Sorption Behavior Research Articles

Selectivity of β-Cyclodextrin Polymer toward Aquatic Contaminants: Insights from Ultrahigh-Resolution Mass Spectrometry of Dissolved Organic Matter.

Selectivity in solid-phase extraction (SPE) materials has become increasingly important for analyte enrichment in sensitive analytical workflows to alleviate detrimental matrix effects. Molecular-level investigation of matrix constituents, which are preferentially extracted or excluded, can provide the analytical chemist with valuable information to learn about their control on sorbent selectivity. In this work, we employ nontargeted Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) to elucidate the molecular chemodiversity of freshwater-derived dissolved organic matter (DOM) extracted by the selective model sorbent β-cyclodextrin polymer (β-CDP) in comparison to conventional, universal SPE sorbents (i.e., Oasis HLB, Supel-Select HLB, and LiChrolut EN). Statistical analysis of MS data corroborated the highly selective nature of β-CDP by revealing the extracted DOM spectra that are most dissimilar to original compositions. We found that its selectivity was characterized by pronounced discrimination against highly oxygenated and unsaturated DOM compounds, which were associated with the classes of lignin-like, tannin-like, and carboxylic-rich alicyclic molecules. In contrast, conventional sorbents excluded less highly oxygenated compounds and showed a more universal extraction behavior for a wide range of DOM compositional space. We lay these findings in a larger context that aids the analyst in obtaining an a priori estimate of sorbent selectivity toward any target analyte of interest serving thereby an optimization of sample preparation. This study highlights the great value of nontargeted ultrahigh-resolution MS for better understanding of targeted analytics and provides new insights into the selective sorption behavior of novel sorbents.

Water Vapor Sorption Kinetics of Beech Wood Modified with Phenol Formaldehyde Resin Oligomers

Beech is an important tree species in Europe. This study aimed to elucidate the influence of four molecular weights of phenol formaldehyde (PF) resin (266, 286, 387, and 410 g/mol) on the sorption behavior of unmodified and modified beech wood samples using a dynamic vapor sorption (DVS) apparatus. The variations in the environmental relative humidity and moisture content (MC) of the samples were recorded, and the DVS isotherms were plotted from the equipment. During the sorption process, the MC of the modified samples decreased in comparison to that of the unmodified samples, and both apparently decreased with the increasing molecular weight of the PF resin. The DVS isotherm hysteresis plot illustrated a reduction in sorption hysteresis for the modified wood with varying PF resins compared to the unmodified samples. Based on the DVS isotherm adsorption and desorption plots, the decrease in the equilibrium of the MC can be attributed to there being fewer sorption sites in the modified samples, which exhibited the lowest hygroscopicity. Overall, the moisture sorption mechanism for both types of samples was clarified, highlighting a clear correlation between the molecular weight of the applied PF resin and its influence on moisture sorption behavior.

Sorption behaviour of atrazine on agricultural soils of different characteristics: equilibrium and kinetics studies

Sorption behaviour of atrazine on agricultural soils of different characteristics: equilibrium and kinetics studies

Polyethersulfone membrane as a single-phase passive sampler: Evaluation of the sampling performance for emerging contaminants in water

The use of polyethersulfone (PES) membranes as single-phase passive samplers was tested for the detection of nine emerging contaminants (three estrogens, bisphenol-A, triclosan and four UV-filters). The sorption and kinetics onto PES were assessed using tap water and synthetic seawater. To obtain a reliable sampling procedure, the accuracy of the extraction method was evaluated in terms of recovery, matrix effect and precision. The recoveries ranged between 66 % and 85 %, while matrix effects resulted acceptable (58 %−126 %), even in field conditions. The affinity of the target compounds for the sorbent was first evaluated by PES-water partition coefficients. Afterwards, several calibrations were performed to study the uptake kinetics, also considering the effect of the flow regime. A linear uptake during a 96-hour deployment was observed for UV-filters and triclosan, allowing the estimation of their sampling rates, which ranged between 0.036 and 0.066 and 0.05–0.10 L/d cm−2 in tap water and synthetic seawater, respectively. Instead, an apparent equilibrium was reached for the estrogens and bisphenol-A within 24 h. To better understand the sorption behavior, Principal Component Analysis was implemented by considering several physico-chemical parameters of the analytes. This approach permitted to identify three groups which reflect the different sorption mechanisms. Finally, a 4-day field exposure of PES was carried out in an Italian harbor along with the collection of spot samples, treated by classical SPE. Five out of the nine analytes were detected in the passive sampler, while only three by classical spot sampling. For the three UV-filters detected using passive sampling, it was possible to evaluate the time-weighted average concentrations, ranging between 0.13 and 9 ng/L. The good performances of this passive sampler make it promising for the short-term monitoring of a range of contaminants in potentially impacted seawater, with enhanced sensitivity compared to classical spot sampling.

