CO2 sequestration into coalbed seams is one of the practical routes for mitigating CO2 emissions. The adsorption mechanisms of CO2 onto Malaysian coals, however, are not yet investigated. In this research CO2 adsorption isotherms were first performed on dry and wet Mukah-Balingian coal samples at temperatures ranging from 300 to 348 K and pressures up to 6 MPa using volumetric technique. The dry S1 coal showed the highest CO2 adsorption capacity of 1.3 mmol g-1, at 300 K and 6 MPa among the other coal samples. The experimental results of CO2 adsorption were investigated using adsorption isotherms, thermodynamics, and kinetic models. Nonlinear analysis has been employed to investigate the data of CO2 adsorption onto coal samples via three parameter isotherm equilibrium models, namely Redlich Peterson, Koble Corrigan, Toth, Sips, and Hill, and four parameter equilibrium model, namely Jensen Seaton. The results of adsorption isotherm suggested that the Jensen Seaton model described the experimental data well. Gibb's free energy change values are negative, suggesting that CO2 adsorption onto the coal occurred randomly. Enthalpy change values in the negative range established that CO2 adsorption onto coal is an exothermic mechanism. Webber's pore-diffusion model, in particular, demonstrated that pore-diffusion was the main controlling stage in CO2 adsorption onto coal matrix. The activation energy of the coals was calculated to be below -13 kJ mol-1, indicating that adsorption of CO2 onto coals occurred through physisorption. The results demonstrate that CO2 adsorption onto coal matrix is favorable, spontaneous, and the adsorbed CO2 molecules accumulate more onto coal matrix. The observations of this investigation have significant implications for a more accurate measurement of CO2 injection into Malaysian coalbed seams.
Metal, carbon and conducting polymer nanoparticles are blended with organic phase change materials (PCMs) to enhance the thermal conductivity, heat storage ability, thermal stability and optical property. However, the existing nanoparticle are expensive and need to be handle with high caution during operation as well during disposal owing to its toxicity. Subsequently handling of solid waste and the disposal of organic PCM after longevity usage are of utmost concern and are less exposed. Henceforth, the current research presents a new dimension of exploration by green synthesized nanoparticles from a thorny shrub of an invasive weed named Prosopis Juliflora (PJ) which is a agro based solid waste. Subsequently, the research is indented to decide the concentration of green synthesized nanoparticle for effective heat transfer rate of organic PCM (Tm = 35-40 °C & Hm = 145 J/g). Furthermore, an in-depth understanding on the kinetic and thermodynamic profile of degradation mechanism involved in disposal of PCM after usage via Coats and Redfern technique is exhibited. Engaging a two-step method, we fuse the green synthesized nanomaterial with PCM to obtain nanocomposite PCM. On experimental evaluation, thermal conductivity of the developed nanocomposite (PCM + PJ) increases by 63.8% (0.282 W/m⋅K to 0.462 W/m⋅K) with 0.8 wt% green synthesized nanomaterial owing to the uniform distribution of nanoparticle within PCM matrix thereby contributing to bridging thermal networks. Subsequently, PCM and PCM + PJ nanocomposites are tested using thermogravimetric analyzer at different heating rates (05 °C/min; 10 °C/min; 15 °C/min & 20 °C/min) to analyze the decomposition kinetic reaction. The kinetic and thermodynamic profile of degradation mechanism involved in disposal of PCM and its nanocomposite of PCM + PJ provides insight on thermal parameters to be considered on large scale operation and to understand the complex nature of the chemical reactions. Adopting thirteen different chemical mechanism model under Coats and Redfern method we determine the reaction mechanism; kinetic parameter like activation energy (Ea) & pre-exponential factor (A) and thermodynamic parameter like change in enthalpy (ΔH), change in Gibbs free energy (ΔG) and change in entropy (ΔS). Dispersion of PJ nanomaterial with PCM reduces Ea from 370.82 kJ/mol-1 to 342.54 kJ/mol-1 (7.7% reduction), as the developed nanomaterial is enriched in carbon element and exhibits a catalytic effect for breakdown reaction. Corresponding, value of ΔG for PCM and PCM + PJ sample within heating rates of 05-20 °C/min varies between 168.95 and 41.611 kJ/mol-1. The current research will unbolt new works with focus on exploring the pyrolysis behaviour of phase change materials and its nanocomposite used for energy storage applications. This work also provides insights on the disposal of PCM which is an organic solid waste. The thermo-kinetic profile will help to investigate and predict the optimum heating rate and temperature range for conversion of micro-scale pyrolysis to commercial scale process.
