Solvent Regeneration Research Articles

The Role of Low-Carbon Fuels and Carbon Capture in Decarbonizing the U.S. Clinker Manufacturing for Cement Production: CO2 Emissions Reduction Potentials

Low-carbon fuels, feedstocks, and energy sources can play a vital role in the decarbonization of clinker production in cement manufacturing. Fuel switching with renewable natural gas, green hydrogen, and biomass can provide a low-carbon energy source for the high-temperature process heat during the pyroprocessing steps of clinker production. However, up to 60% of CO2 emissions from clinker production are attributable to process-related CO2 emissions, which will need the simultaneous implementation of other decarbonization technologies, such as carbon capture. To evaluate the potential of fuel switching and carbon capture technologies in decarbonizing the cement industry, a study of the facility-level CO2 emissions is necessary. This study evaluates the potential for using a single low-carbon fuel as an energy source in clinker production for cement manufacturing compared to conventional clinker production (which uses a range of fuel mixes). In addition, conventional carbon capture (operated with natural gas-based steam for solvent regeneration) and electrified carbon capture configurations were designed and assessed for net-zero emission targets. Carbon emissions reductions with and without biogenic emissions credits were analyzed to ascertain their impact on the overall carbon accounting. Results show that carbon emissions intensity of cement can vary from 571 to 784 kgCO2eq/metric ton of cement without carbon capture and from 166.33 to 438.66 kgCO2eq/metric ton of cement with carbon capture. We find that when biogenic carbon credits are considered, cement production with a sustainably grown biomass as fuel source coupled with conventional carbon capture can lead to a net-negative emission cement (−271 kgCO2eq/metric ton of cement), outperforming an electrified capture design (35 kgCO2eq/metric ton of cement). The carbon accounting for the Scope 1, 2, and biogenic emissions conducted in this study is aimed at helping researchers and industry partners in the cement and concrete sector make an informed decision on the choice of fuel and decarbonization strategy to adopt.

Removal of perfluoroalkyl acids and precursors with silylated clay: Efficient adsorption and enhanced reuse

Organically modified clays (organoclays) have been considered effective adsorbents for the treatment of per- and polyfluoroalkyl substances (PFAS). However, the stability of organoclays prepared through the conventional cation exchange approach has been a major concern for their practical application. In this study, we reported the development of a new organically functionalized clay by grafting pillared clay substrate with an organosilane through covalent bonding. The performance of the silylated clay (QAG-ZrMT) was systematically compared with an organoclay prepared from ion exchange (HDTMA-ZrMT) for the adsorption of two legacy perfluoroalkyl acids: perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), and two precursor compounds 5:3 fluorotelomer carboxylic acid (5:3FTCA) and 6:2 fluorotelomer sulfonic acid (6:2FTS). Compared to HDTMA-ZrMT, QAG-ZrMT showed substantially improved performance for adsorption of less hydrophobic PFAS (e.g., 5:3FTCA), which could be related to the stronger electrostatic interactions between PFAS and QAG-ZrMT than HDTMA-ZrMT. More importantly, QAG-ZrMT could be conveniently regenerated and reused for multiple cycles with robust performance. In contrast, HDTMA-ZrMT almost completely lost its capacity for PFAS removal after regeneration, due to the loss of organic functional groups during solvent regeneration. Results can shed light on the design of efficient and regenerable organoclay adsorbents for remediation of PFAS-contaminated water matrices.

Techno-Economic Feasibility Analysis of Post-Combustion Carbon Capture in an NGCC Power Plant in Uzbekistan