In-situ gas contents of a multi-section coal seam in Sydney basin for coal and gas outburst management

The gas content is crucial for evaluating coal and gas outburst potential in underground coal mining. This study focuses on investigating the in-situ coal seam gas content and gas sorption capacity in a representative coal seam with multiple sections (A1, A2, and A3) in the Sydney basin, where the CO2 composition exceeds 90%. The fast direct desorption method and associated devices were described in detail and employed to measure the in-situ gas components (Q1, Q2, and Q3) of the coal seam. The results show that in-situ total gas content (QT) ranges from 9.48 m3/t for the A2 section to 14.80 m3/t for the A3 section, surpassing the Level 2 outburst threshold limit value, thereby necessitating gas drainage measures. Among the gas components, Q2 demonstrates the highest contribution to QT, ranging between 55% and 70%. Furthermore, high-pressure isothermal gas sorption experiments were conducted on coal samples from each seam section to explore their gas sorption capacity. The Langmuir model accurately characterizes CO2 sorption behavior, with fit coefficients (R2) greater than 0.99. Strong positive correlations are observed between in-situ gas content and Langmuir volume, as well as between residual gas content (Q3) and sorption hysteresis. Notably, the A3 seam section is proved to have a higher outburst propensity due to its higher Q1 and Q2 gas contents, lower sorption hysteresis, and reduced coal toughness f value. The insights derived from the study can contribute to the development of effective gas management strategies and enhance the safety and efficiency of coal mining operations.

Study on the removal of Rhodamine B of Iron(III)-dicarboxylic framework/graphene nanoplatelets composites

In this study, Iron(III)-dicarboxylic framework/graphene nanoplatelets (Fe-BDC/GNPs) composites were synthesized by the ultrasonic method in a water/ethanol mixture solvent. As-prepared composite materials were characterized by XRD, SEM, BET, and laser light scattering techniques. The sorption behaviors of Rhodamine B by the prepared material were studied. The results showed that the material could effectively remove chromogenic organic compounds (RhB) by the adsorption process. The prepared Fe-BDC/GNPs composite revealed high adsorption toward RhB with removal percentage of higher 90% at an RhB initial concentration of 10 ppm after 2 hours. The Freundlich isotherm was more suitable than the Langmuir isotherm and Temkin isotherm for the adsorption process of Rhodamine B onto the synthesized material with R2 = 0,9955. The analytical outputs also revealed that the adsorption kinetics were more accurately represented by the second-order model as both R2 = 0,9974 and qe,cal was approximate to qe,exp.

Investigation of the Transport and Sorption Behaviors of Atrazine and Metribuzine herbicides in Agricultural Soils of the Gölcük Plain

