Kinetic Studies Research Articles

Kinetic and isotherm adsorption studies of Zn (II) ions on hydroxyapatite nanoparticles: Linear and nonlinear analyses

Kinetic and isotherm adsorption studies of Zn (II) ions on hydroxyapatite nanoparticles: Linear and nonlinear analyses

Efficient elimination of 3-monochloropropane-1,2-diol fatty acid ester from palm oil via using activated carbon grafted with Tween80.

In the current study, we attempt to remove 3-monochloropropane-1,2-diol fatty acid ester (3-MCPD ester) from palm oil with developed composite adsorbent (Tween80 modified activated carbon [AC]), and scanning electron microscopy-energy dispersive spectrometer, Fourier transform-infrared spectroscopy, X-ray diffraction, nitrogen content adsorption-desorption and thermogravimetric analysis were used to characterize the modifications. We further examined the adsorption capability of the composite adsorbent for 3-MCPD ester and found that the highest removal efficiency was 87.36% (5.3% of adsorbent dose at 104°C for 29min). This is approximately three times higher than that of pristine AC, implying that the composite can be employed as a novel adsorbent for 3-MCPD ester reduction. Along with the adsorption mechanism of Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin models were also tested. It has been suggested that Freundlich model could best describe the adsorption process. Adsorption was found to be well-fitted by pseudo-second-order kinetics according to the kinetic study. An endothermic and spontaneous adsorption mechanism was demonstrated by the thermodynamic studies.

Synthesis of a New Composite Material Derived from Cherry Stones and Sodium Alginate—Application to the Adsorption of Methylene Blue from Aqueous Solution: Process Parameter Optimization, Kinetic Study, Equilibrium Isotherms, and Reusability

Synthesis of a New Composite Material Derived from Cherry Stones and Sodium Alginate—Application to the Adsorption of Methylene Blue from Aqueous Solution: Process Parameter Optimization, Kinetic Study, Equilibrium Isotherms, and Reusability

Investigating the inhibition of xanthine oxidase by five catechins: Kinetic studies, spectroscopy, molecular docking, and dynamics simulations

Catechins compounds from tea have demonstrated significant inhibitory effects on xanthine oxidase (XOD). However, the precise inhibitory mechanisms of the main catechins on XOD remain to be fully elucidated. This study explored the inhibition mechanisms and binding characteristics of five catechins (GC, EGC, EC, EGCG, and ECG) on XOD through a combination of inhibition kinetics, multi-spectroscopy analysis, molecular docking, and dynamics simulations. Among the catechins, EGCG and ECG exhibited the most potent inhibitory activities against XOD. All five catechins were found to exhibit mixed inhibition, affecting the hydrophobic groups and secondary structure of XOD predominantly through hydrophobic interactions and hydrogen bonding. Molecular dynamics simulations revealed that a 3,4,5-trihydroxybenzoic acid moiety at C3 position significantly enhances the binding affinity of EGCG and ECG to XOD. Additionally, the decrease of β-sheet and random coil induced by EGCG and ECG was found to be crucial for enhancing inhibitory activity of XOD. In vitro cell experiments showed that EGCG and ECG significantly reduced high uric acid levels of BRL-3A cell. This study elucidates the inhibitory mechanisms of catechins on XOD, paving the way for their application as XOD inhibitors to combat hyperuricemia.

Preparation of new green poly (amino amide) based on cellulose nanoparticles for adsorption of Congo red and its adaptive neuro-fuzzy modeling

In this study, a novel green poly(amino amide) nanoparticle based on cellulose nanoparticles (Cell-PAMN) was developed for the efficient adsorption of Congo Red dye. Cellulose nanocrystals obtained from acid hydrolysis of cotton linter were functionalized via Oxa-Michael addition of acrylamide on their surface hydroxyl groups, followed by transamidation with ethylenediamine. The resulting nanoparticles were characterized using FT-IR spectroscopy, SEM, and X-ray diffraction techniques. The as-prepared Cell-PAMN exhibited considerably higher adsorption capacity compared to unmodified cellulose nanoparticles due to the presence of amino and amide functional groups. The adsorption kinetics and the effects of parameters such as contact time and initial dye concentration on the adsorption capacity were investigated. An adaptive Neuro-Fuzzy model was used to study the efficiency of dye removal, accurately predicted the adsorption behavior of Cell-PAMN. The kinetic study results showed that the adsorption process followed a pseudo-second-order kinetic model, with a maximum adsorption capacity of around 40 mg/g. The results demonstrated the potential of the synthesized material for the removal of Congo Red from aqueous solutions, highlighting its applicability in wastewater treatment. This research contributes to the development of sustainable and eco-friendly materials for environmental remediation applications.

