Equilibrium Sorption Research Articles

Microheterogeneous Triplet Oxidation of Hydrophobic Organic Contaminants in Dissolved Black Carbon Solutions under Simulated Solar Irradiation.

Dissolved black carbon (DBC) is proven to accelerate the triplet-mediated photodegradation of hydrophobic organic contaminants (HOCs). However, its photosensitization mechanisms are not clear. In this study, five HOCs including 2,4,6-trimethylphenol, N,N-dimethylaniline, 17β-estradiol, 17α-ethinylestradiol, and bisphenol A were selected as model compounds to explore the triplet-mediated phototransformation of HOCs in illuminated DBC solutions. All five HOCs presented high organic carbon-water partition coefficient (KOC) values in DBC solutions, indicating the strong sorption capacity of DBC for HOCs. When reaching sorption equilibrium, the apparent pseudo-first-order rate constants of HOCs vs log[DBC] were well fitted with a sorption-enhanced phototransformation model (R2 > 0.98). Using the sorption-enhanced phototransformation model, the degradation rates of HOCs determined at intra-DBC (kDBC,HOCs') were 1-2 orders of magnitude higher than those observed in aqueous bulk solution (kHOCsaq). Moreover, typical triplet quenchers (2,4,6-trimethylphenol and oxygen) exhibited a microheterogeneous quenching effect on the triplet-mediated photodegradation of 17β-estradiol. Therefore, our results suggested that HOCs underwent a microheterogeneous photooxidative degradation process in DBC solutions. Furthermore, a sorption-enhanced phototransformation mechanism was proposed to elucidate the microheterogeneous photooxidative behavior of HOCs in DBC solutions. This study provides new insights into the fate and transport of HOCs in aquatic environments.

Modeling the sorption of Ni(II) and Zn(II) by Mn oxide-coated sand: Equilibrium and kinetic approaches.

The behavior of metal cations in oxide-dominated systems is controlled by sorption reactions, which in turn depend on pH. Descriptions of such reactions are of interest for contaminant monitoring or remediation efforts; however, widely used isotherms such as Freundlich or Langmuir neglect the effect of pH and are therefore limited in their applicability. Two pH-dependent isotherms and their kinetic analogs were developed and evaluated regarding their ability to describe equilibrium and time-dependent sorption of Ni and Zn by Mn oxide-coated sand (MOCS). The sorption of Ni and Zn by MOCS at pH 4.0, 5.5, and 7.0 was investigated using batch equilibration and stirred-flow techniques. The affinity of MOCS for either metal cation was highly pH dependent, with greater affinity at higher pH. Both isotherms described the batch data well. Flow interruption during stirred-flow experiments indicated that chemical nonequilibrium existed between solution and sorbed phases of both Ni and Zn and that such nonequilibrium was greater with increasing pH. Both kinetic models provided good descriptions of the solution data from stirred-flow experiments and correctly captured the effect of pH on chemical nonequilibrium. These models offer simple alternatives to surface complexation approaches and are expected to be easily applied to describe equilibrium and time-dependent sorption of a wide range of metal cations by variably charged minerals or oxide-coated media.

A computational pipeline to generate a synthetic dataset of metal ion sorption to oxides for AI/ML exploration

The charged mineral/electrolyte interfaces are ubiquitous in the surface and subsurface–including the surroundings of the geological disposal sites for radioactive waste. Therefore, understanding how ions interact with charged surfaces is critically important for predicting radionuclide mobility in the case of waste leakage. At present, the Surface Complexation Models (SCMs) are the most successful thermodynamic frameworks to describe ion retention by mineral surfaces. SCMs are interfacial speciation models that account for the effect of the electric field generated by charged surfaces on sorption equilibria. These models have been successfully used to analyze and interpret a broad range of experimental observations including potentiometric and electrokinetic titrations or spectroscopy. Unfortunately, many of the current procedures to solve and fit SCM to experimental data are not optimal, which leads to a non-transferable or non-unique description of interfacial electrostatics and consequently of the strength and extent of ion retention by mineral surfaces. Recent developments in Artificial Intelligence (AI) offer a new avenue to replace SCM solvers and fitting algorithms with trained AI surrogates. Unfortunately, there is a lack of a standardized dataset covering a wide range of SCM parameter values available for AI exploration and training–a gap filled by this study. Here, we described the computational pipeline to generate synthetic SCM data and discussed approaches to transform this dataset into AI-learnable input. First, we used this pipeline to generate a synthetic dataset of electrostatic properties for a broad range of the prototypical oxide/electrolyte interfaces. The next step is to extend this dataset to include complex radionuclide sorption and complexation, and finally, to provide trained AI architectures able to infer SCMs parameter values rapidly from experimental data. Here, we illustrated the AI-surrogate development using the ensemble learning algorithms, such as Random Forest and Gradient Boosting. These surrogate models allow a rapid prediction of the SCM model parameters, do not rely on an initial guess, and guarantee convergence in all cases.

