Search Results (644)

Nanofluids are an innovative working medium in solar hot water installations (DHWs), thanks to their increased thermal conductivity and heat transfer coefficient. The aim of this work was to assess the effect of Al₂O₃ nanofluids in a water–ethylene glycol base (40:60%) and with the addition of Tween 80 surfactant (0.2 wt%) on thermal efficiency (ε) and exergy (η_ex) in a plate heat exchanger at DHW flows of 3 and 12 L/min. The numerical NTU–ε model was used with dynamic updating of thermophysical properties of nanofluids and the solution of the ODE system using the ode45 method, and the validation was carried out against the literature data. The results showed that the nanofluids achieved ε ≈ 0.85 (vs. ε ≈ 0.87 for the base fluid) and η_ex ≈ 0.72 (vs. η_ex ≈ 0.74), with higher entropy generation. The addition of Tween 80 reduced the viscosity by about 10–15%, resulting in a slight increase of Re and h-factor; however, the impact on ε and η_ex was marginal. The environmental analysis with an annual demand of Q = 3000 kWh/year and an emission factor of 0.2 kg CO₂/kWh showed that for ε < 0.87 the nanofluids increased the emissions by ≈16 kg CO₂/year, while at ε ≈ 0.92, a reduction of ≈5% was possible. This paper highlights the need to optimize nanofluid viscosity and exchanger geometry to maximize energy and environmental benefits. Nowadays, due to the growing problems of global warming, the analysis of energy efficiency and carbon footprint related to the functioning of a building seems to be crucial. Full article

The sustainable recovery of valuable metals such as Cu and Co from ores is a pressing need considering environmental and economic challenges. Therefore, this study evaluates the effectiveness of deep eutectic solvents (DESs) as alternative leaching agents for Cu and Co extraction. Four DESs were prepared using choline chloride (ChCl) as a hydrogen bond acceptor (HBA) and oxalic acid (OA), ethylene glycol (EG), urea (U) and thiourea (TU) as hydrogen bond donors (HBDs). Leaching experiments were conducted with DESs supplemented with 30 wt.% water at varying temperatures, various solid-to-liquid ratios, and time durations. The ChCl:OA DES demonstrated the highest leaching efficiencies among the DESs tested on pure CuO and CoO, achieving 89.2% for Cu and 92.4% for Co (60 °C, 400 rpm, 6 h, −75 + 53 µm particle size, and 1:10 solid-to-liquid ratio). In addition, the dissolution kinetics, analysed using the shrinking core model (SCM), showed that the leaching process was mainly controlled by surface chemical reactions. The activation energy values for Cu and Co leaching were 46.8 kJ mol⁻¹ and 51.4 kJ mol⁻¹, respectively, supporting a surface chemical control mechanism. The results highlight the potential of ChCl:OA as a sustainable alternative for metal recovery. Full article

Both ground source heat pumps (GSHPs) and energy underground structures are engineered systems that utilize shallow geothermal energy. However, due to the construction complexity and associated costs of energy tunnels, their heat exchange efficiency relative to GSHPs remains a topic worthy of in-depth investigation. In this study, a thermal–hydraulic (TH) coupled finite element model was developed based on a section of the Torino Metro Line in Italy to analyze the differences in and influencing factors of heat transfer performance between energy tunnels and GSHPs. The model was validated by comparing the outlet temperature curves under both winter and summer loading conditions. Based on this validated model, a parametric analysis was conducted to examine the effects of the tunnel air velocity, heat carrier fluid velocity, and fluid type. The results indicate that, under identical environmental conditions, energy tunnels exhibit higher heat exchange efficiency than conventional GSHP systems and are less sensitive to external factors such as fluid velocity. Furthermore, a comparison of different heat carrier fluids, including alcohol-based fluids, refrigerants, and water, revealed that the fluid type significantly affects thermal performance, with the refrigerant R-134a outperforming ethylene glycol and water in both heating and cooling efficiency. Full article

In this study, the ultrasonic-assisted extraction of deep eutectic solvents (UADES) for tea polysaccharides was optimized, and their physicochemical properties and antioxidant activities were analyzed. The optimal DES comprised choline chloride (CC) and ethylene glycol (EG) in a molar ratio of 1:3, with a water content of 40%. The optimized condition was an extraction temperature of 61 °C, an ultrasonic power of 480 W, and an extraction time of 60 min. The UADES extraction rate of polysaccharides (ERP) was 15.89 ± 0.13%, significantly exceeding that of hot water (HW) extraction. The polysaccharide content in the UADES-extracted tea polysaccharides (UADESTPs) was comparable to that of hot-water-extracted tea polysaccharides (HWTPs) (75.47 ± 1.35% vs. 74.08 ± 2.51%); the UADESTPs contained more uronic acid (8.35 ± 0.26%) and less protein (12.91%) than HWTP. Most of the UADESTPs (88.87%) had molecular weights (Mw) below 1.80 × 10³ Da. The UADESTPs contained trehalose, glucuronic acid, galactose, xylose, and glucose, with molar ratios of 8:16:1:10. The free radical scavenging rate and total reducing power of the UADESTPs were markedly superior to those of the HWTPs. Moreover, the UADESTPs had a better alleviating effect on H₂O₂-induced oxidative injury in HepG2 cells. This study develops an eco-friendly and efficient extraction method for tea polysaccharides, offering new insights for the development of tea polysaccharides. Full article

