Enthalpy Research Articles

Chitosan-NiFe2O4 Nanocomposite Synthesis for Effective Removal of Pb(II) and Zn(II) from Aqueous Solution

The purpose of present work is to synthesize and investigate the use of chitosan-based nanobiocomposites integrated with magnetic nanoparticles (NiFe2O4) for the adsorptive removal of Pb(II) and Zn(II) ions from aquatic media. The research is focused on addressing the urgent global problem of heavy metal pollution, especially in aquatic environments, with effective and sustainable solutions. Chitosan nanoparticles are prepared using an ionic gelation method, which are then used to synthesize a magnetic nanobiocomposite via ultrasonication and chemical co-precipitation with Ni and Fe precursors. The structural, morphological, and elemental properties of the resultant chitosan-NiFe2O4 nanobiocomposite (Fe/Ni@Chitosan NCs.) are characterized using XRD, FTIR, and Electron Microscopy (TEM and FE-SEM). The adsorption tests were conducted in a batch system, with varying contact times, pH levels, adsorbent dosages, and temperatures. The experimental adsorption of Pb(II) and Zn(II) ions showed a good fit with model of Langmuir. The nanocomposite's computed Langmuir maximum adsorption capacity (qmax) values were (91.0581, 90.7080) mg/g for Pb(II) at pH (4.0 ± 0.01) and Zn(II) at pH (6.0 ± 0.01), respectively, at a temperature of 45 °C. The thermodynamic assessment involved the determination of change of Gibbs free energy (ΔG), change of enthalpy (ΔH), and entropy ΔS. The observation of a positive ΔH value implies that the interaction between Pb(II) or Zn(II) adsorbed by Fe/Ni@Chitosan NCs is endothermic. On the other hand, a negative ΔG value suggests that the adsorption of these two ions occurs spontaneously.

Research on jet ignition phases and control parameters in an active pre-chamber optical engine under ultra-lean combustion conditions

The active pre-chamber (APC) jet ignition system is one of the primary technologies for achieving ultra-lean combustion and high thermal efficiency in engines. The impact of the jet process within the engine, as well as its control parameters, on emission pollutants (particularly soot particles) remains unclear. This study focuses on examining the effects of various low-flow injection control strategies on engine combustion and emissions by using optical experiments and numerical simulations. It also explores the impact of different ignition advance angles (ignition timings) based on a short pre-chamber mixing interval to observe ignition combustion, flame propagation, and emission characteristics under ultra-lean conditions (λ = 2.0). The main conclusions are as follows. Appropriately increasing the injection mass can enhance engine load. However, further increases in injection mass significantly raise particulate emissions, resulting in an increase in particle number by up to more than 37-fold, especially for small particles in the 5–––10 nm size range. The chemical reaction between the luminous jet flame and the bright incandescent wake jet flame, as captured by high-speed photography, effectively characterizes the various stages of jet ignition. To reduce particulate matter emissions, it is crucial to avoid the foreseeable wake jet flame caused by the enrichment of the jet mixture in the pre-chamber. The low-flow injection timing should neither be too early nor close to the ignition spark timing. The early injection causes fuel to accumulate at the top of the pre-chamber, hindering the jet flame’s propagation into the main combustion chamber. Late low-flow injection leads to fuel enrichment, resulting in uneven mixing and poor atomization and diffusion due to short mixing times. Ignition after a short mixing time interval tends to increase knocking, resulting in intense combustion and an advanced phase, which slightly reduces load and combustion stability. Regarding the heat release ratio, the total heat release from the two combustion stages in the pre-chamber should ideally account for about 5–6 % of the heat release in the main chamber.

On the Optimal Distribution of Traction Forces in Cable Propulsors of Mobile Robots