Pestisitler zararlı organizmaları engellemek, kontrol altına almak, ya da zararlarını bertaraf etmek için kullanılan tarım ilaçlarıdır. Dünyada 3 milyon tona, ülkemizde 30 bin tona ulaşan pestisit tüketimi ürün verimliliği açısından yararlı olsa da aşırı dozda ve bilinçsiz kullanımı neticesinde gıdalarda, toprak, su ve havada insan ve hayvan sağlığı için tehlike arz etmektedir. Dünyada kullanılan tarım ilaçlarının dağılımında herbisitler % 47 ile ilk sırada yer alırken, bunu % 29 ile insektisitler izlemekte, fungisitlerin ise % 19’luk bir payı bulunmaktadır. Atrazin ve metribüzin en çok kullanılan triazin herbisit türlerinden olup yabancı otlara karşı mücadele ederek ürün verimliliğini artırmayı amaçlamaktadır. Bu herbisitler, ulusal ve uluslararası kullanım sonucunda içme sularında ve su ortamında kirlilik açısından sorun teşkil etmektedir. Çevrede geniş alanda kullanımı ve dayanımından ötürü bu tür bileşiklerin taşınımı ve davranışı oldukça önemli olup özellikle Kocaeli civarında literatürde yapılmış herhangi bir çalışma bulunmamaktadır. Yapılacak çalışmanın amacı, atrazin ve metribüzin herbisitlerinin Gölcük Ovası civarındaki farklı türdeki tarım topraklarında tutunma ve taşınma davranışlarının incelenmesidir. Bu çalışma kapsamında bir seri kolon deneyleri gerçekleştirilmiştir. Atrazin ve metribüzin herbisitlerinin fiziksel ortama olan tutunma-geri bırakma davranışının bu tür kirleticilerle kirlenmiş toprakların risk değerlendirmesi için önemli etkileri olup, bu toprakların düzenlenmesinde, yönetilmesinde ve ıslahında oldukça önem arz etmektedir.

Impact of instant controlled pressure drop texturing on the drying of yellow mealworms

Abstract Insects are increasingly being evaluated as promising protein sources for the food and feed sectors. However, to be accepted as a viable food source, insects must undergo proper processing. Drying is a crucial step in insect processing, as it inhibits the growth of harmful microorganisms, improves their stability and extends their shelf life. After drying, insects can be further processed into various forms, to make them more socially acceptable as food and feed. During drying, biological materials are prone to shrinking, which usually affects their quality. Shrinkage of dried biological material results in a compact structure and causes a significant reduction in water diffusivity. It is typically escorted with unsatisfactory organoleptic quality and problems with grinding. Therefore, including retexturing and structure-expanding techniques in regular drying procedures is becoming essential. The instant controlled pressure drop (DIC) technique was suggested as a texturing technique for yellow mealworms. DIC treatment successfully overcame shrinkage at treatment conditions of 0.194 MPa/32 s and above, resulting in enhanced water diffusivity of 1,833 and 682% for DIC-treated larvae at 0.45 MPa/25 s, dried at 50 and 60 °C, respectively, as compared to blanched larvae. Furthermore, DIC caused a 125% increase in the specific surface area of the dried meal, and a more uniform particle size distribution, both of which reflect the influence of this pretreatment on grinding and, consequently, the end product’s quality. Finally, experimental data of sorption isotherms at 20, 30, and 40 °C were fitted with Brunauer-Emmett-Teller (BET), Guggenheim-Anderson-de Boer (GAB), and Oswin models to represent the sorption behaviour.

Transmission porosimetry study on high-quality Zr-fum-MOF thin films.

Crystalline Zr-fum-MOF (MOF-801) thin films of high quality are prepared on glass and silicon substrates by direct growth under solvothermal conditions. The synthesis is described in detail and the influence of different synthesis parameters such as temperature, precursor concentration, and the substrate type on the quality of the coatings is illustrated. Zr-fum-MOF thin films are characterized in terms of crystallinity, porosity, and homogeneity. Dense films of optical quality are obtained. The sorption behavior of the thin films is studied with various adsorptives. It can be easily monitored by measuring the transmission of the films in gas flows of different compositions. This simple transmission measurement at only one wavelength allows a very fast evaluation of the adsorption properties of thin films as compared to traditional sorption methods. The sorption behavior of the thin films is compared with the sorption properties of Zr-fum-MOF powder samples.