Development and characterization of DTMS treated nettle fiber nonwovens for oil spill removal applications

In this work, nonwoven oil sorbent from nettle fiber was developed by changing the hydrophilic surface of nettle fiber to a hydrophobic surface by dodecycltrimethoxysialne (DTMS) treatment. Change in the surface structure of the fiber due to DTMS treatment was confirmed by SEM analysis. Fourier transform infrared analyses showed clear evidence of successful incorporation of DTMS on nettle fiber. The oil sorption capacities of diesel oil and crude oil were 31.39 and 41.89 g/g, respectively, which were found to be considerably higher than commercial oil sorbents. The pseudo first order and pseudo second order kinetic equations were employed to obtain the sorption rate constants and equilibrium sorption capacity. The results showed that the process fits the pseudo second-order kinetic model better for oil sorption than the pseudo first-order kinetic model. Also, the sorption capacities of the unmodified and modified samples were estimated by analyzing the isotherm data using Langmuir and Freundlich adsorption isotherm models. The results show that fitting via the Langmuir isotherm model produced a higher correlation coefficient than fitting via the Freundlich isotherm model. DTMS treated nettle nonwoven fabrics also showed good buoyancy characteristics under both static and dynamic conditions. Due to high oil sorption ability, reusability, and environmental responsiveness, the developed nonwoven oil sorbent can be considered as a potential substitute for organic synthetic fiber for oil spill removal applications.

SORPTION OF CADMIUM, LEAD, AND CHROMIUM (VI) BY CELLULOSIC COMPLEXES OF ARCTIC BROWN ALGAE

The purpose of this work is to establish the mechanism of sorption of heavy metal ions (Cd, Pb, and Cr (VI)) by cellulose complexes (CC) of the arctic brown algae Laminaria digitata and Saccharina latissima. These complexes are fibrous mesoporous materials with active sorption centers -COOH, -OH, and -NH2 and a developed surface, which makes them potentially effective preparations for the enterosorption removal of heavy metal ions. The kinetics and thermodynamics of sorption have been studied as well as the influence of the acidity on the sorption capacity. It has been established that the sorption rate is highest during the first minutes of contact between the two phases; the sorption equilibrium is reached by 60 min. According to the sorption enthalpy values, temperature has a positive effect on sorption (endothermic process), with a maximum sorption capacity at 37 °C. Optimal pH of the medium: 5-6 for cadmium and lead, and 2 for chromium (VI), which indicates the possibility of using this material in a wide range of medium acidity, corresponding to the conditions of the human gastrointestinal tract. The results obtained indicate a high prospect of using CC as an effective enterosorbent for health preservation.

Developing a Chromatographic 99mTc Generator Based on Mesoporous Alumina for Industrial Radiotracer Applications: A Potential New Generation Sorbent for Using Low-Specific-Activity 99Mo.

The commercial low-pressure column chromatographic 99Mo/99mTc generator represents a reliable source of onsite, ready-to-use 99mTc for industrial applications. These generators use fission-produced 99Mo of high specific activity, posing serious production challenges and raising proliferation concerns. Therefore, many concepts are aimed at using low-specific-activity (LSA) 99Mo. Nonetheless, the main roadblock is the low sorption capacity of the used alumina (Al2O3). This study investigates the feasibility of using commercial alumina incorporated with LSA 99Mo to develop a useful 99Mo/99mTc generator for industrial radiotracer applications. First, the adsorption profiles of some commercial alumina sorbents for LSA 99Mo were tested under different experimental conditions. Then, the potential materials to develop a 99Mo/99mTc generator were selected and evaluated regarding elution yield of 99mTc and purity. Among the sorbents investigated in this study, mesoporous alumina (SA-517747) presented a unique sorption-elution profile. It demonstrated a high equilibrium and dynamic sorption capacity of 148 ± 8 and 108 ± 6 mg Mo/g. Furthermore, 99mTc was eluted with high yield and adequate chemical, radiochemical, and radionuclidic purity. Therefore, this approach provides an efficient and cost-effective way to supply onsite 99mTc for radiotracer applications independent of fission-produced 99Mo technology.

