Toth Isotherm Research Articles

Elucidating the Dynamics of Carbamazepine Uptake Using Date Pit-Derived Activated Carbon: A Comprehensive Kinetic and Thermodynamic Analysis

Water contamination with pharmaceuticals such as Carbamazepine (CBZ) presents a significant environmental challenge. This study investigates the use of activated carbon derived from waste date pits (DPAC) for the removal of CBZ from water. The impact of several parameters such as pH, temperature, CBZ concentration, and flow rate on the adsorption were assessed. The generated DPAC demonstrated a specific surface area of 309 m2/g, a pore volume of 0.264 cm³/g, and the pores are mainly distributed at 1.86, 2.73, and 3.43 nm. The Langmuir, Freundlich, Sips, and Toth isotherms were used to fit the experimental data, and the results indicate the occurrence of monolayer adsorption and heterogeneous surface conditions. The Linear Driving Force model was used for kinetic analysis, showing improved fit at higher concentrations. Thermodynamic analyses revealed the process to be endothermic, spontaneous, and entropically driven. The DPAC achieved an adsorption capacity of 14.89 mg/g and maintained 94% effectiveness after the first regeneration cycle and 70% after four cycles. This study highlights the potential of DPAC as a sustainable adsorbent for advanced water purification.

Sctudies on adsorption of Brilliant Green from aqueous solution onto nutraceutical industrial pepper seed spent

The study proposed the removal of Brilliant Green, a cationic dye, by adsorption process from wastewater solution utilizing a low-cost adsorbent such as Nutraceutical Industrial Pepper Seed Spent (NIPSS). The study comprises an investigation of the parametric influence on the adsorption process. The parameters identified are pH, dye concentration, process temperature, quantity of the adsorbent, and particle size. The study of statistics found from experiments was carried out by incorporating Freundlich, Brouers-Sotolongo, Langmuir, Toth, Sips, Jovanovic, and Redlich-Peterson isotherm models. The adsorption kinetics were determined by implementing pseudo-first-order and second-order models, diffusion film models, and Dumwald-Wagner and Weber-Morris models. The experimental adsorption capacity qe was found to be about 130 mg/g. This value was closest to the maximum adsorption of 144.6mg/g predicted by the Brouers-Sotolongo isotherm which had a correlation coefficient (R2) of 0.998. The adsorption kinetics data was confirmed to be a pseudo-second-order model. The change in free energy, enthalpy change, and entropy change were vital thermodynamic factors in concluding that adsorption is almost spontaneous and endothermic process. Change in enthalpy (ΔH°) reduced value indicates the physical nature of the process. The adsorption of BG dye on the adsorbent surface was authenticated by FTIR spectroscopy and SEM imaging. A Central Composite Design (CCD) Quadratic model under Response Surface Methodology (RSM) was implemented for statistical optimization of adsorption capacity for the five parameters studied, namely, time, temperature, concentration of the dye, weight of the adsorbent, and pH. Software Design Expert 7.0 was used to evaluate 3D contour plots. The process of optimization yielded a value of 350 mg/g. Thus, incrementing the adsorption process by 84.2 %. The study provides insights on various dye and adsorbent interaction possibilities and derives that NIPSS is an efficient adsorbent to extract BG dye from wastewater solutions.

On thermodynamics and heat and mass transfer aspects of CH4 adsorption onto coconut shell-based carbonaceous material

The current study investigates the equilibrium methane (CH4) adsorption capacity and the adsorption kinetics of a locally produced coconut shell-derived activated carbon (AC CARB 6X12 60) for pressure and temperatures ranging from 0 to 55 bar and -20 to 70 °C, respectively. The adsorption isotherms and kinetics are determined using an in-house developed adsorption test rig. A maximum methane adsorption uptake of 0.140 kg/kg is obtained at -20 °C and 40 bar pressure. The adsorption equilibrium isotherm data are fitted using Toth, Dubinin-Astakhov (DA), and Modified-DA isotherm models. Afterwards, the kinetics study is done considering pseudo first order, second order, Elovich, and intra-particle diffusion models. In continuation, based on the DA isotherm model, Clausius Clapeyron relation, and Maxwell's relations, the expressions for the crucial thermodynamic parameter of adsorbed phase, i.e., isosteric heat of adsorption, specific heat capacity, enthalpy, and entropy is derived, and same is estimated using DA isotherm parameters. Additionally, the activated carbon's thermophysical properties (i.e., thermal conductivity, thermal diffusivity, and specific heat) are determined using the TPS 2500 S analyzer, which works on the hot-disk principle. Using the most suitable isotherm (DA) and kinetic model (pseudo second order), heat and mass transfer analysis is carried out on novel reactor configuration with an external cooling jacket, double row of cooling pipes with external longitudinal fins for methane storage using a 3D transient model in Comsol Multiphysics. The charge characteristics are studied for gas charging pressure varying from 1 to 50 bar and cooling fluid temperature of -20 to 70 °C. Iso-concentration contours are plotted to identify the pressure-temperature combination resulting in identical storage capacity (i.e., including both gaseous and adsorbed phases). Further simulations are carried out for constant pressure charging and constant flow discharge conditions to expound upon the effects of the dormancy period, gas charging pressure, and cooling/heating fluid temperature. 14% improvement in total discharge amount is obtained with a dormancy period between charging and discharging compared to no dormancy case.

