Equilibrium Sorption Research Articles

Crude oil sorption performance of native and acetylated Siamese senna seed pods

The recurring problem of oil spillage has directed research to the exploration of various agricultural wastes in order to discover new, inexpensive, and environmentally friendly oil sorbents. This research studied the viability of native and acetylated seed pods of Siamese senna as oil spill mop. SEM, BET, and FTIR analyses were employed to assess the adsorption tendency of the adsorbents for crude oil. Investigation of the oil sorption behaviors of the adsorbents involved batch sorption experiments. The SEM analysis revealed improvements in the surface morphology of the acetylated pods. The BET surface area increased from 265.2 m2/g to 335.0 m2/g after acetylation. The FTIR spectra of the oil-treated pods showed that the acetylated pods adsorbed more oil than the native pods. The Langmuir isotherm best described the sorption equilibrium for the adsorbents. Kinetic analysis showed that the sorption processes conformed to the pseudo-second-order model, and were controlled by film diffusion alone or in conjunction with other mechanisms. The results obtained in this work show that Siamese senna seed pods can be used for crude oil sorption from an aqueous medium. The improved oil sorption capacity of the acetylated pod shows that it has more potential to serve as a low-cost alternative for oil spill remediation than the native seed pod.

Bio-Adsorbent for Elimination of Reactive Dye from Aqueous Solution: Kinetic and Statistical Modelling Study

Introduction/Background: The use of various dyes to colour products is a general practice in various industries. The occurrence of these dyes in water, even at small concentrations, is highly noticeable and aesthetically objectionable. In the present study, the applicability of inexpensive and eco-friendly bio-adsorbent has been tested as an alternative substitution of the commercially available activated carbon for the removal of reactive dye from the aqueous solution. Materials and Methods: Bio-adsorbent prepared from pomegranate peel was successfully used to remove the reactive dye (Reactive Black 5) from the aqueous solution. The effects of major parameters such as pH, adsorbent dosage, and contact time on dye removal efficiency were studied. Statistical models were articulated based on selected variables to optimize the decolourisation efficiency of the adsorption process using a full factorial central composite design. Results: Dye removal efficiency of close to 100% was observed at a pH 12 using 1 g adsorbent/ 200 mL dye solution within a contact time of 60 min., yielding a virtually colourless solution. A fixed-bed column study with an initial dye concentration of 100 mg/L at bed depths of 4 cm, 8 cm, and 12 cm yielded a breakthrough time of 300 min, 570 min, and 780 min, respectively. Discussion: Langmuir, Freundlich, and Temkin isotherm models were applied to analyze the sorption equilibrium parameters. The experimental results of the analysis revealed that the Langmuir isotherm fits better than the other isotherms with a linear regression coefficient (R2) of 0.99. The high correlation coefficient (R² > 0.95) and low p-values (< 0.0001) indicate that the model and its terms are significant, making it effective for optimizing operational parameters and accurately predicting the response. Conclusion: The breakthrough curve serves as a tool to evaluate the effectiveness of the prepared adsorbent in real-world applications. The present work not only provides an alternative to commercially available activated carbon for dye wastewater colour removal but also emphasizes the importance of repurposing fruit residues, which could otherwise become environmental pollutants if improperly disposed of.

Batch sorption dynamics and equilibrium for the capture of Ni(II) onto activated carbon developed from yellow dock (Rumex crispus)

Batch sorption dynamics and equilibrium for the capture of Ni(II) onto activated carbon developed from yellow dock (Rumex crispus)

Recovery of precious metals from aqua regia leachate of E-wastes using dithiocarbamate-modified cellulose and development of novel kinetic model

