Chemical Engineering Journal Advances最新文献

The current study aims to investigate the heat and mass transport characteristics of micropolar Maxwell and Williamson nanofluids flowing past a perpendicular cylinder under the influence of combined convective flow using the Buongiorno nanofluid model. The objective is to analyze the axisymmetric flow of these nanofluids around an orthogonal cylinder, highlighting the effects of various physical parameters on temperature profiles and velocity distributions. Maple 23 software was employed to solve the coupled nonlinear differential equations derived from appropriate similarity transformations. The numerical results are presented in tabular and graphical form to show the impacts of key parameters on the selected micropolar nanofluids. The significant outcomes show that the skin friction coefficient, as well as the Nusselt and Sherwood numbers, increase along the axial direction, indicating enhanced heat and mass transfer capabilities. Additionally, the study emphasizes the roles of micro polarity, relaxation time, and viscoelastic properties in modulating these transfer processes. These findings have significant implications for applications in biomechanics, polymer manufacturing, aerosol deposition, and thermal treatment processes, offering valuable insights for future research and industrial practices.

Though the use of per-and polyfluoroalkyl substances (PFAS) is strictly restricted worldwide, PFAS have been increasingly detected in aqueous environment with high human exposure risk. Effective PFAS remediation requires the simultaneous concentration and decomposition of these compounds from dilute solutions, presenting a significant challenge. The present work evaluated the suitability of layered double hydroxide (LDH) materials, promising adsorbents for anionic pollutants, for the removal of long-chain and short-chain PFAS in micro-polluted water. Additionally, it explored their potential for PFAS degradation after modification. The results suggested that LDH adsorbents have limited ability to extract short-chain PFAS such as perfluorobutane sulfonate (PFBS) from water matrices, especially in dilute solutions. Although organic modification of LDHs could enhance their uptake efficacy on PFAS, it cannot improve the decomposition of PFAS. Innovatively, a composite featuring zero-valent iron (ZVI) particles coupled with LDH was developed, in which the nanoscale ZVI core is coated with LDH to adsorb and decompose perfluorooctanoic acid (PFOA) synergistically. Characterization of the composite showed that LDH coating not only hinders the aggregation of ZVI particles, but also reduces the passivation of ZVI. The PFOA removal efficacy of the composite can be further facilitated in acid environment. By-product analysis revealed that the composite decomposed PFOA mainly through decarboxylation and formation of unstable alcohol.

Sewage with a low carbon-to-nitrogen (C/N) ratio can be effectively treated using high-rate algal ponds (HRAPs), consisting of a combined symbiotic system of algae and bacteria. However, HRAPs have been predominantly used in laboratories, but their application in wastewater treatment plants is yet to be realized. Herein, laboratory and pilot-scale experimental studies were conducted using wetland effluent from the Baitabao estuary and effluent from the ecological wastewater treatment plant in Liaozhong County. The ammonia nitrogen (NH₄⁺–N) and chemical oxygen demand (COD) concentrations in the effluent treated using the lab-scale system decreased to <4 and <45 mg L⁻¹, respectively while those in the effluent treated in the pilot-scale test reduced to 1.51 and 9.15 mg L⁻¹, respectively. The primary bacteria in HRAPs were Pseudomonas sp., Massilia sp., Kocuria sp., Bacillus cereus group, and Exiguobacterium acetylicum group, and the dominant algae were Chlorella. Results confirm that HRAPs can effectively treat domestic sewage with low-C/N ratios while meeting China's Pollutant Emission from Urban Sewage Treatment Plants (GB 18918-2002) Level 1A standard. Studies on growth and degradation kinetics reported that (1) the specific proliferation rate of the algal–bacterial mixed system stemmed from the joint action of the specific proliferation rate of single bacteria and Chlorella, (2) there was no mutual inhibition between Chlorella and bacteria in the mixed system, (3) bacteria were responsible for a greater proportion of COD removal, and (4) Chlorella removed NH₄⁺–N primarily via adsorption, absorption, and transformation. This study demonstrates the promising potential of HRAPs for practical implementation.

The study aimed to compare an innovative method, namely liquid CO₂ extraction without high-pressure pump (LCE-WHP), with hydro-distillation (HD), microwave-assisted hydro-distillation (MA-HD) and steam distillation (SD) on yield, physical and biological properties of essential oils (EOs) from fruit peels of three green and one yellow orange cultivars. LCE-WHP oils retained the fragrance of the original fruit peels with yellow color and low content of waxes. For green cultivars, oil yields of LCE-WHP (4.8–5.9%) were significantly higher than those of SD (3.6–5.2%), but lower than those of HD (10.5–12.4%) and MA-HD (11–11.9%). Green cultivars had higher oil yield than yellow cultivar regardless of extraction method. Volatile components of EOs were similar for all methods and cultivars. Limonene was main volatile compound of all EOs with concentrations of 95.3–96.9%. Total polyphenol and carotenoid content of LCE-WHP oils were 2.3–19.1 and 5.9–113.6 folds higher than those of oils extracted by other methods, respectively. EOs extracted by LCE-WHP showed the strongest activities against Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, S. enteritidis, Escherichia coli and Candida albicans as compared to EOs extracted by other methods. Similarly, the antioxidant activities of LCE-WHP oils determined by DPPH and ABTS assay were also the strongest. This is the first report on using LCE-WHP for extracting orange EOs with high quality and biological activities. LCE-WHP has lower capital cost and safer operation than conventional CO₂ extraction methods. Such findings promote the application of LCE-WHP for commercial extraction of orange EOs.