The analysis of methods of distribution of traction forces in various propellers of mobile robotic complexes and transport vehicles is carried out. The problem of synthesizing a method for controlling the distribution of the total traction load between interconnected electric drives of mobile robot propellers, discretely interacting with the support surface, is considered. An underwater mobile robot is simulated with several "walking-like" anchor-cable propellers, which ensure the movement of the underwater mobile robot by pulling the body to the supports located on the bottom. A mathematical model of the rectilinear motion of a mobile robotic device with walking-type propellers has been compiled. A mathematical description of the electric drive of the propulsion of such a mobile robot is proposed, taking into account its kinetic transfer function. It is shown that the total traction effort realized by a mobile robot is the source of the moment of resistance in the electric drive of each mover. In this regard, coefficients characterizing the distribution of traction force have been introduced into the differential equation of electric drives. A feature of the functions of these coefficients is their dependence on the distance traveled, speed and strength of resistance to movement. To optimize the distribution of the total power load between the thrusters, a target functional has been compiled. It is shown that as such a target functional, a requirement for a minimum of total heat losses in an interconnected electric drive of propellers can be formulated. To find the minimum of the accepted functional, the Euler-Poisson equations are compiled. As an additional limitation, the condition of physical feasibility is introduced. The results of solving such an optimization problem are presented on the simplest calculation scheme of two DC electric drives, between which the load is distributed along the rectilinear movement of a solid. As a result of solving the formulated optimization problem, the dependences of control actions for electric drives (voltage for DC electric drives), graphs of changes in the target function providing optimal distribution of traction forces between them are obtained, and the optimality of such distribution is proven.

Pyrolysis features of Dracaena draco lignocellulosic fibers: Kinetic and thermodynamic analysis at various heating rates through coats-redfern method

This study evaluated the thermokinetic and thermodynamic properties of Dracaena draco fibers (DDFs) through thermogravimetric analysis (TGA). The DDFs underwent non-isothermal heating in a nitrogen atmosphere, with 5, 10, and 20 °C/min heating rates starting at 20 °C and reaching 800 °C. TGA analysis demonstrated that the pyrolysis of DDFs took place in three clearly defined phases: dehydration, devolatilization, and solid biochar. The thermokinetic and thermodynamic properties were computed for the devolatilization phase of mass reduction. The Coats-Redfern technique employed twenty-one separate kinetic equations derived from four fundamental solid-state reaction processes. Out of all the diffusivity models (DMs), the Ginstlinge-Brounshtein (DM5), Jander (3D diffusion) (DM7), and Ginstling models (DM8) had the best fit, as indicated by their highest coefficient of regression values (R2 > 0.990) across all the three heating rates. The activation energy values found by the DM5, DM7, and DM8 models are 76.5, 82.32, and 76.47 kJ/mol, respectively, for the 5 °C/min heating rate. The thermodynamic variables, including the entropy, free energy, and enthalpy change, were calculated based on the kinetic data. The study’s findings are significant for evaluating the DDFs' potential as an energy source, constructing reactors, producing chemicals, and understanding the DDFs’s features for composite synthesis.

Synthesis and mesomorphic characterisation of coumarin-Schiff base and carboxylate molecules

ABSTRACT Three novel sets of coumarin-based derivatives viz. Schiff’s bases from 2-oxo-2 h-chromene-3-carboxylic acid with terminal alkyl benzene and alkyl biphenyl cores, methyl- or ethyl-group-derived coumarin esters from 7-hydroxy-4-methyl-2 h-chromen-2-one, and ethyl-7-hydroxy-2-oxo-2 h-chromene-3-carboxylate were synthesised and characterised for mesomorphic properties. The structures of the newly prepared compounds were confirmed by FT-IR, 1H-NMR, 13C-NMR, and elemental analysis. The mesophase textures of all coumarin derivatives were observed under a polarising optical microscope, and the transition temperature and enthalpy change data were measured and recorded using differential scanning calorimetry. Most of the compounds exhibit smectic and nematic mesomorphism monotropically and enantiotropically. Thermal stability was investigated by thermal gravimetric analysis (TGA).

A kinetic and mechanistic study of the self-reaction between two propargyl radicals.