Visible Light-Triggered Catalytic Performance of Reduced Graphene Oxide Decorated With Copper Oxide Nanocomposite for Degradation of Rhodamine B Dye and Kinetics Studies.

Herein, novel nanocomposites based on reduced graphene oxide decorated copper oxide nanoparticles (rGO/CuO) were prepared by the in situ co-precipitation method. The structural, morphological, and optical characterization of as-prepared nanocomposites was performed by powdered x-ray diffraction (p-XRD), scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR), Raman, and ultraviolet-visible (UV-Vis) spectroscopy, respectively. The as-prepared nanocomposites exhibited better photocatalytic activity of rhodamine B dye with maximum ~94% degradation in 120 min with a rate constant of 0.2353 min-1 under optimized conditions. Furthermore, the effects of solution pH and catalyst loading are studied on the degradation process. Therefore, this state-of-the-art strategy for the decoration of CuO nanoparticles onto the surface of rGO nanosheets could be an ideal platform for fabricating highly efficient photocatalysts.

Rationalizing iron-gall ink recipes from antiquity until the 19th century. A kinetic study.

Iron-gall inks, a vital part of our written cultural heritage, are at risk of complete loss due to degradation, a potential loss that we must urgently address. These inks are based on Fe3+-complexes with phenolic compounds, which grow to form a complex network of iron oxyhydroxides. Over time, these black inks turn into brownish tones, with extensive degradation in paper support leading to extensive breaking. The kinetics of iron-gall ink preparation explains the use of iron sulfate, FeSO4, in all ancient recipes to obtain a stable amorphous ink. The novelty of this work shows that a low ratio of Fe3+/polyphenol is a crucial factor in allowing the ink's growth without its degradation. This ratio also prevents the formation of superoxide. This was achieved through a comprehensive research methodology involving spectroscopic techniques in the visible and the near-infrared regions, stopped-flow spectrometry and electrochemical studies.

Integrating ANSYS Fluent Simulation and Aspen Plus for efficient heavy metal ion removal with de-oiled cake

In this study bio-flocculant extracted from the de-oiled cake, a common waste generated while producing oil was used to treat an electroplating industrial effluent. A comprehensive analysis of flocculation efficiency in a simulated reactor using ANSYS Workbench - Fluent, with a focus on optimizing impeller position was carried out. The findings reveal that the optimal impeller position is 2 cm from the tank base, where maximum turbulent kinetic energy (0.02577 m2/s2) and dissipation rate (22.19 m2/s3) were achieved at 200 RPM, enhancing flocculation efficacy. Furthermore, the study identifies 0.5 g L−1 as the optimal flocculant dosage, resulting in 72.70 % and 89.38 % removal of Ni(II) and Cr(VI), respectively. The flocculation process was determined to follow second-order kinetics, with significant improvements in collision efficiency and particle aggregation at the optimized dosage. Fourier Transform Infrared spectroscopy analysis confirmed chemical interactions leading to flocculation, while zeta potential and particle size distribution studies corroborated the stability and effectiveness of the process. A techno-economic analysis was conducted, estimating the total capital investment required for pilot and industrial-scale implementations, highlighting the feasibility and scalability of the proposed treatment method. A holistic framework for enhancing industrial effluent treatment processes by integrated computational fluid dynamics, kinetic studies, and economic evaluation, is the novelty of this research.