Hypothesis: Structural optimization of crosslinkers within a reactive glycerol-based hexagonal lyotropic liquid crystal (HLLC) system is proposed to enhance the interfacial stability of hexagonal mesophases and improve the hexagonal structure retention during polymerization. This targeted modification is anticipated to significantly improve the water filtration efficiency of HLLC-templated nanofiltration. Experiments: The effect of crosslinkers on the interfacial stability of glycerol-based hexagonal mesophases was studied by evaluating their concentration accommodation within the mesophases using ¹³C solid NMR, FTIR and SAXS. Findings: A hydrophilic crosslinker consisting of ten ethylene glycol units shows less interference with the interfacial stability of hexagonal mesophases, therefore contributing to a higher concentration accommodation compared to the one with three ethylene glycol units. This long-chain crosslinker, despite having a low content of reactive groups, effectively connects the cylinders and better retains the hexagonal structures during polymerization than the hydrophobic crosslinker with shorter ethylene glycol units but a higher content of reactive groups. The retained hexagonal nanofiltration membranes show a remarkable pure water permeability of 40 L m⁻² h⁻¹ bar⁻¹ µm, resulting from the strong hygroscopic effect of glycerol and the crumpled surface of membranes due to the flexible nature of the system plasticized by glycerol. Full article

Plastic waste and water pollution demand circular economy-driven innovations. This review examines metal–organic framework (MOF) synthesis from polyethylene terephthalate (PET) waste for wastewater treatment. Depolymerized PET yields terephthalic acid and ethylene glycol—essential MOF precursors. We evaluate the following: (1) PET depolymerization (hydrolysis, glycolysis, ammonolysis) for monomer recovery efficiency; (2) MOF synthesis (solvothermal, microwave, mechanochemical) using PET-derived linkers; (3) performance in adsorbing heavy metals, dyes, and emerging contaminants. PET-based MOFs match or exceed commercial adsorbents in pollutant removal while lowering costs. Their tunable porosity and surface chemistry enhance selectivity and capacity. By converting waste plastics into functional materials, this strategy tackles dual challenges: diverting PET from landfills and purifying water. The review underscores the environmental and economic benefits of waste-sourced MOFs, proposing scalable routes for sustainable water remediation aligned with zero-waste goals. Full article

In this paper, different poly((ethylene glycol)-(propylene glycol)) methacrylate (P(EGPG)MA) hydrogels were synthesized by gamma-radiation-induced polymerization and crosslinking from a monomer–bisolvent mixture using the following monomers: (ethylene glycol)₆ methacrylate (EG₆MA), ((ethylene glycol)₆-(propylene glycol)₃) methacrylate (EG₆PG₃MA), ((propylene glycol)₆-(ethylene glycol)₃) methacrylate (PG₆EG₃MA), and (propylene glycol)₅ methacrylate (PG₅MA), along with different water/ethanol compositions as the solvent. The monomer–bisolvent mixture was exposed to various radiation doses (5, 10, 15, 25, and 50 kGy). Considerable emphasis was placed on optimizing and tuning the reaction conditions necessary for the fabrication of methacrylic networks with pendant EGPG terminals. A further investigation was conducted on the effects of monomer composition, different preparation conditions, and radiation processing on thermal properties, microstructure, swelling behavior, and volume phase transition. Special attention was dedicated to PPG₆EG₃MA hydrogel, whose volume phase transition temperature is near physiological temperatures. This study identifies an optimal radiation dose and a water/ethanol solvent ratio for the synthesis of the radiation-induced hydrogels. Employing ionizing radiation within the sterilization dose range enables the simultaneous fabrication and sterilization of these hydrogels, offering an efficient production process. The findings provide new insights into the role of bisolvent composition on hydrogel formation and properties, and they present practical guidelines for optimizing hydrogel synthesis across a wide range of applications. Full article