The propargyl radical plays a critical role in various chemical processes, including hydrocarbon combustion, flame synthesis, and interstellar chemistry. Its unique stability arises from the delocalization of π-electrons, allowing it to participate in a wide range of reactions despite being a radical. The self-reaction of propargyl radicals is a fundamental step in synthesizing polycyclic aromatic hydrocarbons. In this work, therefore, a computational study into the C3H3 + C3H3 potential energy surface has been carefully characterized. The calculated results indicate that the reaction can occur by H-abstraction or addition of two propargyl radicals together. The H-abstraction mechanism can create the products P3 (H2CCC + H3CCCH) and P4 (H2CCCH2 + HCCCH) but the energy barriers of the two H-abstraction channels are very high (from 12 to 22kcal/mol). In contrast, the addition mechanism of two propargyl radicals forming the intermediates (I1, I5, I12) and the bimolecular products (P1, P2, P7, P11, P12) are dominant. Among the bimolecular products, the P11 (C6H4 + H2) product is the most energetically favorable, and the channel leading to this product is also the most preferred path compared to all other paths throughout the PES. The calculated enthalpy changes of various reaction paths in this study are in good agreement with the available literature data, indicating that the CCSD(T) method is suitable for the title reaction. The overall rate constant of the reaction depends on both temperature and pressure, reducing with temperature but rising with pressure. The calculated results agree closely with the available experimental values ​​and previous calculated data. Thus, it can be affirmed that in addition to the CASPT2 method as applied in the study of Georgievskii et al. (Phys. Chem. Chem. Phys., 2007, 9, 4259-4268), the CCSD(T) method is also very good for the self-reaction of two propargyl radicals. The M06-2X and CCSD(T) methods with the aug-cc-pVTZ basis set were used to optimize and calculate single-point energies for all species of the reaction. The bimolecular rate constants of the dominant reaction paths were predicted in the temperature and pressure ranges of 300-1800K and 0 - 76,000Torr, respectively, using the VTST and RRKM models with Eckart tunneling correction for the H-shift steps.

Enhanced thermal and mechanical properties of flame-retardant expandable graphite modified silk fibroin-based rigid polyurethane foam

At present, in order to reduce the environmental pollution caused by the use of petrochemical products, the preparation of flame-retardant polyurethane foam (PUF) using green raw materials is increasingly attracting widespread attention. A biomass protein-based green flame-retardant rigid PUF (RPUF) with expandable graphite (EG) and silk fibroin (SF) was prepared in a one-step process. Thermal stability, combustion characteristics and compression properties of modified RPUFs were investigated by thermogravimetric analysis, cone test, limiting oxygen index (LOI) test, UL-94 vertical burning test and mechanical compression test. The RPUF with 10 wt% EG (RPUF-SF/EG10) exhibited superior heat resistance, with the highest initial decomposition temperature (Ti), integral programmed decomposition temperatures (IPDT) and activation energy (E). And RPUF-SF/EG10 had the lowest peak heat release rate (PHRR) and total heat release (THR), and it also showed the highest LOI and had a flammability rating of V-0. In Addition, the apparent density and compressive strength of RPUF-SF/EG10 were the largest among the four EG-added materials. The results indicated that RPUF-SF/EG10 had excellent thermal stability, flame retardancy and compression resistance, which was attributed to the synergistic effect of SF and EG in the system. This provided a valuable reference for the development of new, environmentally friendly and high-performance RPUFs.

Revisiting the Extension of SGTE Heat Capacity Data to Zero Kelvin: Combining Classical Fit Polynomials with Debye–Einstein Functions

AbstractIt is demonstrated in this work that a four parameter Debye–Einstein integral is an excellent fitting function for heat capacity values of pure elements from zero Kelvin to room temperature provided that there are no phase transformations in this temperature range. The standard errors of the four parameters of the Debye–Einstein approach are provided. As examples the temperature dependent molar heat capacities of Fe, Al, Ag and Au are calculated in the temperature range from 0 to 300 K. Standard molar entropies, enthalpies and values of a molar Gibbs energy related function are derived from the molar heat capacities and the values are compared to literature data. The next goal focuses on a seamless transition of these low temperature heat capacities to SGTE (Scientific Group Thermodata Europe) unary data. This can be achieved by penalyzing deviations in the heat capacity values and in their temperature derivatives at the transition point. Whereas the constrained heat capacities of Fe and Al mimic the experimental data, the calculated values deviate considerably in case of Ag and Au. As an alternative a smooth transition in the heat capacities and the temperature derivative is achieved by a switch function employed close to the transition region.