Industrial waste, including wastewater and solid waste, often contains toxic heavy metals that necessitate extraction and separation prior to safe disposal or reusing them. Sewage sludge incineration ash (SSIA), a non-incinerable waste, holds significant amounts of heavy metals such as iron, zinc, copper, nickel, chromium, and lead. Recovery and reuse of heavy metals from SSIA and further application of treated SSIA sludge remain challenging. Ethylenediaminetetraacetic acid (EDTA) is widely used for heavy metals chelation in different applications. While its chelation with heavy metals is rapid and easy to achieve, the de-chelation of the metal complexes is otherwise slow (∼3 days) and challenging due to their high stability constants. In this study, we investigate the recovery of heavy metals from SSIA through chelation using EDTA, and develop, for the first time, a method to rapidly de-chelate the EDTA-metal complexes through the facile chilling process (1 – 3 h) that accelerates the separation of EDTA and metal ions. A sequential precipitation of high-purity heavy metals from the EDTA-metal complexes was demonstrated with and without de-chelation. This novel and versatile method allows the separation of many valuable compounds from the treated SSIA, including regenerated EDTA, potassium hexafluorosilicate, iron phosphate, iron(III) hydroxide, iron silicate, titanium phosphate, calcium phosphate, copper(I) thiocyanate, nickel bis(dimethylglyoximate), lead(II) sulfate, and zinc sulfide. This approach opens doors for more sustainable waste management and the recovery of valuable resources from industrial waste.

Heterotrophic microalgae cultivation has been suggested to reduce conventional photo-autotrophic microalgal biomass production costs. In heterotrophic cultivation, the most relevant operational costs are constituted by the supply of pure substrates used as carbon source (e.g., glucose), and the high energy request for culture aeration. In addition, suboptimal conditions of temperature and pH reduce the algal productivity, further increasing production costs. In this work, an attempt was made to define more sustainable and cost-effective strategies for the heterotrophic cultivation of Chlorellaceae and Scenedesmaceae. Several by-products from a local confectionery industry were thus screened as alternative carbon sources. Manufacturing residues from peppermint and liquorice candies production allowed to achieve comparable maximum growth rates (1.44 d^-1), biomass yields (0.33 g COD·g COD^-1) and biomass productivities (370 mg COD·L^-1·d^-1) as those achieved using glucose. A preliminary economic evaluation showed that the operational costs could be lowered of up to 85.6% by substituting glucose with the selected industrial by-products. As for fermentation conditions, high growth rates could be maintained at relatively low dissolved oxygen (DO) concentrations, and in a large range of temperature and pH values. In addition, optimal temperatures (37.0 – 37.2°C), pH values (6.8 – 7.4), and DO concentrations (> 0.5 – 1 mg O₂·L^-1) were identified. On the overall, the study demonstrated the possibility of achieving the reduction of operational costs for heterotrophic microalgae cultivation, while implementing circular economy principles in the framework of resource recovery during the bioremediation of organic waste.