In surface energy tests of asphalt materials, the inaccuracy of the calculation method (e.g., least squares (LS)) and the arbitrary selection of chemical reagent combinations lead to unstable results, threatening the quantitative evaluation of asphalt–aggregate adhesion durability. This study addresses these two scientific deficiencies with the following findings: (1) when simultaneous equations are used to calculate the asphalt surface energy parameters, the total least squares method should be used instead of the classical least squares method to reduce the fitting error; (2) the selection of the reagent combination should be based on which one is the most rational in terms of the physical characterization, leap degree, abnormal values, and other requirements, and the reagent combination with the fewest abnormal values should be chosen as the best scheme. The results show that (1) compared with the classical least squares method, the total least squares method reduces the fitting error between the calculated and real values of asphalt surface energy parameters and improves the accuracy and stability of the calculation results; (2) the best reagent combination scheme is WFSD (distilled water + formamide + dimethyl sulfoxide + diiodomethane). The calculated values of asphalt surface energy parameters were more accurate and reasonable, and the calculation results had no abnormal values. Compared with WFEG (distilled water + formamide + ethylene glycol + glycerol), the error rate of the reagent combination scheme WFSD in calculating the total surface energy of two kinds of asphalt was reduced by 17.71% and 64.80%, respectively. These findings establish a reliable framework for the accurate quantification of surface energy, addressing the critical issue of reagent-dependent variability in the results and strengthening the scientific basis for evaluating the durability of asphalt pavement. Full article

Plasma electrolytic fluorination (PEF) of AZ31 magnesium alloy was carried out by adding different ratios of water to the ethylene glycol-ammonium fluoride electrolyte. The structural composition of the coatings was characterized using SEM, XRD, and EDS, and the effects of water content on the microstructure and corrosion resistance of the PEF coatings were analyzed. The results showed that the addition of water promoted the ionization of ammonium fluoride and increased the conductivity of the glycol electrolyte, which led to a decrease in the termination voltage. However, the coating thickness was not changed by the addition of water. The O element in water was not enough to compete with the F element in the electrolyte and had a small effect on the PEF coating composition, which was still dominated by MgF₂. The addition of water had an effect on the structure of the coating: with an increase in water content, the number of coating penetration holes decreases, and the continuity is enhanced. The pores on the surface of the coating tended to be levelled off and transitioned to the typical coating structure of PEO (plasma electrolytic oxidation). The addition of water to the glycol electrolyte was conducive to improving the corrosion resistance of the coatings. The corrosion resistance of PEF coatings in neutral NaCl corrosive medium firstly increased and then decreased, and the strongest corrosion resistance was obtained when the ratio of glycol and water is 6:4. Full article

The removal of pharmaceutical contaminants like the anticonvulsant carbamazepine (CBZ) from water sources is a growing environmental challenge. This study explores the development of molecularly imprinted polymers (MIPs) tailored for CBZ adsorption using a bulk polymerization approach. Initially, this study focused on selecting the optimal cross-linker, comparing a trifunctional (trimethylolpropane triacrylate, TRIM) and a bifunctional cross-linker (ethylene glycol dimethacrylate, EGDMA) in combination with two common monomers (2-vinylpyridine and methacrylic acid). TRIM-based MIPs demonstrated superior adsorption efficiency and stability due to their higher cross-linking density. To improve sustainability, six bio-based monomers were investigated; of these, eugenol (EUG) and coumaric acid (COU) showed the best CBZ affinity due to π-π interactions and hydrogen bonding. Adsorption tests conducted in pharmaceutical-spiked real wastewater demonstrated that MIPs exhibit a high selectivity for CBZ over other pharmaceuticals like the anti-inflammatory drugs diclofenac (DCF) and ibuprofen (IBU), even at high concentrations. Reaction conditions were further optimized by adjusting the reaction time and the ratio between reagents to enhance selectivity and adsorption performance. These results highlight the potential of bio-based MIPs as efficient and selective materials for the removal of pharmaceutical pollutants from wastewater. Full article

In recent decades, the attention of researchers has been directed towards the study of the dehydration of isopropanol (IPA) through different techniques. Besides its multiple uses in the chemical industry, IPA is also a potential bio-component in eco-friendly gasolines. Extractive distillation is a successful technique for separating IPA from a minimum boiling azeotrope with water. However, the major challenge is the production of fuel-grade IPA (minimum 99.92 mol%) with low expenses. As a consequent step in the investigation of IPA dehydration with propylene glycol as extractive solvent, the present study compares its efficiency and economic viability with two other extractive solvents, namely ethylene glycol (EG) and dimethyl sulfoxide (DMSO). A systematic and comprehensive methodology was developed to design a three-column extractive distillation (TCED) for each investigated solvent. A techno-economic assessment of all the investigated processes concluded that ethylene glycol, followed by propylene glycol, seems to be the most promising solvent in the IPA dehydration process. Further, the heat integration of hot streams (SH flowsheets) demonstrated improvements over 17% in the case of ethylene glycol solvent, around 16% in the case of propylene glycol (PG) solvent, and only 10% (in the case of DMSO solvent) reduction in utility consumption, improving the energy efficiency of TCED processes. Furthermore, SH flowsheets yield a 14% cost saving obtained in terms of total annualized cost (TAC) and, respectively, 8.69%, by comparison with TCED processes. In the case of DMSO solvent, the TAC reduction is only 3.54% due to the capital cost, which has an increase of 3% mainly due to the high solvent cost. Full article

