Effective absorption of dichloromethane using deep eutectic solvents

A critical review on ocean acidification driven by disinfection by-products discharge from ships' ballast water management systems: Impacts on carbon chemistry

The world's blue economy is closely tied to maritime trade, but ballast water from ships often carries harmful aquatic organisms and pathogens, which disrupt the marine environment. To address this, the International Maritime Organization (IMO) mandated ballast water treatment to eradicate these invasive species. However, the treatment processes inherently generate numerous Disinfection by-Products (DBPs). The discharge of these DBPs exacerbates ocean acidification through various acid- and CO2-releasing reactions. The IMO's Ballast Water Working Group has listed 41 high-priority DBPs for risk assessment due to their toxicity and prevalence in treated ballast water. This review quantitatively evaluates changes in pH and carbonate ions in seawater using the PyCO2SYS software package. Results reveal that DBPs can reduce ocean pH by ∼0.057 units and carbonate ion concentrations by 24.06 μmol kg-1 during a single discharge of 1 m3 treated water. In addition, this review outlines the challenges and research gaps for marine ecosystems sustainability.

Effective Absorption of 1,2-Dichloroethane Using Low-Viscosity Deep Eutectic Solvents

Deep eutectic solvents (DESs) as relatively novel green solvents have potential spread wide applications in separation processes, especially for acid gases and volatile organic compounds (VOCs) absorption. However, the high viscosity of typical DESs can decrease the mass transfer rate and increase energy consumption for pumping, thereby limiting their overall efficiency and feasibility in industrial applications. In this work, the efficient absorption of 1,2-dichloroethane (DCE) was intensified by designing a series of low-viscosity DESs, and the absorption performance, separation mechanism, and conceptual industrial process simulation were systematically investigated. The results showed that 3,4-DMOET:ButA with molar ratio of 1:2 was chosen as the suitable absorbent for DCE due to its maximum saturated absorption capacity (2746 mg/g at 20 °C, atmospheric pressure, and saturated content of DCE in the feed gas) and minimum viscosity property (26.51 mPa·s at 20 °C). The absorption mechanism was investigated by 1H NMR, FT-IR and quantum chemical (QC) calculations, indicating that the absorption was a physical process. The weak interaction analysis results illustrated that both HBD and HBA play an important role in the separation. Specifically, C-H···π and C-H···Cl are the main contributors to the HBA-DCE interaction, while C-H···O HB and vdW interactions played a dominant role in the HBD-DCE interaction. According to the process simulation results of DES absorbing DCE, it can be seen that DES exhibits a high DCE removal performance. The process intensification strategy may be directly extended to absorb other VOCs.

Ti3+/Ti4+ and Co2+/Co3+ redox couples in Ce-doped Co-Ce/TiO2 for enhancing photothermocatalytic toluene oxidation

Cerium and cobalt loaded Co-Ce/TiO2 catalyst prepared by impregnation method was investigated for photothermal catalytic toluene oxidation. Based on catalyst characterizations (XPS, EPR and H2-TPR), redox cycle between Co and TiO2 (Co2+ + Ti4+ ↔ Co3+ + Ti3+) results in the formation of Co3+, Ti3+ and oxygen vacancies, which play important roles in toluene catalytic oxidation reaction. The introduction of Ce brings in the dual redox cycles (Co2+ + Ti4+ ↔ Co3+ + Ti3+, Co2+ + Ce4+ ↔ Co3+ + Ce3+), further promoting the elevation of reaction sites amount. Under full spectrum irradiation with light intensity of 580 mW/cm2, Co-Ce/TiO2 catalyst achieved 96% of toluene conversion and 73% of CO2 yield, obviously higher than Co/P25 and Co/TiO2. Co-Ce/TiO2 efficiently maintains 10-hour stability test under water vapor conditions and exhibits better photothermal catalytic performance than counterparts under different wavelengths illumination. Photothermal catalytic reaction displays improved activities compared with thermal catalysis, which is attributed to the promotional effect of light including photocatalysis and light activation of reactive oxygen species.