Coupled sorptive and oxidative antimony(III) removal by iron-modified biochar: Mechanisms of electron-donating capacity and reactive Fe species

Sorption and oxidation are two potential pathways for the decontamination of trivalent antimony (Sb(III))-bearing water, using iron (Fe)-modified biochar (FeBC). Here we investigated the sorption and oxidation behavior of FeBC for Sb(III) in aqueous solutions. Results revealed that Sb(III) removal by FeBC was significantly improved showing the maximum Sb(III) sorption (64.0 mg g−1). Density functional theory (DFT) calculations indicated that magnetite (Fe3O4) in FeBC offered a sorption energy of −0.22 eV, which is 5 times that of non-modified biochar. With the addition of peroxymonosulfate (PMS), the sorption of Sb(III) on FeBC was 7 times higher than that on BC, indicating the sorption capacity of FeBC for Sb(III) could be substantially increased by adding oxidizing agents. Electrochemical analysis showed that Fe modification imparted FeBC higher electron-donating capacity than that of BC (0.045 v. s. 0.023 mmol e− (g biochar)−1), which might be the reason for the strong Sb(III) oxidation (63.6%) on the surface of FeBC. This study provides new information that is key for the development of effective biochar-based composite materials for the removal of Sb(III) from drinking water and wastewater. The findings from this study have important implications for protecting human health and agriculture.

Aged biochar for simultaneous removal of Pb and Cd from aqueous solutions: Method and mechanism

In this study, we prepared maize stover biochar and used artificial simulated aging to prepare three types of aged biochar. The effects of aging on the adsorption capacity of Pb and Cd of biochar were studied. It was found that the pH, ash, and aromaticity of the aged biochar decreased compared to fresh maize straw biochar. On the contrary, the polarity, oxygenated functional groups, specific surface area, and average pore size of the aged biochar increased. The sorption behavior of Pb2+ and Cd2+ on biochar can be well explained by quasi-second-order kinetics and the Langmuir equation. The maximum adsorption of Pb2+ in the single metal system was CBC-N (74.401 mg g−1) > CBC (72.959 mg g−1) > CBC-H (69.421 mg g−1) > CBC-F (66.460 mg g−1), the maximum adsorption of Cd2+ was CBC-N (52.983 mg g−1) > CBC-H (52.728 mg g−1) > CBC-F (50.692 mg g−1) > CBC (45.966 mg g−1). The adsorption of both Pb2+ and Cd2+ by biochar is lower in the binary metal system than in the single metal system, implying a competitive relationship and that biochar is more selective for Pb2+ than Cd2+. The mechanisms for removing Pb2+ and Cd2+ from solution by aged biochar consist mainly of pore filling, electrostatic adsorption, ion exchange, mineral precipitation, π−π interaction, and surface complexation. This paper demonstrates that aged biochar is an ideal adsorbent but that environmental changes and pollutant types should be considered in practical applications.

Investigating the Water Relations in Aqueous Extract Powders of Mango (Mangifera indica) Peel and Seed Waste for Their Use in Food Matrices as a Value-Added By-Product.

This study investigated the potential uses of discarded mango peel and seed parts by analyzing their water sorption behavior, hydration kinetics, and stability when converted into extract powders at pH 3 and 10. The results revealed that peel extracts had a higher water adsorption capacity compared with seed extracts due to differences in their composition. Peel extracts were primarily composed of carbohydrates (approximately 75%) with a low protein content, while seed extracts contained fewer carbohydrates (less than 30%) but higher levels of proteins (more than 30%) and lipids. The critical water content for maintaining the glassy state of peel extract powders during storage was found to be 0.025 and 0.032 g of water/g for extracts obtained at pH 3 and 10, respectively. In contrast, the Tg values of seed extracts remained relatively unchanged across different water content levels, suggesting that proteins and lipids inhibited the water's plasticizing effect in the solid matrix. These findings indicate that both mango waste fractions exhibit distinct hygroscopic behaviors, necessitating different approaches to processing and utilization. These extracts hold potential applications for various food products such as beverages, gels, sauces, or emulsions, contributing to the reduction in waste and the creation of value-added products from mango residues.