The escalating demand and dwindling natural supplies of precious metals (PMs) necessitate innovative hydrometallurgical recovery approaches with rapid kinetics and reduced environmental impact. The current study investigated the sorption and recovery of PMs from electronic waste (e-waste) utilizing dithiocarbamate-modified cellulose (DMC) and its proline derivative with epoxy cross-linkage (DMC-Pro-Epo-6) in aqua regia (AR). The effects of various sorption parameters, such as sorbent dose in feed, HCl: HNO3 ratio, AR dilution times, etc., on PM recovery were explored. Equilibrium for AuIII and PtIV sorption by DMC and DMC-Pro-Epo6 was reached in less than an hour, which is significantly faster than most reported sorbents. The maximum sorption capacities, calculated using the Langmuir equation, were 348.0 mg g−1 for AuIII and 34.7 mg g−1 for PtIV for DMC, while DMC-Pro-Epo6 achieved 350.3 mg g−1 for AuIII and 31.1 mg g−1 for PtIV. These capacities, particularly for the higher sorption capacity of AuIII by DMCs, are attributed to the relativistic effects of gold, soft–soft interactions, and strong sulfur binding. FT-IR, FE-SEM, and EDX analyses elucidated the chelation bonding and mechanisms involved in PM sorption onto DMCs. By utilizing AR-DMC integrated techniques, step-by-step protocols were established for Au recovery from diverse e-waste sources, such as smartphones and smart chip cards. The study also highlighted the importance of chemical pre-concentration of e-waste to remove base metals, facilitating efficient PM recovery. Finally, a key innovation of this work is introducing a new pseudo-mix order fractional model, based on the preference of active sites with fractional assumptions, which more accurately correlates the complex sorption kinetics observed in complex systems.

Effect of particle size on the transport of polystyrene micro- and nanoplastic particles through quartz sand under unsaturated conditions

Micro- and nanoplastics (MNPs) are contaminants of emerging concern recently found in soil ecosystems. Their presence in terrestrial environments and their migration to aquatic environments may become a risk for the health of ecosystems and, through them, of humans. Understanding the interaction between particle properties and physicochemical and hydrodynamic factors is crucial to evaluate their fate and their potential infiltration towards groundwater. This study investigates the impact of particle size on MNPs transport through sand under unsaturated conditions. Infiltration column experiments with polystyrene MNPs ranging from 120 to 10,000 nm were conducted and supported by numerical modelling to derive reactive transport parameters. Results show a significant effect of particle size on the transport of MNPs, with higher recovery values observed for smaller particles (120 nm; 95.11%) compared to larger particles (1,000 nm; 71.44%). No breakthrough was observed for 10,000 nm particles, indicating a complete retention within the quartz sand matrix. DLVO theory confirmed the dominance of electrostatic repulsive forces between MNPs and sand grains, suggesting an unfavourable environment for MNPs to adhere to quartz sand. Consequently, particle retention in the sand matrix occurs predominantly by physical processes. Equilibrium sorption modelling reveals that larger particles (1,000 nm) tend to be immobilized in small pores throats due to straining, resulting in lower recoveries. When they are not trapped, particles tend to travel faster through preferential flows due to a size exclusion effect, evidenced by shorter arrival times at the column outlet compared to tracers. These findings highlight the influence of particle size on the transport and retention of MNPs in quartz sand under unsaturated conditions and contribute to a better understanding of their transport dynamics and environmental fate.

U(Ⅵ) sorption by porous sodium zirconium phosphate pellets from aqueous solution

Zirconium phosphate is the first artificially produced layered phosphate that can sorb a variety of nuclides from solutions. Sodium zirconium phosphate (NZP) was a type of α-zirconium phosphate (α-ZrP). The porous sodium zirconium phosphate pellets (p-NZP-P) with a diameter of more than ∼3 mm were prepared and used for uranium sorption. The p-NZP-P could be immersed in solutions for more than 5 days without dissolving and structurally collapsing. The sorption properties of U(Ⅵ) on p-NZP-P in solutions were investigated by both static and dynamic sorption tests. Synthetic p-NZP-P was analyzed in detail using various characterizations to investigate their character and structural changes. In the static sorption experiment, the equilibrium sorption capacity reached the 77.5 ± 1.5 mg·g−1 when the initial concentration of U(Ⅵ) was 100 mg/L, pHinitial = 4.5, T = 25 ℃. Uranium sorption increased by ∼69 % and ∼215 %, respectively, when the initial uranium concentration was increased from 100 to 300 mg·L−1 and the temperature was increased from 15 to 55 °C. Furthermore, uranium sorption increased by ∼541 % when the initial pH increased from 2.5 to 4.5, while it decreased by ∼39 % when the initial pH increased from 4.5 to 7.0. The sorption data corresponded to the pseudo-second-order kinetic model and the Langmuir isotherm model, as well as the theoretically predicted value of sorption capacity (∼199.9 mg·g−1). The results of the dynamic sorption experiment showed that decreasing the quality, increasing the flow rate and the initial U(Ⅵ) concentration would shorten the breakthrough time. The dynamic sorption data agreed well with the Thomas model. The characterization confirmed the porous properties, while the U(Ⅵ) sorption mechanisms relate to –OH coordination and ion exchange. A radioactive rare earth wastewater treatment test suggested that p-NZP-P could be the potential uranium sorbent due to its good stability and efficiency. This paper opened opportunities for the development of practical materials for treating radioactive wastewater in the application of actual scenarios.