Exploring PFOA adsorption isotherm in the presence of NOM using DBD plasma-modified GAC

Perfluorooctanoic acid (PFOA), a widely used perfluorinated alkyl substance (PFAS), poses significant environmental and health risks. This study investigates PFOA adsorption in the existence of natural organic matter (NOM) using granular activated carbon (GAC) modified with dielectric barrier discharge (DBD) plasma. PFOA’s amphiphilic structure, characterized by a hydrophilic carboxyl group head and a hydrophobic perfluorinated tail, contributes to its versatility and persistence. The selection of the Chao Phraya River (CPR) water as the NOM source, captures the complexity of a major water body subjected to diverse pollution sources. The results were analyzed through the Toth and Temkin isotherm models. Application of the Toth isotherm model reveals enhanced PFOA adsorption capacity in CPR water compared to DI water, emphasizing the influence of NOM. The Temkin isotherm analysis further characterizes the strength and efficiency of the adsorption process, highlighting a stronger interaction between PFOA and plasma-modified GAC in CPR water. The study indicates that the adsorption process in CPR water may be more influenced by PFOA surface coverage on the GAC surface in the presence of NOM. Overall, this research contributes valuable insights into pollutant removal strategies, highlighting the potential of DBD plasma-modified GAC in addressing PFOA contamination challenges in water systems.

Adsorption behaviour of polar solvent and water vapours on Sorbonorit B4 activated carbon

Abstract In this work, the affinity of the heterogeneous Sorbonorit B4 (SB4) activated carbon toward methyl ethyl ketone (MEK), isopropyl alcohol (IPA), n-propyl alcohol (NPA) and isobutyl alcohol (IBA), and water vapours was examined. Adsorption equilibrium measurements demonstrate a higher adsorption capacity of water vapour than organic compounds at relative pressures above 0.4. The adsorption capacities of SB4 at the same vapor pressure followed the order: NPA> IPA> MEK> IBA. The Langmuir, Dubinin-Radushkevich, Dubinin-Astakhov, and Toth isotherm models were chosen to describe experimental results. Based on the multi-temperature isotherms, the values of the isosteric heat of adsorption were determined for various adsorbate loading. The results indicate a strong influence of VOC molecule structures and the surface heterogeneity of SB4 on the adsorption efficiency. For IPA-SB4 pair, the maximum temperature rise in a fixed-bed bed in the adsorption process and the energy requirement for regeneration were calculated and experimentally verified.

Removal of aqueous methylene blue dye over Vallisneria Natans biosorbent using artificial neural network and statistical response surface methodology analysis

Azo-dye compounds prevalent in textile wastewater pose environmental risks. This research focuses on examining the kinetics and removal percentage of methylene blue (MB) using the biosorbent Vallisneria Natans, also known as pata dam (PD). Eight isotherm adsorption models were explored to comprehend the adsorption behaviours. Here, the data was better fit by Toth isotherm than others, indicating the nature of the adsorbent surface. The MB adsorption data were well fit with pseudo-second-order kinetic model, indicating a constant rate evaluation. The artificial neural network (ANN) and response surface methodology (RSM) effectively determined the conditions that resulted in an observed 88.34 % removal of methylene blue (MB). These optimal conditions comprised a 0.85 g/L adsorbent dose, a pH level of 7, a temperature of 42 °C, and a dye concentration of 40 mg/L. The best-performing ANN architecture was a 4–8–1 topology. ANN demonstrate superior modelling capabilities with an R2 = 0.99405, compared to RSM, with an R2 = 0.9837 when predicting the removal percentage of MB. Fourier transform infrared spectroscopy (FTIR) plays a crucial role in comprehending the interactions occurring during the adsorption of MB on the surface of the PD biosorbent. These findings showed that PD could effectively remove MB contaminated wastewater.

