Values Of ΔH Research Articles

Biosorption of Methyl Orange Dye in Single, Binary and Ternary System onto Gingerbread Plum Seed Shell Activated Carbon

The research investigated the potential of gingerbread plum seed shell activated to function as a biosorbent for eliminating methyl orange (MO) dye from water in various dye combinations, including single, binary, and ternary systems alongside methylene blue (MB) and Congo red (CR) dyes. The characteristics of the adsorbent were analyzed through techniques like Scanning Electron Microscopy, Fourier Transform Infrared spectroscopy, and pH point of zero charges. Batch adsorption tests were conducted to examine the adsorption processes' equilibrium behaviors, thermodynamics, and kinetics. The collected data were subjected to different isotherm and kinetics equations. The pseudo-second-order kinetics model provided the best fit for all the sorption systems, irrespective of composition differences, with higher rate constants observed for binary MO+MB= 0.031 g/mg/min system and lower for binary MO+CR= 0.028 g/mg/min and ternary MO+MB+CR= 0.029 g/mg/min systems compared to the single system MO= 0.030 g/mg/min. The maximum monolayer capacity of the adsorbent for methyl orange demonstrated synergistic interaction with the presence of methylene blue and antagonistic interaction with the presence of Congo red dye. The findings indicated that the adsorption processes varied based on the system's composition; they were all spontaneous (with Δ𝐺 values ranging from -1.146 to -10.415 kJ/mol) and exothermic (with Δ𝐻 values between -17.94 and -54.63 kJ/mol). Additionally, randomness decreased, as reflected by Δ𝑆 values of -054.43 and -382.62 J/K for the entire process.

Computational study on the adsorption and mechanisms of the hydrogenation of N-Cbz-protected glycine, alanine, valine, and phenylalanine on palladium, Pd (1 0 0), surface

Materials Studio (MS) is powerful software (with various useful tools) that is designed for simulating and modeling of different molecules and materials in computational chemistry, cheminformatics, bioinformatics, and etc. Density functional theory (DFT), with periodic slab model, is one of the most applied theoretical approaches for understanding surface-adsorbate interaction strength and reactivity. In this study, DFT method have been used via Materials Studio software to study the adsorption (at T = 298.15 K, 308.15 K, and 318.15 K) and hydrogenation (at constant temperature T = 298.15 K) of four series of N-Cbz-protected amino acids (Cbz-aa's include N-Cbz-l-phenylalanine, Cbz-pheala, N-Cbz-l-valine, Cbz-val, N-Cbz-l-alanine, Cbz-ala, and N-Cbz-l-glycine, Cbz-gly) on palladium, Pd (1 0 0), surface. During calculations of this study, a cell with periodic boundary conditions was constructed and each Cbz-aa was located and studied in this cell. For calculations of the hydrogenation of Cbz-aa's on Pd (1 0 0) surface at constant temperature, Materials Studio QMERA (combined QM/MM methods) has been employed. For calculations of the adsorption of Cbz-aa's on Pd (1 0 0) surface at different temperatures, the Materials Studio Sorption module has been applied. In the adsorption processes, average adsorption isosteric heat (Qst) and average total energy or overall system energies (Etotal) were extracted. In the hydrogenation processes, the energy of reaction (ΔH) and energy barrier (Eb) were obtained. In this study, three different mechanisms (mechanism 1: M1, mechanism 2: M2, and mechanism 3: M3) were suggested for the hydrogenation of each Cbz-aa on Pd (1 0 0) surface. We suggested these mechanisms based on the sites (atoms) that are probable for adding two hydrogen atoms (from H2) as well as the strength of bonds that should be broken for adding two hydrogen atoms (from H2). For these three mechanisms, the energy of reaction (ΔH), transition state, and energy barrier (Eb) were calculated. The obtained values of ΔH show that mechanism 3 (M3) provides the most facile mechanism to perform hydrogenation of Cbz-aa's on Pd (1 0 0) surface. Further, the negative sign of ΔH for M3 shows that mechanism 3 is an exothermic reaction in the case of all our studied Cbz-aa's. Hydrogenation and adsorption data show that Qst very slowly decreases and Etotal very slowly increases when temperature increases. Also, molecular weight and stereochemistry of Cbz-aa's molecules are two important factors that affect the values of Qst, Etotal, Eb, and ΔH.

Study on the Optimization, Extraction Kinetics and Thermodynamics of the Ultrasound-Assisted Enzymatic Extraction of Tremella fuciformis Polysaccharides.