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.

Encapsulation of Bamboosa vulgaris culms derived activated biochar into hierarchical permeable, phosphate rich and functionalized alginate aerogel composites and its contribution in U(VI) adsorption

In this study, a facile methodology was designed to encapsulate Bamboosa vulgaris culms derived activated biochar (BVC) in a variable mass ratio, into a three-dimensional hierarchical porous and permeable and amino-thiocarbamated alginate (TSC) to prepare hybrid biosorbents (BVC-MSA). These ultralight and lyophilized phosphate rich macroporous sorbents were rationally characterized through FTIR, XRD, BET, SEM-EDS, elemental mapping, XPS techniques and employed for efficient UO22+ adsorption from aqueous solutions. The phytic acid (PA) was found to be a suitable hydrophilic and phosphorylating agent for the TSC matrix through hydrogen-bonded crosslinking when employed in a correct mass ratio (1:3). The SEM-EDS and XPS analyses confirmed the UO22+ sorption onto BVC-MSA-3 (the most suitable composite with a BVC/TSC mass ratio of 30.0 % w/w) and provided evidence of heteroatom involvement in developing the physico-chemical interactions. The BCV-MSA-3 exhibited the best response as a sorbent during kinetics/sorption process, therefore, it was selected to study the equilibrium sorption studies. The BCV-MSA-3 removal efficiency increased from 12.1 to 94.2 % using 0.2 to 1.8 g/L sorbent dose at pH (4.5). The mentioned sorbent displayed a significant maximum sorption capacity qm (309.55 mg/g at 35 °C) calculated through the best-fitted Langmuir and Temkin models (R2 ≈ 0.99). The sorption kinetics followed the pseudo-second-order (PSORE) model and exhibited fast sorption rate teq (180 min). Thermodynamic parameters clarified that the sorption process is feasible ΔGo (−25.3 to −27.6 kJ/mol kJ/mol), endothermic ΔHo (27.17 kJ/mol), and proceeds with a positive entropy (0.176 kJ/mol.K). The study shows that BCV-MSA-3 could be an alternative and auspicious sorbent for uranium removal from aqueous solution.

Sorption and desorption behavior and mechanism of oxytetracycline on soil aggregates organic matter separated from soils and sediments in the Yellow River Delta

Soil aggregates organic matter (SAOM) is composed of free particulate organic matter (fPOM), intra-aggregate particulate organic matter (iPOM), and mineral-associated organic matter (mSOM), which are major antibiotic sorbents that play a significant role in the soil organic matter (SOM) turnover process. To date, the oxytetracycline (OTC) sorption and desorption behavior and mechanisms on SAOM have not been contrastively analyzed. SAOM organic components have been used to study scientific problems and to determine their influence on the fate and migration of OTC among the SOM turnover process. Results demonstrated that SAOM had great OTC sorption capacity ranging from approximately 12100–513,000 mg kg−1 and the desorption proportion was no more than 33.60%. The slow organic carbon pool (mSOM) had greater OTC accumulation capacity than the intermediate active pool (iPOM) and the active pool (fPOM), while OTC was more likely to reside in the active pool in wetlands (fPOM-w) and oil waste land (fPOM-o) than the organic carbon pool (mSOM-f) in farmland with human activity interference. The hysteresis was affected by SAOM's physical surface characteristics when the OTC initial equilibrium sorption concentration was higher than 200 mg L−1. When it was lower than that, it was affected by the organic carbon composition. Hydrogen bonds, electrostatic interactions, and π-π interactions dominated the SAOM-OTC interactions. The results of this study will be useful for evaluating the long-term behavior and migration of antibiotics in SOM turnover processes and could refine risk assessments of antibiotics contamination in soil environmental systems.

