Sorption Complexes Research Articles

Predictive modeling of microplastic adsorption in aquatic environments using advanced machine learning models.

This study addresses the critical environmental concerns surrounding microplastics, aiming to elucidate the intricate factors influencing their behavior and interactions with organic pollutants. Utilizing advanced artificial neural network modeling techniques, including GRU, LSTM, RNN, and CNN, a comprehensive analysis of microplastic sorption capacity and underlying mechanisms is conducted. The research relies on a meticulously curated dataset encompassing fundamental parameters such as organic compound composition, n-octanol/water partition coefficient, covalent acidity, covalent basicity, molecular polarizability to volume ratio, and the logarithm of the partition coefficient. Findings underscore the significance of understanding the n-octanol/water distribution coefficient (Log D) in predicting organic pollutant fate in aquatic environments, with compounds displaying higher Log D values exhibiting heightened affinity for microplastics, posing substantial ecological and human health risks. Additionally, the study highlights the importance of selecting appropriate models to accurately capture complex sorption processes, especially in varied aquatic environments. Furthermore, the profound impact of acidity, molecular polarizability to volume ratio, and covalent basicity on microplastic behavior is elucidated. Notably, machine learning models and CNNs demonstrate remarkable speed in prediction generation. A comparative analysis of four robust machine learning models establishes fundamental alignment between model predictions and empirical findings. Particularly noteworthy is the RNN model, emerging as the most accurate with an impressive accuracy of 0.967 and a minimum absolute error of 0.38. These results underscore the efficacy of the RNN model in predicting microplastic dynamics, holding promise for significant contributions to addressing microplastic pollution.

Towards a better understanding of sorption of persistent and mobile contaminants to activated carbon: Applying data analysis techniques with experimental datasets of limited size.

The complex sorption mechanisms of carbon adsorbents for the diverse group of persistent, mobile, and potentially toxic contaminants (PMs or PMTs) present significant challenges in understanding and predicting adsorption behavior. While the development of quantitative predictive tools for adsorbent design often relies on extensive training data, there is a notable lack of experimental sorption data for PMs accompanied by detailed sorbent characterization. Rather than focusing on predictive tool development, this study aims to elucidate the underlying mechanisms of sorption by applying data analysis methods to a high-quality dataset. This dataset includes more than 60 isotherms for 22 PM candidates and well-characterized high-surface-area activated carbon (AC) materials. We demonstrate how tools such as distance correlation and clustering can be used effectively to identify the key parameters driving the sorption process. Using these approaches, we found that aromaticity, followed by hydrophobicity, are key sorbate descriptors for sorption, overshadowing steric and charge effects for a given sorbent. Aromatic PMs, although classified as mobile contaminants based on their sorption to soil, are well adsorbed by AC as engineered adsorbent via π-π interactions. Non-aromatic and especially anionic compounds show much greater variability in sorption. The influence of ionic strength and natural organic matter on adsorption was considered. Our approach will help in the analysis of solute-sorption systems and in the development of new adsorbents beyond the specific examples presented here. In order to make the approach accessible, the code is freely available and described on GitHub (https://github.com/Laura-Lotteraner/PM-Sorption), following the FAIR data principles.

Insight into the effect of natural aging of polystyrene microplastics on the sorption of legacy and emerging per- and polyfluorinated alkyl substances in seawater

Microplastics (MPs) are abundant in aquatic environments and due to their small size, surface properties, and strong hydrophobicity, they can easily sorb chemicals, thus potentially acting as pollutant carriers. To date, most studies investigating the sorption of chemicals on MPs have principally focused on virgin MPs. However, MPs in the environment undergo aging effects, which changes their physical-chemical properties and aptitude to interact with chemicals, such as per- and polyfluorinated alkyl substances (PFAS) referred to as “forever chemicals”. In this study, we compared the sorption behavior of nine PFAS, exhibiting different physical-chemical properties, on virgin and naturally aged polystyrene microplastic (PS-MPs) to explore to what extent the environmental aging affects the sorption behavior of the PS-MPs for different legacy and emerging PFAS in seawater. Differences in the morphology and surface properties of aged PS-MPs were examined by infrared spectroscopy, surface area analysis, scanning electron microscopy, and X-ray diffraction. Results revealed that compared to virgin PS-MPs, aged PS-MPs exhibited morphological changes (e.g. cavities, pits, and rough surfaces) with biofilm development and signs of oxidation on the MPs surface. PFAS sorption on PS-MPs was enhanced for the aged PS-MPs compared to virgin PS-MPs with Kd values ranging from 327 L kg−1 for PFOA to 3247 L kg−1 for PFOS in aged PS-MPs. The difference in sorption capacity was mainly attributed to the physical-chemical changes and the adhered biofilm observed in aged PS-MPs. Results also showed that virgin PS-MPs adsorb PFAS mainly through steric hindrance, while the aged PS-MPs may involve more complex sorption mechanisms. This research provides additional insights into the ability of aged MPs as potential carriers of legacy and emerging contaminants in the marine environment.