Renewable energy systems are vital for a sustainable future, where solid-state hydrogen storage can play a crucial role. Perovskite hydride materials have attracted the scientific community for hydrogen storage applications. The current work focuses on the theoretical study using density functional theory (DFT) to evaluate the characteristics of MgXH3 (X = Co, Cu, Ni) hydrides. The structural, vibrational, electronic, mechanical, thermodynamic, and hydrogen storage properties of these hydrides were investigated. The equilibrium lattice parameters were calculated using the Birch-Murnaghan equation of state-to-energy volume curves. The elastic constants (Cij) and relevant parameters, such as Born criteria, were calculated to confirm the mechanical stability of the hydrides. The Cauchy pressure (Cp) revealed brittle or ductile behavior. The outcomes of the Pugh ratio, Poisson ratio, and anisotropy were also calculated and discussed. The absence of negative lattice vibrational frequencies in phonon dispersion confirmed the lattice's dynamic stability. The heat capacity curves of thermodynamic properties revealed that hydrides can conduct thermal energy. The metallic character and ample interatomic distances of hydrides were confirmed by the band structure and population analysis, which confirmed that hydrides can conduct electrical energy and adsorb hydrogen. The density of state (DOS) and partial DOS unveiled the role of specific atoms in the DOS of the crystal. The calculated gravimetric hydrogen storage capacity of MgCoH3, MgCuH3, and MgNiH3 hydrides was 3.64, 3.32, and 3.49wt%, respectively. Our results provide a deeper understanding of its potential for hydrogen storage applications through a detailed analysis of MgXH3 (X = Co, Cu, Ni) perovskite hydride material.
This study presents the kinetics and thermodynamics of biomass pyrolysis. The kinetics of the pyrolysis process was estimated using ten kinetic models from three different mechanisms, namely chemical reaction, diffusion, and nucleation and growth. Results showed that each pyrolysis subdivision was described by a different reaction model, signifying the complex nature of the pyrolysis process. The average values of activation energy determined from the kinetic models for empty fruit bunch, coconut shell, bamboo, and cardboard are 10.2-64.6 kJ/mol, 18.7-186.2 kJ/mol, 8.0-70.8 kJ/mol, and 13.1-277.3 kJ/mol, respectively. The biomass pyrolysis is endothermic and non-spontaneous and would require external energy to initiate the degradation process. The findings are helpful in characterizing the thermal degradation of biomass in exploring its potential as a source of alternative solid fuel.
Water purification using adsorption is a crucial process for maintaining human life and preserving the environment. Batch and dynamic adsorption modes are two types of water purification processes that are commonly used in various countries due to their simplicity and feasibility on an industrial scale. However, it is important to understand the advantages and limitations of these two adsorption modes in industrial applications. Also, the possibility of using batch mode in industrial scale was scrutinized, along with the necessity of using dynamic mode in such applications. In addition, the reasons for the necessity of performing batch adsorption studies before starting the treatment on an industrial scale were mentioned and discussed. In fact, this review article attempts to throw light on these subjects by comparing the biosorption efficiency of some metals on utilized biosorbents, using both batch and fixed-bed (column) adsorption modes. The comparison is based on the effectiveness of the two processes and the mechanisms involved in the treatment. Parameters such as biosorption capacity, percentage removal, and isotherm models for both batch and column (fixed bed) studies are compared. The article also explains thermodynamic and kinetic models for batch adsorption and discusses breakthrough evaluations in adsorptive column systems. The review highlights the benefits of using convenient batch-wise biosorption in lab-scale studies and the key advantages of column biosorption in industrial applications.