In this study, Tremella fuciformis polysaccharides (TFPs) were extracted by ultrasound-assisted enzymatic extraction (UAE) at different extraction parameters in order to explore the potential of ultrasound in intensifying the extraction yield. The effects of experimental conditions on the extraction yields were optimized using response surface methodology, with the optimal ultrasonic power of 700 W, temperature of 45 °C and time of 50 min. The kinetic analysis revealed that UAE significantly promoted the dissolution, diffusion and migration with the maximum yield of 26.39%, which was enhanced by 40.45% and 156.96% compared with individual ultrasonic extraction (UE) and enzymatic extraction (EE). According to the modified Fick's second law of diffusion, the extraction process of TFPs illustrated a good linear correlation (R2 ≥ 0.9), and the rate constant gradually elevated as the temperature increased from 25 to 45 °C, while the presence of ultrasound exerted a vital role in extracting TFPs. Regarding to the thermodynamic results, the positive values of ΔH and ΔG demonstrated that UAE, UE and EE were endothermic and unspontaneous processes. This study provides a theoretical basis for polysaccharide extraction processing.

Kinetics and thermodynamics in microwave-assisted transesterification of palm oil utilizing sulphonated bio-graphene catalysts for biodiesel production

Enhanced reaction performance is what has piqued interest in using graphene-based catalysts in producing biodiesel. However, in-depth analyses were lacking from a kinetic and thermodynamic standpoint. This means that a well-designed experiment is necessary to determine the effect that the graphene catalysts have on the reaction rates and yields. This work addresses the kinetic and thermodynamic aspects of heterogeneously catalyzed transesterification using sulphonated biomass-derived graphene catalysts, i.e., bGO-SO3H and brGO-SO3H. It was accomplished using the pseudo-first order mechanism and the Eyring-Polanyi equation, with all data fitting satisfactorily in both models at the ideal reaction temperature of 353.15 K, resulting in R2 values of 0.9784 (bGO-SO3H) and 0.9884 (brGO-SO3H). The calculated activation energy (Ea) was determined to be 44.45 and 51.73 kJ mol-1 for bGO- and brGO-SO3H, respectively. Additionally, the Gibbs free energy (ΔG) values were determined at −38.09 and −31.81 kJ mol−1 for bGO- and brGO-SO3H, respectively. Meanwhile, the values for ΔH and ΔS were obtained as 41.69 kJ mol−1 and 225.93 J mol−1 K−1, respectively, and 48.96 kJ mol−1 and 228.72 J mol−1 K−1, respectively. These collective outcomes collectively signify the endothermic nature of the reaction and their spontaneity, particularly under elevated temperature conditions.

Highly Porous Carbon Materials Prepared Through KOH‐Assisted CO2‐Activation of Carbonized Waste Tires for Removal of Cr(VI) and Cd(II) from Water

AbstractIn this study, waste tires (WTs) were carbonized under an N2 atmosphere. Subsequently, KOH/WTs‐char with KOH‐assisted CO2 activation was used to prepare activated carbon (AC) as a highly porous carbon material for the removal of Cr(VI) and Cd(II) from water. Various techniques such as elemental analysis, Fourier‐transform infrared spectroscopy, scanning electron microscopy, and N2 adsorption/desorption were employed to investigate the physical and chemical characteristics of the prepared carbons. The WTs‐char activated with KOH under CO2 exhibited a microstructure with a high BET surface area and pore volume of 1841 m2/g and 0.869 cm3/g, respectively, demonstrating excellent adsorbent performance. The maximum removal efficiencies of 99.91 % for Cd(II) and 99.81 % for Cr(VI) were achieved using AC2 carbon under the following conditions: pH 2 for Cr(VI) and pH 5 for Cd(II), contact time of 120 min, adsorbent dose of 0.4 g/100 mL, and temperature of 298 K. The adsorption kinetics followed the pseudo‐second‐order equation, and the equilibrium data fit well with the Redlich–Peterson isotherm equation. The positive values of ▵G indicated that the uptake process for both ions was nonspontaneous and nonfeasible over the temperature studied. Both ions showed negative values of ΔH and ΔS on carbon, suggesting exothermic adsorption and a decrease in disorder. Regeneration studies showed that NaOH was a better desorbing agent than HCl. Cr(VI) desorption resulted in over 90 % removal recovery by AC2 using 1.0 M NaOH even after the fifth cycle. However, the low activation energy indicated that the adsorption was favorable kinetically. Overall, this study demonstrated the effective preparation of highly porous carbon and its successful performance in removing Cr(VI) and Cd(II) ions.

