Avrami Kinetic Model Research Articles

Synthesis and application of MgCuAl-layered triple hydroxide/carboxylated carbon nanotubes/bentonite nanocomposite for the effective removal of lead from contaminated water

A novel multicomponent adsorbent nano-composite was synthesized by intercalating bentonite clay and carboxylated carbon nanotubes (CNT-COOH) into MgCuAl-layered triple hydroxide (MgCuAl-LTH), abbreviated as LTH/CNT-COOH/Bent. The produced nano-composite, its parental materials, and their binary combinations were characterized using various techniques. Pore filling was noted based on the BET analysis, hence, indicating effective component integration in the nano-composite structure. Further, distinct peaks appearing on the FTIR and XRD spectra of the single materials also appeared on the synthesized composites (including the binary combinations of the parental materials), hence, further indicating the successful synthesis of the targeted adsorbents. The effects of process parameters including pH, adsorbent dose, lead initial concentration and contact time on lead removal, were explored. In general, the application of LTH/CNT-COOH/Bent adsorbent yielded a significant improvement in lead adsorption capacity (∼260.8 mg/g) relative to all parental materials and their binary combinations. It was revealed that the adsorbent dose and lead initial concentration are the most significant factors affecting lead uptake onto the synthesized adsorbent and the adsorption kinetics was fast. The obtained results indicated that the Avrami kinetic and Redlich-Peterson isotherm models best fit the lead adsorption kinetics and isotherm experimental results, respectively. Furthermore, the response surface methodology (RSM) technique was employed for optimization of lead removal, achieving near complete removal (>99 %) at LTH/CNT-COOH/Bent dose of 0.5 g/L, lead initial concentration of 40 ppm and a time of 2 h. Additionally, the machine learning (ML) and the ANN based models for lead removal using LTH/CNT-COOH/Bent nano-composite yielded good predictions.

The amorphization of crystalline silicon by ball milling

The transformation of crystalline silicon to amorphous silicon during ball milling was quantitatively measured by x-ray diffraction and electrochemical methods. Amorphous silicon was found to form rapidly from the very initial stages of ball milling. Simultaneously, the grain size of the crystalline silicon phase decreased. Under extended milling times it was found that a maximum of 86 % of the silicon became amorphous. Similarly, the grain size of the crystalline silicon phase could not be reduced below 6 nm. This transformation followed an Avrami kinetic model, which is consistent with a system which reaches a steady state. These observations suggest a mechanism in which ball milling generates defects, resulting in silicon amorphization and grain size reduction, where the degree of amorphization is limited in extent because there exists a limiting silicon grain size below which defects are no longer formed.

Bacterial cellulose microfilament biochar-architectured chitosan/polyethyleneimine beads for enhanced tetracycline and metronidazole adsorption

This study investigates the potential applications of incorporating 2D bacterial cellulose microfibers (BCM) biochar into chitosan/polyethyleneimine beads as a semi-natural sorbent for the efficient removal of tetracycline (TET) and metronidazole (MET) antibiotics. Batch adsorption experiments and characterization techniques evaluate removal performance and synthesized adsorbent properties. The adsorbent eliminated 99.13 % and 90 % of TET and MET at a 10 mg.L−1 concentration with optimal pH values of 8 and 6, respectively, for 90 min. Under optimum conditions and a 400 mg.L−1 concentration, MET and TET have possessed the maximum adsorption capacities of 691.325 and 960.778 mg.g−1, respectively. According to the isothermal analysis, the adsorption of TET fundamentally follows the Temkin (R2 = 0.997), Redlich-Peterson (R2 = 0.996), and Langmuir (R2 = 0.996) models. In contrast, the MET adsorption can be described by the Langmuir (R2 = 0.997), and Toth (R2 = 0.991) models. The pseudo-second-order (R2 = 0.998, 0.992) and Avrami (R2 = 0.999, 0.999) kinetic models were well-fitted with the kinetic results for MET and TET respectively. Diffusion models recommend that pore, liquid-film, and intraparticle diffusion govern the rate of the adsorption process. The developed semi-natural sorbent demonstrated exceptional adsorption capacity over eleven cycles due to its porous bead structure, making it a potential candidate for wastewater remediation.