Separation of CO2 using biochar and KOH and ZnCl2 activated carbons derived from pine sawdust

Due to the CO2 emissions and greenhouse effect, reducing its harmful impacts on climatic conditions is necessary. CO2 adsorption in a microporous carbon structure is one of the more effective separation techniques to avoid this type of emissions. In this work, one biochar (BC) and five activated carbons (ACs) were produced from Pinus radiata sawdust by chemical activation with potassium hydroxide (KOH) or zinc chloride (ZnCl2). Characterization was performed by scanning and transmission electron microscopy (SEM and TEM), surface area and pore size distribution by volumetric N2 and CO2 adsorption experiments using the Brunauer-Emmet-Teller (BET) and Barret-Joyner-Halenda (BJH) methods, respectively, X-ray diffraction (XRD), elemental analysis and X-ray photoelectron spectroscopy (XPS). The performance efficiency of the carbons was analyzed in terms of CO2 adsorption capacity at an absolute pressure range of 0–760 mmHg and at different temperatures (0, 25 and 50 ºC). The apparent and IAST selectivity of CO2 over N2 were determined and all carbons showed preferential sorption for CO2. Langmuir, Freundlich and Toth isotherms were employed to analyze pure CO2 and N2 adsorption data and the Toth isotherm gave the best fit. The carbon activated at 600ºC with KOH at a ratio of 1:4 w/w achieved the largest CO2 uptake (5.79 mmol/g at 0 °C and 750 mmHg) due to a combination between high microporosity (89 %) and surface area (2437 m2/g). This carbon also reached a relatively high selectivity.

Novel nitrogen-enriched activated carbon with tunable microporosity from agricultural and plastic waste for CO2 adsorption

Low-cost nitrogen-enriched activated carbons (PNACs) with high microporosity were prepared by a simple one-step activation doping process using KOH as a chemical activator and melamine formaldehyde (MF) as a nitrogen source. These PNACs have shown great potential as effective CO2 adsorbents. The resulting PNACs were mainly microporous structure, with surface areas ranging from 736 to 2144 m2/g and total pore volumes ranging from 0.565 to 1.366 cm3/g. The CO2 adsorption capacities of PNACs were in the range of 2.53-6.07 mmol/g and 1.59–4.13 mmol/g at 0 °C and 25 °C under 1 bar, respectively. Additionally, the CO2/N2 selectivity of the PNACs ranges from 11.15 to 26.86 at a CO2 partial pressure of 0.1 bar. The experimental isotherm data were analyzed using various equations and the Toth isotherm equation was found to be the most accurate mathematical model to describe the CO2 adsorption isotherm of the activated carbon. This result further confirms that PNACs have a non-homogeneous pore structure. The exceptional CO2 adsorption properties can be attributed to the high microporosity and nitrogen content of the PNACs. The relationship between the physicochemical properties and CO2 adsorption performance of the activated carbon was further investigated by relevance analysis. At 0 °C and 1 bar, it was observed that the pore structure played a predominant role in the CO2 adsorption process of PNACs. During this condition, PNACs mainly exhibited physical adsorption, which was primarily governed by the microporous filling mechanism. However, at 25 °C and 1 bar, both microporosity and nitrogen content contribute equally to the CO2 adsorption effect. This observation confirms that the pore structure and nitrogen functional groups work synergistically to influence the CO2 adsorption performance of PNACs. The adsorption mechanism of PNACs can be described as physical adsorption, driven by the cooperation between nitrogen functional groups and the filling of micropores. This innovative one-step activation doping process successfully converts agricultural and plastic waste into sustainable and high-performance CO2 adsorbents. It provides new insights for mitigating the greenhouse effect and addressing the issue of plastic pollution.

