Absorption-desorption Process Research Articles

Compact, efficient, and affordable absorption Carnot battery for long-term renewable energy storage

The growing penetration of renewable energy poses significant challenges to the stability of the power grid, necessitating the development of advanced energy storage systems to facilitate power grid decarbonization with enhanced flexibility. Nonetheless, current energy storage technologies face obstacles including geographical constraints, high expenses, and short lifespans. In this work, a novel Carnot battery (power-heat-power conversion) based on absorption-desorption processes of hygroscopic salt solutions, absorption Carnot battery (ACB), is proposed for large-scale renewable energy storage with remarkable energy storage density (ESD), competitive round-trip efficiency (RTE), and negligible self-discharging rate (SDR). Through the integration of heat-generation, heat-storage, and power-generation sub-cycles into a single compact system, the ACB can save space and cost compared to previous Carnot batteries. A dynamic model is established with high accuracies to explore the characteristics of the proposed system. The dynamic temperatures, pressures, concentrations, mass flow rates, powers, and efficiencies of the ACB are analyzed to elucidate its energy conversion/storage mechanism. Based on the multi-objective optimization, the optimum operating concentration range of [45%, 60%] is determined, demonstrating the best comprehensive performance with an RTE of 45.80% and an ESD of 16.26 kWh/m3. Compared to the existing energy storage systems, the ACB stands out due to the competitive RTEs (30.5%–48.4%) and higher ESDs (7.6–21.8 kWh/m3). Even during an 80-day standby period, the ACB exhibits a small SDR of only 0.74%, which is significantly lower than that of Rankine pumped thermal energy storage (RPTES) at 33.01%. Despite the ACB yields a higher initial cost, it demonstrates a markedly lower levelized cost of storage (0.342 $/kWh) compared to the RPTES (0.749 $/kWh) because of its higher ESD, thus confirming the economic feasibility of the proposed system.

Bulk Nanostructured Silicide Thermoelectric Materials by Reversible Hydrogen Absorption-Desorption.

The production of bulk nanostructured silicide thermoelectric materials by a reversible hydrogen absorption-desorption process is demonstrated. Here, high-pressure reactive milling under 100bar hydrogen is used to decompose the Ca2Si phase into CaH2 and Si. Subsequent vacuum heat treatment results in hydrogen desorption and recombination of the constituents into the original phase. By changing the heat treatment temperature, recombination into Ca2Si or Ca5Si3 can be achieved. Most importantly, the advanced synthesis process enables drastic and simple microstructure refinement by more than two orders of magnitude, from a grain size of around 50µm in the initial ingot to 100-200nm after the hydrogen absorption-desorption process. Fine precipitates with sizes ranging from 10-50nm are forming coherently inside the grains. Thus, the route is promising and can be used for reducing thermal conductivity due to phonon scattering from grain boundaries as well as through nanostructuring with second-phase precipitates. Moreover, the process is environmentally friendly since hydrogen is reversibly absorbed, desorbed, and can be fully recovered.

Experimental investigation on post-combustion CO2 capture for [Bpy][NO3] and MEA aqueous blends with lower regeneration energy

CO2 capture is an important technology to achieve carbon emission reduction. The key is reducing the energy consumption of the CO2 capture process. Ionic liquids (ILs) blended with organic amines can be used as an efficient CO2 absorbent allowing for low regeneration energy consumption. This work proposes the use of N-butylpyridinium nitrate ([Bpy][NO3]) in combination with organic solvents for CO2 capture. The effects of ILs concentration, reboiler load and flue gas concentration on regeneration energy consumption were studied on a continuous pilot unit for absorption-desorption process. The results showed that the CO2 absorption capacity of 30 wt% MEA + 10 wt% [Bpy][NO3] was 0.1308 g CO2/g solvent, higher than monoethanolamine/water, and the CO2 absorption capacity remained at 74.3% after the five cycles. At 40 °C, the viscosity of IL-amine blending solvents before and after absorption was 2.01 and 3.534 mPa·s, respectively, significantly lower than that of the conventional non-aqueous phase absorbent. The continuous absorption-desorption results showed that the capture rate of IL blending reached more than 95%. The regeneration energy consumption is 34.2% lower than the 30 wt% MEA.