As natural gas-fired combined cycle (NGCC) power plants continue to constitute a crucial part of the global energy landscape, their carbon dioxide (CO2) emissions pose a significant challenge to climate goals. This paper evaluates the feasibility of implementing post-combustion carbon capture, storage, and utilization (CCSU) technologies in NGCC power plants for end-of-pipe decarbonization in Uzbekistan. This study simulates and models a 450 MW NGCC power plant block, a first-generation, technically proven solvent—MEA-based CO2 absorption plant—and CO2 compression and pipeline transportation to nearby oil reservoirs to evaluate the technical, economic, and environmental aspects of CCSU integration. Parametric sensitivity analysis is employed to minimize energy consumption in the regeneration process. The economic analysis evaluates the levelized cost of electricity (LCOE) on the basis of capital expenses (CAPEX) and operational expenses (OPEX). The results indicate that CCSU integration can significantly reduce CO2 emissions by more than 1.05 million tonnes annually at a 90% capture rate, although it impacts plant efficiency, which decreases from 55.8% to 46.8% because of the significant amount of low-pressure steam extraction for solvent regeneration at 3.97 GJ/tonne CO2 and multi-stage CO2 compression for pipeline transportation and subsequent storage. Moreover, the CO2 capture, compression, and transportation costs are almost 61 USD per tonne, with an equivalent LCOE increase of approximately 45% from the base case. This paper concludes that while CCSU integration offers a promising path for the decarbonization of NGCC plants in Uzbekistan in the near- and mid-term, its implementation requires massive investments due to the large scale of these plants.

A Novel Plasma-Enhanced Solvolysis as Alternative for Recycling Composites

In this work, a plasma-assisted solvolysis method is proposed as an alternative method for the oxidative degradation of carbon fiber-reinforced composites (CFRCs). Nitrogen plasma ignition within bubbles in a concentrated nitric acid solution is employed, combining the synergistic effects of traditional nitric acid solvolysis and plasma chemistry. A comprehensive process flowchart, including steps such as composite pretreatment, matrix dissolution, fiber recovery and cleaning, solvent regeneration and reuse, and waste treatment, is also discussed, highlighting their importance in process effectiveness. Moreover, a study on the effect of the composite’s mass on the plasma-enhanced solvolysis process is conducted, and the results are exploited for the calculation of critical parameters such as efficiency, recovery rates, capacity, fibers quality, energy consumption, consumption of raw materials, operational and installation costs, and environmental impact. A preliminary comparison to other recycling methods based on the literature findings is also attempted, and preliminary metrics to assess the sustainability of the recycling process are proposed.

Simulation and optimization for flue gas CO2 capture by energy efficient water-lean ionic liquid solvent

Ionic liquids (IL) are treated as advanced materials for energy-saving carbon dioxide (CO2) capture from flue gas but suffer from serious challenges in energy and mass management. Herein, a water-lean IL-based deep eutectic solvent with 1,8-diazabicyclo [5.4.0] undec-7-ene imidazole ([DBU] [IM]) and ethylene glycol (EG) blends was prepared with a screened proportion of IL:EG=7:3. The CO2 loading and saturated solvent viscosity were 1.89 mol/L and 95 mPa·s, respectively. The foundational properties of the IL-EG solvent were determined by experimental measurements and thermodynamic modeling. The vacuum flashing desorption technology was innovatively adopted for energy-saving solvent regeneration. Industrial-scale process simulation of multistage flashing was used to explore the energy consumption during solvent regeneration. Meanwhile, the segmented cooling paved a route for water separation from water-lean solvent. A comprehensive analysis was performed out to optimize the operating parameters for CO2 absorption and desorption. For the recommended 3-stage flashing configuration, the specific process regeneration energy consumption amounted to only 1.54 GJ/tCO2. Consequently, the total capture cost reduced to 48.1 $/tCO2, marking a decrease of 31.28 %, 16.55 % and 10.25 %, compared with MEA solvent, water-lean solvent and biphasic solvent, respectively. This work offered insights for future endeavors in the development of IL-based CO2 capture process from industrial flue gas.

