategies to promote sustainable development. Herein, a novel method regarding purifying H2S is proposed by using yellow phosphorus and phosphate rock slurry as absorbent. The H2SO4, formed in situ by H2S conversion, can be devoted to decompose phosphate rock, and the spent absorption slurry was applied as raw material for the production of phosphorus chemical products. According to the characterization analysis, it was found that H2S was first oxidized to SO2 via O2 as well as O3 induced by P4. Subsequently, the generated SO2 dissolved rapidly in water to form H2SO4, and then reacted with the main component of phosphate rock, CaMg(CO3)2. Most notably, the active substances, such as, O3, SO4•- and OH•, produced in the reaction process, can oxidize H2S and HS⁻ to these sulfur products. In addition, trace amounts of Fe³⁺ and Mn²⁺ that were dissolved from phosphate rock displayed a promotional effect on the formation of active substances. Consequently, as high as 85% of H2S removal efficiency can be obtained even under acidic condition and low temperature. The proposed H2S purification method offers a promising option for sulfur recovery and H2S pollution control.
Odor emissions from intensive livestock farms have attracted increased attention due to their adverse impacts on the environment and human health. Nevertheless, a systematic summary regarding the characteristics, sampling detection, and control technology for odor emissions from livestock farms is currently lacking. This paper compares the development of odor standards in different countries and summarizes the odor emission characteristics of livestock farms. Ammonia, the most common odor substance, can reach as high as 4,100 ppm in the compost area. Sampling methods for point and area source odor emissions are introduced in this paper, and odor analysis methods are compared. Olfactometers, odorometers, and the triangle odor bag method are usually used to measure odor concentration. Odor control technologies are divided into three categories: physical (activated carbon adsorption, masking, and dilution diffusion), chemical (plant extract spraying, wet scrubbing, combustion, non-thermal plasma, and photocatalytic oxidation), and biological (biofiltration, biotrickling, and bioscrubbing). Each technology is elucidated, and the performance in the removal of different pollutants is summarized. The application scopes, costs, operational stability, and secondary pollution of the technologies are compared. The generation of secondary pollution and long-term operation stability are issues that should be considered in future technological development. Lastly, a case analysis for engineering application is conducted.
Biochar, a carbon-rich material, has been widely used to adsorb a range of pollutants because of its low cost, large specific surface area (SSA), and high ion exchange capacity. The adsorption capacity of biochar, however, is limited by its small porosity and low content of surface functional groups. Nano-metal oxides have a large SSA and high surface energy but tend to aggregate and passivate because of their fine-grained nature. In combining the positive qualities of both biochar and nano-metal oxides, nano-metal oxide-biochar composites (NMOBCs) have emerged as a group of effective and novel adsorbents. NMOBCs improve the dispersity and stability of nano-metal oxides, rich in adsorption sites and surface functional groups, maximize the adsorption capacity of biochar and nano-metal oxides respectively. Since the adsorption capacity and mechanisms of NMOBCs vary greatly amongst different preparations and application conditions, there is a need for a review of NMOBCs. Herein we firstly summarize the recent methods of preparing NMOBCs, the factors influencing their efficacy in the removal of several pollutants, mechanisms underlying the adsorption of different pollutants, and their potential applications for pollution control. Recommendations and suggestions for future studies on NMOBCs are also proposed.
Coke oven gas is an important byproduct of the steel industry as it is used as an energy substitute for natural gas. However, coke gas contains impurities and must be treated before use. One of the steps of the treatment is the absorption process, wherein ammonia and hydrogen sulfide are removed. Considering the increasing use of coke oven gas and, in parallel, the strengthening of compliance with emission restrictions, it is extremely important to make the absorption process more efficient. This work consists of the development of a coke oven gas purification process model to evaluate solutions that would allow greater removal of hydrogen sulfide. The developed model was validated with data from an industrial plant, with errors of less than 6% for the most relevant variables. Among the three configurations tested, the best configuration represented a 5% increase in removal efficiency. This result is in line with scientific efforts in the search for environmentally responsible solutions. In addition, the improvement in the performance of this process allows for the use of coal with a higher sulfur content (responsible for generating hydrogen sulfide) at processes upstream of coke oven gas purification. Since coal with a higher sulfur content is cheaper and abundant, unlike low sulfur coal, an economic analysis was developed that allowed the financial impact of this modification to be quantified. The proposed modification resulted in a reduction of 15% of raw materials costs.