Novel nonaqueous solvent for carbon capture: Effects of glycol and water on CO2 absorption, desorption and energy penalty

Amidine-alcohol solution is an efficient absorbent for CO2 capture with high CO2 loading and low regeneration temperature compared with 30 wt% monoethanolamine (MEA) solution. However, the high viscosity restricts its further utilization in the industry. To decrease the viscosity of amidine-alcohol solutions during the absorption of CO2, different glycols including ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,3-butanediol and 1,4-butanediol were adopted in 1,5-diazabicyclo [4,3,0] non-5-ene (DBN)-glycol solutions for CO2 absorption. Both the absorption and desorption performances of those absorbents in the reaction with CO2 were investigated including the viscosity and regeneration energy. The CO2 loading can reach as high as 5.87 mol·kg−1 in DBN-1,3-propanediol solution, which is more than 3 times higher than that of 30 wt% MEA. Meanwhile, the viscosities for DBN-glycol-CO2 systems can be decreased more than 95% compared with 1,8-diazabicyclo [5,4,0] undec-7-ene (DBU)-glycerol-CO2 system. And DBN-ethylene glycol-CO2 system shows the lowest viscosity among the five glycols systems. With DBN-1,4-butanediol solution as an absorbent, the regeneration energy can be decreased as low as 1.38 GJ·ton−1 CO2, which is 62% lower than that of 30 wt% MEA. After 9 cycles of absorption–desorption process, the CO2 loading can be kept about 72% of the initial loading. Furthermore, the effect of water on absorption, desorption, viscosity and regeneration energy was also studied. It shows that the presence of water can increase the absorption rate and has little effect on the final CO2 loading while decreasing the desorption rate. Meanwhile, the presence of water increases the regeneration energy of DBN-ethylene glycol-H2O-CO2 system. However, considering the regeneration energy and viscosity, DBN-ethylene glycol solution is a promising solution for carbon capture and the regeneration energy can be decreased about 51 % even with 5 wt% water compared with 30 wt% MEA.

Solid Waste of Fly Ash toward Energy-Efficient CO2 Capture

Catalytic CO2 absorption–desorption has attracted broad interest due to its potential for improving CO2 absorption efficiency and reducing energy consumption in CO2 separation. However, most utilized catalysts are synthetic and pure, with the development of a natural and hybrid catalyst with acid–base bifunctional catalytic characteristics remaining a significant challenge. In this work, three fly ashes (1-FA, 2-FA, and 3-FA) with different compositions were used as catalysts, and the provided synergistic benefits in the overall MEA-CO2 absorption–desorption processes were evaluated. The results showed that Brønsted acid sites, Lewis acid sites, and Lewis base sites were available on the fly ash surface, which provided proton and electron donation capability. 1-FA exhibited the best catalytic performance by enhancing the CO2 cyclic absorption capacity by 6.7–26.1%, improving the CO2 desorption rate with the highest value of 96.0%, and decreasing the sensible heat by 24–28% compared to MEA as a blank run. Furthermore, 1-FA exhibited comparable catalytic performance to typical HZSM-5. The results of this study demonstrated that fly ash with zero cost and high availability could serve as a good hybrid catalyst candidate for CO2 absorption and desorption.

Facile Fabrication of Monodispersed Carbon Sphere: A Pathway Toward Energy-Efficient Direct Air Capture (DAC) Using Amino Acids.

Direct removal of carbon dioxide (CO2 ) from the atmosphere, known as direct air capture (DAC) is attracting worldwide attention as a negative emission technology to control atmospheric CO2 concentrations. However, the energy-intensive nature of CO2 absorption-desorption processes has restricted deployment of DAC operations. Catalytic solvent regeneration is an effective solution to tackle this issue by accelerating CO2 desorption at lower regeneration temperatures. This work reports a one-step synthesis methodology to prepare monodispersed carbon nanospheres (MCSs) using trisodium citrate as a structure-directing agent with acidic sites. The assembly of citrate groups on the surface of MCSs enables consistent spherical growth morphology, reduces agglomeration and enhances water dispersibility. The functionalization-assisted synthesis produces uniform, hydrophilic nanospheres of 100-600nm range. This work also demonstrates that the prepared MCSs can be further functionalized with strong Brønsted acid sites, providing high proton donation ability. Furthermore, the materials can be effectively used in a wide range of amino acid solutions to substantially accelerate CO2 desorption (25.6% for potassium glycinate and 41.1% for potassium lysinate) in the DAC process. Considering the facile synthesis of acidic MCSs and their superior catalytic efficiency, these findings are expected to pave a new path for energy-efficient DAC.