Comprehensive investigation of almond shells pyrolysis using advance predictive models

This research focused on comprehensive characterization and assessment of almond shells pyrolysis for bioenergy potential through thermogravimetric analysis from ambient temperature to 900 °C at different heating rates of 10, 15, and 20 °C/min in inert environment. Iso-conversional model-free methods like Friedman, Ozawa-Flynn-Wall (OFW), and Kissinger-Akahira-Sunose (KAS) were used for kinetic analysis. Average activation energies (Ea) evaluated using Friedman, OFW, and KAS methods were 198.45 kJ mol−1, 204.43 kJ mol−1, and 204.97 kJ mol−1, respectively. The evaluation of thermodynamic parameters, including ΔH‡, ΔG‡, and ΔS‡, was also assessed. The average values of ΔH‡, ΔG‡, and ΔS‡, were found to be 199.4 kJ mol−1, 172.17 kJ mol−1 and 42.60 kJ mol−1 respectively. The reaction mechanism was obtained from combined kinetics. A high R2 value of 0.9933 demonstrates strong agreement between the combined kinetic analysis results and the experimental data. The distribution activation energy model was assessed employing four pseudo elements identified as PC1, PC2, PC3, and PC4. Artificial Neural Network (ANN) and Boosting regression trees (BRT) were used for the prediction of Ea of almond shells pyrolysis. The detailed understanding of thermokinetics and creating customized predictive and innovative modelling techniques like ANN and BRT sets a new benchmark for developing customized models for thermochemical conversion of varieties of almond shells.

Studying removal of anionic dye by prepared highly adsorbent surface hydrogel nanocomposite as an applicable for aqueous solution

In this study, a Sodium alginate-g-poly (acrylamide-clay)/TiO2 hydrogel nanocomposite [SA-g-p(AM-Bn)/TiO2] was synthesized using the biopolymer sodium alginate (SA), acrylamide (AM), and bentonite clay (Bn) as hybrid materials embedded with titanium dioxide nanoparticles (TiO2NPs) for the removal of toxic Congo Red (CR) dye from an aqueous solution. The [SA-g-p(AM-Bn)/TiO2] nanocomposite has been described on the basis of thermal stability, morphological analysis, estimation of functional group, and crystalline/amorphous character by TGA, EFSEM/EDX, TEM, FT-IR, and XRD analysis, respectively. The effects of operational parameters toward the CR dye adsorption on [SA-g-p(AM-Bn)/TiO2], including contact time, adsorbent dosage, initial concentration, initial pH, and temperature were investigated. The maximum adsorption efficiency was found to be 185.12 mg/g for [SA-g-p(AM-Bn)/TiO2] in 100 mg/L of solution CR at pH 6.0 within 1 h. The equilibrium isotherms, kinetics, and thermodynamics parameters of adsorption were examined, and results showed that the isotherm fitted the Freundlich model and the kinetics adsorption model of CR followed pseudo-first-order, thus indicating physisorption of anionic-CR onto the sorbent due to the development of an electrostatic attraction bond. Thermodynamic parameters for [SA-g-p(AM-Bn)/TiO2] have values (ΔG and ΔH) reflecting the spontaneous and endothermic nature of the adsorption processes. Moreover, [SA-g-p(AM-Bn)/TiO2] presented outstanding excellent reusability and recyclability with a relatively best removal percentage as compared to [SA-g-p(AM-Bn)] and suggested their applicability towards the textile industry and water purification purposes.

Tuning bio-derived solvents for the rapid solubilization of astaxanthin-rich extracts from non-conventional bacterium Paracoccus carotinifaciens

Astaxanthin (AXT) is a ketocarotenoid widely used in food, feed, and pharmaceutical industries. Its biological sourcing is preferred over chemical methods due to higher physiological and commercial value. Paracoccus carotinifaciens, an aerobic marine Gram-negative bacterium, is known for producing a carotenoid mixture with AXT as the main component. This study explores the use of bio-based solvents, both pure and mixed, for extracting AXT-rich extracts (ARE). Using COSMO-SAC, a quantum chemistry-based thermodynamic model, we assessed the AXT-solvent affinity. The ethyl acetate: acetic acid mixture (EtOAc:AA) gave the best results, with 1.41 mg/mL of ARE. The solvent selection process was evaluated through the Eco Scale to compare with conventional methods. Next, optimization of extraction conditions resulted in 3.28 mg/mL of ARE at 78 °C, 10 min, and a solid-to-liquid ratio of 0.5 g/mL. Ultrasound-assisted extraction (UAE) was employed to tuning the mass-transfer process, leading to an increase of ARE (18.9 %) in reduced processing time. Concerning the stability of ARE in the EtOAc:AA mixture, the half-life (t1/2) reached 18 and 26 days under the light and dark conditions, respectively at 25 °C. In both light and dark conditions, positive enthalpy (ΔH) values revealed an endothermic process and both entropy (ΔS) and Gibbs free energy (ΔG) values suggest that the degradation of ARE is less disordered and non-spontaneous process. The solvent mixture was effectively reused for three cycles under optimally tuned conditions without a significant decline of ARE extraction efficiency.