Computational insights into asymmetric cross-aldol carboligation in choline chloride/ethylene glycol deep eutectic solvents

Limited research has been conducted on the exploration of chemical reactions in deep eutectic solvents (DES) using density functional theory (DFT). In this study, a comprehensive analysis of the mechanism of a cross-aldol reaction in DES through DFT calculations at the M06-2X/6-311+G(d,p)//M06-2X/6-31G(d,p) level was carried out for the first time. The aldol reaction mechanism comprised two primary stages, namely, enolization and addition, with the former identified as the rate-determining step. In this paper, an explicit explanation of the functions of catalysts, solvents and water, with results that aligned well with experimental findings, has been provided. The theoretical analysis indicated that the -COOH group of the catalyst could enhance the stability of transition states by forming a polygonal reaction center, compared to the -OH group or water, thus favoring the reaction process. The increased susceptibility of the catalyst was attributed to the enhanced ionization of the proton in the -COOH group. Findings from the IGM analysis indicated that the stability of the system was enhanced through the formation of hydrogen bonds (HBs), resulting from the interaction between DES and the substrates. It was also noted that the number of HBs did not directly correlate with the system's stability. Notably, the most stable configuration involved the disruption of the solvent structure when DES interacted with the reactants. The introduction of water compensated for the solvent's deficiency by forming new O-H⋯Cl bonds, leading to the formation of additional hydrogen bonds and thereby enhancing the system's stability. Furthermore, the impact of substituent groups was evident through the formation of an O-H⋯ONO bond, which was generated by the interaction between ethylene glycol and the -NO2 group. The substituent effect played a crucial role in the reaction and elucidated the necessity of solvent disruption. The computational analysis revealed an increase in the energy barrier when the -NO2 group was substituted with -H, -Cl and -Br. In addition, the study offered a comprehensive understanding of the influence of DES and the role of the additional third component in the reaction.

A Review on the Application of Deep Eutectic Solvents in Polymer-Based Membrane Preparation for Environmental Separation Technologies

The use of deep eutectic solvents (DESs) for the preparation of polymer membranes for environmental separation technologies is comprehensively reviewed. DESs have been divided into five categories based on the hydrogen bond donor (HBD) and acceptor (HBA) that are involved in the production of the DESs, and a wide range of DESs' physicochemical characteristics, such as density, surface tension, viscosity, and melting temperature, are initially gathered. Furthermore, the most popular techniques for creating membranes have been demonstrated and discussed, with a focus on the non-solvent induced phase separation (NIPS) method. Additionally, a number of studies have been reported in which DESs were employed as pore formers, solvents, additives, or co-solvents, among other applications. The addition of DESs to the manufacturing process increased the presence of finger-like structures and macrovoids in the cross-section and, on numerous occasions, had a substantial impact on the overall porosity and pore size. Performance data were also gathered for membranes made for various separation technologies, such as ultrafiltration (UF) and nanofiltration (NF). Lastly, DESs provide various options for the functionalization of membranes, such as the creation of various liquid membrane types, with special focus on supported liquid membranes (SLMs) for decarbonization technologies, discussed in terms of permeability and selectivity of several gases, including CO2, N2, and CH4.

A Novel Method of Self-Cross-Linking of Syringaldehyde with Activated Methoxy Groups via Cross-Coupling for Lignin-Based Wood Adhesives

As steric hindrance, methoxy groups are limiting the valorization of hardwood lignin. This paper reports a novel method of self-cross-linking of the syringaldehyde with activated methoxy groups (-OCH3) via cross-coupling reaction to obtain thermosetting polymers for lignin-based wood adhesives. The methoxy groups of syringaldehyde have been activated via cross-coupling reaction by substituting Ar-OCH3 with Ar-CH2-SiMe3, and dichloromethane, leading to cross-linking via methylene bridges to build a thermosetting polymer. FTIR spectra showed a decrease in the intensity of a -CH3 and -OH group, owing to the substitution of the methoxy group. 13C NMR spectra also supported these results with the -SiMe3 signal that disappeared after the cross-linking reaction. Furthermore, cross-linking between the activated methoxy groups was confirmed with a strong exothermic peak at 130 °C, resulting in an increase in the adhesion strength as hot-pressing temperature increased from 160 to 180 °C. These results suggest that the cross-linking between the activated methoxy groups of syringaldehyde is an important understanding of valorizing hardwood lignin via building thermosetting polymers for lignin-based adhesives.