Experimental and dynamic molecular study of zinc extraction from sphalerite concentrate in ternary deep eutectic solvent

The utilization of deep eutectic solvents (DESs) as a novel class of solvents in metal production offers a promising alternative to aqueous solutions due to their biocompatibility and non-aqueous nature. This study investigated the leaching of sphalerite concentrate using a ternary stable DES composed of choline chloride (ChCl), p-toluene sulfonic acid (PTSA), and ethylene glycol (EG) (at a molar ratio of 1:1:1). The effects of time, temperature, and milling time on zinc recovery were examined within specific ranges (20–1440 min, 40–100 °C, and 0–24 h, respectively). The study revealed the significant influence of time and temperature on zinc dissolution efficiency within ChCl:PTSA:EG. Higher temperatures and longer leaching times were found to improve efficiency substantially. The research emphasized the crucial role of milling time, demonstrating that longer durations enhanced zinc efficiency by introducing more defects on the sphalerite surface and reducing particle size. Under optimized conditions, including a temperature of 100 °C, 24 h of ball milling, and 1440 min of leaching, a zinc recovery of 99.7% was achieved. Infrared analysis confirmed the chemical stability of the solvents during the leaching process. The sphalerite leaching process involved the formation of zinc chloride ion complexes and evolution H2S gas. An unexpected finding is the presence of lead sulfate in the leach residue, which may be attributed to sulfide oxidation to sulfate species. The Avrami kinetic model provided an excellent fit with the sphalerite dissolution data in ChCl:PTSA:EG DES, indicating that the rate-controlling step was primarily influenced by the diffusion process. R2 values for kinetics fitting data were in the range of 0.87–0.97 for temperature of 40–100 °C. The molecular dynamic (MD) simulation findings indicated robust electrostatic interactions between the metal ions Zn2+ and Fe2+ and the Cl− ions of the ChCl molecules. Additionally, the MD calculations showed that the metal ions formed complexes with some O-S-O atoms within the PTSA molecule.

Dynamic breakthrough performance of low concentration CO2 adsorption in fixed-bed column with porous amino acid ionic liquid composites

Low concentration carbon dioxide (CO2) capture from air or confined spaces currently faces significant challenges, such as relatively poor dynamic adsorption breakthrough performance and cyclic stability. In our previous work, functionalized ionic liquid (IL) tetraethylammonium glycine ([N2222][Gly]) and porous molecular sieve (SBA-15) were combined to synthesize porous amino acid IL composite 60 wt% [N2222][Gly]@SBA-15 with microporous and ultra-microporous structures, which provide a new pathway for low concentration CO2 capture. In order to further obtain the dynamic CO2 adsorption breakthrough performance of this material under simulated actual working conditions, the effects of temperatures, relative humidity (RH) and CO2 concentrations on CO2 adsorption and desorption breakthrough performance of 60 wt% [N2222][Gly]@SBA-15 in a fixed-bed column were systematically studied in this work. The results indicated that CO2 adsorption capacity is up to 1.81 mmolCO2/g-adsorbent at 298.15 K, 1 bar and 0 % RH under 1 vol% CO2-containing gas mixture balanced with N2 and reaches 2.44 mmolCO2/g-adsorbent at 15 % RH due to the mechanism change of CO2 reaction with primary amine from 2: 1 under dry gas to 1: 1 stoichiometry in the presence of moisture. Moreover, the adsorbent maintains good cyclic adsorption-desorption performance. Further, CO2 adsorption breakthrough behaviors were well fitted by Avrami kinetic model, and the CO2 adsorption rate of 60 wt% [N2222][Gly]@SBA-15 was controlled by intra-particle diffusion. This work implied that IL-modified adsorbents have great potentials for low concentration CO2 capture applications.