KINETIC STUDY OF ESTERIFICATION CATALYZED WITH ALUMINUM SULFATE AIMED AT CONVERTING LEVULINIC ACID INTO METHYL LEVULINATE

Recycling lignocellulosic biomass is a sustainable alternative to the petrochemical industry since it allows the production of valuable, sustainable, and environmentally friendly chemical products, such as levulinic acid (LVA) and levulinate esters. Methyl levulinate (MLV), for example, has been assessed as a fuel additive with low toxicity, high lubricity, and flash point stability. In this respect, the present investigation details a kinetic study of methyl esterification catalyzed with aluminum sulfate aimed at converting levulinic acid into methyl levulinate. The reactions were carried out in a Parr Instruments stainless steel reactor to assess the effect of temperature (120, 140 and 160 °C) and reaction time (30, 60, 120 and 180 min) on LVA conversion into MLV, maintaining a constant LVA:methanol ratio of 1:8 and aluminum sulfate catalyst concentration of 0.04 mol.L-1. The maximum LVA-MLV conversion of 93.04 % was obtained at a temperature of 160 °C and reaction time of 60 minutes. The pseudo first-order kinetic model exhibited the best fit to the experimental data, with correlation coefficients (R²) greater than 0.96, and it was used to calculate activation energy, obtaining a value of 10.19 kcal.mol-1.

A facile and green synthesis of corn cob-based graphene oxide and its modification with corn cob-K2CO3 for efficient removal of methylene blue dye: Adsorption mechanism, isotherm, and kinetic studies

In recent years, the treatment of synthetic dyes has become an environmental concern. In this study, a single step calcination process was used to develop the inventive, simple, and inexpensive adsorbent CC-GO/CC-K2CO3 composite. The composite was employed for the treatment of methylene blue (MB), a cationic dye. Several characterization methods including powder XRD, FTIR, XPS, BET, FESEM, EDX, Raman, and HRTEM techniques were utilized for the analysis of the composite. The surface area and mean pore diameter of CC-GO/CC-K2CO3 were 32.651 m2 g-1 and 3.71 nm, respectively. The adsorption experiment showed that optimal parameters for the removal of MB dye are at an adsorbent dose of 60 mg, initial dye concentration of 80 mg/L, contact time of 150 min, and pH value of 12 at room temperature. Under optimized conditions, CC-GO evidences a removal efficiency of 70.34 ± 1.36 % while after incorporation with CC-K2CO3 the removal capacity sharply increases up to 98.10 ± 0.4 %. Kinetic and isotherm models were used to analyze the removal rate constant and equilibrium adsorption capacity under various adsorption environments. The adsorption study was found to follow the models of pseudo-second order kinetic and Freundlich isotherm. The CC-GO/CC-K2CO3 composite has the maximum adsorption capacity (MAC) of 160.77 mg/g established by the Langmuir isotherm. The prepared composite has demonstrated the capacity to be recycled up to three times with a gradual decrease in its adsorption behavior, exhibiting removal efficiency of 61.66 ± 2.04 %.A cost estimation study of the composite was also performed to assess its cost effectiveness.

Synthesis of hydrotalcite and titanium dioxide (HT-TiO2) composite for application in heterogeneous photocatalytics processes

The objective of the study was to synthesize a composite of hydrotalcite and titanium dioxide (HT-TiO2) for application in heterogeneous photocatalytic processes to the degradation of organic pollutants in aqueous media. The composites were characterized by X-ray diffraction and surface area, then an experimental design was carried out to evaluate the influence of pH and temperature on the adsorption capacity of pollutants against the anionic dye indigo carmine using a kinetic study. Photocatalytic tests were carried out in a chamber equipped with a UV lamp and hydrogen peroxide as an auxiliary oxidant in degradation. The adsorption results corroborated with the order of surface areas obtained, where the adsorption capacity followed the order of HT, HT-TiO2 5 %, HT-TiO2 10 %, and TiO2, respectively, obtaining removals up to 96.94 %. For the heterogeneous photocatalytic tests, the best conditions of the experimental design were used for each semiconductor, with a removal of up to 99.96 % being observed in 2 h. The use of hydrogen peroxide as an auxiliary oxidant reduced the reaction time to 45 min, demonstrating how joint effluent treatment techniques can increase the speed and efficiency of the process.

Exploring Synthesis Strategies and Interactions between MOFs and Drugs for Controlled Drug Loading and Release, Characterizing Interactions through Advanced Techniques.