Driven by the need for solutions to address the global issue of waste accumulation from human activities and industries, this study investigates the thermal behaviors of empty fruit bunch (EFB), tyre waste (TW), and their blends during co-pyrolysis, exploring a potential method to convert waste into useable products. The kinetics mechanism and thermodynamics properties of EFB and TW co-pyrolysis were analysed through thermogravimetric analysis (TGA). The rate of mass loss for the blend of EFB:TW at a 1:3 mass ratio shows an increase of around 20% due to synergism. However, the blend's average activation energy is higher (298.64 kJ/mol) when compared with single feedstock pyrolysis (EFB = 257.29 kJ/mol and TW = 252.92 kJ/mol). The combination of EFB:TW at a 3:1 ratio does not result in synergistic effects on mass loss. However, a lower activation energy is reported, indicating the decomposition process can be initiated at a lower energy requirement. The reaction model that best describes the pyrolysis of EFB, TW and their blends can be categorised into the diffusion and power model categories. An equal mixture of EFB and TW was the preferred combination for co-management because of the synergistic effect, which significantly impacts the co-pyrolysis process. The mass loss rate experiences an inhibitive effect at an earlier stage (320 °C), followed by a promotional impact at the later stage (380 °C). The activation energy needed for a balanced mixture is the least compared to all tested feedstocks, even lower than the pyrolysis of a single feedstock. The study revealed the potential for increasing decomposition rates using lower energy input through the co-pyrolysis of both feedstocks. These findings evidenced that co-pyrolysis is a promising waste management and valorisation pathway to deal with overwhelming waste accumulation. Future works can be conducted at a larger scale to affirm the feasibility of EFB and TW co-management.
Pickering foams have great potential for applications in aerated foods, but their foaming ability and physical stability are still far from satisfactory. Herein, solid lipid particles (SLNs) were fabricated by using diacylglycerol of varying acyl chain lengths with modification by a protein. The SLNs showed different crystal polymorphisms and air-water interfacial activity. C14-DAG SLN with a contact angle ∼ 79° formed aqueous foam with supreme stability and high plasticity. Whey protein isolate and sodium caseinate (0.1 wt %) considerably enhanced the foamability and interfacial activity of SLNs and promoted the packing of particles at the bubble surface. However, high protein concentration caused foam destruction due to the competitive adsorption effect. β-sheet increased in protein after adsorption and changed the polymorphism and thermodynamic properties of SLN. The foam collapsing behaviors varied in the presence of protein. The results gave insights into fabricating ultrastable aqueous foams by using high-melting DAG particles. The obtained foams demonstrated good temperature sensitivity and plasticity, which showed promising application prospects in the food and cosmetic fields.
In order to characterize enzyme activity and stability corresponding to temperature effects, thermodynamic studies on commercial immobilized lipase have been carried out via enzymatic transesterification. An optimum temperature of 40 degrees C was obtained in the reaction. The decreasing reaction rates beyond the optimum temperature indicated the occurrence of reversible enzyme deactivation. Thermodynamic studies on lipase denaturation exhibited a first-order kinetics pattern, with considerable stability through time shown by the lipase as well. The activation and deactivation energies were 22.15 kJ mol(-1) and 45.18 kJ mol(-1), respectively, implying more energy was required for the irreversible denaturation of the enzyme to occur. At water content of 0.42%, the initial reaction rate and FAME yield displayed optimum values of 3.317 g/L min and 98%, respectively.
Hyperthermostable enzymes are highly desirable biocatalysts due to their exceptional stability at extreme temperatures. Recently, a hyperthermostable carboxylesterase EstD9 from Anoxybacillus geothermalis D9 was biochemically characterized. The enzyme exhibited remarkable stability at high temperature. In this study, we attempted to probe the conformational adaptability of EstD9 under extreme conditions via in silico approaches. Circular dichroism revealed that EstD9 generated new β-sheets at 80 °C, making the core of the hydrolase fold more stable. Interestingly, the profiles of molecular dynamics simulation showed the lowest scores of radius of gyration and solvent accessible surface area (SASA) at 80 °C. Three loops were responsible for protecting the catalytic site, which resided at the interface between the large and cap domains. To further investigate the structural adaptation in extreme conditions, the intramolecular interactions of the native structure were investigated. EstD9 revealed 18 hydrogen bond networks, 7 salt bridges, and 9 hydrophobic clusters, which is higher than the previously reported thermostable Est30. Collectively, the analysis indicates that intramolecular interactions and structural dynamics play distinct roles in preserving the overall EstD9 structure at elevated temperatures. This work is relevant to both fundamental and applied research involving protein engineering of industrial thermostable enzymes.