Antibiotics pollutants in agricultural soil: Kinetic, sorption, and thermodynamic of ciprofloxacin

The entry of antibiotics, as pollutants, into the environment has created great concerns. Environmental dynamics of antibiotics based on soil chemical properties need to be a better understanding of their chemical behavior. This research is focused on studying the adsorption behavior and kinetic mechanisms of ciprofloxacin (CIP) in an agricultural soil. For this purpose, a batch experiment was conducted at different times (5 min–24 h), and using initial concentrations of CIP (0–1 mmol L−1) in the soil. The adsorption processes as affected by pH and ionic strength were assessed based on the modeling with response surface methodology (RSM). According to the results, the sorption equilibrium was found within 240 min, and the pseudo second-order model was the best for describing the data. Increasing the initial CIP concentration increased CIP adsorption, but increases in ionic strength and pH had an inverse effect. Based on RSM modeling, the CIP adsorption was 7.31 and 7.03 (mg g−1) in the presence of NaCl and CaCl2 electrolytes, respectively, in the optimized conditions (pH 6.5 and ionic strength 0.01 mol L−1). The spontaneous nature of CIP adsorption was determined based on thermodynamic calculations (ΔG° = −10.8 to −12.4 kJ mol−1). The interaction of pH and ionic strength was described with the quadratic model. The obtained results contribute to understanding the CIP fate in the soil environment and facilitate decisions regarding entry and controlling soil contamination due to this antibiotic.

The effect of adsorbent shaping on the equilibrium and kinetic CO2 adsorption properties of ZIF-8

To be used at scale, adsorbents must be shaped into macroscopic objects, e.g. pellets, granules, and monoliths. Shaping may involve various processing steps and additives that collectively contribute to the final equilibrium and kinetic sorption properties of the adsorbent. Understanding the fundamental links between these processing steps and the resulting sorption performance is needed to rationalise the design of shaped adsorbents. Our study aims to advance the state of knowledge in this area. By focusing on ZIF-8, a prototypical metal organic framework (MOF), and CO2, a common small gas adsorbate, we compared a commercial binderless ZIF-8 extrudate and two purpose-made ZIF-8 pellets shaped with a blend of binders. We used analytical, spectroscopic, and imaging techniques to characterise the samples’ chemical, textural, and morphological properties. In addition, we collected equilibrium and kinetic CO2 adsorption data at 283, 293, and 303 K and up to 1 bar. The binderless ZIF-8 extrudate exhibited a homogeneous structure with BET area, micro- and meso-porosity only slightly reduced compared to ZIF-8 powder. The ZIF-8 pellets also maintained the overall BET area of the ZIF-8 powder, but displayed enhanced macroporosity and skeletal density as well as reduced microporosity – features that likely result from the pressure-induced strains of pelletisation. The extrudates are much less mechanically robust than the pellets. All samples displayed CO2 adsorption capacity in line with the CO2 uptake of their respective components. The CO2 kinetics measurements reveal clear distinctions between binderless ZIF-8 extrudate and ZIF-8 pellets, the latter indicating a behaviour associated with the additional presence of macropores. Our study presents quantifiable evidence for the effect of adsorbent shaping on gas adsorption equilibria and kinetics, providing a valuable resource for preliminary process design.

Electrospun nanofibrous membranes based on fluorine-free polyimide for swift oil spill cleanup and emulsion separation

The urgent need to mitigate environmental damage caused by oil and organic pollutants in oil production industries and spill accidents necessitates effective removal methods. This study introduces novel nanofibrous membranes composed of fluorine-free polyimide, which was formed by electrospinning of BPADA-TrMPD, produced by polycondensation reaction in one-step and at high temperature using 4,4′-(4,4′-isopropylidenediphenoxy)bis-(phthalic anhydride) (BPADA) and 2,4,6-trimethyl-m-phenylenediamine (TrMPD). The resulting membranes exhibited a hydrophobic nature with a water contact angle of 114° and an oil contact angle of ∼ 0°. The adsorption performance of the nanofibers was explored using Saudi crude oil and non-polar organic solvents (i.e., n-hexane and dodecane). The developed membranes exhibited a crude oil uptake ranging from 35 to 60 g g−1 and demonstrated rapid removal capabilities, reaching equilibrium sorption capacity within a few minutes for crude oil. Moreover, these membranes displayed remarkable flux of 1991, 1508, and 206 L m−2h−1 for dodecane, n-hexane, and crude oil, respectively. The capability of the fluorine-free mats designed for oil spill cleanup was validated through its application in treating actual samples. The durability and recyclability of the membranes were showcased by regenerating them through mechanical treatment.