Membranes are considered promising tools for gas sweetening due to their lower footprint (i.e., area and energy requirement, considering elimination of solvent/absorbent and its associated regeneration procedures), and ease of scale-up. Performing membrane gas separation is strongly dependent on membrane materials. With a 0.38-nm pore size, the SAPO-34 membrane surpasses the upper bond limit for CO 2 /CH 4 separation. However, preparing defect-free and high-performance zeolite membranes is quite challenging. This paper reviews gas transport and separation mechanisms in SAPO-34 membranes, and it discusses prospective approaches for obtaining membranes with defect-free selective layers and hence high separation performance. Highlights, as well as the authors’ perspectives on the future development of SAPO-34 membranes in the field of gas separation, are pointed out.
The H2S removal performances of four deep eutectic solvent (DES) based nanofluid (NF) systems were measured using dynamic absorption experiment. The Cu containing NF system is found to be an excellent absorbent for H2S removal with a significantly enhanced desulfurization performance compared with DES original solution. Besides, the NF systems have relatively high regeneration performance. The NF systems and Cu nanoparticles before and after absorption as well as after regeneration were characterized by Fourier transform infrared (FT-IR) spectra, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscope (TEM) and energy dispersive spectrum (EDS). It is found that the ethanolamine, choline cation and sulfur were accumulated on the surface of Cu nanoparticles after absorption, and the bulk elements on the surface were identified as Cu and S after regeneration. The S⁻² was existed in the form of Cu2S, and some sulfur was oxidized to zero-valent sulfur after regeneration.
The development of membranes for the concurrent removal of CO2 and H2S from natural gas continues to elude researchers and frustrate industrial adoption of membrane technologies. A long-observed performance trade-off exists where glassy polymers generally lend themselves to diffusion-controlled CO2/CH4 separations, while rubbery polymers excel in solubility-controlled H2S/CH4 separations. These orthogonal separation preferences complicate materials development in pursuit of a membrane capable of simultaneous acid gas removal from concentrated sour gas feeds with high efficiency. Herein, we report our examination of alkoxysilyl-substituted vinyl-added poly (norbornene)s (VAPNBs) for the removal of CO2 and H2S from simulated natural gas feeds. This study investigates the sour gas separation performance of ten distinct VAPNBs that systematically vary in alkoxysilyl substitution to evaluate their ability to perform this challenging separation. High-pressure mixed gas permeation testing highlights structure-property relationships stemming from previously observed design principles related to side chain polarity and sterics that lead to high H2S/CH4 selectivities, exceptional CO2 and H2S permeabilities, and notable improvements in CO2/CH4 permeation properties compared to a well-studied alkylsilyl VAPNB derivative. By combining permeation analysis and pure gas sorption measurements, changes in the Langmuir contributions were found to be influential on acid gas separation performance. These results provide insight and opportunity to further expand this work in order to bring to market membranes capable of simultaneously removing CO2 and H2S from natural gas.
We report the influence of structural features on the properties of porous carbonaceous materials obtained using soft-templating coupled with hydrothermal carbonisation. Our results demonstrate that using d-glucose with Pluronic P123 results in a more homogeneous particle size distribution of carbon spheres compared with d-fructose. The textural properties of the carbon materials, both surface area and pore volume, have improved when the carbonisation temperature was increased from 550 °C to 900 °C, while the amount of C=C bonds was also increased. Physical activation with CO2 was found to open the pores and thereby improve textural properties, including total pore volume, micropore volume, and surface area. Concomitantly, the CO2 and H2S uptake also underwent significant enhancement, achieving a maximum CO2 adsorption capacity of 8.37 mmol/g at 0 °C and 1 bar, and ca. 6 mmol/g at room temperature and 1 bar. The same samples showed about 25.7 mmol/g adsorption capacity for H2S at room temperature and atmospheric pressure, with approximately 32% process efficiency.