Nanostructured poplar wood via delignification and ammonium dihydrogen phosphate-SiO2 modification towards remarkable flame retardant performance: Synergistic effect and enhanced mechanism

Developing efficient methods to prepare high-performance flame retardant and smoke suppression wood is crucial for the application. Herein, nanostructured poplar wood (DWI-4) with remarkable flame retardant and smoke suppression performance was fabricated by impregnating ammonium dihydrogen phosphate (ADP) and nano-silica (SiO2) into delignified wood (DW-4). With the delignification treatment, lignin was partially removed, and numerous pores and cracks were developed on the cell wall of wood, allowing more ADP-SiO2 particles to be impregnated into wood. As a result, ADP-SiO2 particle was not only anchored in the lumens (pores) of wood, but also was penetrated and embedded into the cell wall, achieving the synergistic modification of the lumen and cell wall of wood. As anticipated, the produced DWI-4 featured outstanding flame retardant and smoke suppression performance. The peak heat release rate (pHRR) of DWI-4 was as low as 38.2 kW m−2, which was only 8 % of that of natural wood (NW). And the total heat release (THR) and total smoke production (TSP) demonstrated reductions of 73.9 % and 64.4 % comparing to NW. Moreover, the compressive strength of DWI-4 increased by 31.4 % comparing to NW. The structure of residual char of DWI-4 was more stable and the gas intensity produced by the combustion of DWI-4 decreased remarkably. Therefore, the synergy of delignification and ADP-SiO2 impregnation significantly enhanced the flame retardant and smoke suppression performance of wood and the enhanced mechanism was revealed. The nanostructured poplar wood with excellent flame retardant and smoke suppression performance was prepared, providing an effective method for the functional improvement of wood and expanding the fields of application.

MXene-coated polystyrene microparticles for amorphous photonic crystal coating with enhanced color saturation, flame retardancy, and electromagnetic interference shielding

To enhance the color saturation of the amorphous photonic crystal (APC) coating composed of polystyrene (PS) microparticles, MXene nanosheets were deposited on the surface of the PS microparticles through strong electrostatic attraction. Three distinct colored APC coatings were achieved using Mayer rod-coating methods, employing PS microparticles of varying sizes. The intrinsic black nature of MXenes results in these coatings exhibiting high brightness of structural colors under ambient lighting conditions. Additionally, the three distinct colored APC coatings demonstrate high color saturation and low angular dependence. The thermal stability and flame retardancy of PS and PS@MXene microparticles with different MXene content were investigated. PS@MXene microparticles (three different diameters) containing 5 wt% MXene exhibited char residues of 11.0, 8.7, and 6.7 wt% at 700 °C during decomposition, whereas pure PS microparticles showed a char residue of <1.7 wt%. The peak heat release rate and total heat release of the PS@MXene microparticles were lower than those of pure PS, as characterized by a microscale combustion calorimeter. Furthermore, crack-free APC coatings on a black polyurethane substrate were successfully prepared using the Mayer rod-coating method, assisted by polyacrylic acid and ethylene glycol. The APC coatings containing PS@MXene microparticles with 5 wt% MXene, deposited on the surface of the polyurethane film, demonstrated shielding performances of approximately 20 dB. This work presents a straightforward and environmentally friendly method for constructing multifunctional APC coatings.

The enhancement effects of internal convection on the heat transport of condensing droplets out of pure steam and moist air

In this work, the effect of internal convection on the heat transport of condensing droplets is theoretically and numerically focused on considering two typical working scenes (pure steam and moist air). A three-dimensional transient multiphysics model is first constructed by elaborately coupling time-dependent multiple physics during the dynamic growth of condensing droplets. Considering variable surface wettability and industrially universal applications, heat transport characteristics of condensing droplets in these two scenes are comparatively analyzed over a wide range of the droplet radius (500–1000 μm), contact angle (60–120°), and subcooling (1–50 K). It is found that internal convection resulting from the thermocapillary effect and curved vapor/liquid interface plays a progressively prominent role as the contact angle and subcooling increase, accordingly dominating heat transport within droplets. In the steam scene, internal convection is activated neighboring the triple-phase contact line at which the temperature gradient exists solely. In comparison, in the air case, the external vapor diffusion promotes a non-uniform temperature profile over the droplet surface, and the temperature gradient is extended toward the whole surface with stronger internal convection and heat transport enhancement. In general, the quantitative analysis demonstrates that driven by strong internal convection, the total heat flow rate through the droplet can be increased by several times for both two scenes. Furthermore, using the fundamental dimensionless groups governing internal convection, we put forward an empirical correlation of the droplet Nusselt number in two condensing scenes over wide working conditions.