Application of sodium dodecyl sulfate modified zeolite for effective adsorption of kinetic hydrate inhibitor compounds from aqueous solution

In present research, natural and modified zeolites with sodium dodecyl sulfate (SDS) were investigated for removing kinetic hydrate inhibitor (KHI) compounds from waterbodies. Natural zeolite (NZ) and SDS-modified zeolite (SMZ) presented BET surface area of 44.83 and 23.71 m2/g and pore volume of 0.031 and 0.078 cm3/g, respectively. Experimental conditions namely the effect of solution pH (3–9), temperature (15–45 ℃), initial concentration (100–500 mg/L), and varying adsorbent dosage (15–45 g/L) were surveyed. The maximum removal efficiency of KHI was attained at 53.1 % and 43.6 % for SMZ with an increase in adsorbent quantity and solution pH. The findings exhibited that the KHI removal percentage and capability of KHI decreased from 46 to 37 % and 0.86 to 0.68 mg/g for SMZ, respectively. Furthermore, the pseudo-second order was fitted on the adsorption mechanism with R2 > 0.98 at different concentrations and the experimental data was illustrated by Freundlich isotherm R2 > 0.98 at different temperatures. It was found that values of ΔH° in the KHI adsorption on NZ and SMZ were −12.99 and −10.3 kJ mol−1, which predicted an exothermic adsorption and ΔS° < 0 showed the solid-solute interface declined randomness. The results of this study suggest that SMZ is an economical and high potential adsorbent for KHI wastewater treatment.

Effect of pre-treatments and frying conditions on the formation of starch-lipid complex in potato starch chips during deep-frying process

This study examined the influence of various pretreatment methods, frying durations, and temperatures, as well as the type of frying oil, on the formation and structure of starch-lipid complexes in fried potato chips. Potato starch was processed into dough, sliced, and subjected to deep frying following various pretreatments. Structural analysis showed that steaming as a pretreatment facilitated the generation of V-type starch-lipid complexes, whereas resistant starch type III (RS3) materialized in the desiccated samples instead of the anticipated complexes. The rate of starch-lipid complex formation initially surged but subsequently declined as treatment time increased. A reduction in treatment temperature from 190 °C to 170 °C was conducive to complex formation. Moreover, the maximum relative crystallinity (19.74 %) and ΔH value (7.76 J/g) were recorded for potato starch slices pretreated by steaming and frying in palm oil. Rapeseed oil, which is rich in unsaturated fatty acids (89.98 %), inhibits complex formation. The study concludes that pretreatment methods exert a substantial effect on the formation of starch-lipid complexes and that extended frying duration and elevated temperature may reduce this formation. Oils with longer-chain fatty acids and a lower degree of unsaturation were favorable for complex formation.

Exploring bioenergy prospects from malt bagasse: Insights through pyrolysis with multi-component kinetic analysis and thermodynamic parameter estimation