Effect of heavy metal co-contaminants on the sorption of thirteen anionic per- and poly-fluoroalkyl substances (PFAS) in soils

Understanding the sorption behavior of per- and poly-fluoroalkyl substances (PFAS) in soils are essential for assessing their mobility and risk in the environment. Heavy metals often coexist with PFAS depending on the source and history of contamination. In this study, we investigated the effect of heavy metal co-contaminants (Pb2+, Cu2+ and Zn2+) on the sorption of 13 anionic PFAS with different perfluorocarbon chain length (C3-C9) in two soils with different properties. Results revealed that Pb2+, Cu2+ and Zn2+ had little effect on the sorption of most short-chain compounds, while the presence of these heavy metals enhanced the sorption of long-chain PFAS in two soils. The distribution coefficients (Kd) of several long-chain PFAS linearly increased with increasing concentrations of heavy metal, especially in the presence of Pb2+ (ΔKd/Δ [Pb2+] > 3 for PFOS and PFNA vs <1 for PFPeS and PFHxS). While several mechanisms may have contributed to the enhancement of sorption of PFAS, the heavy metals most likely contributed through enhanced hydrophobic interactions of PFAS by neutralizing the negative charge of adsorption surfaces in soils and thus making it more favorable for their partitioning onto the solid phase. Moreover, the increase in the concentrations of heavy metals led to a decrease in the pH of the system and promoted sorption of long-chain compounds, especially in soil with lower organic carbon content. Overall, this study provides evidence that the presence of co-existing heavy metal cations in soils can significantly enhance the sorption of long-chain PFAS onto soil, thereby potentially limiting their mobility in the environment.

Understanding the sorption behavior of tri, tetra and hexavalent f cations on metal–organic framework (MOF), ZIF-67: experimental and theoretical investigation

ABSTRACT Metal–organic frameworks (MOFs) are a class of compounds with modern-age technological importance due to diverse structural topologies, porosity, and modularity. ZIF-67 has been synthesized for efficient extraction of f cations in different oxidation states (UO2 2+, Th4+ and Eu3+) from aqueous pH medium exhibiting the trend in sorption efficiency as: Kd Th(6.19 × 103) > Kd U (5.20 × 103) > Kd Eu (1.58 × 103) in accordance to their chemical potential. Langmuir isotherm was found to be predominate with sorption capacity 85.9 mg g−1, 137.4 mg g−1 and 50.6 mg g−1 for U, Th and Eu, respectively. The sorption predominantly proceeded via pseudo 2nd order rate kinetics with rate constants: k2 U ~0.089 g mg−1 min−1, k2 Th ~0.011 g mg−1 min−1 and k2 Eu ~0.04 g mg−1 min−1. The processes were found to be spontaneous as revealed from negative ΔG values; and endothermic in nature (ΔHU ~10.5 kJ mol−1; ΔHTh ~12.8 kJ mol−1; ΔHEu ~8.3 kJ mol−1). The sorption proceeded via the formation of an inner sphere complex as indicated from their enhancement in the entropy values on sorption due to the release of water molecules. The Density Functional Theory (DFT) predicted selectivity using binding energy (ZIF-67-Eu3+ ~ -60.90 eV, ZIF-67-Th4+ ~ -70.78 eV, ZIF-67-Th4+ ~ -69.52 eV) is in line with the experimental selectivity of Th4+ > UO2 2+ > Eu3+. Total density of states (TODS) and Projected density of States (PODS) were estimated in order to understand the interaction between the ZIF-67 and f cations.

N-cyanoguanidine modified-black peanut shell biochar: fabrication and its sorption for Cu(II) and Co(II) in a single and mixed solutions