Hydrocarbon Extraction with Ionic Liquids

Separation and reaction processes are key components employed in the modern chemical industry, and the former accounts for the majority of the energy consumption therein. In particular, hydrocarbon separation and purification processes, such as aromatics extraction, desulfurization, and denitrification, are challenging in petroleum refinement, an industrial cornerstone that provides raw materials for products used in human activities. The major technical shortcomings in solvent extraction are volatile solvent loss, product entrainment leading to secondary pollution, low separation efficiency, and high regeneration energy consumption due to the use of traditional organic solvents with high boiling points as extraction agents. Ionic liquids (ILs), a class of designable functional solvents or materials, have been widely used in chemical separation processes to replace conventional organic solvents after nearly 30 years of rapid development. Herein, we provide a systematic and comprehensive review of the state-of-the-art progress in ILs in the field of extractive hydrocarbon separation (i.e., aromatics extraction, desulfurization, and denitrification) including (i) molecular thermodynamic models of IL systems that enable rapid large-scale screening of IL candidates and phase equilibrium prediction of extraction processes; (ii) structure-property relationships between anionic and cationic structures of ILs and their separation performance (i.e., selectivity and distribution coefficients); (iii) IL-related extractive separation mechanisms (e.g., the magnitude, strength, and sites of intermolecular interactions depending on the separation system and IL structure); and (iv) process simulation and design of IL-related extraction at the industrial scale based on validated thermodynamic models. In short, this Review provides an easy-to-read exhaustive reference on IL-related extractive separation of hydrocarbon mixtures from the multiscale perspective of molecules, thermodynamics, and processes. It also extends to progress in IL analogs, deep eutectic solvents (DESs) in this research area, and discusses the current challenges faced by ILs in related separation fields as well as future directions and opportunities.

Environmental Sustainability of π-Electron Donor-Based Deep Eutectic Solvents for Toluene Absorption: A Life-Cycle Perspective

The novel π-electron donor-based deep eutectic solvents (DESs) have been shown to be a promising type of absorbent with excellent performance on toluene absorption. However, their greenness or sustainability is still unclear. Thus, to bridge the gap and give a comprehensive evaluation for their industrialization potential, the life cycle assessment (LCA) was used to evaluate the potential environmental impacts incurred from their production and usage for absorbing toluene. The environmental profiles are also compared with that of popular choline chloride (ChCl) based DES, common organic solvent triethylene glycol (TEG) and ionic liquid ([EMIM][Tf2 N]). The results indicate that among the involved hydrogen bond acceptors (HBAs), TEBAC generally imparts lower environmental impacts than other HBAs but has higher impacts than ChCl. Although TEBAC-PhOH is not the most environmentally friendly absorbent during the production stage, its outstanding absorption performance minimizes the environmental impact when absorbing the same mass of toluene. Furthermore, the environmental impacts of the toluene absorption process using TEBAC-PhOH is significantly lower than that of [EMIM][Tf2 N], slightly lower than TEG. Therefore, considering both absorption performance and environmental impacts, TEBAC-PhOH can be used as a promising "green and sustainable" toluene absorbent to traditional absorbents and ionic liquids.

VOCs emission from a final landfill cover system induced by ground surface air temperature and barometric pressure fluctuation

Volatile organic compounds (VOCs) emission flux and their concentration profiles were measured at a final municipal solid waste (MSW) landfill cover in Hangzhou, China. The influencing parameters, especially ground surface air temperature and pressure were monitored concomitantly. Furthermore, a numerical model incorporating coupled thermo-hydro-chemical interaction to assess VOCs emission from this final landfill cover (LFC) system was developed and validated with the field test results. The tested total VOC emission flux from the final cover is 0.0124 μg/m2/s, which indicates that the total amount of VOCs emitted into the atmosphere is 391 mg/m2 annually. Among these, dichloromethane (DCM) dominated VOCs emission flux during May, comprising 51.8% of the total emission flux. The numerical simulation results indicated that the diffusive emission flux of VOCs varied consistently with the fluctuation of atmospheric temperature. Whereas, the advective flux varied inversely with the fluctuation of barometric pressure. The highest difference in diffusive emission flux induced by temperature variation is 183 μg/m2/day and occurred in spring. Moreover, the results demonstrated that the impact of atmospheric temperature and pressure fluctuation on the emission of VOC from final covers is non-negligible when reasonably assessing the risks of landfill and landfill gas emission budget.