Malt bagasse is a by-product of little commercial value in the brewing industry. Under this scenario, the current study represents the first investigation aiming to determine the kinetic triplet and thermodynamic parameters for malt bagasse pyrolysis using a multi-component kinetic approach to elucidate its bioenergy prospects. The pyrolysis progress profiles of malt bagasse were obtained through slow pyrolysis experiments on a thermogravimetric scale in an inert atmosphere, employing four distinct heating rates (10, 15, 25, and 40 °C min−1). This investigation also used the Frazer-Suzuki deconvolution function to elucidate the relative contributions of hemicellulose, cellulose, and lignin to malt bagasse pyrolysis. Activation energies for devolatilization reactions were determined by the isoconversional methods of Friedman, Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, and Starink, and revealed the lowest and highest mean values for pseudo-hemicelluloses (158.3−215.3 kJ mol−1) and pseudo-lignin (279.5−294.8 kJ mol−1), respectively. Frequency factors in malt bagasse pyrolysis ranging from 8.9 × 1016 and 2.2 × 1023 min−1 offer evidence of a simplified reaction chemistry pathway in the conversion towards bioenergy production. The integral master plot indicates the involvement of order-based and geometrical contraction-based mechanisms in malt bagasse pyrolysis. After defining multiple kinetic triplets, a differential equation encompassing contributions from all pseudo-components was formulated, and the simulated results aligned closely with experimental data, accurately describing pyrolysis progress profiles with at least 92.8% precision. The thermodynamic analysis reveals positive ΔH and ΔG values, indicating the non-spontaneous nature of malt bagasse pyrolysis. Higher disorder in the resultant products is attributed to volatile release and molecular rearrangement and is signified by positive ΔS values compared to the initial reactants. This study provided valuable insights into the valorization of malt bagasse, offering crucial information for optimizing pyrolysis reactors, scaling, and designing malt bagasse conversion into valuable biofuels, constituting an effort towards bio-circular economy principles based on the zero-waste concept.

Gamma radiation synthesis of hydroxyethyl cellulose/acrylic acid/CYANEX 471X hydrogel for silver ions capture from acidic nitrate medium

The current novelty in this study is to recover silver ion with selective extractant such as cyanex 471X (triisobutylphosphine sulfide) through a clean and green method with high efficiency. Herein, a sustainable hydrogel (HEC/AAc/CX3) was fabricated from triisobutylphosphine sulfide, hydroxyethyl cellulose (HEC), and acrylic acid (AAc) using gamma irradiation polymerization and implanted for the sorption of silver Ag (I) ions from a nitrate acidic medium. Different techniques were employed for characterization of HEC/AAc/CX3 hydrogel such as FT-IR, SEM, XRD, and EDX, before and after the sorption process of Ag(I) ions. Gel content and swelling kinetics ratio of hydrogels at different irradiation doses (10, 20, 30, 40, and 50 kGy) were studied. The Fickian diffusion model results indicate that HEC/AAc/CX3 hydrogel is non-Fickian diffusion, which confirmed that the diffusion and relaxation rates are compatible and were selected for further sorption of Ag(I). The irradiated HEC/AAc/CX3 hydrogels, which contain 0.1 g of cyanex 471X, were employed for batch sorption of 100 mg/L Ag(I) from an acidic solution, and the suggested conditions were pH = 1, time = 60, and v/m = 0.05 L/g, which gives a sorption percentage of 75%. The values of thermodynamic parameters ΔH, ΔG, and ΔS were evaluated as—62.80 kJ/mol, 5 kJ/mol, and -227 J/mol, which indicate that the sorption system was exothermic and nonspontaneous in nature. The maximum adsorption capacity of irradiated HEC/AAc/CX3 for Ag(I) was found to be 12 mg. g−1 at 298 K. Furthermore, the maximum desorption percent of Ag ions from HEC/AAc/CX3 was found to be 70% and achieved with 0.5 M NH4SCN after one desorption cycle. The prepared hydrogel proved its selectivity towards silver ions with facile desorption steps and reusability cycles.Graphical

Performance evaluation of facile synthesized CA-PVA-GO composite for the mitigation of Cr(Ⅲ) and C.I. acid violet 54 dye from tannery wastewater