Optimized preparation of multi-matrix activated carbon for CO2 capture by response surface methodology: The advantages of co-pyrolysis of biomass and plastics

In this paper, low-cost activated carbons (ACs) using apple tree pruning waste and waste polyethylene terephthalate (PET) plastic bottles as precursors were prepared by a two-step chemical activation, and the synergistic mechanism between the two precursors during carbonization was investigated. Response surface methodology (RSM) was employed to analyze the impact of PET ratio and carbonization conditions (carbonization temperature, heating rate) on the pore structure and CO2 adsorption performance of the activated carbon. The results demonstrate that the PET ratio and carbonization conditions significantly influence the pore structure and CO2 adsorption performance of the activated carbon. By optimizing the preparation conditions, the RSM-predicted CO2 uptake at 1 bar and 25 °C closely matches the experimental value, both reaching 4.49 mmol/g. Additionally, at 1 bar and 0 °C, the CO2 uptake of the activated carbon was found to be 7.03 mmol/g. The activated carbon AC0.2-8-515 exhibits exceptional characteristics, including a highly developed specific surface area of 1808 m2/g and a significant microporous volume of 0.67 cm3/g. It also demonstrates good selectivity for CO2/N2 (13.44) and exhibits ease of regeneration with excellent cycling stability even after multiple cycles. The isotherm data obtained from experimental measurements are fitted using Langmuir, Freundlich, and Toth isotherm equations. Among these models, the Toth isotherm equation provides the best fit to the data. Furthermore, the co-pyrolysis process contributes to an increased yield of PET pyrolysis fixed carbon. This study presents a novel solution to address the issues of carbon dioxide capture and white pollution, offering promising prospects for future development.

Rice husk ash as sorbent for solid phase extraction of diclofenac, ibuprofen and carboplatin residues from waters

Carboplatin, ibuprofen and diclofenac are among drugs classified as emergent pharmaceutical contaminants that impact negatively the environment. Development of affordable procedures for their quantification and removal from waters is gained interest in the scientific community. The present study was aimed at the characterization of rice husk ash as sorbent for the solid phase extraction of mentioned drugs in waters. Optimal sorbent dose, pH dissolution and contact time were selected. Up to the best of our knowledge, the good performance of rice husk ash for extraction of carboplatin, ibuprofen and diclofenac from aqueous dissolutions is demonstrated for the first time in the present study, achieving a maximum sorption capacity of 5.843 mg.g−1, 2.321 mg.g−1 and 2.316 mg.g−1, respectively, which are higher than those reported for others pharmaceutical products with husk rice ashes. Kinetic of sorption was well modeled by a Lagergren pseudo first order model for diclofenac and by a pseudo second order model of Ho for ibuprofen and carboplatin. Sorption at equilibrium conditions was well modeled by Freundlich and Toth isotherms for diclofenac and ibuprofen, while Sips, Toth and Dubinin-Radushkevich isotherms adjusted well for carboplatin. Kinetic and at equilibrium conditions studies confirmed the high complexity of involved sorption mechanisms in the three adsorbate/rice husk ash systems considered.

Isotherm and kinetic studies for sorption of Cr(VI) onto Prosopis cineraria leaf powder: A comparison of linear and non‐linear regression analysis

AbstractThis research investigated the utilization of Prosopis cineraria leaf powder (PCLP) as biosorbent in the removal of Cr(VI) from aqueous solution. The maximum monolayer biosorption capacity of Cr(VI) onto PCLP after 2 h was 10.283 mg g−1 under optimum conditions: initial concentration 10 mg L−1, pH 5, dose 0.4 g L−1 and temperature at 293 K. For equilibrium modeling, two‐parameters (Langmuir, Freundlich, Temkin) and three parameters (Redlich‐Peterson, Sips and Toth) isotherm models were used to fit the equilibrium data. Kinetic modeling was performed using Lagergren pseudo‐first‐order, pseudo‐second‐order, Elovich, Weber‐Morris intraparticle diffusion, and Bangham's model. Both linear and nonlinear regression were compared coupled with several error functions to determine the best fit and model parameters were evaluated. The results revealed that nonlinear method best explain the experimental data revealing Temkin (R2 = 0.9938) and pseuso‐second‐order (R2 = 0.9935) models as the best‐fitted models with lower error functions. Therefore, the present investigation convinced that PCLP could be used as cost effective, efficient and eco‐friendly biosorbent to reduce Cr(VI) concentration in aqueous solution.