Anthropogenic activities are significantly altering the chemistry of the oceans. One major implication of human activities is ocean acidification, which refers to the increase in ocean pH in response to the addition of CO2. This CO2 is being absorbed in the ocean from the atmosphere due to increased anthropogenic emissions from the combustion of fossil fuels. Another effect is the loss of oxygen from ocean waters, known as deoxygenation. Oxygen is lost from the oceans both as an effect of warming Earth surface temperatures and as a result of changing biogeochemical cycles. Finally, human activities are altering nutrient cycles. Urban and agricultural activities cause nitrogen and phosphorus loading in coastal regions, while the damming of rivers reduces silica fluxes to the ocean. Fertilizer production and fossil fuel combustion also increase nutrient delivery via atmospheric pathways. In this article, these three themes will be explored, including a discussion of the biological and ecological implications, the current observations and projections, and context from the geologic record.
Coalbed methane (CBM) is an unconventional natural gas, and vigorous development of CBM has great significance for improving the current status of global coal mine safety production, alleviating market gas supply pressure, and protecting the ecological environment. CBM mainly consists of CH4, CO2 and a small amount of H2S. In order to improve the comprehensive energy utilization efficiency of CBM, it is necessary to capture both CO2 and H2S from CBM. In this paper, a comprehensive 2D model was established by COMSOL Multiphysics for simultaneously removing CO2 and H2S in CBM. The K2CO3/potassium lysinate (PL) mixed solution was employed as the absorbent in a membrane contactor. The impacts of gas and liquid velocities, liquid concentration and temperature on the absorbent performance were studied. The results obtained by using the simulated membrane contactor were consistent with the experimental data in the literature. The results indicate that the gas velocity was the most significant influential factor to the gases removal efficiency. Furthermore, it was concluded that the K2CO3/PL mixed solution had better decarburization performance than the single K2CO3 solution. The optimal operating conditions for simultaneous removal process by using K2CO3/PL mixed solution were obtained by response surface method. More importantly, the blends of amino acid salts and carbonate solution have great prospects in the membrane absorption of acid gases from CBM.
Recent interest in developing high performance polymeric membranes has evolved the molecular transport performance in gas separation and pervaporation. The synthesis of polymer with novel structures may improve the separation performance of a membrane. However, it always accompanies undeterminable risk such as economic costs and development duration. Polymer blends have gained interdisciplinary interest as promising modification strategy owing to the advantages of being versatile, straightforward and least expensive besides having cost- and time-effective routes in developing membranes with desirable separation performance. Despite these advantages, polymer blends have encountered the main challenges of compatibility at the molecular level, resulting in unsatisfactory membrane separation performance. The thermodynamic properties of polymer blends lead to different phase behaviors of the end products such as being miscible, immiscible and partially miscible. Due to the significant importance of compatibility in polymer blends, this review summarizes the fundamental understanding of phase behaviors, molecular interactions, separation properties and prediction models from the polymer blend membranes. Moreover, the recent progress on state-of-the-art polymer blend membranes in various energy-related applications, especially for gas separation and pervaporation will be reviewed. Lastly, the perspectives on the current challenges and future opportunities to facilitate polymer blend membranes will be discussed.