Untreated tannery wastewater contains a large amount of toxic metals, dyes, and other pollutants, which pose adverse effects on the ecosystem and public health. In this work, a calcium alginate-poly vinyl alcohol-graphene oxide (CA-PVA-GO) composite was prepared to remove metals and dyes, particularly Cr(Ⅲ) and CI acid violet 54 (AV54) dye, from tannery wastewater. FESEM, FTIR, and XRD analyses were applied to characterize the GO and CA-PVA-GO. Different operational variables, viz. pH (3.0–5.5 for Cr(III) and 2–7 for dye), dosage (0.164–2.46 g/L), contact time (10–60 min), initial concentration (39, 65, 98, and 201 ppm for Cr(III) and 21.5, 38.5, 54.5, and 61.75 ppm for dye), and temperature (298, 308, 318, and 328 K) were studied to evaluate the efficiency of the CA-PVA-GO composite. The optimum conditions for Cr(Ⅲ) and AV54 dye adsorption were found to be pH (5.0 and 3.0), dosage (0.82 g/L for both), and time (45 and 60 min), respectively, with 35.35 ± 1.43% and 84.63 ± 2.54% removal efficiency. The experimental data was analyzed through the Langmuir and Freundlich isotherms. The maximum adsorption capacity (qm) was observed at 173.01 and 74.68 mg/g for Cr(Ⅲ) and AV54 dye, respectively. The pseudo-second-order kinetic model was fitted better (R2 = 0.981, 0.995, 0.92, and 0.995) than first-order for AV54 dye adsorption. Thermodynamic analyses revealed that the Cr(Ⅲ) and AV54 dye adsorption processes were spontaneous and exothermic. The value of Gibbs free energy (ΔG) for Cr(III) adsorption was obtained at −7.433, −4.508, −2.626, and −1.311 kJ/mol, whereas it was −5.178, −4.867, −4.628, and −4.555 kJ/mol for dye. The values of ΔH and ΔS were −67.257 and −0.198 kJ/mol for Cr(III) and −10.852 and −0.019 kJ/mol for the dye removal. The regenerated CA-PVA-GO composite was reused successfully. Different physicochemical parameters, viz., concentration, pH, TDS, EC, BOD5, and COD of chrome tanning and dyeing effluents, were analyzed before and after the adsorption. The results of chromium and dye removal from tannery wastewater were 53.18% and 93.91%, revealing that the developed eco-friendly CA-PVA-GO composite could be an operative adsorbent for tannery wastewater treatment and possibly scaled up to an industrial level.

Synthesis, characterization and adsorption studies of hydroxy ethyl cellulose grafted polyacrylic acid hydrogels; using basic yellow-28 as model dye

Novel hydrogels of hydroxy ethyl cellulose and polyacrylic acid (HEC-G-pAAc) were created by varying the ratio of hydroxy ethyl cellulose to acrylic acid and were characterized using analytical techniques. The synthesized hydrogels were characterized through SEM, TGA, FTIR, pH studies and Fick’s law. The SEM images revealed that the fabricated hydrogels have different adsorption sites for the dyes. According to the TGA results the decomposition of the hydrogels occurs in three successive stages (22–200 °C, 200–310 °C, 310–500 °C). The optimum pH for the adsorption of basic yellow-28 is on the HEC-G-pAAc is pH-8 as it was observed in the pH studies. The optimum temperature for the adsorption of basic yellow-28 is on the HEC-G-pAAc was found to be 293 K.The Basic Yellow-28 dye was successfully removed from wastewater with a 98% effectiveness using synthetic hydrogels as an adsorbent. The adsorption parameters were calculated using a number of different kinetic models like pseudo-second order, Elovich, intraparticle-diffusion and Bangham kinetic models. The pseudo-2nd order kinetics model was found to best fit the kinetics data, while the Langmuir isotherm offered the most thorough explanation of the adsorption process. Basic Yellow-28 dye was removed to the greatest extent by the synthesized hydrogels (pAAc = 156 mg/g, 10%HEC-G-pAAc =166.3 mg/g, 20%HEC-G-pAAc =176.2 mg/g) after 90 min of contact at 293 K. The process was exothermic because the values of ΔH were found to be negative (ΔH = −4.93, −6.49 and −5.741 kJ/mol for pAAc, 10%HEC-G-pAAc and 20%HEC-G-pAAc respectively). The adsorption process in this study is spontaneous, as clear from the negative values of ΔG, (ΔG = −4.81, −5.34 and −5.40 kJ/mol for pAAc, 10%HEC-G-pAAc and 20%HEC-G-pAAc at 293 K respectively). The adsorption process on synthesized hydrogels showed decrease in dis-orderness that was clear from its negative values.

REVIEW OF THERMODYNAMIC AND PHYSICO-CHEMICAL PARAMETERS INFLUENCING METHYLENE BLUE ADSORPTION ON ACTIVATED CHARCOAL OF NATURAL ORIGIN

Methylene blue (MB) is a phenothiazine derivative used in microbiology, surgery, diagnostics and as a sensitizer in the photo-oxidation of organic pollutants. These numerous uses of methylene blue could lead to its accumulation in wastewater, causing harmful effects on the environment and living beings. To combat these harmful effects, numerous wastewater treatment processes, particularly physicochemical, were implemented. Adsorption techniques are particularly used to find new natural, biodegradable and inexpensive adsorbents to treat colored waste from structures such as medical and pharmaceutical laboratories. The aim of the present study was to carry out a relevant bibliographical review of the physico-chemical and thermodynamic parameters that can influence this adsorption of methylene blue on activated carbons of natural origin. The results showed a remarkable elimination of methylene blue. However, parameters such as particle size, adsorbent mass, pH, contact time, initial methylene blue concentration, agitation speed and temperature showed that the adsorption capacity of MB on biosorbents was influenced by these quantities. Similarly, the positive and negative enthalpy values (ΔH°) indicated that adsorption process could be endothermic or exothermic. Other thermodynamic parameters, such as the negative value of Gibbs free energy (ΔG°) and the positive value of entropy (ΔS°), also showed that the adsorption process was feasible and spontaneous.