Sorption of 32Si and 45Ca by isotopic exchange during recrystallisation of cement phases

The uptake kinetics of 32Si and 45Ca on cement minerals including C-S-H phases, portlandite, AFm phases, ettringite, and aged hardened cement paste were determined through batch sorption experiments. A two-step uptake kinetics was observed, with a fast initial step during ∼1 day followed by a much slower second step, not yet completed after one year. The working hypothesis that the fast uptake is caused by exchange of the radioisotopes with stable isotopes adsorbed on the mineral surface, whereas the slow uptake step is due to uptake in the crystal lattice during recrystallisation, was tested with the help of phenomenological models that combine surface adsorption and homogeneous recrystallisation. The experimental data could be reproduced satisfactorily using a refined version of the formerly published continuous homogeneous recrystallisation (CHOR) model, supporting the working hypothesis and allowing equilibrium sorption coefficients (Rd; L kg−1) for these radionuclides to be calculated on a mechanistic basis. This provides insight into the intrinsic rates and mechanisms of interaction between cementitious materials and their pore fluids which contain dissolved calcium and silicon.

Dye Sorption from Mixtures on Chitosan Sorbents.

This article presents studies on the sorption of the anionic dyes Reactive Black 5 (RB5) and Reactive Yellow 84 (RY84) from solutions of single dyes and from dye mixtures onto three chitosan sorbents-chitin, chitosan DD75% and chitosan DD95%. In this work, the influence of pH on sorption efficiency, the sorption equilibrium time for the tested anionic dyes and the sorption capacity in relation to the individual dyes and their mixtures were determined. It has been found that the sorption process for both dyes was most effective at pH 3 for chitin and chitosan DD75 and at pH 4 for chitosan DD95%. The obtained results were described by the double Langmuir equation (Langmuir 2). The obtained constants made it possible to determine the affinity of the tested dyes for the three sorbents and the sorption capacity of the sorbents. For RB5, the highest sorption capacity for chitosan DD95% was achieved with sorption from a single solution-of 742 mg/g DM and with sorption from mixed dyes-of 528 mg/g DM. For RY84, the highest efficiency was also achieved for chitosan DD95% and was 760 mg/g DM for a single dye solution and 437 mg/g DM for a mixture of dyes.

Chitosan/Poly(maleic acid-alt-vinyl acetate) Hydrogel Beads for the Removal of Cu2+ from Aqueous Solution.

Covalent cross-linked hydrogels based on chitosan and poly(maleic acid-alt-vinyl acetate) were prepared as spherical beads. The structural modifications of the beads during the preparation steps (dropping in liquid nitrogen and lyophilization, thermal treatment, washing with water, and treatment with NaOH) were monitored by FT-IR spectroscopy. The hydrogel beads have a porous inner structure, as shown by SEM microscopy; moreover, they are stable in acidic and basic pH due to the covalent crosslinking. The swelling degree is strongly influenced by the pH since the beads possess ionizable amine and carboxylic groups. The binding capacity for Cu2+ ions was examined in batch mode as a function of sorbent composition, pH, contact time, and the initial concentration of Cu2+. The kinetic data were well-fitted with the pseudo-second-order kinetic, while the sorption equilibrium data were better fitted with Langmuir and Sips isotherms. The maximum equilibrium sorption capacity was higher for the beads obtained with a 3:1 molar ratio between the maleic copolymer and chitosan (142.4 mg Cu2+ g-1), compared with the beads obtained using a 1:1 molar ratio (103.7 mg Cu2+ g-1). The beads show a high degree of reusability since no notable decrease in the sorption capacity was observed after five consecutive sorption/desorption cycles.

Sorption kinetics of salt-in-porous-matrix composites: The effect of expanded natural graphite on cooling power