A Sensory Shelf-Life Study for the Evaluation of New Eco-Sustainable Packaging of Single-Portion Croissants.

Understanding the correlation between straightforward analytical methods and sensory attributes is pivotal for transitioning to sustainable packaging while improving product quality. In this context, the viability of eco-sustainable packaging alternatives for single-packaged croissants has been investigated through examining the correlations between analytical methods, sensory attributes, employing quantitative descriptive analysis (QDA), and consumer survival analysis. The performance of biaxially oriented polypropylene (BOPP), a petrochemical plastic film, against paper-based, compostable, and biodegradable films over a 150-day croissant storage period was compared in this study, examining both physiochemical and sensory perspectives. The results showed a correlation between a lower water vapour barrier in packaging materials and increased moisture migration and croissant hardness, as assessed by the Avrami kinetic model. Notably, given its reduced barrier properties, the compostable film accelerated sensory profile deterioration, as evidenced by QDA results. Shelf-life estimation, assessed by consumer rejection, underscored the viability of the biodegradable film for up to 185 days, surpassing BOPP, paper-based, and other biodegradable alternatives. Using linear regression, physiochemical parameters associated with predicted shelf-life were elucidated. Overall, croissants were rejected by 50% of consumers when they reached humidity levels below 18%, water activity below 0.81, firmness exceeding 1064 N, pH above 4.4, and acidity below 4.5. Based on the results of this study, biodegradable packaging emerges as a promising alternative to traditional BOPP, offering a sustainable opportunity to extend the shelf-life of croissants.

Kinetic analysis of aroma compound release from Citrus aurantium essential oil-casein-phospholipid-nanocomposites

In this study, Citrus aurantium essential oil encapsulated in casein-phospholipid nanocomposites (CAEO–CS–PL-NCs) was prepared and evaluated for controlled-release capacity of aroma compounds. The particle size of the nanocomposites was strongly influenced by the phospholipid concentration in the nanocomposites. The Avrami and Korsmeyer-Peppas kinetic models were used to analyze the aroma release kinetics of freeze-dried CAEO–CS–PL-NCs (FD-CAEO–CS–PL-NCs) at different temperatures and relative humidities. FD-CAEO–CS–PL-NCs were stored for various times with tea leaves to evaluate their potential for making scented teas. The Avrami kinetic analysis indicated that the release of aroma compounds from FD-CAEO–CS–PL-NCs conformed to diffusion-limited, or first-order kinetics, depending on the temperature and relative humidity. The Korsmeyer-Peppas kinetic analysis indicated that the release of aroma compounds from FD-CAEO–CS–PL-NCs involved three release mechanisms, Fickian diffusion, non-Fickian diffusion and the erosive mechanism. The release mechanism involved varied depending on different conditions and different aroma compounds, and at low temperature and relative humidity effective controlled release of aroma compounds was achieved, resulting from intermolecular interactions with the casein micelles. FD-CAEO–CS–PL-NCs showed significantly sensory scores increasing effect of scented tea. The findings will facilitate future developments in the formulation of scented teas, by incorporating aromatic essential oils from fruits and flowers, in the form of essential oil-casein-phospholipid nanocomposites.

Synergistic effect of surfactant and silica nanoflowers support on CO2 capture from simulated flue gas by solid amine adsorbents

Solid amine adsorbents were synthesized by functionalizing silica nanoflowers (MSN) with large pore volume using Pluronic P123 (P123) and Polyethyleneimine (PEI) to explore their synergistic effect of CO2 capture. At the optimal loading of 65 wt% PEI and 5 wt% P123, the adsorbent (65PEI/5P123-MSN) displayed peak adsorption performance of 4.12 mmol/g under the dry condition. Notably, the introduction of 3 vol% moisture further increased the adsorption capacity of 65PEI/5P123-MSN to 5.33 mmol/g. Meanwhile, the Avrami kinetic model and the thermodynamic analysis shows that adding P123 reduces adsorption heat (55.89 kJ/mol) and regeneration energy (2.01 GJ/ton) of the adsorbent.