Synthesis and characterization of hematite biocomposite using cassava starch template for aqueous phase removal of fluoride

In this study, facile synthesis of α-Fe2O3 biocomposite was mediated by cassava starch as a soft template. Batch mode evaluated its sorption behavior for fluoride removal from aqueous media. Characterization studies using analytical techniques confirmed the existence of porous α- Fe2O3 biocomposite with heterogeneous surfaces having a varied affinity for fluoride. The sorption process was optimized using central composite design (CCD) in response surface methodology (RSM) with a good model prediction (R2 = 0.9066). A study of the interaction effect showed the synergy of process variables on fluoride removal with the result's intensity indicated by the nature of contour plot curvature. Based on the RSM optimization, an optimum fluoride removal efficiency of 85.26 % can be achieved at an initial fluoride concentration of 55 mg/L, α- Fe2O3 biocomposite dose of 0.55 g, pH of 7.5, and contact time of 95 min. Sorption equilibrium data were well modeled by Freundlich isotherm (0.9916), indicating multilayer sorption on a heterogeneous surface of the sorbent with a varied affinity for fluoride. Presence of co-existing anions reduced fluoride removal efficiency in the order PO43− > HCO3− > SO42− > NO3− > CƖ− . At the same time, its kinetics was better modeled by pseudo-second-order kinetics (R2 = 0.9764), showing that the sorption process is rate-limiting. The sorption thermodynamics study showed that the process was spontaneous, exothermic, and entropy-driven physisorption. Hence, the results signify that the green synthesized α- Fe2O3 biocomposite could be a potential sorbent for sustainable defluoridation.

Optimization and mechanisms of rapid adsorptive removal of chromium (VI) from wastewater using industrial waste derived nanoparticles

Nowadays, the existence of metal ions in the environment like chromium (VI) is of significant worry because of its high toxicity to many life forms. Therefore, in this study, an inexpensive and eco-friendly nano-adsorbent was produced from the waste of drinking water industry for effective elimination of Cr (VI) from wastewater. The mineralogical and morphological characterization and compositions of the bulk and nano- adsorbents were performed. The adsorption capabilities of nWTRs for Cr(VI) under different experimental conditions of adsorbent dosage, time, Cr (VI) concentration, solution pH, and competitive ions were investigated. The nWTRs adsorbent exhibits very rapid adsorption potential (92%) for Cr (VI) within the first 15 min. Langmuir model showed high predictive capability for describing Cr (VI) sorption equilibrium data. The estimated maximum sorption capacity (qmax) of nWTRs and bWTRs was found to be 40.65 mg g−1 and 2.78 mg g−1 respectively. The sorption kinetics data of Cr (VI) were perfectly fitted to the model of second-order kinetics. High immobilization capability of nWTRs for sorbed Cr (VI) is evident as most of adsorbed Cr (VI) was associated with the residual fraction. The nWTRs efficiency of Cr (VI) removal from wastewater using batch and column techniques were 98.12 and 96.86% respectively. Electrostatic interactions, outer sphere complexation and pore filling are the main mechanisms suggested for binding of Cr(VI) with functional groups of nWTRs. This study demonstrates that the green low-cost nWTRs have the potential to decontaminate industrial wastewater effluents containing Cr (VI).