Regulatory factors and climatic impacts of marine heatwaves over the Arctic Ocean from 1982 to 2020

AbstractArctic warming has been substantially greater than that in the rest of the world and has had an important influence on the global climate. This study first explores the temporal and spatial evolutionary characteristics of marine heatwaves (MHWs) over the Arctic Ocean in multiyear ice (MYI), first‐year ice (FYI), and open‐water (OPW) regions from 1982 to 2020. MHWs in the Arctic Ocean show obvious spatial and seasonal variations, mainly occurring over the FYI region in the JAS (July–August–September, JAS), and their occurrences have a significant increasing trend in recent decades, accompanied by an abrupt increase since 2010. Furthermore, a multivariable network‐based method is adopted to delineate the relationship between different climatic factors and MHWs in the Arctic Ocean and the climatic impacts of MHWs. The results show that the correlations between different climatic factors and MHWs in JAS in 2010–2020 are generally stronger than those in 1982–2009, and the main influencing factors of MHWs in different ice covers are different. MHWs in the MYI region are mainly affected by freshwater dilution processes, such as sea‐ice concentrations (SIC), precipitation, and mixed‐layer salinity. For the FYI region, the 2‐m air temperature and total heat flux mainly affect MHWs by thermodynamic processes, and the 500‐hPa geopotential height affects MHWs mainly by large‐scale atmospheric circulation. The MHWs in the OPW region are mainly related to the SIC, 850‐hPa geopotential height, and 10‐m v‐wind, indicating that they are correlated with atmospheric processes and wind fields. MHWs in JAS are also revealed to reduce or delay the formation of sea ice in OND (October–November–December, OND) by storing more abnormal heat, indicating that unfrozen ocean surfaces may lead to enhanced Arctic amplification in the following seasons.

The intramolecular aggregation of phosphaphenanthrene groups and benzene-terminated effect within linear phosphonate oligomers effectively enhanced the flame retardancy and toughness of epoxy resin

To explore the potential of a flame retardant molecular structure that simultaneously enhances the flame retardancy and physical properties of epoxy resin (EP), benzene-terminated linear phosphonate oligomers Bz-DQPC-n were synthesized. Compared with the previously prepared linear bisphenol phosphonate oligomers DQPC-n, the benzene-terminated effect of Bz-DQPC-n molecules endows EP composites with better flame retardancy and toughness. In the vertical combustion (UL 94) test, Bz-DQPC-n/EP reached a V-0 rating. For the Bz-DQPC-2 molecule, the results revealed that under the same phosphorus contents, the limiting oxygen index (LOI) value of the Bz-DQPC-2/EP reached 38.2 %, which was higher than that of DQPC-2/EP. Furthermore, the peak heat release rate (pk-HRR) and total heat release rate (THR) of Bz-DQPC-2/EP were 677 kW/m2 and 83 MJ/m2. These values decreased by 54.7 % and 27.2 % in comparison to pure EP, respectively. In addition, the incorporation of Bz-DQPC-n can enhance the glass transition temperature (Tg) of EP composites. The flame retardant mechanism research demonstrated that Bz-DQPC-n molecules produced phosphorus-containing free radicals and aromatic compound fragments during gas-phase pyrolysis. These phosphorus-containing free radicals can interrupt or inhibit the combustion chain reaction process. A proportion of the aggregated phosphaphenanthrene groups decomposed to produce aromatic compounds that remained in the condensed phase, thereby enhancing the quality of the char layer. The investigation of the impact of the end-capping effect within Bz-DQPC-n molecules on the flame retardant behavior of EP composites offers a valuable reference for designing phosphaphenanthrene compounds with high flame retardant efficiency.