Synthesis, characterization, and CO2 adsorption properties of pure ETS-10

Synthesis of titanosilicate ETS-10 with high purity and crystallinity is a big challenge due to its limited crystallization region. ETS-10 was synthesized and characterized by SEM, EDX, BET, and TGA/DTA methods. The effect of synthesis parameters including pH of the gel, crystallization temperature and time, and the potassium source, were studied using the one-at-a-time (OFAT) approach. The results showed that the ETS-10 with the highest purity was achieved considering the gel pH of 11.3, and the crystallization time and temperature of 72 h and 230 °C. It was also revealed that there was considerable interaction between the potassium source with other synthesis parameters. Afterward, CO2 adsorption of the pure synthesized sample was obtained at 298 K using a volumetric setup. The Dual-site Langmuir, Toth, and UNILAN isotherms were applied to model the obtained equilibrium adsorption data. The CO2 adsorption capacity of the synthesized pure ETS-10 was obtained equal to 3.37 mmol/g. Finally, the adsorption kinetics data were modeled using the PNO model with n = 3.5. The results showed that about 90% of the equilibrium absorption was achieved in only 25 s, which indicates the remarkable capability of using pure ETS-10 for CO2 capture by the PSA method.

Degradation of Aniline & Para- Chloroaniline from Water by Adsorption Coupled with Electrochemical Regeneration

Treatment methods for water-containing organics are gaining significant attraction in modern-day research. Amines are an important organic compound class encountered in industrial wastewater streams. The current research paper focuses on studying the adsorption behavior of aniline and parachloro-aniline using a graphite-based adsorbent, namely, Nyex-1000, and the subsequent regeneration of the adsorbent. To determine Nyex-1000's adsorption capacity, several parameters, including time, pH, and concentration, were assessed. Adsorption isotherms, kinetics, and used adsorbent regeneration were also investigated. The adsorption of aniline and parachloro-aniline was found to be quite rapid owing to its non-porous nature. Moreover, the low energy requirement makes the process quite economical due to the high electrical conductivity of the adsorbent. The adsorption data was fitted to Langmuir, Freundlich, Redlich Peterson, Sips, and Toth isotherm models. In aniline’s case, Langmuir and Parachloro-aniline Sips models gave the best fitting with the highest R2 value. A regeneration efficiency of 100% was observed in case of both aniline and parachloro-aniline by passing a charge of 5 and 10 coulombs per gram through the adsorbent bed 10 mm in thickness. Adsorption for parachloro-aniline was found to be 0.88 mg/g, and for aniline was found to be 0.40 mg/g. The reduction in adsorption capacity was minimal after several adsorption and regeneration cycles. This study found that spent adsorbent could be regenerated effectively through electrochemical regeneration.

Developing Versatile Contactors for Direct Air Capture of CO2 through Amine Grafting onto Alumina Pellets and Alumina Wash-Coated Monoliths.

The optimization of the air-solid contactor is critical to improve the efficiency of the direct air capture (DAC) process. To enable comparison of contactors and therefore a step toward optimization, two contactors are prepared in the form of pellets and wash-coated honeycomb monoliths. The desired amine functionalities are successfully incorporated onto these industrially relevant pellets by means of a procedure developed for powders, providing materials with a CO2 uptake not influenced by the morphology and the structure of the materials according to the sorption measurements. Furthermore, the amine functionalities are incorporated onto alumina wash-coated monoliths that provide a similar CO2 uptake compared to the pellets. Using breakthrough measurements, dry CO2 uptakes of 0.44 and 0.4 mmol gsorbent-1 are measured for pellets and for a monolith, respectively. NMR and IR studies of CO2 uptake show that the CO2 adsorbs mainly in the form of ammonium carbamate. Both contactors are characterized by estimated Toth isotherm parameters and linear driving force (LDF) coefficients to enable an initial comparison and provide information for further studies of the two contactors. LDF coefficients of 1.5 × 10-4 and of 1.2 × 10-3 s-1 are estimated for the pellets and for a monolith, respectively. In comparison to the pellets, the monolith therefore exhibits particularly promising results in terms of adsorption kinetics due to its hierarchical pore structure. This is reflected in the productivity of the adsorption step of 6.48 mol m-3 h-1 for the pellets compared to 7.56 mol m-3 h-1 for the monolith at a pressure drop approximately 1 order of magnitude lower, making the monoliths prime candidates to enhance the efficiency of DAC processes.