The potential of a novel Fe/EDTA/carbonate-based scrubbing process for the simultaneous removal of H2S and CO2 from biogas was studied by evaluating the influence of Fe/EDTA molarity (M), carbonate concentration (IC), biogas (B), air (A) and liquid (L) flow rates on biogas upgrading performance using a Taguchi L16(4⁵) experimental design. The ANOVA demonstrated that molarity of the Fe/EDTA solution was a significant factor influencing H2S concentration (0.035 % at 0.00 M to 0.000 % at 0.05 M). IC impacted on the concentrations of CO2 (13.1 and 4.5 % at 4000 and 10,000 mg L⁻¹, respectively), N2 and CH4 (85.9 and 94.5 % at 4000 and 10,000 mgIC L⁻¹, respectively). The biogas flow rate affected the concentrations of CO2 (2.5 to 13.8% at 10 and 40 mL min⁻¹, respectively), O2, N2 and CH4 (95.9 to 85.4% at 10 and 40 mL min⁻¹, respectively). Likewise, the recycling liquid flow rate affected CO2 (8.3 and 5.9 % at 5 and 30 mL min⁻¹, respectively), O2, N2 and CH4 (90.5 and 93.3 % at 5 and 40 mL min⁻¹, respectively) concentrations. Finally, the air flow rate impacted on CO2 (10.8 and 6.7 % at 800 and 1000 mL min⁻¹, respectively), H2S, N2 and CH4 (87.9 and 92.2 % at 800 and 1000 mL min⁻¹, respectively) concentrations. Process optimization provided the optimal conditions for each control factor. Continuous biogas upgrading operation at M2-IC1-B2-A4-L4 (0.05 M, 10,000 mgIC L⁻¹, 10 mL min⁻¹, 1000 mL min⁻¹ and 30 mL min⁻¹, respectively) provided CH4, CO2, O2, N2 and H2S concentration in the upgrading biogas of 97.4, 1.4, 0.29, 0.97 and 0%, respectively, which complied with biomethane regulations.
A new H2S removal reactive adsorbent was prepared from a biosolid by the addition of pluronic surfactant F 127 prior to a simple pyrolysis at 950 oC at two heating regimes. The materials were extensively characterized and tested as H2S removal media from air. The results show over 250 % increase in the H2S removal efficiency compared to the adsorbent obtained without the surfactant addition. Hydrogen sulfide was converted mainly to elemental sulfur. While the surfactant increased the carbon content and volume of mesopores, slow pyrolysis additionally contributed to the development of micropores, increased a carbon structural order, and resulted in an enhanced dispersion of catalytic centers (Ca and Fe oxides) on the surface. It also increased the amount of nitrogen in pyridinic configurations. All of these facilitated electron transfers, thus promoting oxidation reactions, and provided the sites increasing H2S interactions with the surface and also those acting as a storage system for elemental sulfur.
Bio-oil is a highly valuable product derived from biomass pyrolysis which could be used in various downstream applications upon appropriate upgrading and refining. Extraction and fractionation are two promising methods to upgrade bio-oil by separating the complex mixture of bio-oil compounds into distinct fine chemicals and fractions enriched in certain classes of chemical compounds. In this review, various extraction techniques for bio-oil (organic solvent extraction, water extraction, supercritical fluid extraction, distillation, adsorption, chromatography, membrane, electrosorption and ionic liquid extraction), their associated features (extraction mechanisms involved, advantages and disadvantages), the characteristics of bio-oil extracts and their applications are presented and critically discussed. It was revealed that the most promising technique is via organic solvent extraction. Furthermore, the technological gaps and bottlenecks for each separation techniques are disclosed, as well as the overall challenges and future prospects of oil palm biomass-based bio-oil value chain. This review aims to provide key insights on bio-oil upgrading via extraction and fractionation, and a proposed way forward via technology integration in establishing a sustainable palm oil mill-based biorefinery.
This work presented experimental and modeling studies on the simultaneous absorption of H2S and CO2 into the N-methyldiethanolamine (MDEA) and piperazine (PZ) solution in a rotating packed bed (RPB). The effect of different operating conditions, including MDEA concentration (CMDEA), PZ concentration (CPZ), liquid volumetric flow rate (L), temperature (T) and high gravity factor (β) on the absorption efficiencies of H2S and CO2 (ηH2S and ηCO2) were investigated. The results showed that ηH2S and ηCO2 were significantly affected by CMDEA, CPZ, L and β. ηH2S and ηCO2 could reach 99.98% and 96.51% respectively. Furthermore, an artificial neural network (ANN) model was established to predict ηH2S, ηCO2 and mass-transfer coefficient (KGa). Results showed that the predicted values were in good agreement with the experimental values (within deviations of ±10% for H2S and CO2). This work provides a potential technology of simultaneous absorption of H2S and CO2 for the biogas upgrade.