Carbon dioxide capture from the Kraft mill limekiln: process and techno-economic analysis

In this work, a techno-economic assessment of carbon dioxide capture from limekiln flue gas of a pulp and paper mill (Mill A) and a linerboard mill (Mill B) using a Monoethanolamine (MEA) absorption desorption process was carried out. We coupled the ASPEN Plus simulator with a derivative-free optimization (DFO) tool to identify the optimal configuration for minimizing the total capture cost. The capture costs were calculated using CAPCOST, a modular program for equipment cost estimation, and appropriate coefficients. Eight degrees of freedom, the direct contact cooler stages, the absorber stages, the stripper stages, the solvent lean loading, the solvent weight concentration, the stripper inlet temperature, the flue gas inlet temperature, and the amount of CO2 captured, were selected for process and flowsheet optimization. Additionally, we evaluated the effect of steam integration and Sect. 45Q of the existing federal tax credit for carbon capture and sequestration on CO2 capture costs. The total capture costs per tonne of CO2 were $64.9 for Mill A and $69.7 for Mill B. When steam integration and Sect. 45Q are considered, the costs dropped to − $2.5 and $2.6 for Mill A and Mill B, respectively. The sensitivity of CO2 capture cost to changes in the inlet flue gas flowrate, flue gas CO2 mol%, and the electricity and MEA prices were investigated. The sensitivity analysis results revealed that the capture costs vary from − $5.9 to $5.9 per tonne of CO2 captured.

Screening of Absorbents for Viscose Fiber CS2 Waste Air and Absorption–Desorption Process

Screening of absorbents is essential for improving the removal rate of carbon disulfide (CS2) waste air by absorption. In this work, the UNIFAC model in Aspen Plus was utilized to calculate the excess Gibbs function and absorption potential of the binary system of CS2 with various alcohols, ethers, esters, amines, and aromatic hydrocarbons. The results were used to quantitatively compare the efficiency of each solvent for CS2 absorption. The theoretical predictions were then verified by absorption experiments in a packed tower. The results showed that the performance of various solvents to CS2 roughly followed the order of esters < alcohols < amines < heavy aromatics < glycol ethers. Meanwhile, N-methyl-2-pyrrolidone (NMP) is the optimal absorbent for CS2 waste air treatment. Additionally, the process parameters of absorption and desorption of NMP were optimized. The results illustrated that the average mass removal efficiency of CS2 by NMP is 95.2% under following conditions: liquid–gas ratio of 3.75 L·m−3, a temperature of 20 °C, and inlet concentration lower than 10,000 mg·m−3. Under the conditions of 115 °C, 10 kPa, and a desorption time of 45 min, the average desorption rate of CS2 is 99.6%, and the average water content after desorption is 0.39%. Furthermore, the recycled lean liquid can maintain an excellent CS2 purification effect during the recycling process.

Metal Oxides Enhance the Absorption Performance of N-Methyldiethanolamine Solution during the Carbon Dioxide Capture Process.

Fly ash from coal-fired power plants can enter chemical absorbents along with flue gas. Silica and metal oxides are the main components of fly ash. To explore the effect of the metal oxides on absorbents, we analyzed the integrated CO2 absorption-desorption process using N-methyldiethanolamine (MDEA) as the standard and an amine absorbent after adding different metal oxides. The effects of each metal oxide on CO2 capture by the MDEA solution, including CO2 reaction heat, absorption rate, cyclic loading, and carbonation rate, were assessed. It was found that supplementation with appropriate calcium oxide and magnesium oxide proportions accelerates the CO2 absorption rate and shortens the saturation time of the MDEA solution by 9%-17%. Magnesium oxide and calcium oxide were precipitated as carbonates during absorption. The CO2 reaction heat of the MDEA solution increased by 95% after adding magnesium oxide, thereby significantly increasing the energy consumption of the desorption process. On the basis of the experimental studies, the increase in CO2 absorption rate by MDEA after adding MgO and CaO may be mediated through two different mechanisms.