Convective heat transfer parameters in the film cooling with thermal radiation

Thermal radiation is a large contributor to the total heat transfer of combustion systems so that it cannot be neglected, with the improvement of gas temperature and infrared stealth requirements. This paper deeply investigated the convective parameters in film cooling with thermal radiation through theoretical analysis and numerical simulation. A method to obtain the convective driving temperature under radiation was proposed and demonstrated. Research found that the film cooling effectiveness with radiation should be expressed by the mixing temperature rather than the adiabatic wall temperature. Although heat transfer and mass transfer under radiation cannot be theoretically analogized due to the radiant source term in the energy equation, the concentration cooling effectiveness without and with radiation remains approximately the same. The numerical results indicate that although conjugate coupling plays a crucial role in determining convective and radiative heat fluxes, the coupling of radiation and convective parameters is very weak. Radiation has little influence on the film cooling effectiveness (η) and the convective heat transfer coefficient (hf). Convective parameters can be decoupled from radiation with negligible loss of accuracy. This allows the non-radiation convective parameters η and hf to be directly used for calculating the convective heat flux under radiation, with relative deviations of less than 5%.

Anti-cancer and anti-microbial drug encapsulated lipid vesicles as drug delivery systems: Calorimetric and spectroscopic study

Lipid-based drug delivery systems (DDS) have attracted considerable interest for their capacity to achieve controlled drug release and encapsulate a variety of drug molecules—hydrophobic, hydrophilic, and amphiphilic—enabling diverse therapeutic applications. The research focuses on the structural and functional aspects of lipid-based vesicles that encapsulate both anti-cancer and anti-microbial drugs. The study employs ultrasensitive isothermal titration calorimetry and differential scanning calorimetry to gain mechanistic insights into the partitioning of drugs in the lipid-based DDS, release mechanisms, and binding interactions with serum proteins after the release.The structural properties of 5-fluorouracil (5-FU) suggest that the drug can partition into the outer region of the bilayer, where it forms hydrogen bonds with the polar heads of the amphiphilic lipid chains. Kanamycin indicates strong partitioning into liposomes as it displays a binding constant of the order of 106. Erythromycin exhibits limited partitioning into the bilayer, as assessed by fitting ITC data using a sequential two-binding site model. The values of change in enthalpy and entropy reflect the interaction nature and desolvation process during the drug's partitioning into liposomes. Thermodynamic signatures and transition temperatures obtained from ITC and DSC studies indicate that no diffusion-based drug release occurs from DPPC and DSPC-based liposomes. The interaction heat between the released drug and carrier serum albumin protein is very low and shows no consistent pattern. This suggests that the drugs are stably encapsulated in the drug delivery system (DDS), with no significant leakage over time. Insights from such studies on the influence of drug molecule structure on its partitioning into various lipid vesicles and further release of the same drugs from it guide in criteria for developing improvised drug delivery systems.

A 3D nitrogen-rich heat-resistant supramolecular MOF with superior energetic performances assembled from Zn(II) and 5-aminotetrazole

Heat-resistant explosives are pivotal for specialized applications demanding high thermal stability, essential in both civil and military sectors, especially in extreme environments. Our study focuses on the synthesis of a 3D nitrogen-rich supramolecular energetic metal-organic framework (MOF), Zn(ATZ)2 (1), using the 5-aminotetrazole (HATZ) ligand and Zn(II) ion. Structural analysis indicates that compound 1 adopts the orthorhombic CmCm space group and possesses a robust 2D network, characterized by strong π-π packing interactions between 2D layers, offering exceptional thermal stability up to 322 °C with minimal mechanical sensitivity. The standard molar enthalpy of formation (ΔfHo) and heat of detonation (ΔHdet) for compound 1 are calculated to be 7.08 kJ/g and 7.34 kJ/g, respectively. Remarkably, the ΔfHo of compound 1 significantly exceeds those of traditional heat-resistant explosives like RDX (0.32 kJ/g), HNS (0.17 kJ/g), TNT (–0.295 kJ/g), and TATB (–0.54 kJ/g), and is also higher than those of most reported energetic MOF materials. Similarly, its ΔHdet value surpasses those of common explosives such as TNT (4.144 kJ/g), HMX (5.525 kJ/g) and RDX (5.71 kJ/g), as well as the majority of reported energetic MOFs. Compound 1 also demonstrates impressive detonation properties with a velocity (D) of 7.22 km s-1 and a pressure (P) of 21.95 GPa, outperforming many other energetic MOF materials. These superior energetic characteristics position compound 1 as a strong candidate for heat-resistant explosives, showcasing its potential for future applications in demanding environments.