This study explores various aspects of Metal-Organic Frameworks (MOFs), focusing on synthesis techniques to adjust pore size and key ligands and metals for crafting carrier MOFs. It investigates MOF-drug interactions, including hydrogen bonding, van der Waals, and electrostatic interactions, along with kinetic studies. The multifaceted applications of MOFs in drug delivery systems are elucidated. The morphology and structure of MOFs are intricately linked to synthesis methodology, impacting attributes like crystallinity, porosity, and surface area. Hydrothermal synthesis yields MOFs with high crystallinity, suitable for catalytic applications, while solvothermal synthesis generates MOFs with increased porosity, ideal for gas and liquid adsorption. Understanding MOF-drug interactions is crucial for optimizing drug delivery, affecting charge capacity, stability, and therapeutic efficacy. Kinetic studies determine drug release rates and uniformity, vital for controlled drug delivery. Overall, comprehending drug-MOF interactions and kinetics is essential for developing effective and controllable drug delivery systems.

Fe3O4/sugarcane bagasse magnetic composite: a low-cost and green adsorbent for enhanced adsorption of Rhodamine B from aqueous solutions

In this study, we have designed and synthesized an eco-friendly Fe3O4/sugarcane bagasse magnetic composite (Fe3O4/SCB). We investigated its application for efficiently removing Rhodamine B (RhB) from textile wastewater, a significant step towards addressing the environmental issue of textile dye pollution. The composite, made from sugarcane bagasse (SCB), a secondary product from the sugarcane industry, proved an effective adsorbent. The composite Fe3O4/SCB was characterized by PXRD, FT-IR, FE-SEM, VSM, BET N2 adsorption-desorption, and pHpzc. Results from batch adsorption studies show that the removal of RhB was 93.6 ± 1.16% using a composite dose of 1g/L, a RhB concentration of 10mg/L, a contact period of 60min, and a solution pH of 3 at 323K of solution temperature. The kinetic studies indicate that the pseudo-second-order model most accurately describes adsorption. Meanwhile, the equilibrium data is well-represented by the Freundlich isotherm. Further, the analysis of thermodynamic results, such as the changes in ∆Go, ∆So, and ΔHo, revealed that the adsorption was spontaneous, feasible, and endothermic. The adsorption mechanism involved chemisorption and physisorption, with significant roles played by electrostatic interactions and hydrogen bonding. Desorption studies identified 0.5M NaOH as an effective desorbing agent, and the composite demonstrated excellent reusability over four adsorption-desorption cycles. Overall, the Fe3O4/SCB, with its easy preparation, abundance, cost-effectiveness, efficiency, and eco-friendly nature, presents a promising solution for effectively removing toxic RhB from aqueous solutions, inspiring further research and potential real-world applications.

Mononuclear phenoxy-imine Mg(II) compounds as catalysts for the ring-opening copolymerization of epoxides with CO2

The ring-opening copolymerization (ROCOP) of epoxides with CO2 is an efficient gateway for synthesizing sustainable aliphatic polycarbonates. The demand for the use of biocompatible metals for the copolymerization is an appealing research goal. The oxophilic Mg(II) has been employed as a metal center in homodinuclear and heterodinuclear catalyst frameworks. However, there is scarce literature involving mononuclear Mg(II) compounds. This work investigates the catalytic activity of two series of phenoxy-imine containing mononuclear Mg(II) compounds for the copolymerization studies of epoxides with CO2 in conjugation with cocatalyst tetraphenylphosphonium chloride (TPPCl). The two series of Mg(II) compounds differed from each other in the number of ancillary ligands attached to the Mg(II) center. The two epoxides employed for the study include cyclohexene oxide (CHO) and propylene oxide (PO). The catalytic activity of the disubstituted Mg(II) compounds was higher compared to monosubstituted compounds. In addition, the dependence of catalytic activity and percentage of carbonate linkage with the variation in the substituent of the phenolate core and imine side arm were studied. At 40 bar CO2 pressure and 80 °C, the catalyst exhibited carbonate linkage up to 97 % for ROCOP with cyclohexene oxide (CHO) with the percentage of the highest m-centered tetrad reaching up to 94 %. The mechanism for the ROCOP of CHO with CO2 is proposed based on kinetics studies and experimental data, which is further supported by density functional theory-based calculations.