Probing the differences in CO2 adsorption/desorption behaviors of solid amine sorbents in fixed and fluidized beds

Circulating fluidized bed temperature swing adsorption (CFB-TSA) CO2 capture process using solid amine sorbents has become a widely recognized solution to reduce stationary sources CO2 emissions. The successful design and operation of the adsorber and desorber requires much information on the CO2 adsorption and desorption behaviors of the sorbents in fluidized bed reactors. However, among the existing studies, little attention has been paid to desorption performance, which is equally important as adsorption performance. And almost all of them were conducted in TGAs or fixed beds, the lack of research in fluidized beds making it difficult to guide the design of industrial fluidized bed reactors. In addition, the systematic comparison of the above-mentioned adsorption/desorption behaviors and bed hydrodynamics (e.g. pressure drops) in fixed and fluidized beds can help provide theoretical support for the optimization of adsorbers, desorbers and coolers, which has not been reported yet. Therefore, we for the first time investigated the CO2 adsorption/desorption behaviors as well as hydrodynamics in both fluidized and fixed beds using a solid amine sorbent in a temperature swing adsorption (TSA) experimental rig. The results show that the sorbent exhibits faster adsorption and desorption kinetics in fluidized beds than those in fixed beds, as reflected by the fitted parameters of the Avrami kinetic model and the change of bed temperature during adsorption and desorption tests. And the bed pressure drops in fluidized beds are also much lower than that in fixed beds, especially at high superficial gas velocities and high sorbent loadings. By further discussion, a fluidized bed can also achieve lower equipment investment and less sorbent loading compared to multiple fixed beds in parallel. This study demonstrates the advantages of fluidized beds over fixed beds in large-scale TSA units in view of higher reactor efficiency, lower energy consumption and equipment investment.

Microstructure, deformation behavior, and dynamic recrystallization kinetics of FeNiMnCu-based high entropy alloys prepared by mechanical alloying and spark plasma sintering

In the present research, FeNiMnCuX (X: Co, Cr, Mo, Ti, W) high entropy alloys (HEAs) were successfully fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). SPS transformed the base and Co-containing alloys into FCC structures, Cr- containing alloys changed into a mix of FCC and BCC structures, while other alloys formed a combination of FCC/BCC structure and an intermetallic compound. The base alloy and alloys with Co, and Cr additions exhibited plastic deformation in cold compression tests, whereas other alloys exhibited brittle behavior. During hot compression tests, dynamic recrystallization occurred with a peak in flow stress followed by a gradual decrease to a steady state stress in alloys with Co, Mo, Ti and W additions. The highest peak stresses were observed at 800 °C for Ti- and W- containing alloys. The dynamic recrystallization and fractional softening kinetics are explained by the Avrami kinetic model. An Avrami exponent around 1 was obtained based on the kinetics of dynamic recrystallization for the alloys doped with Co, Mo, Ti, and W.

Unravelling the kinetics, isotherms, thermodynamics, and mass transfer behaviours of Zeolite Socony Mobil - 5 in removing hydrogen sulphide resulting from a dark fermentative biohydrogen production process.