Facile preparation of multifunctional cellulose nanocrystals from coffee residue via hydrothermal technique: Prolific roles on the water purification, antibacterial and antifungal applications

In this work, the facile preparation of coffee residue (CR)-derived multifunctional cellulose nanocrystals (CNCs) via hydrothermal technique has been successfully attempted. The morphological structure, functionality, crystalline pattern, surface chemistry, elemental content and surface charge were evaluated. The adsorptive property was assessed using both anionic and cationic aqueous pollutants, chlorpyrifos and methylene blue (MB), and simulated by the non-linear isotherm models and kinetic equations. Its unique antibacterial and antifungal functions were tested against both gram-negative/positive bacterial and fungal species. The particle length and diameter, aspect ratio, crystallinity index, sulfate group content and zeta potential of this newly prepared rod-shaped CNCs were identified to be 432.39 nm, 23.57 nm, 18.34, 75.0 %, 0.21 mmol/g and −32.7 mV, respectively. CR-CNCs recorded an outstanding adsorptive feature for both MB and chlorpyrifos, with the monolayer adsorption capacities of 403.02 mg/g and 159.75 mg/g, respectively. The adsorptive uptakes could be effectively preserved via solvent regeneration technique, even after 5 adsorption-desorption runs. Excellent inhibition efficiencies against both gram-negative/gram-positive bacteria, and fungal species have been detected, with the growth-inhibition zones ranging from 10.9 to 26.7 mm. The novel protective roles of the newly prepared CR-CNCs against both biological and water contaminants have been well-elucidated.

Pre-treatment of waste hydrated cement used for replacement of fine aggregate using amine-based CO2 solvent

In the realm of construction and demolition (C&D) waste, a small fraction of hydrated cement waste is typically repurposed to generate supplementary cementitious material or filler for concrete. However, the conventional method of utilizing it in powder form demands significant energy consumption to achieve the necessary fineness. Therefore, this study proposes a method to use a waste-hydrated cement paste as a fine aggregate as well as the pre-treatment method to enhance its properties. The pre-treatment involves carbonating hydrated cement in a fully CO2-dissolved amine-based CO2 solvent, specifically a monoethanolamine (MEA) solution. This process eliminates vulnerable phases, such as calcium hydroxide, resulting in a higher compressive strength of mortar when incorporating the treated hydrated cement as fine aggregate. Notably, the use of fully CO2-dissolved 1% and 10% MEA solutions during carbonation demonstrates superior performance and increased CO2 uptake. Additionally, the developed pre-treatment method uses MEA CO2 solvent directly, commonly utilized for CO2 capture in industrial flue gas. It is an alternative for solvent regeneration without the need for a heating process, potentially reducing overall energy consumption.

Synergistic coordination-regulated separation of nickel and cobalt from spent Ni(II) and Co(II) bearing choline chloride/ethylene glycol electrolyte: Theoretical and experimental investigations

Developing efficient and environmentally friendly metal recovery technologies from secondary resources is crucial for enhancing resource utilization and promoting environmental sustainability. However, metals with similar physicochemical properties pose significant challenges in the recovery process, particularly for nickel and cobalt. Herein, we present a coordination-regulated approach utilizing water-, temperature-, and pH-codrived to achieve sequential precipitation recovery of nickel and cobalt from waste choline chloride/ethylene glycol (Ethaline) electrolyte containing Ni(II) and Co(II) ions. By carefully adjusting water content, temperature, and pH, we can control the speciation of Ni(II) ([NiCl(H2O)2(EG)2]+) and Co(II) ([CoCl2(H2O)2(EG)2]0) ions in the Ethaline-based electrolyte, thereby facilitating nickel preferential precipitation. Additionally, further introducing water into the Co(II)-rich phase promotes the formation of [CoCl(H2O)3(EG)2]+ complex ions, leading to efficient separation of cobalt. When oxalic acid is used as a precipitant, the recovery efficiencies for nickel and cobalt reach 96.3% and 97.5%, respectively, with purities of 97.8% and 98.5%. Importantly, distilling the water-containing solvent allows for regeneration of Ethaline with a yield rate as high as 97.1%, while maintaining its structural stability. This proposed strategy offers a promising pathway for sustainable metal recovery from spent Ethaline electrolytes containing metal ions while enabling solvent regeneration.