Polyaromatic hydrocarbons (PAHs) are priority pollutants due to their mutagenicity, persistence, and proven carcinogenicity. Consequently, we investigated the photooxidative degradation of prototypical toxic PAHs, namely anthracene (ANTH) and phenanthrene (PHEN), and naphthalene (NAPH) utilizing magnetic CrFe₂O₄ nanoparticles under visible light LED irradiation. The prepared nanoparticles, characterized by P-XRD, IR, and SEM, reveal a cubic (FCC) structure and an average particle size of 25.6 nm. On Ab initio study we employed spin polarized first-principle calculations using the Full-Potential Linearized Augmented Plane-Wave (FLAPW) method with GGA-mBJ potentials implemented in the Wien2k package to investigate the properties of CrFe₂O₄ spinel compound; the calculations reveal that CrFe₂O₄ adopts a cubic crystal structure with space group 227 (Fd-3 m), and exhibits semiconductor characteristics in both spin channels, featuring indirect band gaps of 1.12 eV (spin-up) and 0.43 eV (spin-down) at the Γ-L and K-Γ points, respectively. Furthermore, the material demonstrates ferromagnetic behavior, with a spin magnetic moment of 20 µB per unit cell. Optical spectra analysis concurs with band structure calculations, suggesting the suitability of this material for photovoltaic applications. The CrFe₂O₄ magnetic nanoparticles were synthesized through an eco-friendly approach using Boswellia carteri resin as a natural surfactant in an aqueous medium. Our synthesized materials exhibited excellent photocatalytic performance, leading to a rapid exponential decay of ANTH and PHEN over 3 h under visible LED light. The effect of different radical scavengers revealed the role of the percentage of active species OH, h^+, and ˙O²⁻ in the oxidation of selected PAHs. At neutral pH, the photo-degradation of PAHs (200 g L⁻¹) by CrFe₂O₄ (10 mg) followed first-order kinetics and the Langmuir model (R²: 0.99). Exceptional degradation efficiencies were achieved, with ANTH exhibiting a removal efficiency of 99 %, PHEN of 90 %, and NAPH of 86 %. These results show the effectiveness of the synthesized materials as benign and environmentally friendly magnetic nanoparticles for removing carcinogenic PAHs, offering a sustainable, green, and reusable (n = 7) catalytic system to address this environmental challenge.

Background

The optimization of flow and temperature patterns in industrial reactors is crucial for achieving efficient and uniform chemical reactions. This study's major goals are to pinpoint possible areas for improvement in the NH₃ oxidation reactor's performance and to deal with the problem of uneven flow distribution inside the reactor.

Methods

In this study, the reactor building design has been changed by extending the feed pipeline vertically and increasing the number of incoming feed streams in order to achieve uniformity in the property distribution on the catalyst surface of an industrial NH₃ Oxidation reactor. Thus, using the CFD approach and the finite volume method, a three-dimensional model has been suggested. The results are contrasted with the actual geometrical configuration. The property alteration along the catalyst surface and the reactor length have been assessed.

Significant findings

By expanding the feed pipeline, the flow pattern at the reactor entry is fully developed and becomes uniform. As a result, NO₂ production could go up by as much as 11 %. The rates of NH₃ conversion, NO yield, and HNO₃ generation consequently increased by 12.5 %, 3.1 %, and 8.0 %, respectively. Additionally, this alteration results in a uniform distribution of temperature and pressure across the catalytic surface, prolonging the lifetime of the catalyst. The pressure and temperature difference over the surface of the catalyst with the original reactor configuration was also found to be approximately 250 Pa and 423.15 K, according to the data. Pressure and temperature difference were reduced to 15 Pa and 273.15 K, respectively, as the feed line's length was increased at the same time.

Municipal sludge is rich in nutrients and microbial populations, making it a potential soil amendment to enhance fertility. This study aimed to investigate the impact of municipal sludge application on microbial populations and assess its suitability as a fertilizer. The results indicated a significant increase in organic matter content in sandy soil after municipal sludge application (from 9.57 to 23.62 mg·kg⁻¹). Available potassium and phosphorus levels improved from poor to intermediate, and available nitrogen reached an excellent level. Plant parameters such as wet weight, diameter, root length, and aboveground height also showed improvement with municipal sludge addition. High-throughput sequencing revealed Shannon and Simpson indices exceeding 5.26 and 0.98, respectively, across all substrates except B1, indicating enhanced microbial community structure and diversity in sandy soil. Redundancy analysis highlighted the pivotal role of total phosphorus, available phosphorus, organic matter, available nitrogen, total nitrogen, and available potassium in enriching microbial abundance and diversity. In conclusion, using municipal sludge as fertilizer is feasible and beneficial for soil safety, fertility, and microbial populations enhancement.

The formation of products of incomplete destruction (PIDs) from fluoropolymer incineration is poorly understood and it is imperative to environmental impact studies. The lack of analytical standards limits the experimental approaches targeting product analysis. To navigate this challenge, computational modeling of the thermal degradation of fluoropolymers provides simulated product distributions. However, it is essential to benchmark reactive forcefields to accurately simulate fluoropolymer pyrolysis. The present work describes a protocol to perform accurate simulations of the thermal degradation of fluoropolymers to probe the PIDs. The ReaxFF force field was applied to reproduce the experimental bulk density and glass transition temperature of polytetrafluoroethylene (PTFE). The benchmarked methodology developed has been extended to provide simulated product distributions and mechanistic insights which are in excellent agreement with primary literature. On the basis of our simulated data, we observe a degradation mechanism that proceeds through three primary steps: 1) initiation of random backbone cleavage, 2) C₂F₄ unzipping through β–scission (as opposed to CF₂ unzipping), and 3) secondary product formation. An extension of the developed protocol has the potential to simulate the thermal degradation of non-polymeric per- and polyfluoroalkyl substances (PFASs) in addition to long-chain fluoropolymers.