Sorption and post-sorption performances of Cd, Pb and Zn onto peat, compost and biochar

The development of waste-derived sorbents to immobilize potentially toxic elements (PTEs) is a promising strategy, contributing to the achievement of sustainable development goals (SDGs). Therefore, this study aimed to assess the sorption performance of cadmium (Cd), lead (Pb) and zinc (Zn), comparing sorbents derived from organic fraction of municipal solid waste (composts and biochars) with peat. The physicochemical characterization, equilibrium of sorption, post-sorption analyzes and bioaccessibility were investigated. Results showed that the sorbents have distinct characteristics; however, each material have their particularities favorable to sorption. For instance, peat and composts have the highest cation exchange capacity (800–1100 mmolc kg−1), while biochar produced at 700 °C has the highest specific surface area (91.21 m2 g−1). The sorption equilibrium data revealed the actual sorption capacity and was well explained by the Freundlich and Langmuir isotherms and, in some cases, by the Dubinin-Radushkevich model. Post-sorption analyzes indicated the occurrence of several sorption mechanisms, driven by the physicochemical properties. Electrostatic interaction stood out for peat and compost. The FTIR spectrum for peat proved the complexation with oxygenated functional groups. The composts showed variations in the released cations (e.g. Ca2+ and K+), indicating cation exchange. Differently, for biochars, the XRD patterns showed that precipitation or coprecipitation seems to be one of the main mechanisms, especially for Cd and Pb. Regarding human bioaccessibility, the results of the gastric phase simulation (pH∼1.20) revealed lower percentages of Pb (33–81%) than Cd (91–99%) or Zn (82–99%), especially for the highest concentrations. Nevertheless, in numerical terms, all bioaccessible concentrations inspire care. In conclusion, among the sorbents, composts and biochars presented the best sorption performances and, therefore, have great potential for environmental applications. Furthermore, the bioaccessibility findings indicate that these assays, still little used in experiments with sorbents, are an important tool that should be better explored in the assessment of the environmental risk associated with contamination.

Efficient removal of europium radionuclides from natural and seawater using mesoporous carbon-based material

Liquid radioactive waste (LRW) presents the most significant environmental hazard due to its high aggregate activity and rapid distribution in the environment. The paper presents the structure and adsorption characteristics features of a new nanocomposite material namely mesoporous carbon (MPC). Characterization studies depicts that the material obtained consisted of bundles of carbon nanotubes coated with a uniform layer of porous carbon shell. The study on the MPC porous structure disclosed that the resulting material possess a combination of micro and mesopores with a predominant size of 1–6 nm and a specific surface area of 2360 m2 g−1. Adsorption characteristics of the MPC were studied using the sorption of 152Eu radionuclide from natural and seawater. Activated charcoal, coconut charcoal, and a gel-type strong-acidic sulfonic cation exchanger were used as reference materials. The synthesized MPC was found to have the distribution coefficients (Kd) of 152Eu over 3 × 106 cm3 g−1, which was 1–3 orders of magnitude higher than for the reference sorbents. The kinetics study of the 152Eu sorption on the MPC showed that the sorption equilibrium was attained in 5 min, three times less than the activated charcoal. High adsorption of MPC is associated with the colloidal of europium species on the developed surface of the carbon sorbent. Results conclude that the synthesized mesoporous carbon material makes a promising adsorbent for removing europium and other radionuclides, namely, cerium, lanthanum, zirconium, plutonium, and americium, from neutral solutions, where those radionuclides exist in either colloidal or pseudo colloidal form.

Can aged microplastics be transport vectors for organic micropollutants? – Sorption and phytotoxicity tests

Microplastics have been investigated over the last decade as potential transport vectors for other pollutants. However, the specific role of plastic aging, in which plastics change their characteristics over time when exposed to environmental agents, has been overlooked. Therefore, sorption experiments were herein conducted using virgin and aged (by ozone treatment or rooftop weathering) microplastic particles of LDPE – low-density polyethylene, PET – poly(ethylene terephthalate), or uPVC – unplasticized poly(vinyl chloride). The organic micropollutants (OMPs) selected as sorbates comprise a diversified group of priority substances and contaminants of emerging concern, including pharmaceutical substances (florfenicol, trimethoprim, diclofenac, tramadol, citalopram, venlafaxine) and pesticides (alachlor, clofibric acid, diuron, pentachlorophenol), analyzed at trace concentrations (each ≤100 μg L−1). Sorption kinetics and equilibrium isotherms were obtained, as well as the confirmation that the aging degree of microplastics plays a major role in their sorption capacities. The results show an increased sorption of several OMPs on aged microplastics when compared to pristine samples, i.e. the sorption capacity increasing from one or two sorbed substances (maximum 3 μg g−1 per sorbate) up to nine after aging (maximum 10 μg g−1 per sorbate). The extent of sorption depends on the OMP, polymer and the effectiveness of the aging treatment. The modifications (e.g. in the chemical structure) between virgin and aged microplastics were linked to the increased sorption capacity of certain OMPs, allowing to better understand the different affinities observed. Additionally, phytotoxicity tests were performed to evaluate the mobility of the OMPs sorbed on the microplastics and the potential effects (on germination and early growth) of the combo on two species of plants (Lepidium sativum and Sinapis alba). These tests suggest low or no phytotoxicity effect under the conditions tested but indicate a need for further research on the behavior of microplastics on soil-plant systems.