Synthesis of desulfurization solvent networks based on process characteristics: New insights of desulfurization units and a novel synthesis method

Synthesis of desulfurization solvent network (DSN) can reduce the solvent circulation and the energy consumption for solvent regeneration. Based on the desulfurization process characteristics, this work proposes a novel graphic to explore the operating limitations of a desulfurization unit. A feasible operating window of the desulfurization unit is presented with three boundary lines to constrain the solvent reuse. Different cases for the solvent reuse between units are analyzed in details, and two rules for rich solvent reuse are proposed and proven. A novel hierarchical method is developed for the DSN synthesis. A refinery case is investigated using the proposed method. Four DSN designs are obtained, and the fresh solvent consumption can be reduced by 13.7 %. The accuracy of the four designs is verified by rigorous simulation, showing a maximum relative error of 1.22 %. The proposed method can show clear insights in DSN synthesis and give reliable and concise designs.

Quantitative recovery and regeneration of basic deep eutectic solvent for biomass treatment with industrialized membrane-based strategy

As a new type of ionic liquids, basic deep eutectic solvents have been reported as emerging medium for biorefinery, extraction, catalysis and so on. Quantitative recovery with recycling of basic DES was important for the scale utilization of biomass and the environmental conservation. An electrodialysis-based method was designed for divisionally regenerating basic DES choline chloride-monoethanol amine (ChCl-MEA) after pretreatment of wheat straw. Influence of primary process parameters on recovery of ChCl-MEA was studied and recovery economy of ChCl-MEA was analyzed. Recovery ratio of ChCl and MEA varied within 89.2 %-96.0 % and 93.3 %-97.9 %. Energy consumption of ChCl-MEA recovery changed within 4.2–29.4 kW·h/kg. Transport rate of basic DES ChCl-MEA altered in the range of 12.2–464.7 mmol/(m2·min). Process economy analysis proved that recovery cost of basic DES ChCl-MEA was less than 7 % (0.81–7.07 $/kg) of DES purchase cost. Insight brought by this study indicated a technically feasible and economical approach for basic DES recycling after biomass pretreatment.

Main features of a novel extraction-hydrogenation unit

The potential for coupling a continuous hydrogenation reactor with a continuous extraction unit was investigated through computer simulation of series of mixers/settlers coupled to a slurry reactor in a closed loop.The process has the potential to replace the regeneration of extraction solvents by distillation. Additionally, the system eliminates the need to treat the entire feedstock when refining a complex mixture. It is believed that the reaction of the extract retains valuable components in the feed that are not extracted and could undergo undesirable hydrogenation.The parameters for the simulation model were obtained from correlations and published data. The system was expected to exhibit a pseudo-first-order reaction rate in relation to the impurity concentration due to its low concentration in the extract. This is expected to result in high hydrogen-to-impurity ratios, which can be advantageous from a reaction driving force perspective.Solvent degradation by hydrogenation and solvent-impurity reactions are thought to be the main problems for the extraction-hydrogenation process.

Enhanced removal of toxic Disperse Blue 35 dye through cloud point extraction: influence of parameters and solvent regeneration

Abstract The release of the dye Disperse Blue 35 (DB35) into water has serious environmental and health consequences, due to its toxicity and resistance to degradation. This paper investigates the effectiveness of cloud point extraction (CPE) to remove this industrial dye from aqueous solution by Lutensol AO7 and Triton X-114, two environmentally friendly nonionic surfactants. First, the partial phase diagrams of the water–surfactant binary systems are constructed. Then, the effects of pollutants, sodium sulfate and cetyltrimethylammonium bromide on the cloud point temperature (T c) are determined. The experimental results are expressed by four responses: Extraction efficiency (E), residual concentrations of solute and surfactant in the dilute phase (X s,w and X t,w, respectively) and the volume fraction of coacervate (Ф c). An empirical smoothing method was applied. For each parameter, the results obtained were modeled using the response surface methodology (RSM) and represented on three-dimensional diagrams. The results show that the efficiency of dye extraction with Lutensol AO7 and Triton X-114 at a concentration of 6 wt% is about 95 % and 82 %, respectively. The influence of salt and ionic surfactant on the effectiveness of CPE for the removal of DB 35 dye was determined. The regeneration of surfactant was only achieved by pH adjustment.