Sorption heat transformers and thermal energy storage systems are emerging technologies that utilize and store low-grade waste heat for heating and cooling applications. The performance of sorption systems is not only affected by systems’ operating conditions, and overall systems’ design but also by sorption material or composite parameters such as thermal diffusivity, composition, and pore structure, among others. In this study, CaCl2-based salt-in-porous-matrix composites of different compositions and coating thicknesses were synthesized. During synthesis, salt to silica gel and polyvinyl alcohol to silica gel ratios were fixed and the thermal additive (expanded natural graphite) to silica gel ratio was varied with care from 0 to 0.26 (or 0 to 20.5 wt.%, additive to silica gel ratio). The thickness of samples varied from 2.3 to 8.3 ± 0.1 mm. The composites were characterized by a transient plane source (thermal conductivity and thermal diffusivity), nitrogen adsorption porosimetry (specific surface area and total pore volume), and thermogravimetric sorption analysis (water sorption equilibrium) methods. A custom-built gravimetric large pressure jump (G-LPJ) testbed was used to study water sorption kinetics (water uptake vs. time) for selected samples. The thermal conductivity and diffusivity of the studied composite samples have shown significant enhancements, e.g., 240% (0.11 W/(m·K) vs. 0.37 W/(m·K)) and 310% (0.21 mm2/s vs. 0.87 mm2/s), respectively, by adding 12.5 wt.% expanded natural graphite (additive to silica gel ratio is 0.14) as a thermally conductive additive (additive to silica gel ratio) because of thermal percolation effect. This ratio of expanded natural graphite to silica gel was found to be optimal for studied composition. The results indicate that sorption composites with higher thermal diffusivity offer notably higher specific cooling power and improved sorption kinetics, compared to the composites without expanded natural graphite of the same thickness (850 W/kg vs. 480 W/kg at 70% water conversion for samples with thickness of 5.3 mm).

Investigating the synergetic effect of tungsten oxide doping into the 1,3-dicarbonyl moiety grafted chitosan and phytic acid impregnated sodium alginate for efficient U(VI) adsorption

In this work, chemical modification of the chitosan with ethyl acetoacetate was performed through a base-catalyzed reaction in which epichlorohydrin facilitated the insertion as well as nucleophilic substitution reaction to graft the 1,3-dioxo moiety across the linear chains of the base biopolymer to establish specificity and selectivity for U(VI) removal. The modified chitosan (EAA-CS) was intercalated into phosphate rich alginate matrix (PASA). Later on, the WO3-doped composites with different WO3 to PASA mass ratio were prepared and characterized using FTIR, XPS, SEM-EDS, XRD, and elemental mapping analysis. WO3 significantly contributed to chemically stable inorganic-organic composites with improved porous texture. Among the prepared composites, MCPS-3 microspherical beads, having mass ratio of 30.0 % w/w, exhibited excellent sorption capacity for U(VI) at an optimal pH 4.5. The successful U(VI) sorption was validated by the existence of two U4f peaks at 392.25 and 381.36 eV due to U4f5/2 and U4f7/2 sub-peaks with an intensity ratio of 3:4, respectively. Batch mode sorption kinetics followed pseudo-second-order rate equation (R2 ≈ 0.99, qe,th ≈ 116.88 mg/g, k2 = 0.86 × 10−4 g/mg.min−1) and equilibrium sorption data aligns with Langmuir (R2 = 0.99, qm = 343.85 mg/g at 310 K and pH = 4.5, KL = 2.00 × 10−2 L/mg) and Temkin models (R2 ≈ 0.99). Thermodynamic parameters ΔHo (30.51 kJ/mol), ΔSo (0.19 kJ/mol.K) and ΔGo (−25.64, −26.89, and − 27.91 kJ/mol) at 298, 305, and 310 K, respectively, suggested that the uptake process is feasible, endothermic and spontaneous. Based on these findings, it is reasonable to conclude that MCPS-3 could be a better hydrogel-based biomaterial for appreciable uranium recovery.

The Use of Beech Bark (Latin: Fagus sylvatica) and Birch Bark (Latin: Betula pendula Roth) for the Removal of Cationic Dyes from Aqueous Solutions

The aim of this work was to determine the sorption capacity of the cationic dyes Basic Red 46 (BR46) and Basic Violet 10 (BV10) on the prepared sorbents: beech bark (BBe) and birch bark (BBi). Two fractions of bark were used in the research: fine (2–3 mm) and coarse (4–5 mm). The carried out tests made it possible to determine the influence of the pH value on the sorption efficiency, the sorption equilibrium time and the maximum sorption capacity of the two tested sorbents. The Langmuir model and the Freundlich model were used to describe the obtained experimental data. Beech and birch barks are effective sorbents for cationic dyes; however, the efficiency of dye sorption on both bark sorbents depends on the type of cationic dye. According to the obtained data, beech and birch bark sorbents showed higher sorption efficiency for Basic Red 46 than for Basic Violet 10. The pH correction was a necessary condition for sorption, and the sorption pH value for the cationic dyes Basic Red 46 and Basic Violet 10 was be determined individually for each dye. The most favourable pH value for the sorption of the BR46 dye on the beach and birch bark sorbents was pH = 6, while for the dye BV10, it was pH = 3. The sorption equilibrium time for Basic Red 46 was 300 min and for Basic Violet 10–240 min. The fine fraction of beech bark had the highest sorption capacity for both BR46 (128.45 mg/g dry matter) and BV10 (18.07 mg/g dry matter).