A new analytical model for transport of multiple contaminants considering remediation of both NAPL source and downgradient contaminant plume in groundwater

The contamination of groundwater aquifers by chlorinated solvents is a water-resource issue of great importance worldwide. Such contaminants are difficult to treat because they are often released as dense non-aqueous phase liquids (DNAPLs). Research shows that the application of remediation technologies to both the NAPL source and dissolved plume can lead to more efficient remediation, rather than to either alone. In these remediation efforts, analytical models that evaluate behavior and fate of contaminants do provide a better understanding of the performance of these remedial technologies. To the best of our knowledge, there exist no analytical model of simulating the plume migration of multiple contaminants with capabilities of accounting for both NAPL source and plume remediation simultaneously and different retardation for original chlorinated solvent contaminant and its degradation byproducts. In this study, we present a new analytical model for remediating both NAPL source and downgradient contaminant plume in groundwater at sites contaminated with chlorinated solvents and their degradation products with different retardation factors as well as considering both NAPL source and plume remediation simultaneously. A source model that accounts for the depletion of mass by the processes of dissolution or first-order decay reactions, corresponding with the removal or destruction of the source mass, is coupled to a plume reactive transport model. The source model is accounted for by relating source mass to the flux-averaged source discharge concentration through a power function. The developed analytical model considers 1-D advection, 3-D dispersion, first-order decay reactions and ingrowth as well as linear isothermal equilibrium sorption. The proposed analytical solution was derived through successive application of the Laplace transform in time and the double finite Fourier cosine transform regarding y and z. The correctness of the analytical model and its auxiliary FORTRAN computer program code are proved by showing excellent agreements between the simulated plume concentrations of all contaminants obtained from the derived analytical model and from a semi-analytical model available in the literature. Application of the proposed analytical solutions illustrates that the use of identical retardation factors for all contaminants may lead to underestimation or overestimation of the mobility of the contaminants, in cases when the retardation factors of the individual contaminants are greatly different from the identical retardation factor value adopted in all contaminants. From the experiments on six scenarios corresponding six remedial treatments, we found out that both the enhanced source decay and partial removal of source mass are main controlling factors at reducing the concentrations of all the contaminants, whereas plume decay leads to effective reduction in the concentrations of PCE, however, rather it causes unfavorable increases of the concentrations of the degradation byproducts.Ultimately, the developed model is used to better understand the impacts of various possible combinations of remedial efforts and management decisions on remediation of the subsurface contamination and quantify the benefit of a certain remediation decision.

Physical and flammability properties of treated sugar palm fibre reinforced polylactic acid composites

The aim of this study is to determine the physical properties and flammability of a composite of polylactic acid (PLA) reinforced with chemically treated sugar palm fibre (SPF). Seven different SPF parameters have been evaluated: untreated, alkaline treatment with three alkaline solution concentrations of 4, 5 and 6% and 50 mL of benzoyl chloride treated SPFs at three different soaking times (10, 15 and 20 min). 30 wt.% of SPF reinforced with 70 wt.% PLA composites have been prepared by using a Brabender plastograph mixer and compression moulding. The 6% alkaline treated SPF/PLA composites resulted in the lowest water absorption and thickness swelling of 7.09% and 4.69%, respectively. These composites reached the lowest ‘maximum equilibrium sorption’ value [Formula: see text] of 5.94%. Benzoyl chloride treated SPF/PLA composites (for 15 min soaking) exhibited the highest density of 1.34 g/cm3 and void content had reduced from 14% to 0.7%. The flammability of the c omposites is characterised by the horizontal UL-94 and vertical UL-94V burning test. Through the flammability test, the outcomes reveal that treated SPF/PLA composites are highly fire-resistant, except for 6% alkaline treated SPF/PLA composites. Morphologies of the composites have been analysed using the scanning electron microscopy. The results revealed that the maximum surface roughness and fewer voids were accomplished after 6% alkaline treatment of SPF. The novel treated SPF/PLA composites are appropriate for the application of automobile components.

