ACS Engineering Au最新文献

Adsorption is a promising technique for the removal of persistent contaminants, since it is a relatively cheap process with low energy requirements and does not produce secondary contamination. However, the large-scale implementation of an adsorption process usually involves a dual column process for either pressure swing or temperature swing operations. Therefore, the reusability of adsorbents is a key characteristic to consider and evaluate but is often overlooked during the development of new materials. To be reused, the adsorbent should successfully release the contaminant by a desorption or regeneration step without compromising the chemical and physical stability of the matrix. The efficiency of desorption/regeneration methods depends greatly on the chemical characteristics of the contaminants, the nature of the adsorbents, and the adsorption mechanisms responsible for the adsorbent–adsorbate interactions. This review focuses on the desorption strategies that have been used for the regeneration of biobased hydrogels and hydrogel composites, materials that have been successfully applied in the adsorption of wastewater contaminants. The strategies can be divided into chemical and physical methods. The chemical methods include the use of desorption agents, photocatalytic oxidation, and CO₂ bubbling; and the physical methods include thermal and ultrasonic treatments. These regeneration strategies have shown different efficiencies as well as specific advantages and drawbacks that need to be considered to select the most suitable method for a specific application.

Nanofiber mats containing poly(3,4-ethylenedioxythiophene) (PEDOT) hold potential for use in wearable electronic applications. Unfortunately, the use of PEDOT is often limited by the acidic nature of polystyrenesulfonate (PSS), a common dispersant for PEDOT. In this study, we explored the impact of increasing the pH value of PEDOT:PSS/poly(vinyl alcohol) (PVA) precursors on the morphological and electrical properties of the resultant electrospun fibers. Specifically, electrospun nanofibers were analyzed using scanning electron microscopy, bright-field microscopy, and two-point probe measurements. We discovered that neutral and even slightly basic PEDOT:PSS/PVA precursors could be electrospun without affecting the resultant electrical properties. While cross-linking effectively stabilized the fibers, their electrical properties decreased after exposure to solutions with pH values between 5 and 11, as well as with agitated soap washing tests. Additionally, we report that the fiber mats maintained their stability after more than 3000 cycles of voltage application. These findings suggest that PEDOT:PSS-based fibers hold potential for use in wearable textile and sensor applications, where long-term durability is needed.

Since the industrial revolution, energy demand has increased, resulting in an increase in the atmospheric carbon dioxide concentration. Increasing CO₂ concentration contributes to global warming and climate change. Strategies to alleviate CO₂ emissions by reducing fossil fuel usage and replacing them with renewable energy sources have been devised to resolve this issue. In addition, there are several ways to reduce atmospheric CO₂ concentrations including capture, utilization, and sequestration (CCUS). Electrochemical conversion of CO₂ is a value-added approach to reducing carbon dioxide emissions as well as producing valuable chemicals, feedstocks, and building blocks. In this review, we report on the electrochemical reduction of CO₂ to alcohols and the progress made over the past five years. Alcohols are critical liquid fuels with a higher energy density, ease of storage, and transportation. Herein, we discuss the possible mechanisms for converting CO₂ to alcohols and various electrocatalysts employed for this conversion. Detailed studies compared the performances of the electrocatalysts based on the faradaic efficiency, current density, product selectivity, and stability. Furthermore, various types of electrochemical devices that can be used for the conversion of CO₂ to alcohol are also discussed. Finally, the challenges and perspectives for further research are presented.

This perspective provides the collective opinions of a dozen chemical reaction engineers from academia and industry. In this sequel to the “Vision 2020: Reaction Engineering Roadmap,” published in 2001, we provide our opinions about the field of reaction engineering by addressing the current situation, identifying barriers to progress, and recommending research directions in the context of four industry sectors (basic chemicals, specialty chemicals, pharmaceuticals, and polymers) and five technology areas (reactor system selection, design and scale-up, chemical mechanism development and property estimation, catalysis, nonstandard reactor types, and electrochemical systems). Our collective input in this report includes numerous recommendations regarding research needs in the field of reaction engineering in the coming decades, including guidance for prioritizing efforts in workforce development, measurement science, and computational methods. We see important roles for reaction engineers in the plastics circularity challenge, decarbonization of processes, electrification of chemical reactors, conversion of batch processes to continuous processes, and development of intensified, dynamic reaction processes.