A N-cyanoguanidine (NCY)-modified black peanut shell biochar was fabricated via NCY to modify waste black peanut shell. X-ray diffraction, Fourier transform infrared, scanning electron microscope–energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy were used to characterize its performance. Sorption experiments were made to perceive its sorption for Cu(II) and Co(II) and disclosed that Cu(II) had higher sorption selectivity in mixed binary and four-metal solution. Sorption kinetics showed that Cu(II) and Co(II) sorption fitted well with pseudo-1st–order kinetic and diffusion-chemisorption models. Sorption isotherms revealed that Langmuir model can better describe its sorption behavior for Cu(II) and Co(II) and its maximum Qm could reach up to 185.66 and 80.59 mg/g at 45 °C, respectively. Thermodynamic factors indicated that Cu(II) and Co(II) sorption on NCY-modified black peanut shell biochar was an endothermic and spontaneous manner. Both effective diffusion coefficients (kIp) and mass-transfer coefficients (DEx) proved that Cu(II) and Co(II) sorption comprised multiple-step paces. The major mechanism included electrostatic attraction, mass transfer, complex and chelation, and diffusion-chemisorption. This finding suggests that NCY-modified black peanut shell biochar can be potentially applied to dispose Cu(II) and Co(II)-bearing wastewater from spent new power batteries.

Extract yields of two commercially valuable wood species in Central Africa: Bilinga and Tali, their nature and role in water sorption activities

ABSTRACT This paper aimed at determining the quantity, nature and role of extracts during the sorption behavior of two Central African hardwood species: Nauclea diderrichii (Bilinga) and Erythrophleum suaveolens (Tali) at 30, 40, 50, 60 and 70°C using relative humidities (RH) between 5.3% and 97%. For this purpose, extract contents and their nature were determined by solvent extraction and mass spectrometric analysis (MALDI-TOF/MS) respectively. The ABC model whose parameters were used to determine the monolayer moisture capacity (EMCm) also described type II sigmoidal sorption isotherms. The results showed that acetone extracts were the highest in Tali (7.88%) and Bilinga (6.92%). MALDI-TOF results found 10 new chemical components out of 24 in Tali (saponins, flavonoids, glycosides, alkaloids and stilbenes) while 16 were identified as saponins, acids and flavonoids in Bilinga. Acetone-soluble extracts had the most significant effect on the hygroscopic nature of wood. Extracted wood recorded higher equilibrium moisture contents (EMC), monolayer moisture capacities and lower sorption differences. For native wood, water-repellent polyphenols like alkaloids and stilbenes and newly identified components there in, rendered Tali less hygroscopic than Bilinga. The nature of extractives would be an effective alternative to explore the chemical compounds, which can best improve the hygroscopic response of wood.

A Preliminary Sorption Study of Uranium on MnO2 (Pyrolusite) in the Presence of Siderophore Desferrioxamine B—The Mechanism of a Ternary System

Manganese oxides have influential sorptive properties to efficiently sequester metals, such as uranium. Sorption can become complicated by metal chelating siderophores, which create a ternary system that is capable of multiple feasible mechanisms. This study analyzes the sorption behavior of desferrioxamine B (DFOB) and desferrioxamine D (DFOD) onto pyrolusite, β-MnO2, in the presence of U(VI) at pHs 6 and 8. The electrostatic adsorption performance is shown to have a 23% difference between the DFOB and DFOD surface sorption at pH 6. Inner-sphere coordination was identified through hydrolysis products of succinate and acetate. Together, these behaviors indicate a ternary complex system where both metals and ligands interact with the surface. Therefore, uranium in the environment can be attenuated by the conditions of a complex configuration involving multiple species and functional groups. This mechanism needs to be considered for any future modeling or strategies involving radionuclide remediation.

1D Mn coordination polymer derived from sulfanilic acid: Synthesis, structure, adsorption properties and Hirshfeld surfaces analysis