Microporous and nanoporous metal oxides are potential adsorbents for separating H2S from natural gas. Structured porous adsorbents have the potential to improve the energy and production costs in gas separation and catalysis applications by providing higher production rates. Zinc, Manganese, and Iron oxide nanoparticles are among the most potential and most extensively employed materials. Applying this framework, other novel metal oxides have been recognized for separation of H2S from representative H2S/CH4. In the present study, we investigate the performance of Molybdenum oxide nano-particles as an adsorbent for H2S removal and compare it with the performance of zinc oxide nano-particles. The effects of operating conditions such as temperature (65–89 °C), pressure (10–19 bar), initial concentration of H2S in the feed stream (38–73 ppm), and space velocity (0.018–0.045 m s⁻¹) on H2S adsorption from sour gas are evaluated. Our analysis shows that Molybdenum oxide nano-particles have an adsorption capacity of 0.081 and 0.074 g H2S/g Molybdenum oxide in low temperature and low concentration of H2S using non-spherical and spherical Molybdenum oxide sorbent, respectively. Proceeding by two adsorption isotherms, the Langmuir and Freundlich isotherms, analysis of variance displayed that both models can fit the adsorption data of H2S on Molybdenum oxide nanoparticles very well, while the Freundlich isotherm seems to provide R² value of 0.98–0.99, indicating a better prediction of our experimental data.
To improve the absorption efficiency of alkaline liquor treated with hydrogen sulphide in coal mines, a single sodium carbonate lye was taken as the basic raw material to modify the absorption of lye by adding the surfactant sodium dodecyl benzene sulfonate (SDBS) and the oxidant hydrogen peroxide. Respectively, the effects of different concentrations of surfactants and oxidants in sodium carbonate solution on the removal of hydrogen sulphide gas were investigated. The results show that the concentration of sodium carbonate solution is positively correlated with the removal rate of hydrogen sulphide. When the concentration of sodium carbonate solution increases to 2%, the initial removal rate of hydrogen sulphide is close to 100%, however, the problem of secondary dissipation of hydrogen sulphide is more significant after vibration. With the increase of SDBS and hydrogen peroxide concentration, the removal rate of hydrogen sulphide from sodium carbonate solution respectively increases to 93.1% and 86.2%. Finally, through experimental analysis and in situ measurements, the optimal ratio of the modified lye in the hydrogen sulphide treatment of this experiment is as follows: the concentration of sodium carbonate solution is shown to be 2%, the concentration of surfactant is 0.4%, and the concentration of oxidant is 0.6%. On this basis, by comparing the 40,201 working face of Xiaozhuang Coal Mine with the 40,202 working face, it is concluded that the average removal rate of the modified lye is 93.5%, and the treatment effect of removing hydrogen sulphide is significant.
Gas separation studies typically investigate polymeric materials in the context of pure gas, and occasionally binary mixed gas properties, yet real world separations involve a myriad of components that can affect separation performance. The purification of sour gas demands efficient separations of both H2S and CO2 from natural gas, making realistic testing critical. In this work, we introduce a novel crosslinking scheme of the commercially ubiquitous polymer, poly(ethylene glycol) (PEG), via a facile route amenable to thin film composite formation. We crosslinked a systematic series of telechelic PEG oligomers with average molecular weights of 200–2050 g mol⁻¹ and investigated the gas transport properties of the corresponding membranes in pure, binary CO2/CH4, and ternary H2S/CO2/CH4 sour gas mixtures. Crosslinking effectively eliminated PEG crystallinity for molecular weights up to 1000 g mol⁻¹ and favorably increased CO2/CH4 selectivity. Though previously unexplored for H2S separations, crosslinked PEG membranes demonstrated exceptionally high H2S/CH4 selectivities ranging from 65-116 in ternary sour gas feeds. We achieved tunable transport performance of CO2/CH4 and H2S/CH4 separations by balancing PEG content with crosslink density to disrupt crystallinity. Crosslinked PEG derived from a 2050 g mol⁻¹ oligomer showed a semi-crystalline microstructure, defining the upper limit of PEG chain length of this system for gas separation applications. Thermal and diffraction studies on the PEG membranes further revealed only amorphous morphologies up to 1000 g mol⁻¹ and that the resulting membranes spanned both glassy and rubbery regimes, which resulted in profound differences on CO2/CH4 and H2S/CH4 transport performance.