Sensitivity analysis of parameters on carbon dioxide desorption processes from aqueous monoethanolamine solution

AbstractCarbon dioxide (CO2) capture technologies are crucial for mitigating climate change, with post‐combustion capture (PCC) using chemical absorption being a leading method. However, the energy‐intensive solvent regeneration process presents a significant challenge, consuming up to 50% of the total energy in carbon sequestration. Despite extensive research on absorption, desorption studies remain limited. This study focuses on the desorption analysis through experimental runs in a pilot‐scale tray column with varying flow rates, validating an Aspen Plus model. The research compares the impact of the number of stages, feed stage position, column pressure, and reflux ratio between equilibrium and rate‐based models. The findings reveal enhanced desorption efficiency through optimized operational conditions, including reduced flow rates, additional equilibrium stages, feeding stage positioning closer to the condenser, elevated pressures, and lower reflux ratios. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Eco-friendly solvent-based liquid-liquid extraction of phenolic acids from winery wastewater streams

This study proposes liquid-liquid extraction (LLE) for the recovery of phenolic acids from winery wastewater replacing common volatile organic compounds (VOCs) with environmentally friendly solvents. On one hand, terpenes (α-pinene and p-cymene) and terpenoids (eucalyptol and linalool) were selected as green solvents and compared to common VOCs (ethyl acetate or 1-butanol). On the other hand, gallic acid (GA), vanillic acid (VA), syringic acid (SA) and caffeic acid (CA) were selected as phenolic acids to be recovered. The extraction performance was evaluated under different operation conditions: solvent-to-feed ratio, initial concentration of phenolic acids and temperature.This work also evaluated the back-extraction whole process global recovery and solvent regeneration, by means of aqueous NaOH solution. Eucalyptol has shown the highest overall global extraction performance (21.07 % for GA, 93.21 % for VA, 78.79 % for SA, and 80.57 % for CA) and lower water solubility compared to the best performing VOC solvent (1-butanol). Therefore, eucalyptol can be a potential eco-friendly solvent to replace VOCs for sustainable phenolic acid recovery from winery wastewater. Finally, to ensure a clean water stream after the LLE, the traces of solvent were completely removed by electrooxidation with boron-doped diamond anode at a current density of 422.54 A/m2.

Comparative analysis of lead and cadmium extraction capacities of hydrophobic deep eutectic solvents

In this study, a total of eight hydrophobic deep eutectic solvents (HDESs) were prepared and evaluated for their efficacy in extracting lead and cadmium from aqueous solutions. The physical and thermal properties of these HDESs were characterized. Among the HDESs tested, the thymol:decanoic acid system, with a molar ratio of 1:1, exhibited the highest distribution ratios for lead and cadmium, with values of 0.79 and 0.55, respectively. The extraction performance of the thymol:decanoic acid system was further investigated by considering various factors such as contact time, pH, mass ratio of water to HDES, and HDES molar ratio. After optimization, the thymol:decanoic acid HDES demonstrated significantly improved extraction efficiency for lead (up to 93.49 %) and cadmium (up to 76.70 %) at initial concentrations of 1000 ppm and 100 ppm, respectively. The extraction mechanism was found to be primarily driven by the complexation and partitioning effects of thymol:decanoic acid with lead or cadmium, as confirmed by the noticeable changes in harmonic frequencies (730, 1337, and 1515 cm−1) observed in the IR spectra analysis before and after extraction. Additionally, the performance of the thymol:decanoic acid HDES was evaluated through solvent regeneration using a multi-stage extraction and reuse approach.