Research into the speciation of sulfur and hydrogen molecules produced through the complex process of thermophilic dark fermentation has been conducted. Detailed surface studies of solid-gas systems using real biogas (biohydrogen) streams have unveiled the mechanisms and specific interactions between these gases and the physicochemical properties of a zeolite as an adsorbent. These findings highlight the potential of zeolites to effectively capture and interact with these molecules. In this study, the hydrogen sulphide removal analysis was conducted using 0.8 g of the adsorbent and at various reaction temperatures (25-125 °C), a flow rate of 100 mL min-1, and an initial concentration of approximately 5000 ppm hydrogen sulphide. The reaction temperature has been observed to be an essential parameter of Zeolite Socony Mobil - 5 adsorption capacity. The optimum adsorption capacity attains a maximum value of 0.00890 mg g-1 at an optimal temperature of 25 °C. The formation of sulphur species resulting from the hydrogen sulphide adsorption on the zeolite determines the kinetics, thermodynamics, and mass transfer behaviours of Zeolite Socony Mobil - 5 in hydrogen sulphide removal and Zeolite Socony Mobil - 5 is found to improve the quality of biohydrogen produced in thermophilic environments. Biohydrogen (raw gas) yield was enhanced from 2.48 mol H2 mol-1 hexose consumed before adsorption to 2.59 mol H2 mol-1 hexose consumed after adsorption at a temperature of 25 °C. The Avrami kinetic model was fitted for hydrogen sulphide removal on Zeolite Socony Mobil - 5. The process is explained well and fitted using the Temkin isotherm model and the investigation into thermodynamics reveals that the adsorption behaviour is exothermic and non-spontaneous. Furthermore, the gas molecule's freedom of movement becomes random. The adsorption phase is restricted by intra-particle diffusion followed by film diffusion during the transfer of hydrogen sulphide into the pores of Zeolite Socony Mobil - 5 prior to adsorption on its active sites. The utilisation of Zeolite Socony Mobil - 5 for hydrogen sulphide removal offers the benefit of reducing environmental contamination and exhibiting significant applications in industrial operations.

Dry desulphurisation of gas streams using KCC-1 mesoporous silica functionalised with deep eutectic solvents.

Sulphur dioxide, a toxic gas pollutant, is mainly generated by the combustion of fossil fuels and the smelting of sulphur-bearing mineral ores. Removal of SO2 gas or desulphurisation can be accomplished in industries using a variety of processes; the most efficient is wet flue gas desulphurisation (FGD). However, wet FGD has challenges, such as the requirement for wastewater treatment, excessive water usage, and the necessity for chloride protective coating. Despite having a lesser adsorption capacity than wet FGD, dry FGD can efficiently remove SO2 from the effluent gas stream and avoid the issues associated with wet FGD, provided that the sorbents are modified and regenerable. An alternative dry desulphurisation strategy by using fibrous mesoporous silica (KCC-1) modified with deep eutectic solvents (DES), choline chloride-glycerol (DES1) and choline chloride-ethylene glycol (DES2) is studied in this paper. KCC-1 modified with DES1 is found to increase SO2 adsorption capacity to 4.83 mg g-1, which is 1.73 times greater than unmodified KCC-1 and twice higher than KCC-1 modified with DES2 attributed to the sorbent's high porosity. Increasing reaction temperature and SO2 concentration reduce the adsorption capacity to 1.73 mg g-1 and 2.73 mg g-1, respectively. The Avrami kinetic model and the Toth isotherm model best reflect SO2 adsorption on the modified KCC-1, indicating that SO2 molecules are adsorbed exothermically in multilayer adsorption on a heterogeneous surface through a combination of physical and chemical processes. The higher SO2 adsorption capacity of the modified KCC-1 suggests that choline chloride-glycerol can provide additional sites for SO2 adsorption in dry FGD technology.

Adsorption properties of M-UiO-66 (M = Zr(IV); Hf(IV) or Ce(IV)) with BDC or PDC linker.