In this study, a response surface methodology (RSM) approach using central composite design (CCD) was investigated to develop a mathematical model and to optimize the effects of pH, adsorbent amount and temperature related to the hexavalent chromium removal by biosorption on peanut shells (PSh). The highest removal percentage of 30.28% was found by the predicted model under the optimum conditions (pH of 2.11, 0.73 g of PSh and 37.2 °C) for a 100 mg/L initial Cr(VI) concentration, which was very near to the experimental value (29.92%). The PSh was characterized by SEM, EDX, FTIR, BET, XRD analyses. Moreover, a Langmuir isotherm fitted well (R2 = 0.992) with the experimental data, and the maximum adsorption capacity was discovered to be 2.48 and 3.49 mg/g respectively at 25 and 45 °C. Kinetic data were well foreseen by pseudo second order. Thermodynamic study depicted that biosorption of Cr(VI) onto PSh was spontaneous and endothermic. Regeneration of the PSh using NaOH showed a loss <5% in the Cr(VI) removal efficiency up to three recycle runs. In summary, the Cr(VI) removal onto economic, sensitive and selective biosorbent (PSh) was optimized using CCD to study biosorption behaviors.
Knowledge about the thermal and storage behavior of produced protein is important for the purpose of storage, transport and shelve life during industrial application. Recombinant bromelain thermal and storage stability were measured and compared to the commercial bromelain using Differential Scanning Calorimetry (DSC). Recombinant bromelain is more stable than commercial bromelain at higher temperature but the stability was reduced after 7 days of storage at 4oC. Higher energy is needed to break the bond between amino acid chains in recombinant bromelain as shown by the enthalpy obtained, suggesting that recombinant bromelain has good protein structure and conformation compared to commercial.
In this study, we address the effect of the cis-double bond in 1,2-dioleoyl-sn-glycero-3-phosphoethanolamide-N-[methoxy(polyethylene glycol)-2000, DOPE PEG2000 (DP), on the Langmuir monolayer of C18 fatty acids-namely, stearic acid (SA), oleic acid (L1), linoleic acid (L2), and linolenic acid (L3)-with the same head group but different degrees of saturation on their hydrocarbon chains. Negative values of Gibbs free energy of mixing (ΔG mix) were obtained throughout the investigated ranges of the unsaturated C18 fatty-acid (L1, L2 and L3) mixed systems, indicating that very strong attractions occurred between molecules in the monolayers. The bend and kink effects from the cis-double bond(s) in the hydrocarbon chain affected the membrane fluidity and molecular packing in the monolayers, which resulted in a greater interaction between unsaturated C18 fatty acids and DP. The most thermodynamically stable mole composition of unsaturated C18 fatty acids to DP was observed at 50:1; this ratio is suggested to be the best mole ratio and will be subsequently used to prepare DP-C18 fatty-acid nanoliposomes. The presence of cis-double bonds in both hydrocarbon chains of DOPE in DP also created an imperfection in the membrane structure of lipid-drug delivery systems, which is expected to enhance lipid-based systems for antibody conjugation and drug encapsulation.
Multiple spectroscopic techniques, such as fluorescence, absorption, and circular dichroism along with in silico studies were used to characterize the binding of a potent inhibitor molecule, CCG1423 to the major transport protein, human serum albumin (HSA). Fluorescence and absorption spectroscopic results confirmed CCG1423-HSA complex formation. A strong binding affinity stabilized the CCG1423-HSA complex, as evident from the values of the binding constant (Ka = 1.35 × 106-5.43 × 105 M-1). The KSV values for CCG1423-HSA system were inversely correlated with temperature, suggesting the involvement of static quenching mechanism. Thermodynamic data anticipated that CCG1423-HSA complexation was mainly driven by hydrophobic and van der Waals forces as well as hydrogen bonds. In silico analysis also supported these results. Three-dimensional fluorescence and circular dichroism spectral analysis suggested microenvironmental perturbations around protein fluorophores and structural (secondary and tertiary) changes in the protein upon CCG1423 binding. CCG1423 binding to HSA also showed some protection against thermal denaturation. Site-specific marker-induced displacement results revealed CCG1423 binding to Sudlow's site I of HSA, which was also confirmed by the computational results. A few common ions were also found to interfere with the CCG1423-HSA interaction.