Enhancing CO2 desorption efficiency with Non-Aqueous Catalyst-Enhanced Tri-Blend amines

The substantial energy demand of CO2-loaded solvent regeneration constitutes a significant economic challenge for the industrial applications of CO2 capture and utilization technologies. The nano-catalysts have the capability to improve CO2 desorption while reducing the energy demands for solvent regeneration. This study focuses on examining the absorption–desorption performance of non-aqueous tri-blend amines (monoethanolamine (MEA), methyl diethanol amine (MDEA), and piperazine (PZ)) utilizing different amounts of catalysts including HZSM-5, H-ferrierite (FER), and H-mordenite (MOR), γ-aluminium-oxide (Al2O3), titanium-oxide (TiO2), magnesium oxide (MgO), indium-oxide (In2O3). The incorporation of solid catalysts leads to a substantial enhancement in the desorption performance of tri-blend amines and reduced energy consumption in comparison to blank tests. Higher desorption efficiency occurred with the presence of lower catalyst amounts. The sequence of CO2 desorption heat duty performance reduction with 0.125 g catalyst, was as follows: MgO (70.9 %) > In2O3 (80.2 %) > HZSM-5 (84.1 %) > Al2O3 (84.2 %) > FER (87.1 %) > MOR (88.4 %) > TiO2 (89.7 %), relative to blank test (100 %). HZSM-5 exhibited the highest desorption factor as 4.25*10-7 mol3/kJmin while increasing the desorption rate to 2.37*10-3 mol/min. This study provides the desorption performance of non-aqueous amine blends with energy-efficient catalysts, highlighting their potential as promising materials for carbon capture and storage applications with improved energy efficiency.

Thermo- economic feasibility of solar-assisted regeneration in post-combustion carbon capture: A diglycolamine-based case

The solvent regeneration in the post-combustion carbon capture process usually relies on steam from the power plant steam cycle. This heat duty is one of the challenges of energy consumption in PCC (Post-combustion Carbon Capture). However, this practice results in a significant energy penalty, leading to a substantial reduction in the capacity of the Power Plant, estimated to be between 19.5 and 40 %. This paper investigate the techno-economic feasibility of a solar-assisted regeneration process for the PCC industrial scale with diglycolamine solvent. The study aims to assess the impact of system configuration modifications, such as LVC (Lean Vapor Compression), SPCC (Solar Post-combustion Carbon Capture), and combinations of trough or compound solar collectors with LVC, on energy efficiency and overall plant performance. With 3E analysis for SPCC configuration results show that this configuration. However, reducing energy consumption and energy penalty factor, exhibits a decrease in exergy and exergoeconomic efficiency compared to the other configurations in terms of exergy and exergoeconomic aspects. However, the LVC + SCSS (Solar Combined Separator-Stripper) configuration demonstrates the best performance across the 3E aspects, resulting in a reduction energy penalty to 12.2 % and improvements of 38 % and 4.2 % in exergy and exergoeconomic factors, respectively.

Adsorption performance of 1,4-dioxane by MCM-22 and Beta zeolites and their bio-zeolite composite system in the presence of co-contaminants

Addressing the significant challenge of efficiently separating 1,4-dioxane from aquatic environments using traditional adsorbents is crucial. In this study, we evaluated the adsorption performance of MCM-22 and Beta zeolites. Both were identified as highly effective adsorbents. Equilibrium adsorption of 1,4-dioxane was achieved within 20 min for an initial concentration of 500 mg L-1 on both MCM-22 and Beta zeolites. At 288 K, the maximum adsorption capacities fitted by Langmuir isotherm were 79.66 mg g−1 for MCM-22 and 121.66 mg g−1 for Beta zeolite. Fixed-bed column studies demonstrated that the Yan model properly predicted the behavior of both zeolites under varying flow rates. Additionally, MCM-22 exhibited a wider pore size distribution compared to Beta zeolite, while Beta zeolite demonstrated a higher volume of ultra-micropores (<1 nm) than MCM-22. This highlights the importance of pore volume filling in facilitating excellent adsorption of 1,4-dioxane by both zeolites. Further analysis via FTIR and 1H NMR confirmed the significance of Brønsted acid sites in 1,4-dioxane adsorption. The adsorption performance of both zeolites remained unaffected by initial pH values ranging from 2 to 11, as well as variations in ionic strength or the presence of natural organic matter (NOM) for both zeolites. However, the co-existence of 1,1-dichloroethene (1,1-DCE) resulted in competitive adsorption with 1,4-dioxane, leading to a notable decrease in adsorption capacity of 1,4-dioxane. In contrast, the presence of metal ions Cu2+ and Ag+ did not compete for adsorption sites with 1,4-dioxane. Our study demonstrated the effectiveness of the bio-zeolite system in regenerating spent adsorbents, surpassing water and solvent regeneration methods in efficiency and recyclability. Although addressing the persistence of 1,1-DCE remains a challenge, bio-zeolites emerge as versatile tools for mitigating the bio-inhibition of heavy metals, such as Cu2+ and Ag+, while offering a sustainable solution for 1,4-dioxane bioremediation.