Enabling the direct solution of challenging computer-aided molecular and process design problems: Chemical absorption of carbon dioxide

The search for improved CO2 capture solvents can be accelerated by deploying computer-aided molecular and process design (CAMPD) techniques to explore large molecular and process domains systematically. However, the direct solution of the integrated molecular-process design problem is very challenging as nonlinear interactions between physical properties and process performance render a large proportion of the search space infeasible. We develop a methodology that enables the direct and reliable solution of CAMPD for absorption–desorption processes, using the state-of-the-art SAFT-γ Mie group contribution approach to predict phase and chemical equilibria. We develop new feasibility tests and show them to be highly efficient at reducing the search space, integrating them in an outer-approximation algorithm. The framework is applied to design an aqueous solvent and CO2 chemical absorption–desorption process, with 150 CAMPD instances across three case studies solved successfully. The optimal solvents are more promising than those obtained with sequential molecular design approaches.

Effect of moisture absorption-desorption cycles, UV irradiation and coupling agent on the mechanical performance of pinewood waste/polyethylene composites

<abstract> <p>The effects of UV radiation, a maleic anhydride grafted polyethylene (MAPE) coupling agent and moisture cycling exposure on wood plastic composites (WPC) made from pinewood waste (PW) and high-density polyethylene (HDPE) on their tensile and flex properties, were studied. First, the effect of UV radiation and the presence of anhydride grafted polyethylene on the absorption-desorption behavior of the compounds was evaluated and then its effect on the mechanical properties. Scanning electron microscopy (SEM) was used to analyze the surfaces of the samples subjected to these factors and their subsequent damage in fracture zones of the samples. The moisture absorption-desorption process exhibited a two-stage mechanism: the first is significant increases in the absorption values in the first five cycles, and a second stabilization stage that occurs from the sixth cycle onwards. The first stage includes several steps: initial absorption and delamination; capillary action and polymer-wood interaction; and swelling, fiber-matrix interaction and mechanical damage. The second stage involves the balance and stabilization step. Statistically, it was found that the changes in the humidity values in the absorption and desorption cycles show that UV radiation has a significant contribution with the effect of increasing the absorption and desorption values, while the presence of anhydride grafted polyethylene as a lesser effect with an effect of decreasing those values. The tensile and flexural properties of the compounds were significantly affected by UV radiation and moisture cycling. Taking the sample without anhydride grafted polyethylene and without treatments as a reference, only a slight increase of 5–12% in its tensile and flexural properties was observed, while treatments with UV radiation and absorption-desorption cycles reduced them by up to 45%. The SEM analysis confirmed the deterioration of the composites in the form of microcracks, delamination, interfacial voids and mechanical failures in both the wood filler and the polyethylene matrix, especially in the samples exposed to ultraviolet radiation, where this deterioration was lower in the samples containing anhydride grafted polyethylene.</p> </abstract>

Phase transformation of hydride-phase Nd2Co7 with superlattice structure

We investigated the phase stability of Nd2Co7 with a superlattice structure, its hydrogenation properties, and phase transformation during hydrogen absorption–desorption process. The results showed that Ce2Ni7-type and Gd2Co7-type structures coexisted in the annealed sample up to 1273 ​K. The Gd2Co7-type phase disappeared at temperatures above 1323 ​K. We successfully synthesized a largely single-phase Ce2Ni7-type Nd2Co7 when the alloy was annealed at 1373 ​K, followed by quenching in ice water. The phase transformation follows the order: hexagonal Nd2Co7 (space group P63/mmc) → hexagonal Nd2Co7H2.7 (space group P63/mmc) → orthorhombic Nd2Co7H8.1 (space group Pbcn), upon hydrogen absorption. Anisotropic lattice expansion along the c axis was observed in Nd2Co7H2.7. The unit cell of Nd2Co7H8.1 underwent isotropic expansion along the a, b, and c axes. However, the volume expansions of the MgZn2-type cell, CaCu5-type cell I, and CaCu5-type cell II were uneven at 36.0%, 8.9%, and 13.0%, respectively.