The increasing CO2 emissions and their direct impact on climate change due to the greenhouse effect are environmental issues that must be solved as soon as possible. Metal-organic frameworks (MOFs) are one class of crystalline adsorbent materials that are thought to have enormous potential in CO2 capture applications. In this research, the effect of changing the metal center between Zr(IV), Ce(IV), and Hf(IV), and the linker between BDC and PDC has been fully studied. Thus, the six UiO-66 isoreticular derivatives have been synthesized and characterized by FTIR, PXRD, TGA, and N2 adsorption. We also report the BET surface area, CO2 adsorption capacities, kinetics, and the adsorption isosteric heat (Qst) of the UiO-66 derivatives mentioned family. The CO2 adsorption kinetics were evaluated using pseudo-first order, pseudo-second order, Avrami's kinetic models, and the rate-limiting step with Boyd's film diffusion, interparticle diffusion, and intraparticle diffusion models. The isosteric heats of CO2 adsorption using various MOFs are in the range 20-65 kJ mol-1 observing differences in adsorption capacities between 1.15 and 4.72 mmol g-1 at different temperatures due to the electrostatic interactions between CO2 and extra-framework metal ions. The isosteric heat of adsorption calculation in this report, which accounts for the unexpectedly high heat released from Zr-UiO-66-PDC, is finally represented as an increase in the interaction of CO2 with the PDC linker and an increase in Qst with defects.

Development of composite amine functionalized polyester microspheres for efficient CO2 capture.

In order to reduce the impact of greenhouse gases on the environment, the development of various new CO2 capture materials has become a hot spot. In this work, a novel composite amine solid adsorbent was prepared by simultaneously using tetraethylenepentamine (TEPA) and 2-[2-(dimethylamino) ethoxy] ethanol (DMAEE) for amine functionalization on the polyester microsphere carrier. The introduction of methyl methacrylate (MMA) with high glass transition temperature into the polyester carrier makes the carrier microspheres have high hardness. At the same time, the carrier also contains active epoxy groups and hydrophobic glycidyl methacrylate (GMA, which can undergo ring-opening reaction with composite amines to achieve high-load and low-energy chemical grafting of amines on the carrier. The composite aminated polyester microspheres were used as an efficient adsorbent for CO2 in simulated flue gas. The results show that the synergistic effect of TEPA-DMAEE composite amine system in the adsorbent is beneficial to the improvement of CO2 capture capacity. When the total amine content in the impregnating solution is 45 wt% and the composite amine ratio is TEPA: DMAEE = 6: 4, the CO2 adsorption capacity can reach the optimal value of 2.45mmol/ g at 70°C. In addition, the composite amine microsphere adsorbent has cyclic regeneration performance. Importantly, through kinetic fitting, the Avrami kinetic model fits the CO2 adsorption better than the quasi-first-order and quasi-second-order kinetic models, which proves that physical adsorption and chemical adsorption coexist in the adsorption process. This simple, long-term stable and excellent selective separation performance makes amine-functionalized adsorbents have potential application prospects in CO2 capture.

Wood biochar as a point source CO2 adsorbent-impact of humidity on performance

Adsorption of carbon using biobased materials is a sustainable approach to point source carbon capture and storage, particularly if the biomass is a “waste” and the adsorbent can then be re-used in soils. In this work, biochar derived from fast pyrolysis of softwood residues (sawdust) was investigated as a CO2 adsorbent under humid conditions to determine the effect of water on biochar adsorption performance. Dry and wet adsorption experiments were run at concentrations of CO2 between 20–80 vol.% (balanced with N2) at 20 °C. Water concentrations were set by saturating the N2 stream and resulted in 0.5–1.8 vol.% (relative humidity of 20%–80%). For the dry gas experiments, the adsorption capacities doubled (0.83–1.98 mmol/g) as the CO2 concentration increased from 20% to 80%. The capacity did not change between wet and dry experiments for 20, 40, and 60 vol.% CO2; however, at 80 vol.% CO2, the adsorption capacity increased by 38% for the “wet” gas from the dry gas. This is potentially due to carbonates formed due to CO2 dissolution/reaction in water. The adsorption time was not impacted by the range of water concentrations studied. The Avrami kinetic model best represented the rate of adsorption in both dry and wet conditions. The fact that neither the biochar adsorption capacity nor its adsorption rate was negatively impacted by water shows that biochar can be a promising option for stack gases, which contain water vapor. However, more experiments at higher temperatures are required.