A thermochemical heat storage system using Ca(OH)₂/CaO in a fluidized bed reactor (FBR) is integrated with a biomass power plant of a steam Rankine cycle (SRC) as one of the Carnot battery systems that are expected to provide renewable electricity highly flexibly. This study utilizes the proposed fluidized bed model under the nonsteady state operation to evaluate the energy efficiency and cost by varying the fluidized bed configuration and the power generation capacities. In addition, the performances of the SRC and those of the organic Rankine cycle (ORC) were compared, and the fuel cost reduction by the biomass savings was considered. The levelized cost of storage (LCOS) of the SRC in the base case (6.25 MW_e, bed volume = 100 m³, bed height/diameter ratio = 4, FBR inlet gas velocity = 0.087 m/s) was 0.804 and 0.197 USD/kWh_e when the charging electricity cost was 0.100 and 0 USD/kWh_e, respectively. The charging electricity cost has a dominant effect on the LCOS. The stored energy efficiency and the round-trip efficiency were 58.2 and 13.7% (without biomass saving), respectively, and the net power generation was 1247.3 MWh_e/year. The effect of fluidized bed volume, bed height/diameter ratio, and power generation capacity of the SRC has a slight influence on the energy efficiency and LCOS. However, the gas velocity in the FBR has a substantial influence on the net energy generation and LCOS. In the case that power generation capacity is 3 MWe and the charging electricity cost is 0 USD/kWh_e, the LCOS is 0.204 USD/kWh_e (SRC) and 0.520 USD/kWh_e (ORC), respectively, indicating that SRC has a cost advantage for a 3 MW_e-class power plant. This is because SRC has higher power generation efficiencies (24.3%) than that of the ORC (11.4%), generating more electricity from the stored heat. The effect of biomass saving on LCOS was 0.026–0.053 USD/kWh_e (SRC) and 0.096 USD/kWh_e (ORC). Increase of power generation efficiency and/or effective utilization of exhaust heat from the turbine is important to increase energy efficiency and decrease LCOS.

The design and discovery of novel porous materials that can efficiently capture volatile organic compounds (VOCs) from air are critical to address one of the most important challenges of our world, air pollution. In this work, we studied a recently introduced metal–organic framework (MOF) database, namely, quantum MOF (QMOF) database, to unlock the potential of both experimentally synthesized and hypothetically generated structures for adsorption-based n-butane (C₄H₁₀) capture from air. Configurational Bias Monte Carlo (CBMC) simulations were used to study the adsorption of a quaternary gas mixture of N₂, O₂, Ar, and C₄H₁₀ in QMOFs for two different processes, pressure swing adsorption (PSA) and vacuum-swing adsorption (VSA). Several adsorbent performance evaluation metrics, such as C₄H₁₀ selectivity, working capacity, the adsorbent performance score, and percent regenerability, were used to identify the best adsorbent candidates, which were then further studied by molecular simulations for C₄H₁₀ capture from a more realistic seven-component air mixture consisting of N₂, O₂, Ar, C₄H₁₀, C₃H₈, C₃H₆, and C₂H₆. Results showed that the top five QMOFs have C₄H₁₀ selectivities between 6.3 × 10³ and 9 × 10³ (3.8 × 10³ and 5 × 10³) at 1 bar (10 bar). Detailed analysis of the structure–performance relations showed that low/mediocre porosity (0.4–0.6) and narrow pore sizes (6–9 Å) of QMOFs lead to high C₄H₁₀ selectivities. Radial distribution function analyses of the top materials revealed that C₄H₁₀ molecules tend to confine close to the organic parts of MOFs. Our results provided the first information in the literature about the VOC capture potential of a large variety and number of MOFs, which will be useful to direct the experimental efforts to the most promising adsorbent materials for C₄H₁₀ capture from air.