The subject of the current paper is cooling heat sinks using the TPMS structure. An experiment was conducted using water and a mixture of 10% vol. ethylene glycol in water, which was used to cool heat sinks in the presence of the TPMS structure. The gyroid was developed using 3D printing with three different porosities: 0.7, 0.8, and 0.9, respectively. The shell network is a single domain, and fluid is circulated at various flow rates. A comparison with the numerical model, as simulated using COMSOL software (version 6.2), showed good agreement. A uniform temperature distribution is a clear indication of uniform cooling. Then, the TPMS structure is changed from one domain to two unconnected domains, and a different flow rate is applied to each domain entry. This approach is unique in that it investigates the cooling of the heat sink with a two-domain structure, which has not been previously studied. The novelty of this paper lies in utilizing two TPMS structure domains to cool the heat sink. Thus, dual-domain TPMS heat sinks are implemented and optimized with separate inlets. Statistical testing of the model for the Nusselt number and the performance evaluation criterion is performed using Fisher’s statistical test to analyze variance (ANOVA). It was found that the cooling heat sink is more accurate with two-domain systems. The average Nusselt number polynomial is found to vary linearly with the two-inlet velocity, the porosity and the fluid Prandtl number. Similar linearity is found for the performance evaluation criterion. The optimum Nusselt number equals 77, the PEC equals 49 for a porosity of 0.85, and the Prandtl number is 36.9. Full article

To address the limitations of a traditional Fourier-transform infrared (FTIR) spectrometer, including its bulky size, high cost, and unsuitability for on-site industrial detection, this study developed a Fourier-transform near-infrared (FT-NIR) absorption testing system utilizing Micro-Electro-Mechanical System (MEMS) technology for detecting trace water content in ethylene glycol. The modeling performances of three algorithms including Support Vector Machine Regression (SVMR), Principal Component Regression (PCR), and Partial Least Squares Regression (PLSR) were systematically evaluated, with PLSR identified as the optimal algorithm. To enhance predictive accuracy of water trace, spectral data were preprocessed using smoothing combined with first-derivative processing, and optimal selection of absorption wavelength feature was performed using interval Partial Least Squares (iPLS). Cross-batch external validation demonstrated a Limit of Detection (LOD) of 0.026% with 95% confidence which satisfies the rapid screening requirements for water exceedances (>0.1%) in industrial applications. These findings provide a robust technical foundation for developing handheld, in situ water detection devices. Full article

The effects of a series of sodium salts (Na₃PO₄, Na₂CO₃, Na₂SO₄, Na₂SO₃, Na₂MO₄, Na₂CrO₄, and Na₂WO₄) on the phase separation of poly(ethylene glycol) (PEG) solutions in water at PEG concentrations of 0.5 to 30 wt.% were studied. The salts’ effects on phase separation are found to correlate with the change in the entropy related to the structural changes in water during anion hydration. The same salts’ effects on phase separation in aqueous solutions of branched PEG and polyvinylpyrrolidone at a polymer concentration of 10 wt.% were also examined. The results obtained support the assumption that phase separation in aqueous polymer–salt systems is an entropy-driven process. Full article

The presented study focuses on evaluating the mixing properties of structures derived from the so-called sheet-gyroid geometry and their modifications as advanced mixing elements in renewable energy technologies. Using numerical simulations based on computational fluid dynamics (CFD), the hydrodynamic characteristics of the basic sheet-gyroid structure and five geometric modifications were analyzed under laminar flow conditions simulating the mixing of water and ethylene glycol. The evaluation was conducted using the parameters mixing index and performance index, which express the efficiency of fluid homogenization and its associated energy demands. The results show that all tested geometries significantly improve the degree of mixing compared to an empty channel. The highest concentration homogeneity and best energy efficiency were achieved by the twisted sheet-gyroid structure. This geometric modification exhibits the highest value of the performance index, confirming its ability to achieve excellent mixing with minimal pressure losses. The results of the study demonstrated that, despite similar hydraulic losses among some of the structures, their fluid mixing performance differs, which highlights the importance of targeted geometric design of sheet-gyroid structures. These findings are essential for the design of efficient mixers in technological applications where intensive mixing combined with minimal energy consumption is a critical factor. Full article