Hybrid membranes assembled from a polymeric matrix and an inorganic filler are considered one of the most promising membranes for energy-efficient gas separations due to their high performance and low-cost fabrication. Rigid polymer matrices often exhibit lasting porosity and consequently have been gradually employed to fabricate separation membranes of high permeance. Metal–organic frameworks (MOFs) are a key class of fillers that have fueled the exploration of advanced hybrid-membrane technologies for gas separation. In this short review, an evolutional pathway for more advanced MOF/polymer hybrid-membrane morphologies and their modules are highlighted along with state-of-the-art applications. Here, we address key issues such as selecting the appropriate MOF filler and polymer matrix, improving filler/matrix compatibility within hybrid membranes, and, most importantly, how to scale up MOF/polymer hybrid membranes efficiently and economically for large-scale industrial applications.
Plasticization is a well-understood drawback of polymer membranes in many applications; however, recent studies have demonstrated surprising advantages of this phenomenon for demanding natural gas sweetening for some glassy polymer dense film membranes. Moving beyond dense film membranes, the current study focuses on cellulose triacetate (CTA) hollow fiber membranes to use the benefits of controlled plasticization for realistic raw natural gas sweetening. Natural gas sweetening can be complicated by co-existence of condensable hydrocarbons, e.g. C2H6, C3H8 and toluene with the main H2S/CO2/CH4 ternary mixture; moreover, the operating temperature and pressure adds another dimension to this important separation. In this study, we consider an aggressive gas composition of high H2S (20 mol.%), low CO2 (5 mol.%), and significant amounts of C2H6 (3 mol.%) and C3H8 (3 mol.%) as well as trace amount of toluene (100–300 ppm) with CH4 comprising the rest of the feed. Various temperatures (35 °C and 50 °C) and pressures (6.9–31.3 bar) are also considered. We show a controlled plasticization benefit for the CTA hollow fiber membrane, with attractive CO2 and H2S permeance (>110 GPU) and selectivity (22–28) for CO2 and H2S over CH4 at 35 °C and 31.3 bar. The current study represents a major step forward in processes for membrane-based natural gas sweetening using practical asymmetric membranes.
Aerobic composting and anaerobic digestion with hydrolysis pretreatment are two mainstream methods used to recycle and reclaim sewage sludge. However, during these sludge treatment processes, many odors are emitted that may cause severe emotional disturbance and health risks to those exposed. This study identified odor pollution (i.e. sensory influence, odor contribution, and human risks) from samples collected during sludge aerobic composting throughout different seasons as well as during anaerobic digestion with hydrolysis pretreatment. Odor intensity, odor active values, and permissible concentration-time weighted averages for ammonia and five volatile sulfur compounds were assessed. The results revealed serious odor pollution from all sampling sites during aerobic composting, especially in winter. Excessively strong odors were identified in the composting workshop, with total odor active values between 997 and 8980 which accounted for 78.45%-96.18% of the total sludge aerobic composting plant. Levels of ammonia and dimethyl disulfide in the ambient air were high enough to harm employees' health. During anaerobic digestion, excessively strong odors were identified in dehydration workshop 2, and the total odor active values of six odors reached 32,268, with ammonia and hydrogen sulfide levels significant enough to harm human health.