CoMo/g-C3N4 as a highly effective, reusable, non-noble metal-based catalyst for H2 production via NaBH4 hydrolysis focused on stationary application under mild conditions: A kinetic study

Among hydrogen storage chemicals for proton exchange membrane fuel cells (PEMFCs), sodium borohydride stands out for yielding exceptionally pure hydrogen. This study synthesized cobalt-molybdenum catalysts supported on g-C3N4 using an ultrasonic-assisted impregnation method. Various CoMo/g-C3N4 catalysts with different CoMo mass ratios were created, all showing high hydrogen production and complete NaBH4 conversion under mild conditions. Catalytic activity depends on the cobalt-molybdenum mass ratio, with optimal performance at a 1:1 ratio (w/w), maintaining up to 83% activity over 5 cycles. The effect of operating conditions on hydrogen release was explored, resulting in the rate law: rH2 = 1.708 × 10-3 [NaBH4]1.25 [Catalyst dosage]1.39 [NaOH]0.44 at 298 K, with a low activation energy of 22.9 kJ mol−1. Molybdenum's promoting effect prevented significant deactivation of the cobalt catalyst, ensuring complete NaBH4 conversion to H2 and good stability over multiple cycles.

Sorption properties of a new modified flax fibre sorbent

The purpose of this study is to develop a modified sorbent of flax waste and investigate its sorption properties towards Cu (II) ions. The authors conducted the modification in two steps. The first step was oxidation of flax fibre cellulose with sodium metaperiodate to dialdehyde cellulose, the second one was the addition of taurine to increase the sorption characteristics of the modified sorbent. The paper presents the conditions for the periodate oxidation reaction of flax fibre and the treatment of the resulting dialdehyde cellulose with taurine. We determined the sorption characteristics of the modified sorbent in comparison with the original flax fibre. Kinetic studies allowed us to establish the time of reaching sorption equilibrium in the heterophase system ‘aqueous solution of metal salt-sorbent’ and determine the reaction order using pseudo first and pseudo-second order kinetics models. The authors processed the sorption isotherms obtained during the experiments using the Langmuir model. The maximum sorption capacity increased by 3 times compared to the original flax fibre. IR spectroscopy confirmed the improvement of equilibrium and kinetic characteristics of flax fibre occuring as a result of the appearance of new sorption centres in its structure.

Comparison of adsorption potential of methylene blue and 17β-stradiol on biochar, activated biochar and catalytic biochar from lignocellulosic waste

This work compares the adsorption capacity of methylene blue (MB) and 17β-stradiol (17β-S) onto biochar (B), activated biochar (AB) and catalytic biochar (CB), obtained through pyrolysis of residual lignin of the second-generation (2G) ethanol production process from a sugarcane industry. K2CO3 was used as activating agent and catalyst. Biochars were characterized by the techniques of point of zero charge, nitrogen adsorption and desorption, SEM and FTIR. Kinetic, isothermal and thermodynamic adsorption studies were carried out. Biochars behaved according to the pseudo-second order (PSO) kinetic model, with similar removal percentages of MB using AB and CB. In contrast, AB showed significantly higher removal percentages of 17β-S than CB. The Sips model agreed to isothermal adsorption data of 17β-S onto all biochars. For MB adsorption, Freundlich model agreed to data using B and AB, and Langmuir model was more suitable for CB. The process was viable, spontaneous, endothermic and showed increase in entropy, except for 17β-S adsorption onto CB. Consequently, the activated and catalytic pyrolysis processes increased the adsorptive potential of biochar derived from 2G lignocellulosic residue. Finally, CB and AB obtained significant removal percentage values of MB (85.8–99.3 %) and 17β-S (37.6–76.7 %), where CB is favorable due to its simpler preparation steps.

Novel magnetic metal ferrite-mango starch composite for the removal of dyes in single and ternary dye mixtures from aqueous solutions: kinetic and thermodynamic studies