The interaction between troxerutin and pepsin was studied by multispectral method and molecular docking simulation

The mechanism of action and quenching mode between troxerutin and pepsin were investigated in this study using ultraviolet-visible absorption spectroscopy, Fourier transform infrared spectroscopy, fluorescence spectroscopy, three-dimensional fluorescence spectroscopy, synchronous fluorescence spectroscopy, circular binary chromatography, and molecular docking simulation. The fluorescence spectroscopy results demonstrated a reduction in the fluorescence intensity of pepsin upon addition of troxerutin, indicating its quenching effect on pepsin. By employing the Stern-Volmer equation to determine KSV and Kq values, it can be inferred that troxerutin exhibits static quenching as the predominant mode of interaction with pepsin. By conducting experiments, the binding constant KA and the number of binding sites n for troxerutin and pepsin were determined, with the number of binding sites n being close to 1, indicating the presence of a specific binding site between troxerutin and pepsin. Thermodynamic analysis was employed to calculate the thermodynamic parameters at 298 K. The negative values of ΔH and ΔS suggest that van der Waals forces and hydrogen bonding are predominant in mediating the interaction between troxerutin and pepsin. The negativity of ΔG indicates the spontaneity of the reaction. The results of molecular docking simulations demonstrate that troxerutin binds to the central active region of pepsin, with hydrogen bonds, van der Waals forces, hydrophobic interactions and adverse collisions contributing to the binding forces between troxerutin and pepsin. Based on the analysis of UV–vis absorption spectrum, three-dimensional fluorescence spectrum, synchronous fluorescence spectrum, and infrared spectrum, it is evident that troxerutin modulates the microenvironment surrounding tryptophan amino acid residues in pepsin. This modulation leads to a reduction in polarity and hydrophilicity while increasing hydrophobicity, consequently inducing alterations in the secondary structure of pepsin. By measuring the binding distance, it is calculated that 0.5 R0 < r < 1.5 R0 and r < 7 nm, indicating the occurrence of non-radiative energy transfer between troxerutin and pepsin. Analysis of the circular dichroism spectrum confirms that pepsin predominantly adopts a β-folded (β-sheet) conformation, providing evidence for the interaction between troxerutin and pepsin. Furthermore, troxerutin induces alterations in the microenvironment of pepsin's structure, ultimately resulting in changes to its secondary structure. These findings shed light on the binding mechanism underlying troxerutin and pepsin interactions while offering valuable reference data for future research and applications involving troxerutin.

Hydrazide-linked perylene-based porous organic polymer: An innovative approach for removing organic dyes from aqueous solution

The presence of toxic pollutants in the aquatic environment is a significant environmental concern that requires the development of effective methods for their removal. This study focuses on applying perylene and triazine-based porous organic polymer (PT-POP) to effectively eliminate hazardous pollutants from industrial settings. Specifically, PT-POP was synthesized using two monomers, namely 3,4,9,10 perylenetetracarboxylic dianhydride (PTCDA) and 2,4,6 tris(hydrazino)-s-triazine (THTZ). The resulting PT-POP has outstanding adsorption performance and high chemical and thermal stability, making it an attractive adsorbent material. Based on the thermogravimetric analysis, it has been confirmed that PT-POP is thermally stable. The presence of aromatic rings in PT-POP is responsible for the extraordinary stability of the polymer. Then, the performance of PT-POP in the adsorption of cationic Nile blue and anionic Direct Fast Scarlet 4BS (DFS-4BS) was studied. The optimization process involves adjusting several factors, including temperature, concentration, pH, time, and adsorbent dosage. The highest adsorption capacities (qM) for the Nile blue dye and the DFS-4BS dye were 280.16 mg. g−1 and 87.50 mg. g−1, respectively. The adsorption behavior best fits the pseudo-second-order kinetic model, and the Langmuir isotherm showed the most agreement with adsorption isotherms for both. The thermodynamic study shows that the adsorption process for both dyes is spontaneous and endothermic, as evidenced by the negative value of ΔG and the positive value of ΔH. The findings show that PT-POP is more inclined toward cationic dyes due to its negative surface charge.