Complex dielectric permittivity measurements of propylene glycol (PG) in ethanol at various mole fractions were measured by using open-ended coaxial probe technique at different temperatures in the frequency range 0.02
Interactive association of an antifungal drug, climbazole (CBZ) with the carrier protein in bovine circulation, bovine serum albumin (BSA) was explored by fluorescence and absorption spectroscopy along with in silico techniques. The fluorescence and absorption spectral alterations of the protein upon addition of CBZ affirmed the complex foration between CBZ and BSA. The inverse temperature dependence behaviour of the KSV values as well as the hyperchromic result of the protein's absorption signals characterized CBZ-triggered quenching of BSA fluorescence as the static quenching. A weak binding affinity (Ka = 3.12-1.90-× 103 M-1) was reported towards the CBZ-BSA association process. Interpretation of thermodynamic data (entropy change = +14.68 J mol-1 K-1 and enthalpy change = -15.07 kJ mol-1) and in silico analyses anticipated that hydrophobic forces, van der Waals forces and hydrogen bonds were the key intermolecular forces in the complex stabilization. Inclusion of CBZ to BSA produced microenvironmental perturbations around Tyr and Trp residues, and also significantly defended temperature-induced destabilization of BSA. The binding locus of CBZ was detected in the proximity of Sudlow's sites I (subdomain IIA) and II (subdomain IIIA) of BSA, exhibiting greater preference towards site II, as revealed by competitive site-marker displacement investigations and in silico analysis. The stability of the CBZ-BSA complex was further validated by the molecular dynamics simulation assessments.
The oil palm kernel shell biochar (OPKS-B) and oil palm kernel shell activated carbon (OPKS-AC) were used as a framework to entrap urea using adsorption method. Batch adsorption studies were performed to gauge the influence of contact time on the adsorption of urea onto both OPKS-B and OPKS-AC. To evaluate the physicochemical traits of the studied materials, energy dispersive X-ray spectrometer (EDS), N2-sorption, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), elemental analysis, differential thermal gravity (TG/DTG) and thermal gravity were applied. Result shows OPKS-AC has a better sorption capacity for urea compared to OPKS-B. The Langmuir isotherm model better justified the sorption isotherms of urea. For the adsorption process for both OPKS-B and OPKS-AC, the pseudo-second-order kinetic model was picked as it best fitted the experimental sorption outcome with the superior R2 values of > 65.1% and > 74.5%, respectively. The outcome of the experiments showcased that the maximum monolayer adsorption capacity of the OPKS-AC towards urea was 239.68 mg/g. OPKS-AC has showed promising attributes to be picked as an organic framework in the production of controlled release urea fertiliser for a greener and environmentally friendly agricultural practices.
A series of fibrous aminated adsorbents for CO2 adsorption were prepared by covalent incorporation of poly (glycidyl methacrylate) (PGMA) by graft copolymerization of GMA onto electron beam (EB) irradiated polyethylenepolypropylene (PE/PP) fibrous sheets and subsequent amination with ethylenediamine (EDA), diethylenetriamine (DETA), or tetraethylenepentamine (TEPA). The physico-chemical properties of the adsorbents were evaluated using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric (TGA), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) analysis. All the adsorbents displayed typic primary and secondary amine features combined with a decrease in both of crystallinity and surface area of PE/PP, and such a decrease was higher in adsorbents with longer aliphatic chain of the amine. Of all adsorbents, TEPA-containing fibres showed the highest CO2 adsorption capacity and thus was further investigated for CO2 capture from CO2/CH4 mixtures of different gas ratios under various pressures and temperatures. The selectivity of CO2 over CH4 and equilibrium isotherms, kinetics, and thermodynamics of the adsorption on the fibrous aminated adsorbent were all investigated. The Sips model was found to best fit the isotherm of CO2 adsorption suggesting the presence of a combination of monolayer and multilayer adsorptions. The adsorption kinetic data was found to best fit Elovich model reflecting chemisorption. The ΔG°, ΔS°, and ΔH° showed positive values suggesting that the adsorption of CO2 on the present fibrous adsorbent was non-spontaneous with an increase in randomness implying that the process was endothermic. Overall, it can be suggested that PE/PP-g-PGMA/TEPA adsorbent has a strong potential for separation of CO2 from NG.