Multi objective optimization of the amines- CO2 capture absorption-desorption process by a non-equilibrium rate model

The global concentration of CO2 in the atmosphere is increasing rapidly. CO2 emissions have an impact on global climate change. Carbon dioxide capture technologies have been proposed as a promising alternative to reducing CO2 emissions from fossil fuel power plants with post-combustion capture. Amine-based chemical absorption is considered the most industrially developed technology for this kind of process. In this work, a strategy for defining the relationships between design and the operational policies in CO2 capture technologies is addressed. The solution to the problem consists in maximizing the percentage of the CO2 removal, while the stripper reboiler duty is minimized. Since both objective functions in conflict, a multi-objective optimization approach is proposed to achieve a trade-off. Moreover, due to the highly non-ideal behavior in the heat and mass transfer phase, a fully rigorous model was used to capture this strongly non-linear behavior. In addition, an economic evaluation of the heating and cooling utilities in the stripper according to the operation process is carried out. The results show the importance of considering the significance between the influence of operating variables (i.e., temperature, liquid solvent flow rate, and operating pressure) on the amount of CO2 removed and the associated reboiler duty. It shows that both optimal operating policies can be traded-off. Finally, with 30 wt% of MEA solvent, the compromise solution presents a 77% CO2 capture with an energy consumption of 4.98 GJ/t of CO2 for the reboiler service, a cost of heat utilities per year of $3971 capturing 142.29 kg/h of CO2.

Crystal structure of deuteride phase of Nd-Ni alloy by X-ray and neutron diffraction

The hydrogen-absorbing alloys currently used in industry form residual hydrogen that reduces the alloy’s reversible hydrogen capacity, decreasing its useful life. RNi3 intermetallic compounds, which have a PuNi3-type crystal structure composed of MgZn2-type and CaCu5-type cells that exhibit structural change in relation to their hydrogenation properties, have been the focus of much research, but only a few of those reports focus on the interplay between residual hydrogen and alloy structure. Thus, this study seeks to clarify the residual hydrogen occupation mechanisms in MgZn2-type and CaCu5-type cells during the hydrogen absorption-desorption process. The structural changes and deuterium occupation in NdNi3Dx were investigated using X-ray diffraction (XRD) and neutron powder diffraction (NPD). Rietveld refinement was performed for NdNi3, NdNi3D2.6, NdNi3D3.2, NdNi3D4.0, and NdNi3D4.8, during the deuterium absorption-desorption process. The deuterium capacity reached 0.9 D/M at the first absorption process and 0.7 D/M of residual deuterium was formed after the first desorption at 248 K. For NdNi3D2.6 (phase II), the residual deuterium contents of MgZn2-type and CaCu5-type cells were determined to be 1.0 D/M and 0.4 D/M, respectively. The residual deuterium preferred the deuterium site in the MgZn2-type cell. The deuterium capacity was 1.2 D/M in the first absorption process at 213 K and the residual deuterium was 1.0 D/M at the end of the first desorption. The severe peak broadening observed in the XRD and neutron diffraction patterns of NdNi3D4.0 and NdNi3D4.8 indicate that the deformation of the metal sublattice of the deuteride phase was deformed over 0.8 D/M.