The impact of PAC-loaded polymer membrane thickness on chloroform removal and comparison of solvent and thermal membrane regeneration methods.

Powdered activated carbon (PAC) has better adsorption performance than granular activated carbon (GAC) and is widely used in water purification. In most cases, PAC is dosed into water directly, then precipitated as sludge, and landfilled. In this study, PAC was mixed with a polymer and dissolved in dimethylformamide (DMF) solvent to form a PAC-loaded membrane, which was then tested for chloroform removal. The chloroform adsorption capacity of the PAC membrane increased with increasing membrane thickness because of higher carbon loading. However, regardless of membrane thickness, the flux of the PAC membranes was similar since flux resistance predominantly occurred at the top dense polymer surface. This dense surface can be removed by sandpaper polishing, where the adsorption capacity of the polished PAC membranes was 20% higher than the unpolished membranes because of more even distribution of feed water on the polished surface. Removal of the dense surface via polishing increased the flux by 97% to 130%, exceeding the flux of typical household carbon block filters. Using DMF to regenerate the membrane recovered 48% to 66% of the initial adsorption capacity. Thermal regeneration of the exhausted PAC membrane at 250°C was more effective than DMF regeneration (both in terms of cost and performance), with 83% to 94% PAC membrane regeneration efficiency over four regeneration recycles. After four thermal regeneration cycles, flux increased by 300% and the membrane became brittle because of thermal aging of the polymer, indicating that a total of 6h of regeneration time (equivalent to three cycles in this study) was the limit for effective PAC membrane performance. PRACTITIONER POINTS: Powdered activated carbon was immobilized on a membrane to remove chloroform from water. Thicker membranes increased adsorption capacity but did not impact flux. Flux and capacity increased using polishing to remove the dense polymer surface and more evenly distribute flow across the membrane. Thermal regeneration of the membrane at 250°C was effective for up to three cycles and outperformed solvent-based regeneration. PAC-loaded filters are relevant for applications such as household carbon block filtration.

Effective amine solvent regeneration over NiO-modified SBA-15 catalysts for energy-saving CO2 capture

Catalytic amine regeneration can decrease the energy required for regeneration; therefore, high economic and energy efficiency can be expected for CO2 capture. These factors necessitate the development of an inexpensive and easily synthesizable catalyst that can exhibit a high desorption efficiency. When selecting a catalyst, its physicochemical properties must be considered, because they markedly affect the chemical reaction between CO2–amine–catalyst. In this study, mesoporous silica SBA-15, particularly, rod-type SBA-15, wrinkled SBA-15 (modified from rod-type SBA-15), and NiO-impregnated rod-type and wrinkled SBA-15 catalysts were investigated in terms of the CO2 desorption rate and heat duty in a CO2–rich 5 M monoethanolamine (MEA) solution at 86 ℃. The physicochemical properties of the catalysts were compared to investigate their effect on the CO2 desorption efficiency. The performance of wrinkled SBA-15 impregnated with 10 wt% NiO in a CO2–rich MEA solution was optimal, exhibiting a 12 % higher CO2 desorption rate and 19.9 % lower heat duty than the MEA solution without a catalyst. Furthermore, the stability and reproducibility of the catalysts were confirmed through repeated experiments under identical conditions. Based on the experimental results and analysis, a plausible desorption mechanism for CO2–MEA–catalyst was proposed. It is expected that the regeneration heat duty during the CO2 regeneration can be effectively reduced by a catalyst, eventually applied to the CO2 capture.