Odanacatib (ODN) is a selective cathepsin K inhibitor that acts as an anti-resorptive agent to treat osteoporosis. ODN is also found effective in reducing the effect of severe periodontitis. The interaction between ODN and human serum albumin (HSA) was investigated using spectroscopic, microscopic, and in silico approaches to characterize their binding. The fluorescence intensity of HSA increased upon the addition of increasing concentrations of ODN accompanied by blueshift in the fluorescence spectrum, which suggested hydrophobic formation around the microenvironment of the fluorophores upon ODN binding. A moderate binding affinity was obtained for ODN-HSA binding, with binding constant (Ka) values of ∼104 M-1. Circular dichroism results suggested that the overall secondary and tertiary structures of HSA were both only slightly altered upon ODN binding. The surface morphology of HSA was also affected upon ODN binding, showing aggregate formation. Drug displacement and molecular docking results revealed that ODN preferably binds to site III in subdomain IB of HSA, while molecular dynamics simulations indicated formation of a stable protein complex when site III was occupied by ODN. The ODN-HSA complex was mainly stabilized by a combination of hydrogen bonding, hydrophobic interactions, and van der Waals forces. These findings provide additional information to understand the interaction mechanism of ODN in blood circulation and may help in future improvements on the adverse effects of ODN.
The binding mode of antineoplastic antimetabolite, floxuridine (FUDR), with human serum albumin (HSA), the leading carrier in blood circulation, was ascertained using multi-spectroscopic, microscopic, and computational techniques. A static fluorescence quenching was established due to decreased Ksv values with rising temperatures, suggesting FUDR-HSA complexation. UV-vis absorption spectral results also supported this conclusion. The binding constant, Ka values, were found within 9.7-7.9 × 103 M-1 at 290, 300, and 310 K, demonstrating a moderate binding affinity for the FUDR-HSA system. Thermodynamic data (ΔS = +46.35 J.mol-1.K-1 and ΔH = -8.77 kJ.mol-1) predicted the nature of stabilizing forces (hydrogen-bonds, hydrophobic, and van der Waals interactions) for the FUDR-HSA complex. Circular dichroism spectra displayed a minor disruption in the protein's 2° and 3° structures. At the same time, atomic force microscopy images proved variations in the FUDR-HSA surface morphology, confirming its complex formation. The protein's microenvironment around Trp/Tyr residues was also modified, as judged by 3-D fluorescence spectra. FUDR-bound HSA showed better resistance against thermal stress. As disclosed from ligand displacement studies, the FUDR binding site was placed in subdomain IIA (Site I). Further, the molecular docking analysis corroborated the competing displacement studies. Molecular dynamics evaluations revealed that the complex achieved equilibrium during simulations, confirming the FUDR-HSA complex's stability.
In this research article, novel starch phosphate grafted polyvinyl imidazole (StP-g-PIMDZs) was synthesized. Firstly, a phosphate group was attached to starch polymer via a phosphorylation reaction. Next, 1-vinyl imidazole (VIMDZ) was grafted on the backbone of starch phosphate (StP) through a free radical polymerization reaction. The synthesis of these modified starches was confirmed by 1H NMR, 31P NMR and FT-IR techniques. The grafting of vinyl imidazole onto StP diminished the crystallinity. Due to the insertion of the aromatic imidazole ring, the StP-g-PIMDZs demonstrated greater thermal stability. The StP and StP-g-PIMDZs were used as sorbents for the adsorption of methylene blue dye (MBD) from the model solution. The maximum removal percentage for starch, StP, StP-g-PIMDZ 1, StP-g-PIMDZ 2 and StP-g-PIMDZ 3 was found to be 60.6%, 66.7%, 74.2%, 85.3 and 95.4%, respectively. The Pseudo second order kinetic model and Langmuir adsorption isotherm were best suited to the experimental data with R2 = 0.999 and 0.99, respectively. Additionally, the thermodynamic parameters showed that the adsorption process was feasible, spontaneous, endothermic and favored chemi-sorption mechanism.