Assessment of the Detoxification Potential of Modified Biochar from Annona senegalensis Stem Bark on Cr6+ and Cu2+ in Aqueous Solution: An Equilibrium, Kinetic and Thermodynamic Studies

Background: Environmental contamination of the air, water, soil, and food has become a threat to the continued existence of many plant and animal communities in the ecosystem. The chemically activated stem bark of Anonna senegalensis was examined for equilibrium sorption. Methods: This study aimed to assess the adsorption of Cr6+ and Cu2+ onto Annona senegalensis carbon (ASC) according to the following parameters: pH, solution temperature, starting metal ion concentration, agitation duration, dose of adsorbent, particle size, and carbonization temperature using a simultaneous batch adsorption method. Pseudo-first order, pseudo-second order, intra-particle diffusion kinetic, Freundlich, Langmuir, Temkin, and Dubinin-Radushkevich isotherm models were all fitted using the equilibrium sorption data that were produced. Thermodynamic parameters of the adsorption studies were also evaluated. Results: The physicochemical analysis of ASC showed ash content of 7.21 ± 0.02%, moisture content of 11.73 ± 0.29%, and porosity of 0.99 ± 0.08 with bulk density of 0.18 g/cm3. The heavy metalloaded scanning electron microscope (SEM) micrograph showed a filled pit, and the XRD diffractogram, as well as FTIR spectra, revealed peaks that were different from the raw spectra, implying functionalization. The sorption data gave optimum conditions of the adsorption process to be pH of 6, agitation time of 88 minutes, adsorbent dose of 2.5 g/g, initial metal ion concentration of 5 mg/L, temperature of 30°C, particle size of 0.154 mm and carbonization temperature of 400°C. Conclusion: The Langmuir isotherm was found to give the best-fit conformation of all the models based on superior R2 (R2 ≥0.99). Dubinin-Radushkevich proved the mechanism to be physisorption. The pseudo-second-order kinetic model best fits the data with R2 of 0.998 and 0.986 for Cr6+ and Cu2+. Thermodynamic results of the study revealed that ΔHᵒ for Cr6+ and Cu2+ were 32.78 and 27.14 KJ/mol and are all positive, implying an endothermic process and confirming the physisorption mechanism. The entropy change, ΔSᵒ, was also positive, revealing a high degree of disorderliness at the sorbate/sorbent interphase. The standard Gibbs free energy, ΔGᵒ, were all negative, showing spontaneity and feasibility.

Simulation of a zeolite thermochemical heat storage reactor: Impact assessment of isotherm model selection

Efficient modeling of thermochemical heat storage reactors is required to predict their performance in various operating conditions and optimize their design. Such modeling necessitates an accurate description of the properties of storage materials, which is still challenging to this day. This paper specifically investigates the influence of the choice of the sorption isotherm model. To this aim, the Langmuir, Dubinin-Astakhov (DA) and modified Brunauer-Emmet-Teller (BET) isotherm models are studied. The 1D model of an open fixed bed reactor based on the hydration and dehydration of zeolite 13X is presented. The model couples heat and mass transfer and uses the linear driving force approximation. Experimental investigations are also performed to characterize the sorption equilibrium of the material, its adsorption kinetics at the reactor scale and the resulting heat storage performance. The model is validated simultaneously on the basis of mass and of heat transfer measurements (i.e., breakthrough and temperature curves).The BET isotherm is shown to be the most relevant for the description of water adsorption on zeolite 13X because it considers multilayer adsorption. It fits the experimental isotherm best. At the reactor scale, the modified BET model also provides the best results, closely followed by the DA model. Still, for consistent predictions, the characterization of the chosen sorbent (i.e., the experimental data used to correlate the isotherm model or the heat of sorption) is of utmost importance and the initial water loading must be adequately specified.