Removal of Rhodamine B dye by adsorption onto an eco-friendly zeolite and machine learning modeling

The present work aims to synthesize and characterize a zeolite doped with cobalt (ZO-Co) from such as rice husk, residual sludge and pumice stone for application in the removal of RhB dye by adsorption. Experimental design and machine learning were used to verify the ideal condition of RhB adsorption, as well, as ecotoxicity tests against Lactuca sativa L. seeds were carried out. ZO-Co showed diffraction peaks of the tsaregorodsevite phase, groups containing hydroxyl, silicates and aluminosilicates. The ideal condition by machine learning (ML) was [RhB] of = 130 mg/L, [ZO-Co] = 0.6 g/L, pH ≈ 7, and T = 298.15±2 K. The best experimental fit for the adsorption data was the isotherm of Khan (equilibrium) and Avrami (kinetic model), where the maximum adsorption capacity was 259.17 mg g−1 with 83.66 % of the RhB removal. It is noteworthy that in ecotoxicity tests ZO-Co showed root radicular growth of 29.74 mm in 7 days. Therefore, cobalt-doped ZO can be effectively used for the adsorption by organic pollutant RhB correlating topics of environment and nanotechnology.

Equilibrium and Kinetic Insights into the Comprehensive Investigation of CO2, CH4, and N2 Adsorption on Cation-Exchanged X and Y Faujasite Zeolites.

The adsorption equilibria and kinetic performance of CO2, CH4, and N2 on pelletized cation-exchanged faujasite zeolites (with alkali, alkaline earth, and transition metal ions) have been investigated by an innovative volumetric apparatus simultaneously. The standard instrumental analytical techniques, including X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy (EDX), and atomic absorption spectroscopy (AAS), were utilized to characterize binder-free modified zeolites. EDX and AAS analyses revealed that the ion exchange was successfully achieved. The results indicate that the type of cation present in the zeolite framework and the Si/Al ratio can have a significant impact on the adsorption capacity and kinetic performance. The obtained isotherms were determined by three isotherm models, and the Langmuir-Freundlich (Sips) model was found to show the best agreement with the experimental isotherm data for all gases. The CO2 uptakes of KX, MgX, and CaX reached 4.13, 4.79, and 5.48 mmol/g, respectively. The effective binary and kinetic selectivities of CO2/CH4 and CO2/N2 were also calculated. Among all samples, KX showed the highest CO2/CH4 and CO2/N2 selectivities of 54.46 and 91.62, respectively. Pseudo-first-, pseudo-second-order, and Avrami kinetic models were fitted to the experimental kinetic data to analyze the adsorption kinetics. Finally, the macropore diffusion coefficient (Dp) and microporous diffusional time constant (Dc/rc2) were estimated by correlating the micropore-macropore kinetic model with the experimental fractional uptake curves. Among the ion-exchanged zeolite samples, the K+ form exhibits a suitable performance in terms of kinetic behavior and adsorption capacity.

Statistical modelling and kinetics of copper loss to printed circuit board (PCB) fibreglass during PCB ammine leaching