Adsorptive removal of Safranine T dye from aqueous solutions using sodium alginate–Festuca arundinacea seeds bio–composite microbeads

In this study, composite microbeads were prepared using Festuca arundinacea seeds and sodium alginate biopolymer at different ratios and utilized as sorbents for the sorption of Safranine T from wastewater. The sorbents were characterized by FTIR, SEM, XRD, and BET analysis. According to BET analysis, the specific surface area of the adsorbents was calculated to be 10.99 m2/g and the surface was found to be mesoporous. The optimum conditions for adsorption studies including initial pH (2−12), concentration (10–50 mg/L), contact time (0–150 min), and adsorbent mass (0.05 g/50 mL-0.25 g/50 mL) were determined at 25 °C. The raw data obtained from sorption tests were applied to Freundlich, Langmuir-1, Langmuir-2, Langmuir-3, Langmuir-4, Temkin, Toth, and Koble-Corrigan isotherm models. The best results were obtained from the Langmuir-2 and accordingly the qm values were calculated as 454.54, 833.33, and 625.00 mg/g for FA, FA-SA-20, and FA-SA-30 at 25 °C, respectively. Adsorption kinetic data illustrated that the process followed the PSO model. Reusability and desorption studies were performed for composite microbeads. Additionally, the thermodynamic studies were performed at 25, 35 and 45 °C. Considering all these results, it was seen that the FA-SA-20 composite had the highest adsorption capacity and the best desorption efficiency.

Multiscale modeling of ammonia adsorption on zinc sulfate-doped activated carbon: Sensitivity analysis, parameter identification, and model validation

In this study four models are developed and validated to describe the dynamic adsorption of ammonia on zinc sulfate-doped activated carbon, ranging from simple single-scale to complex multiscale models. They are based on equations for mass balance, thermodynamics, hydrodynamics, and adsorption kinetics. Since the values of the parameters are needed for the implementation of the models, the doped activated carbon is characterized and ammonia isotherms measurements are performed at three different temperatures, i.e., 288, 303, and 313 K. A method based on parameter sensitivity analysis is used to evaluate the estimability of the unknown parameters of the Toth isotherm equation. Experimental breakthrough curves were then measured at various ammonia concentrations and gas flow rates. These curves were used to determine the overall mass transfer and axial dispersion coefficients, as well as the effective and intracrystalline diffusion, involved in the model equations. The models were implemented and solved using Comsol Multiphysics®. The study showed that the adsorption process was limited by the diffusion of ammonia and adsorption on the zinc sulfate crystal. The models were validated using breakthrough curves different from those used for parameter identification. The agreement between model predictions and measurements was evaluated using performance indices and confirmed by a Kolmogorov-Smirnov statistical test.

Organo-modified Montmorillonite-based adsorbents for selective removal of Iron(II) from aqueous solutions

The use of clays for the adsorption of contaminants from water has gained significant attention in recent decades. Clays and their modified forms have been extensively studied for their ability to adsorb both inorganic and organic pollutants. The purpose of this study is to investigate the use of montmorillonite (k10), local montmorillonite (MMT-Na), and their 1,10-phenanthroline modified forms (k10-phen and MMT-phen) for the adsorption of iron(II) ions. Adsorption of iron(II) on k10 and MMT-Na has been observed to be physical; however, adsorption on k10-phen is chemical. Nevertheless, iron (II) adsorption on MMT-phen combines physical and chemical adsorption. To characterize all these clays, X-ray diffraction (XRD), Infrared spectroscopy (IR), thermogravimetric analysis (TGA), and BET nitrogen adsorption–desorption isotherm were performed. In order to determine the specific surface area of the clays, the BET and methylene blue methods were used, and both ways were quite similar. A cation exchange capacity (CEC) of 39 meq/100 g for k10 and 85 meq/100 g for MMT-Na is calculated. To optimize the Fe(II) adsorption on clays, pH, clay mass, and contact time were studied. The adsorption isotherms were analyzed using linear and nonlinear Langmuir, Freundlich, Dubinin-Radushkevich, Sips, and Toth isotherms. A study of adsorption kinetics was conducted using linear, nonlinear, and differential pseudo first and second orders. An Elovich model has been applied to the obtained data about chemisorption character. Boyd and Weber& Morris's intraparticle diffusions have also been examined. Upon adsorption of Fe(II) on all clays, the standard free energies were negative, confirming the spontaneous nature of the adsorption process. As a result of the endothermic nature of the adsorption, the enthalpies are positive. In the presence of other cations, k10-phen and MMT-phen demonstrated the most excellent selectivity in uptaking Fe(II).