Condensable Gases Capture with Ionic Liquids

Condensable gases are the sum of condensable and volatile steam or organic compounds, including water vapor, which are discharged into the atmosphere in gaseous form at atmospheric pressure and room temperature. Condensable toxic and harmful gases emitted from petrochemical, chemical, packaging and printing, industrial coatings, and mineral mining activities seriously pollute the atmospheric environment and endanger human health. Meanwhile, these gases are necessary chemical raw materials; therefore, developing green and efficient capture technology is significant for efficiently utilizing condensed gas resources. To overcome the problems of pollution and corrosion existing in traditional organic solvent and alkali absorption methods, ionic liquids (ILs), known as "liquid molecular sieves", have received unprecedented attention thanks to their excellent separation and regeneration performance and have gradually become green solvents used by scholars to replace traditional absorbents. This work reviews the research progress of ILs in separating condensate gas. As the basis of chemical engineering, this review first provides a detailed discussion of the origin of predictive molecular thermodynamics and its broad application in theory and industry. Afterward, this review focuses on the latest research results of ILs in the capture of several important typical condensable gases, including water vapor, aromatic VOCs (i.e., BTEX), chlorinated VOC, fluorinated refrigerant gas, low-carbon alcohols, ketones, ethers, ester vapors, etc. Using pure IL, mixed ILs, and IL + organic solvent mixtures as absorbents also briefly expanded the related reports of porous materials loaded with an IL as adsorbents. Finally, future development and research directions in this exciting field are remarked.

Effective Absorption of Dichloromethane Using Carboxyl-Functionalized Ionic Liquids

Dichloromethane (DCM) is recognized as a very harmful air pollutant because of its strong volatility and difficulty to degrade. Ionic liquids (ILs) are considered as potential solvents for absorbing DCM, while it is still a challenge to develop ILs with high absorption performances. In this study, four carboxyl-functionalized ILs-trioctylmethylammonium acetate [N₁₈₈₈][Ac], trioctylmethylammonium formate [N₁₈₈₈][FA], trioctylmethylammonium glycinate [N₁₈₈₈][Gly], and trihexyl(tetradecyl)phosphonium glycinate [P₆₆₆₁₄][Gly]-were synthesized for DCM capture. The absorption capacity follows the order of [P₆₆₆₁₄][Gly] > [N₁₈₈₈][Gly] > [N₁₈₈₈][FA] > [N₁₈₈₈][Ac], and [P₆₆₆₁₄][Gly] showed the best absorption capacity, 130 mg DCM/g IL at 313.15 K and a DCM concentration of 6.1%, which was two times higher than the reported ILs [Beim][EtSO₄] and [Emim][Ac]. Moreover, the vapor-liquid equilibrium (VLE) of the DCM + IL binary system was experimentally measured. The NRTL (non-random two-liquid) model was developed to predict the VLE data, and a relative root mean square deviation (rRMSD) of 0.8467 was obtained. The absorption mechanism was explored via FT-IR spectra, ¹H-NMR, and quantum chemistry calculations. It showed a nonpolar affinity between the cation and the DCM, while the interaction between the anion and the DCM was a hydrogen bond. Based on the results of the study of the interaction energy, it was found that the hydrogen bond between the anion and the DCM had the greatest influence on the absorption process.

VOCs absorption from gas streams using deep eutectic solvents - A review

Volatile organic compounds (VOCs) are one of the most severe atmospheric pollutants. They are mainly emitted into the atmosphere from anthropogenic sources such as automobile exhaust, incomplete fuel combustion, and various industrial processes. VOCs not only cause hazards to human health or the environment but also adversely affect industrial installation components due to their specific properties, i.e., corrosive and reactivity. Therefore, much attention is being paid to developing new methods for capturing VOCs from gaseous streams, i.e., air, process streams, waste streams, or gaseous fuels. Among the available technologies, absorption based on deep eutectic solvents (DES) is widely studied as a green alternative to other commercial processes. This literature review presents a critical summary of the achievements in capturing individual VOCs using DES. The types of used DES and their physicochemical properties affecting absorption efficiency, available methods for evaluating the effectiveness of new technologies, and the possibility of regeneration of DES are described. In addition, critical comments on the new gas purification methods and future perspectives are included.