Two-dimensional (2D) nanomaterial-MoS₂ (molybdenum disulfide) has gained interest among researchers, owing to its exceptional mechanical, biological, and physiochemical properties. This paper reports on the removal of organic dyes and an emerging contaminant, Ciprofloxacin, by a 2D MoS₂ nanoflower as an adsorbent. The material was prepared by a green hydrothermal technique, and its high Brunauer-Emmett-Teller-specific area of 185.541m²/g contributed to the removal of 96% rhodamine-B dye and 85% Ciprofloxacin. Various characterizations, such as X-ray diffraction, scanning electron microscopy linked with energy-dispersive spectroscopy, and transmission electron microscopy, revealed the nanoflower structure with good crystallinity. The feasibility and efficacy of 2D MoS₂ nanoflower as a promising adsorbent candidate for the removal of emerging pollutants was confirmed in-depth in batch investigations, such as the effects of adsorption time, MoS₂ dosages, solution pH, and temperature. The adsorption mechanism was further investigated based on thermodynamic calculations, adsorption kinetics, and isotherm modeling. The results confirmed the exothermic nature of the enthalpy-driven adsorption as well as the fast kinetics and physisorption-controlled adsorption process. The recyclability potential of 2D MoS₂ exceeds four regeneration recycles. MoS₂ nanoflower has been shown to be an effective organic pollutant removal adsorbent in water treatment.

This article describes an experimental apparatus of artificial photosynthesis, which generates methane gas from water and carbon dioxide with the aid of sunlight energy. This apparatus was designed on the basis of our previous 100 m²-scale photocatalytic solar hydrogen production mini-plant, which continuously produced filtered hydrogen gas for more than several months. A catalytic CO₂ methanator was attached, converting photogenerated H₂ into CH₄. The overall setup was successfully operated, and photosynthetic CH₄ was accumulated. Several versions were examined by changing the sizes of the composing assemblies and choosing specific purposes for experiments. The performances of the water-splitting photocatalytic panels, the hydrogen filtration subsystem, and the methanator are illustrated. One of the versions was implemented in the competition of the European Innovation Council (EIC) Horizon Prize on Artificial Photosynthesis “Fuel from the Sun” in 2022. For future expansion as artificial photosynthetic plants, the technical issues related to scaling up the plant size are extracted and discussed from these results.

This study investigated the performance of tandem catalysts, comprising a physical mixture of ZnZrO_x and MFI-type zeolites, in one-pass CO₂ hydrogenation. To finely adjust both the acidic properties and the pore structures, an alkali treatment was applied to a commercial zeolite. The alkali treatment resulted in enhanced catalytic activity and increased yields of C_2–4 olefin, C_2–4 paraffin, and C₅₊ hydrocarbon products, meanwhile suppressing coke formation and increasing the olefin to paraffin ratios. Comprehensive characterizations revealed that the development of the mesopore structure contributed to the observed enhancements in activity and hydrocarbon yields, with the decreased acid number rationalizing the increase in olefin to paraffin ratios. Reduced coke formation was attributed to both mesopore formation and increased external surfaces and optimized acid properties..

The accumulation of waste plastics poses a significant environmental challenge, leading to persistent pollution in terrestrial and aquatic ecosystems. A practical approach to address this issue involves the transformation of postconsumer waste plastics into industrially valuable products. This study focuses on an example of harnessing the carbon content in these polymers for carbon-demanding industrial processes, thereby reducing waste plastics from the environment and alleviating the demand for mined carbon resources. Employing quantum simulations, we examine the viability of polychloroprene as a carburizing agent in the steelmaking process. Our simulations reveal that polychloroprene exhibits excellent carbon diffusivity in molten iron, with a theoretical diffusion coefficient of 8.983 × 10^–5cm² s^–1. This value competes favorably with that of metallurgical coke and surpasses the carbon diffusivity of other polymers, such as polycarbonate, polyurethane, and polysulfide. Additionally, our findings demonstrate that the chlorine content in polychloroprene does not permeate into molten iron but instead remains confined to the molten iron and slag interface.