A one-dimensional Mn coordination polymer formulated; [Mn2(C6H7NO3S)2Cl4O4]n (1) (where = C6H7NO3S is sulfanilic acid) was synthesized via the hydrothermal method by reacting aqueous solutions of MnCl2·4H2O and sulfanilic acid. The X-ray studies demonstrate layered arrangement of monomers in the coordination polymer interconnected by weak hydrogen bonds. The vibrational frequencies of functional groups and bonds within the polymer were analyzed using infrared spectroscopy. The thermal degradation of the coordination polymer structure was studied under non-isothermal conditions in an argon atmosphere using thermogravimetric (TG) and differential thermal analysis (DTA), revealing a decomposition process occurring in four to five distinct stages. The sorption properties of the coordination polymer were investigated using N2 gas in an Autosorb IQ device at 77 K, resulting in a surface area of 318.4642 m²/g. Additionally, the sorption behavior of benzene and water vapor on the polymer was investigated at room temperature, yielding a result of 70.82 m²/g for benzene vapor and 172.66 m²/g for water vapor. The molecular fragment, [Mn2(C6H7NO3S)2Cl4O4] as the monomer unit are used for calculating the Hirshfeld surface of this compound that reveals strong N-H∙∙∙Cl intermolecular hydrogen bonding and π–π interactions.

Retention of trivalent actinides (Am, Cm) and lanthanides (Eu) by Ca feldspars

Abstract. The transport of radionuclides in the environment is a major problem for the safety assessment of radioactive waste repositories. Storage in deep geological repositories is considered a safe disposal strategy because of their ability to isolate hazardous components from the biosphere for hundreds of thousands of years. Minor actinides (i.e. Am, Cm and Np) dominate the radiotoxicity of spent nuclear fuel over geological timescales. In underground repositories, reducing conditions are expected, and therefore the trivalent oxidation state is dominant for Am and Cm as well as possibly for Pu. For investigations of the mobility of the trivalent actinides Am3+ and Cm3+, the less toxic trivalent rare earth elements, in particular Eu3+, are commonly used. Besides clay and salt, crystalline rock is considered a possible host rock for deep geological repositories. Crystalline rock (e.g. granite) consists mainly of quartz, mica and feldspar. The latter forms common aluminosilicates making up ∼60 vol. % of the earth's crust, but their sorption behaviour is not well understood, especially for the Ca-bearing members of the group. Here, we study the sorption of trivalent actinides and their rare earth element homologues on plagioclase which are Ca-bearing feldspars, quantitatively and mechanistically. Zeta potentials of various Ca feldspars show an unexpected increase at pH 4–7, which becomes more pronounced as the amount of Ca in the crystal lattice increases. This can be interpreted by assuming uptake of Al3+ and/or the precipitation of an Al phase, where Al originates from feldspar dissolution at different pH values. Nevertheless, only minor differences were found in the retention and surface speciation of Cm3+ on Ca and K feldspars (Neumann et al., 2021). Ca feldspar has a slightly higher potential to retain trivalent metal ions compared to K feldspar. An inner-sphere (IS) complex and its two hydrolysis forms have been identified on both minerals, but the hydrolysis of the IS complex is stronger in the Ca-rich mineral. A surface complexation model for Ca feldspar was developed by combining the batch sorption data and the spectroscopically identified surface complexes to describe the experimental data. These data will be the basis for the improvement of transport simulations for a reliable safety assessment of potential radioactive waste repositories in crystalline rock.

Ultra-high capacity, multifunctional nanoscale sorbents for PFOA and PFOS treatment

Here, we describe surface functionalized, superparamagnetic iron oxide nanocrystals (IONCs) for ultra-high PFAS sorption and precise, low energy (magnetic) separation, considering perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). As a function of surface coating, sorption capacities described are considerably higher than previous studies using activated carbon, polymers, and unmodified metal/metal oxides, among others. In particular, positively charged polyethyleneimine (PEI) coated IONCs demonstrate extreme sorption capacities for both PFOA and PFOS due to electrostatic and hydrophobic interactions, along with high polymer grafting densities, while remaining stable in water, thus maintaining available surface area. Further, through a newly developed method using a quart crystal microbalance with dissipation (QCM-D), we present real-time, interfacial observations (e.g., sorption kinetics). Through this method, we explore underpinning mechanism(s) for differential PFAS (PFOA vs PFOS) sorption behavior(s), demonstrating that PFAS functional head group strongly influence molecular orientation on/at the sorbent interface. The effects of water chemistry, including pH, ionic composition of water, and natural organic matter on sorption behavior are also evaluated and along with material (treatment) demonstration via bench-scale column studies.