Kinetic Study of Malathion Biosorption Using Dry Cells of an Isolated Bacillus sp. S14

Pesticides Pollutants are a major ecological issue because they kill organisms that are not their intended targets. Even in trace amounts, their diversity, toxicity, and durability are harmful to natural systems. High levels of malathion in the air, water, or food can make breathing difficult, tighten the chest, cause nausea, cramps, diarrhoea, watery eyes, impaired vision, salivation, perspiration, headaches, and even cause death. Two kinetic models—pseudo-1st- and pseudo-2nd order were used to examine the sorption isotherm of malathion onto Bacillus sp. S14, and they were fitted using non-linear regression. The pseudo-1st order model was found to be the best model by statistical analysis based on root-mean-square error (RMSE), adjusted coefficient of determination (adjR2), bias factor (BF), accuracy factor (AF), corrected AICc (Akaike Information Criterion), Bayesian information criterion (BIC), and Hannan-Quinn information criterion (HQC). A kinetic study employing the pseudo-1st order model at 150 PPM yielded an equilibrium sorption capacity qe of 4.19 mg/g (95% confidence interval from 4.137448 to 4.257148) and a pseudo-1st-order rate constant, k1 of 0.53. (95 percent confidence interval from 0.510371 to 0.559508). Further analysis is required to give evidence for the chemisorption mechanism commonly associated with this kinetic.

Functionalized polyvinyl alcohol aerogel for efficient and selective removal of arsenite from aqueous matrices

The removal of arsenic (As) from wastewater and groundwater has become a critical environmental issue. In this study, a novel sorbent, dithiocarbamate-functionalized cross-linked polyvinyl alcohol (DFCPVA) aerogel was successfully developed to address this issue. The aerogel was analyzed for its ability to remove arsenite (AsIII) from aqueous matrices, and it showed excellent sorption performance for AsIII under both acidic and neutral conditions. The AsIII sorption efficiency of DFCPVA was not significantly hindered by competing metal ions present in the solution. The pseudo-second-order kinetic model described the sorption well, and the Langmuir model fit the equilibrium sorption isotherm more closely than the Freundlich model. It was anticipated that the sorption rate of AsIII by DFCPVA would be rapid, as equilibrium was established in 15 min. The maximum sorption capacity of DFCPVA was 535 µmol g−1, as determined by the isotherm study. Sorption experiments, Fourier transform infrared (FTIR) spectroscopy, and X-ray absorption spectroscopy (XAS) studies demonstrated that the sorption of AsIII by DFCPVA followed a chelation mechanism. The sorption capacity of DFCPVA was slightly decreased when stored at 40 ℃ for one month; however, the capacity was not reduced when it was stored in a refrigerator (i.e., cold condition).

Selective removal of uranium from an aqueous solution of mixed radionuclides of uranium, cesium, and strontium via a viable recyclable GO@chitosan based magnetic nanocomposite

This work reports the performance study of a new magnetite@graphene oxide@chitosan nanoadsorbent synthesized by using magnetite, graphene oxide, and chitosan for selective adsorption of uranium(VI) ions from an aqueous solution containing salts of uranium, cesium, and strontium ions. Detailed analysis was done to get an insight into the structural features, elemental composition, surface micromorphology of the synthesized nanoadsorbent by using different techniques like Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Energy-dispersive X-ray spectroscopy (EDX), Scanning electron microscopy (SEM), and High-resolution transmission electron microscopy (HR-TEM). Initial studies revealed that magnetite@graphene oxide@chitosan nanoadsorbent proved to be an efficient adsorbent for removing uranium ions (84.39 %), cesium (7.17 %), and strontium (8.44 %) from an aqueous solution of mixed radionuclides. Several batch experiments were conducted by varying effective parameters such as adsorbent mass, pH, contact time, initial adsorbate concentration, and temperature to deduce the best conditions for maximum removal of uranium selectively from a mixed radionuclide aqueous solution. Maximum U(VI) adsorption capacity was 504 mg/g in 30 min at a pH of 6 and room temperature. For the as-prepared adsorbent, the equilibrium sorption and sorption rate closely matched the Langmuir model and was well fitted in a pseudo-second-order kinetic model. Thermodynamic parameters for the adsorbent (ΔH 22.06 KJ/mol, and ΔG˂0) show that U(VI) sorption is an endothermic and spontaneous process. Furthermore, cyclic adsorption-desorption studies show that the adsorbent can be used gainfully even after 10 cycles with only a minor decrease in its removal efficiency (97.50–90 %). Extraction studies using 15 mg initial adsorbent dose suggest that (42–34.75 ppm) of U(VI) can be recovered per cycle from a 50 ppm uranium solution. Conclusively this can be a viable method for removal extraction dual application for U(VI) from water.