Adsorption of Methylene Blue Dye and Analysis of Two Clays: A Study of Kinetics, Thermodynamics, and Modeling with DFT, MD, and MC Simulations.

The purpose of this research was to learn more about the primary and secondary properties of Moroccan natural clay in an effort to better investigate innovative adsorbents and gain access to an ideal adsorption system. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy analysis (SEM-EDX) and X-ray fluorescence were employed for identification. SEM revealed clay grains, including tiny particles and unevenly shaped sticks. First- and second-order rate laws, representing two distinct kinetic models, were applied in the kinetic approach. Adsorption of dye MB onto natural clay was studied, and the results agreed with the 2 s order model. The significant correlation coefficients support the inference that the adsorption process was governed by the Langmuir model. Subsequent DFT analyses demonstrated that the methylene blue dye's HOMO and LUMO surfaces are dispersed across most of the dye's components, pointing to a strong interaction with the clay. To determine how the dye might be adsorbed onto the clay, we employed quantum descriptors to locate its most nucleophilic and electrophilic centers. Endothermic reactions are evident during the MB adsorption process on clay, as indicated by the positive values of ΔH0 and ΔS0 (70.49 kJ mol-1of RC and 84.19 kJ mol-1 of OC and 10.45 J mol-1 K-1 of RC and 12.68 mol-1 K-1 of OC, respectively). Additionally dye molecules on the adsorbent exhibit a higher order of distribution than in the solution, indicating that the adsorption process is spontaneous.

Fabricating pentaazatetraethylene modified sulfonated polyacrylamide for dye adsorption from aqueous media: isotherms and kinetics models.

In this study, pentaazatetraethylene-modified sulfonated polyacrylamide (PAm-SO3-N5) was synthesized and used as a novel efficient adsorbent to remove calmagite from aqueous media. To this end, a central composite design (CCD) was applied to reduce the number of reaction variables (i.e., adsorbent concentration, temperature, initial concentration, and pH) on calmagite removal. The results showed that calmagite was entirely adsorbed by the PAm-SO3-N5 within 30 min. In addition, a pseudo-second-order (PSO) model was prepared as the optimum formula to fit the kinetics information. The modeling results revealed that film diffusion and adsorption are rate-limiting stages to remove the dyes. Using a Langmuir isotherm to fit the equilibrium data, the highest equilibrium adsorption was calculated to be 1732.5 mg/g. In the present study, the ΔH value indicates that the adsorption is of chemical type. Also, the negative sign of ΔS° shows that PAm-SO3-N5 removes calmagite during a relatively stable process with randomness in the system. The increase in ΔG° values with increasing temperature indicates a descending trend in the feasibility degree of calmagite adsorption. Eventually, recycling the adsorbent for 7 cycles to adsorb calmagite dye showed no remarkable activity loss.

Microwave promoted graft copolymerization of poly(ethylacrylate) onto k-carrageenan for removal of Cd and Ni from aqueous solution

Microwave promoted graft copolymerization of poly (ethyl acrylate) onto kappa-carrageenan in presence of a redox pair (ascorbic acid and potassium persulfate) led to the formation of a novel copolymer hydrogel, kappa-carrageenan-graft-poly (ethylacrylate). By varying the reaction conditions such as the microwave power, reaction time, concentration of kappa-carrageenan, ascorbic acid and persulfate, copolymers of highest percentage grafting was obtained and characterized by FT-IR, SEM, TGA and XRD. The copolymer was evaluated as an adsorbent for the adsorption of Ni(II) and Cd(II). Various adsorption parameters such as contact time, pH, initial metal ion concentration, temperature, electrolyte strength and adsorbent dosage were varied to obtain the optimum conditions for the adsorption. The adsorption data for Cd(II), fitted better for Langmuir and Ni(II), fitted much better for Freundlich adsorption isotherm model. Maximum adsorption obtained for cadmium ions and nickel ions was 308.6 mg/g-1 and 305.8 mg/g-1 respectively. The adsorption of both metal ions followed pseudo second order kinetic model. The positive ΔH values endorsed the adsorption process to be endothermic in nature. The negative values of ΔG indicate the spontaneity of the adsorption process while the positive ΔS values showed that the adsorption of metal ions proceeded with increased randomness at the surface of the copolymer. High recovery percentage of the metal ions from the adsorbent indicates that the copolymer can be used for more adsorption cycles.