Absorption-desorption process of internal curing water in ultra-high performance concrete (UHPC) incorporating pumice: From relaxation theory to dynamic migration model

This study aims to clarify the absorption-desorption process of internal curing water by pumice in ultra-high-performance concrete (UHPC) system based on relaxation theory. More exactly, the dynamic migration process of water from pumice in UHPC and its micro/macro properties are analyzed by 1H nuclear magnetic resonance, backscattering electron, nanoindentation, etc. The results reveal that the prewetted pumice could delay the water release time for 1 h compared with dry pumice (5.5 h), and can continue to absorb about 14% of free water from the end of the mixing process to the beginning of water release. Notably, the release rate of water from prewetted pumice in UHPC is up to 80%, which is beneficial to the alleviation of internal relative humidity decline rate and thus reduces the autogenous shrinkage of UHPC. In addition, the use of prewetted pumice improves the microstructures of UHPC, where compared with river sand, its transport distance of water entraining reaches at 35 μm–55 μm and its interfacial transition zone (ITZ) structure is also denser. Finally, a relaxation theory-based dynamic model is successfully established, which can be used to illustrate the water migration process and predict migration distance in the UHPC system.

Innovative battery thermal management system based on hydrogen storage in metal hydrides for fuel cell hybrid electric vehicles

This study proposes a new approach for dealing with the thermal management of batteries in fuel cell hybrid electric vehicles, by introducing a new concept of on-board energy storage system which integrates the battery pack with a metal hydride tank. The rationale behind this solution is to use the exothermic absorption and endothermic desorption processes of hydrogen in metal hydrides for heating and cooling the battery pack, respectively, thus ensuring an optimal thermal management control. An experimental investigation is carried out on a prototype in order to proof the concept and preliminary assess its feasibility for actual implementations. The results show that the system is capable to effectively control the temperature variations within the battery pack: for 1C and 1.5C constant-current discharge tests, a desorption of 30%–40% of hydrogen, over the total amount stored into the metal hydride tank of the system, allows the final average temperature of the battery pack to be around 15 °C lower than the one reached without thermal management. Moreover, it is found that the system is potentially capable of providing a suitable thermal management for more than four hours under realistic driving conditions. The proposed energy storage system also achieves inherently high gravimetric and volumetric energy densities, with theoretical values equal to 182 Wh/kg and 530 Wh/L, respectively. These estimates represent reference values for further design improvements.

Modeling moisture and solids transfer kinetics during a novel microwave assisted water absorption-desorption process of dry red gram (Cajanus cajan L.) splits

The microwave-assisted water absorption and desorption of dry polished red gram splits were done to reduce its anti-nutritional compounds, improve cooking characteristics, save energy and reduce water requirements. The newly developed process was compared with soaking of red gram splits in water at ambient and 60 °C. Peleg model and modified Azuara model were used to study the water absorption and solid loss kinetics while considering the dry matter holding capacity and surface tension of red gram. The process showed 61.40% db moisture gain and 6.30% db solid loss in 7 min. Further, microwave drying at optimum condition (1.25 W/g and 1.5 pulsation ratio) that was determined using response surface methodology resulted in 50 and 10 min of drying and cooking times, respectively. Compared with raw and conventionally treated samples, the microwave process resulted in a product with an improved rehydration ratio and solids dispersion of 3.00 and 31.90%, respectively. The total specific energy consumption in microwave treatment was 93% lesser than the control methods. • Microwave treatment improved the quality and cooking characteristics of red gram splits. • Microwaves accelerated water absorption by reducing the surface tension. • Low solid loss and high dry matter holding capacity was observed after microwave treatment. • The water absorption and solid loss kinetics were best described by Azuara models. • Total energy consumption in microwave processing was 93% lesser than conventional methods.

New insight and evaluation of secondary Amine/N-butanol biphasic solutions for CO2 Capture: Equilibrium Solubility, phase separation Behavior, absorption Rate, desorption Rate, energy consumption and ion species