Hydrocarbon Sorption in Flexible MOFs-Part I: Thermodynamic Analysis with the Dubinin-Based Universal Adsorption Theory (D-UAT).

The analysis of empirical sorption equilibrium datasets is still vital to gain insights into material–property relationships as computational methods remain in development, especially for complex materials such as flexible MOFs. Therefore, the Dubinin-based universal adsorption theory (D-UAT) was revisited and evaluated as a simple visualization, analysis, and prediction tool for sorption equilibrium data. Within the theory, gas properties are normalized into corresponding states using the critical temperatures of the respective sorptives. The study shows theoretically and experimentally that the D-UAT is able to condense differences of sorption data visualized in reduced Dubinin plots to just three governing parameters: (a) the accessible pore volume, (b) the reduced enthalpy of sorption, and (c) the framework’s reduced free energy differences (in case of flexible behavior). This makes the theory a fast visualization and analysis tool, the use as a prediction tool depends on rough assumptions, and thus is not recommended.

Efficacy of heat-treated glycine max husks in crude oil removal from simulated and real contaminated waters: modeling, regeneration and reusability

The treatment of oil spilled water surfaces using raw glycine max husks (RGMH) and carbonized glycine max husks (CGMH) were reported. The sorbents were characterized by BET, TGA, FTIR and SEM techniques. The sorption of oil was by batch method. The experiment was performed at optimum conditions of pH (3), sorbent dose (0.1 g), oil concentration (8 g/L), time (90 min) and temperature (303 K). Equilibrium isotherm analysis showed that Langmuir model offered the best fit in both sorbents with higher regression (R2) and lower chi square (χ 2 ) in comparison with other models. Also, maximum monolayer sorption capacities of 3.47 and 4.35 g/g were achieved for RGMH and CGMH respectively. Kinetic study showed that the pseudo-second-order model fitted most in relation to other models and at sorption equilibrium time of 70 and 60 min for RGMH and CGMH respectively. The suitability of n-hexane for regeneration was established and the reusability after three successions of sorption-desorption analysis was comparatively better in CGMH. Also, the sorbents were utilized to remove oil not just from simulated but also real contaminated waters. Therefore, a realistic means of oil spill management has been provided.

Effective biosorption of Cu(II) using hybrid biocomposite based on N-maleated chitosan/calcium alginate/titania: Equilibrium sorption, kinetic and thermodynamic studies

In this research work, a hybrid biocomposite based on N-maleated chitosan, amino-thiocarbamate functionalised calcium alginate and anhydrous Titania nanoparticles (NMC-MCA-TiO2) was fabricated. The study involves the one pot facile synthesis of N-maleated chitosan and amino-thiocarbamate functionalised alginate under moderate conditions. Sorbent was conditioned in the form of hydrogel beads and characterized through FT-IR and SEM analysis. Newly grafted functional groups could act as potential chelating sites for enhanced Cu(II) sorption. Modified biopolymers were organo-functionalised which provided excellent support for immobilization of Titania nanoparticles (TiO2) as inorganic filler. Kinetic data illustrated the manifestation of intrinsic chemisorption instead of simple bulk/film diffusion. Equilibrium sorption data fitted well with Freundlich adsorption model (R2 ≈ 0.99) which designated the heterogeneous nature of sorbent. Maximum sorption capacity of biosorbent was found 192 mg/g at 298 K and pH = 6.0. Standard Gibbs free energy change ∆Go (−21.53, −21.97, and − 22.42 kJ/mol), standard enthalpy change ∆Ho (5.12 kJ/mol) and standard entropy change ∆So (0.09 kJ/mol K−1) values suggested that the sorption process to be spontaneous and endothermic. The sorbent 3NMC-MCA-TiO2 could be competitive candidate for economical and rapid adsorptive removal of Cu(II) from dilute contaminated liquids.