Isotherm, kinetics, thermodynamics, recyclability and mechanism of ultrasonic assisted adsorption of methylene blue and lead (II) ions using green synthesized nickel oxide nanoparticles

One of the urgent global problems demanding effective mitigation strategies is the pollution caused by organic dyes and metal ions like methylene blue and lead (II) ions. In recent times, the increasing applications of nickel oxide nanoparticles in biomedicine, catalysis, sensors in optoelectronic materials, and the prevention of environmental pollution have attracted researchers' interest across the globe. Herein, Psidium guajava leaves extract was utilized to synthesize green nickel oxide nanoparticles (PG-NiONPs). Surface and analytical techniques were employed to characterize PG-NiONPs and were thereafter applied to remove methylene blue and lead (II) ions from wastewater. The results revealed the quantified presence of phytochemicals such as alkaloids, phenols, tannins, flavonoids and saponins in the Psidium guajava leaves extract. The prepared PG-NiONPs revealed a crystalline phase, functional groups, mesoporous and microstructural arrangements typical of nickel oxide nanoparticles. The surface area of PG-NiONPs was obtained as 85.40 m2/g. The best ultrasonic-assisted adsorption of MB and Pb(II) ions was achieved at pH values of 6 and 5 for MB and Pb(II), a contact time of 60 min, an adsorbent mass of 40 mg/L, and a temperature of 50 °C, respectively. The maximum MB and Pb(II) adsorption capacities of 495.58 and 508.56 mg/g were evaluated. The experimental data corroborated with the pseudo-second-order and Toth isotherm models. The adsorption of MB and Pb(II) over green PG-NiONPs was a thermodynamically spontaneous process. The PG-NiONPs indicated good recyclability with high stability even after 8 adsorption cycles. Overall, the PG-NiONPs is a potential adsorbent for improved toxic dyes, metal ions and other scavengers removal from wastewater.

Application of isotherms models and error functions in activated carbon CO2 sorption processes

This work is concerned with the calculations using eight different isotherm models (Langmuir, Freundlich, Halsey, Temkin, Toth, Sips, Radke-Prausnitz, and Redlich-Peterson) to fit the experimental isotherm data of CO2 on activated carbon (AC). Moreover, systematic and comprehensive modeling of non-linearized isotherms was performed by developing an algorithm for determining their parameters and analyzing seven error functions. To determine the best-fitted isotherm model and error function, we used the sum of normalized errors (SNE) procedure. The modeling results obtained showed that the Redlich-Peterson, Radke-Prausnitz, and Toth isotherm models are best suited to the empirical data, with relatively high R2 determination coefficients. Finally, the SNE method allowed the selection of the chi-square test (χ2) and the HYBRID error as universal indicators in nonlinear regression to select the set of optimized isotherm parameters. The interpretation of the assumptions of the isotherm models, which featured a strong correlation with the experimental data, allowed a conclusion to be drawn about the sub-monolayer adsorption mechanism on the heterogeneous surface of the AC. The acquired modeling findings are expected to establish a certain theoretical foundation for the characterization of CO2 adsorption equilibrium studies at the interface between porous solid materials and gases.

Ammonia capture by adsorption on doped and undoped activated carbon: Isotherm and breakthrough curve measurements

Doped and undoped activated carbons were characterized by scanning electron microscopy, energy dispersive spectrometry, helium pycnometry, mercury intrusion porosimetry, and adsorption isotherms of nitrogen and carbon dioxide. The adsorption isotherms of ammonia were measured at 278, 293, 303, and 318 K and pressures up to 105 kPa using a manometric system on both activated carbons. These measurements showed that the doped activated carbon had the highest ammonia adsorption capacity, especially at low ammonia partial pressures. The Toth isotherm model was used to correlate the adsorption isotherms and estimate the isosteric heats of adsorption at 278 K and at zero fractional loading that were 25.6 and 41.9 kJ.mol−1 for undoped and doped activated carbon, respectively. Ammonia breakthrough curves were measured with both activated carbons in a pilot column. The behavior of doped and undoped activated carbon during adsorption/desorption cycles shows that despite the possibility of regeneration and enhancement of undoped activated carbon, the doped activated carbon provides better single use performance. A study of the operating parameters of doped activated carbon was conducted to evaluate the effects of ammonia concentration, gas flow rate, operating temperature, and relative humidity. The occurrence of two independent ammonia adsorption mechanisms (chemical and physical) on the doped activated was demonstrated.