ABSTRACT Magnetic metal ferrites attached to biowastes are proven to be promising adsorbents for the removal of dyes from water. Magnetic composites with biopolymers are gaining interest in the field of treatment of wastewater because of their selective nature, recyclability, low cost and environmental compatibility. In this work, Zinc ferrite composite with starch, extracted from mango seed kernel (ZFNMS) was synthesised. Characterisation techniques, such as FTIR, XRD, FESEM, BET, TGA and pHzpc, were used for the structural analysis of ZFNMS. ZFNMS was used to remove Methylene blue, Crystal violet and Brilliant green dyes in single and multiple (ternary) dye systems. The kinetics of adsorption by ZFNMS revealed that pseudo-second-order of kinetics was most appropriate for this study. Maximum adsorption capacities using ZFNMS for CV, BG and MB dyes were 142.9, 101.2 and 105.8 mg/g, respectively. The values of adsorption energies using ZFNMS were 200.5, 494.3 and 183.6 KJ/mol for CV, BG and MB dyes, respectively. Thermodynamic data revealed the spontaneous nature of the adsorption of dyes by ZFNMS and it was found that chemical adsorption was taking place in the present study. Regeneration of the adsorbent was done for successive five cycles and showed significant results. Thus ZFNMS is an ideal adsorbent for cationic dyes removal from water.

Effect of 4,4′-dialkyl-2,2′-bipyridine ligands on the hydrolysis of dichlorodioxomolybdenum(VI) catalyst precursors and the switch from homogeneous epoxidation to heterogeneous systems

Molybdenum catalysts have been industrially recognized, for decades for liquid phase epoxidation, which is an important chemical reaction process, since epoxides are used for many industrial applications. In this work, molybdenum oxide hybrid catalysts, prepared by a reflux hydrolysis methodology, performed effectively as heterogeneous catalysts or reaction-induced self-separating catalysts under mild reaction conditions; in the two cases, the catalyst separation and reuse are facilitated. Specifically, catalysts with the general formula [MoO3(L)], possessing polymeric chain-like (L = 4,4′-dimethyl-2,2′-bipyridine (1)) or oligomeric (L = 4,4′-dinonyl-2,2′-bipyridine (2)) structures comprising corner-sharing {MoO4N2} units, were synthesized and characterized by various complementary techniques (ATR FT-IR, Raman, 13C{1H} CP MAS NMR spectroscopy, PXRD, SEM, TGA, elemental analysis, ICP-OES and N2 sorption isotherms). Small chemical differences in the organic synthesis precursor had important structure directing effects on the type of hybrid material formed. The hybrids promoted olefin epoxidation with H2O2 or tert-butylhydroperoxide (TBHP) as oxidant. For example, 1 catalyzed the conversion of biobased olefins (70 °C) and lignin-based isoeugenol (50 °C) with TBHP to useful bioproducts, in heterogeneous phase, leading to an epoxide yield of 100 % for DL-limonene (3:1 M ratio of 1,2-epoxy-p-menth-8-ene to 1,2:8,9-diepoxy-p-menthane), 81 % epoxide yield for fatty acid methyl esters, and 80 % Licarin A selectivity at 40 % isoeugenol conversion. For dienes (DL-limonene, methyl linoleate), kinetic modelling studies suggested that the formation of the monoepoxides was faster than that of diepoxides, accounting for enhanced monoepoxide selectivity.

Experimental and kinetic study of methanol/ethanol assisted oxidative degradation of ammonia in supercritical water

Ammonia is a refractory intermediate during supercritical water oxidation (SCWO) of nitrogen-containing wastes, and alcohols are usually introduced as auxiliary fuels to accelerate its degradation. The kinetics of methanol/ethanol assisted oxidative degradation of ammonia in supercritical water have been investigated in a flow reactor, covering alcohol-to-ammonia ratios of 0.2–2.0. During SCWO of ammonia-methanol mixtures, ammonia was mostly converted to N2, with N2O as the main by-product. Increasing methanol concentration facilitated effectively the degradation of ammonia. For the cases with ethanol assistance, high concentrations of HCN were detected at the investigated temperature. Increase in ethanol concentration enhanced ammonia conversion, but had a non-monotonic influence on N2 production. A detailed chemical kinetic model was developed by integrating the nitrogen chemistry with methanol/ethanol mechanisms. The model performance was further validated by comparing to the present and literature data. The model reproduced the ammonia conversions at different conditions fairly well, but overpredicted the N2 yield and underpredicted the NO2 and HCN yields slightly. Based on the model, reaction mechanism was inferred and important elementary steps were identified through kinetic analyses. Finally, the influence of process parameters on ammonia degradation rate was numerically explored. This study is expected to facilitate the application of SCWO technology for N-containing wastes treatment.