Mass transfer process in the adsorption of Cibacron Blue (CB) on untreated pea pods (UPPs): kinetic and thermodynamic studies

ABSTRACT In recent decades, there has been extensive use of synthetic dyes in the dye-based industries, particularly the textile sector. Therefore, the aim of this study was to evaluate the adsorption of Cibacron Blue (CB) onto untreated pea pods (UPPs) in a batch system. The effects of the initial CB concentration (10–20 mg/L), solution pH (2–12), adsorbent dose (0–4 g/L), particle size (50–500 μm), and temperature (295–318 K) on the CB adsorption were investigated in batch configuration to determine the optimum conditions. Analyses of UPPs were characterized by Fourier Transform Infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET), and point-of-zero charge (pHpzc = 5.6). Under optimized conditions (pH: 2.5, particle size: 50 μm, time: 40 min, adsorbent dose: 2.5 g/L, and agitation speed: 250 rpm), up to 30.30 mg/g at 25 °C is removed from the solution. The adsorptions kinetics obey rather a pseudo-second-order kinetic model with a determination coefficient of R2 = 0.999. The adsorption isotherms have been used for the determination of thermodynamic parameters, i.e. the negative free energy ΔG° (−4.33 to 0.783 kJ/mol), negative enthalpy change ΔH° (−54.63 kJ/mol), and entropy (ΔS° = −0.1705 kJ/mol.K) indicate that the CB adsorption onto UPPs is spontaneous and exothermic in nature.

Influences of heat flow on corrosion behavior and interfacial reaction kinetics

Heat transfer surface of heat exchange devices often suffers from severe corrosion, and their corrosion behavior is dramatically influenced by both surface temperature and heat flow. In this work, a novel heat transfer interface corrosion testing system was designed and built based on a simulation calculation analysis (COMSOL Multiphysics 6.0 software). By the aid of it, effects of different heat flux on corrosion performance of steel Q235 was investigated through mass loss and electrochemical methods in 0.5 mol/L H2SO4 solution at controlled interface temperatures. Results indicate that variations in concentration and temperature impose a great contribution to corrosion rate but not corrosion mechanism. However, heat flow not only changed the concentration of reactants near the interfacial surface but also affected the rate and kinetic mechanism of corrosion. Positive heat flow could reduce corrosion rate of heat transfer surface, while negative heat flow increased corrosion rate. Heat flow significantly altered parameters of the corrosion reaction rate constant (such as pre-exponential factor, activation energy, entropy change, and enthalpy change), and an approximate exponential relationship between corrosion rate and heat flux was proposed.

Highly efficient CO2 capture by a non-aqueous amine-based absorbent of 3 aminopropanol/polyethylene glycol 200: Experimental and computational simulation

In the present work, a novel non-aqueous 3-aminopropanol/polyethylene glycol 200 (3AP/PEG200) absorbent for efficient carbon dioxide (CO2) capture was designed using environment-benign and non-toxic polyethylene glycol 200 (PEG200) as an alternative to water. The mechanism, physical, thermodynamic, and kinetic properties of absorption process was investigated through a combination of experimental and multi-scale computational simulation approaches including molecular dynamics (MD) simulation and quantum chemical (QC) calculations. It was found that the addition of PEG200 not only enhanced the thermal stability of the absorbent, but also did not significantly increase the viscosity. In addition, kinetic studies revealed that the absorption process conforms to a pseudo-first-order equation, with the activation energy (Ea) value of 20.40 kJ/mol, significantly lower than that of the benchmark 30 % monoethanolamine (MEA) aqueous solution used in industrial CO2 capture. Furthermore, the enthalpy change (ΔH) and entropy change (ΔS) values were found to be more negative than those of other liquid absorption systems, indicating that the 3AP/PEG200 absorbent is favorable for CO2 absorption even at low partial pressures. Most importantly, the absorption system exhibited good regeneration capability, as demonstrated by five absorption–desorption cycle experiments. In conclusion, the non-aqueous 3AP/PEG200 absorbent exhibits low viscosity, high thermal stability, enhanced absorption capacity, and excellent cyclic performance, positioning it as a promising candidate for CO2 absorption in industrial applications.

Tailoring of carboxymethyl guar gum hydrogels via gamma irradiation for remarkable removal of cationic and anionic dyes from simulated solutions

Tailoring of carboxymethyl guar gum hydrogels via gamma irradiation for remarkable removal of cationic and anionic dyes from simulated solutions