• MAE + n-butanol + H 2 O system for CO 2 capture was first proposed. • The phase change mechanism and energy consumption of the system were investigated. • The influence of temperature on absorption capacity was explored. • The developed biphasic absorbent has excellent energy saving advantages. Effective phase-change solvent system, n-methyl-2-hydroxyethylamine (MAE) + water-insoluble alcohol + H 2 O, was developed for CO 2 capture. First, a preliminary screening of several alcohols was carried out and showed that the MAE/n-butanol/water system had the potential to become an excellent phase change absorbent. Then, through phase change experiment, absorption experiment, desorption experiment, and theoretical energy consumption analysis, the MAE:n-butanol:water ratio of 3:4:3 possessed the most impressive CO 2 capture performance. Theoretical calculation of CO 2 desorption energy consumption showed that in comparison with 30 wt% monoethanolamine (MEA), 50% of reboiler heat duty can be reduced in case of the 3:4:3 system. In addition, equilibrium phase diagram of the three components showed that concentration of n-butanol significantly affected the phase separation. The two-phase species distribution after phase separation was determined using Nuclear magnetic resonance spectroscopy (NMR). This work also shows that temperature has influence on absorption and desorption performance. Finally, the absorbent stability test during absorption–desorption process confirmed that MAE/n-butanol/water absorbent had a great potential for capturing CO 2 .

Modeling Differential Enthalpy of Absorption of CO2 with Piperazine as a Function of Temperature.

Temperature-dependent correlations for equilibrium constants (ln K) and heat of absorption (ΔHabs) of different reactions (i.e., deprotonation, double deprotonation, carbamate formation, protonated carbamate formation, dicarbamate formation) involved in the piperazine (PZ)/CO2/H2O system have been calculated using computational chemistry based ln K values input to the Gibbs–Helmholtz equation. This work also presents an extensive study of gaseous phase free energy and enthalpy for different reactions using composite (G3MP2B3, G3MP2, CBS-QB3, and G4MP2) and density functional theory [B3LYP/6-311++G(d,p)] methods. The explicit solvation shell (ESS) model and SM8T solvation free energy coupled with gaseous phase density functional theory calculations give temperature-dependent reaction equilibrium constants for different reactions. Calculated individual and overall reaction equilibrium constants and enthalpies of different reactions involved in CO2 absorption in piperazine solution are compared against experimental data, where available, in the temperature range 273.15–373 K. Postcombustion CO2 capture (PCC) is a temperature swing absorption–desorption process. The enthalpy of the solution directly correlates with the steam requirement of the amine regeneration step. Temperature-dependent correlations for ln K and ΔHabs calculated using computational chemistry tools can help evaluate potential PCC solvents’ thermodynamics and cost-efficiency. These correlations can also be employed in thermodynamic models (e.g., e-UNIQUAC, e-NRTL) to better understand postcombustion CO2 capture solvent chemistry.

Exploring the adsorption behavior of benzotriazoles and benzothiazoles on polyvinyl chloride microplastics in the water environment

As a kind of emerging pollutant, microplastics (MPs) play an important role as a carrier for pollutant migration in the water environment. Carried by the MPs, benzotriazoles, and benzothiazoles (collectively referred to as BTs)11The target analysis selected in BTs and the corresponding abbreviations: BTR, 1H-Benzotriazole; 1-OH-BTR, 1-Hydroxy-benzotriazole; 5TTR, 5-Methyl-1H-benzotriazole; XTR, 5,6-Dimethyl-1H-benzotriazole; 5-Cl-1H-BTR, 5-Chloro-1H-benzotriazole; 2-OH-BTH, 2-Hydroxy-benzothiazole; 2-MeS-BTH, 2-Methylthio-benzothiazole; 2-NH2-BTH, 2-Amine-benzothiazole. are ubiquitous water contaminants. In this paper, the adsorption behavior of BTs on polyvinyl chloride (PVC) MPs was first studied systematically to explain the adsorptive mechanisms and the consequential pollution caused by the absorption-desorption process. The studies on kinetics, isotherms, and thermodynamics revealed that the adsorption of BTs on PVC MPs was a multi-rate, heterogeneous multi-layer, and exothermic process, which was affected by external diffusion, intra-particle diffusion, and dynamic equilibrium. The factors including pH, salinity, and particle size also influenced the adsorption process. In the multi-solute system, competitive adsorption would occur between different BTs. The desorption of BTs from PVC MPs was positively associated with the increase of adsorption amount. Based on the results, the adsorption mechanisms of PVC MPs were clarified, involving hydrophobic interaction, electrostatic force, and non-covalent bonds. It was demonstrated that BTs in the water environment could most probably be accumulated and migrated through MPs, and eventually carried into organisms, posing an increased risk to the ecological environment.