The Influence of Calendering on the Moisture Sorption Behavior of Electrodes for Lithium-Ion Batteries

Moisture is considered to be one of the most critical contaminants in Lithium-ion batteries (LIBs), as it impairs the electrochemical performance and poses high safety risks. To reduce the moisture in the cells below a critical level, electrodes and separators for LIBs need to be post-dried before cell assembly. However, the moisture adsorption, desorption and re-adsorption behavior of electrodes is defined by the chosen material system, the manufacturing route and the microstructure of the coatings. The microstructure, in turn, is significantly determined by the calendering step, which predominantly aims at increasing the specific density and consequently, the volumetric energy density of the electrode coatings. As the calendering step decisively changes the microstructure of the electrode coatings, it can be assumed that it accordingly must have an impact on the moisture sorption behavior of the electrodes during further processing. The sorption equilibrium of electrode coatings mainly depends on the surface of the particles, the sorption in the binder system and, to a certain extent, on the capillary condensation. LIB cathodes are most commonly manufactured with polyvinylidene fluoride (PVDF) as a binder. PVDF is very hydrophobic, which is why we can assume that the moisture sorption of these cathodes is fundamentally determined by sorption on the surface and, to a lesser degree, on capillary condensation. In contrast, the moisture sorption of LIB anodes produced with a carboxymethyl cellulose/styrene-butadiene (CMC/SBR) binder system is assumed to be mainly defined by moisture sorption of the very hygroscopic binder system. Changes to the surface should only have a small influence.Hence, it is expected that the impact of the calendering step on the moisture sorption is far more pronounced for the cathodes than for the anodes. To prove this theory and analyze the impact of the calendering step in detail, the influence of different densities on the moisture sorption behavior, microstructural properties and electrochemical performance of NCM622 cathodes with PVDF binder and graphite anodes with CMC/SBR binder system is investigated. Therefore, the electrodes are calendered to three different densities in dry room atmosphere, post-dried in vacuum and assembled into coin cells.Focusing on the cathode, after calendering an increasing moisture content is observed for increasing density, measured by Karl Fischer Titration and proved by sorption measurements. Although post-drying significantly reduces the moisture content of the cathodes, the course trend is still the same with the lowest moisture at a low density and the highest moisture at high density. Via SEM analysis, a rising amount of active material particle cracks is detected with increasing density. BET measurements show that this phenomenon is accompanied by an increasing specific surface area. Hence, the increased moisture uptake of cathodes with higher density can be mainly traced back to their higher specific surface area, caused by particle cracking during calendering. Further analytics display that the chosen post-drying parameters lead to an increase of cohesion strength for all cathodes, whereas the influence on the electrical resistance depends on the density of the cathode. The electrochemical testing shows that the increased electrochemically active surface area of the cathodes with higher density results in a good performance during formation and at lower C-rates. However, the reduced porosity lowers the ionic conductivity and leads to capacity losses at higher C-rates. [1]Concerning the anode, as expected, the influence of the calendering step on the moisture sorption is much smaller. Although the specific surface area of the anodes also increases with rising density, a significant increase of moisture is not observed. Hence, the influence of the changes in microstructure is overlapped by the hygroscopic binder system of the anodes. Post-drying increases the adhesion strength of all anodes, whereas the electrical resistance seems to decrease to a small degree. The electrochemical analysis of the anodes shows a deterioration of performance with increasing density, due to limitations of the ionic conductivity at lower porosities.Altogether, we will show that for NCM622 cathodes with PVDF binder, the moisture uptake increases with increasing density after calendering, whereas there is no change in moisture content at graphite anodes with CMC/SBR binder system. These findings make an important contribution to a better process understanding and consequently, improved moisture management along the entire process chain of Lithium-ion batteries.[1] F. Huttner, A. Diener, T. Heckmann, J. C. Eser, T. Abali, J. K. Mayer, P. Scharfer, W. Schabel, A. Kwade, Increased Moisture Uptake of NCM622 Cathodes after Calendering due to Particle Breakage, J. Electrochem. Soc. 168 090539 (2021), doi.org/10.1149/1945-7111/ac24bb, CC BY 4.0