ABSTRACT PCB dust leach feed contains fibreglass particles responsible for incomplete copper recovery observed during PCB dust leaching. Interaction of fibreglass particles with ammine leach solution was studied by varying contact time, operating temperature and pulp density at different initial concentrations. Box Behnken RSM design was utilised to design the experimental tests. The 3D plots, ANOVA, Pearson correlation and multiple regression analysis show the initial copper concentration impacts the response QCu most. Of the five non-linear adsorption kinetic models employed, Elovich and Avrami's kinetic model best fitted the experimental data with R2 of 0.9632 and 0.9435, respectively. The pHpzc analysis of fibreglass particles shows the material possesses a neutral surface charge at pH = 7.1. Evaluation of the kinetic models and pHpzc analysis of copper losses to PCB fibreglass particles supports dual mechanisms of physisorption and ion exchange co-occurring in the solid–liquid systems. At 1 g fibreglass particles in 100 mL of 50 mg/L copper ammine leach solution, maximum loss of about 1.5 mg/L copper was obtained in 12 h. This clearly indicates limitation to maximum target metal recovery. Copper loss to fibreglass particles occurs during PCB leaching up to an amount which depends on the mass fraction of the glass fiber particles in the pulp, leach solution concentration and time.

Ethyl cellulose-based microcapsules of Citrus aurantifolia (Christm.) Swingle essential oil with an optimized emulsifier for antibacterial cosmetotextiles

Antibacterial microcapsules of Citrus aurantifolia (Christm.) Swingle essential oil (LOs) covered by ethyl cellulose biopolymer were prepared and applied to cotton fabric. The microencapsulation of the LOs was accomplished through a simple coacervation process, whereas the immobilization onto the cotton fabric was based on the pad dry method with citric acid as a binder. Optimization of the type and weight of the emulsifier was considered to result in the best properties of the microcapsules. Employing 1 g of tween-80, the best LO microcapsules were successfully obtained up to 46.7 ± 3.8% yield, with spherical morphology and a well-distributed size range of 0.5–2 μm. The oil content (OC) and encapsulation efficiency (EE) of the microcapsules were achieved at 95.4 ± 0.8% and 77.9 ± 6.6% correspondingly. According to Avrami's kinetic model, the release performance of the LOs microcapsules in 2 h was ruled by the first-order kinetic mechanism with the remaining LOs of 37.7%. The LO microcapsules were successfully immobilized onto cotton fabric with a % add-on of 20.1%. Upon a standard washing test, the attached LOs microcapsules demonstrated 5 cycles of resistance against normal washing, with a mass reduction of the microcapsules up to 52.2%. Further antibacterial assays showed that the cotton fabrics immobilized by the LOs microcapsules exhibited a high inhibition, especially towards Gram-negative bacteria E. coli and K. pneumoniae. Thus, it can be potentially developed for antibacterial functional textile.

Magnetic ternary layered double hydroxides for efficient removal of 1-naphthalene acetic acid from waters: Adsorption behavior and mechanism

The removal of pollutants requires environmental protection technology to use the least energy consumption, realize the reuse of substances, and ensure the health of the ecosystem and human body. Layered double hydroxides (LDHs) are widely used as adsorbents due to their excellent tunable structure properties and biocompatibility. In this study, magnetic CoMgAl LDH (C-MLDH) and magnetic FeMgAl LDH (F-MLDH) were prepared by coprecipitation method with adding Co element and Fe element respectively on the basis of classical MgAl LDH for the adsorption of 1-naphthoacetic acid (NAA) in water. The morphology and characteristics of the synthesized LDHs were investigated. The pH, adsorbent concentration, kinetics, temperature, isotherm and thermodynamics of the adsorbent were studied to explore the adsorption mechanism. The results showed that the Liu isotherm model and Avrami kinetic model can fit the adsorption isotherm and kinetic data well, respectively. The both synthesized magnetic ternary LDHs had high adsorption capacity of NAA, which reached 258.5 mg/g and 288.5 mg/g for C-MLDH and F-MLDH, respectively. The adsorption of NAA by C-MLDH and F-MLDH was both spontaneous and endothermic. There were two main adsorption mechanisms, one was adsorption by forming hydrogen bonds with hydroxyl groups on the surface of the adsorbent, and the other was anion exchange. The adsorption capacity of magnetic ternary LDHs mainly depended on the shell LDHs, the addition of Co and Fe elements could promote the adsorption reaction, enhance the adsorption capacity, and the promotion effect of Fe element was better than Co.