Boosting Electrochemical Degradation of Water Pollutants Using Sulfur‐Rich Porous Polyimide‐Derived Laser‐Induced Graphene Catalytic Membrane

Water pollution is an inevitable concern associated with technological advancement. To address this problem, it is necessary to significantly shorten the manufacturing process of porous materials while enabling effective pollutant removal. Herein, a facile, rapid, and scalable approach is reported to obtain sulfur‐doped hierarchically porous laser‐induced graphene (S‐LIG) as a catalytic membrane with three‐dimensional networks by localized laser irradiation, along with possible adsorption and electrochemical degradation mechanisms for pollutant removal. S‐LIG is derived from sulfur‐containing porous polyimide film which is prepared via thermally induced phase separation followed by stepwise thermal imidization. Methylene blue (MB) adsorption behavior on the S‐LIG membrane closely fits the pseudo‐second‐order and Freundlich isotherm models, suggesting a complex sorption mechanism, including both strong chemical interaction and physical adsorption. Furthermore, S‐doping enhances catalytic activity for generating reactive oxygen species (ROS), aiding MB degradation via indirect oxidation, and improves direct oxidation on the anode by accelerating electron transfer at the electrodes. This results in a stable 93% MB degradation at a low 1.5 V after 24 h. Additionally, the impact of solution pH reveals that electrostatic attraction forces under basic conditions and the high generation of ROS under acidic conditions favor adsorption and electrochemical oxidation.

Selective Sorption of Noble Metals on Polymer Gel Modified with Ionic Liquid.

The solid phase extraction of Au, Ir, Pd, Pt, and Rh on a polymer gel modified with ionic liquid containing methylimidazolium groups (MIA-PG) has been investigated. The positively charged surface of the sorbent is highly suitable for the sorption of stable chlorido complexes of the studied analytes, while the retention of base metals Cu, Fe, Ni, Zn, and Mn is negligible. Optimization experiments performed showed that, at 0.05 M HCl, the degree of sorption of Au, Ir, Pd, and Pt is above 95%, and only for Rh, the maximum degree is 65%; complete elution is achieved in the mixture of thiourea in HCl. The results obtained from the equilibrium adsorption studies are fitted in various adsorption models, such as Langmuir and Freundlich, and the model parameters have been evaluated. The kinetics analysis indicated that the adsorption of Au, Ir, Pd, Pt, and Rh onto the sorbent follows the pseudo-second-order model. Intraparticle diffusion and ion exchange reactions were the rate-limiting steps. Analytical procedures were developed for Pd, Pt, and Rh determination in road dust and soil and for Au determination in copper ore and copper concentrate. The procedures are validated by the analysis of certified reference materials. Analytical figures of merit confirmed their applicability in routine laboratory practice.

A FAIR comparison of activated carbon, biochar, cyclodextrins, polymers, resins, and metal organic frameworks for the adsorption of per- and polyfluorinated substances

Per- and polyfluorinated substances (PFAS) have complex sorption behaviors, complicating removal from water and selection of suitable adsorbents. We evaluated adsorption of 44 PFAS across four adsorbent groups: activated carbon and biochar (AC and BC), cyclodextrin-based adsorbents (cyclodextrins), polymer-based adsorbents and resins, and inorganic adsorbents and metal organic frameworks (MOFs). We analyzed over 500 adsorption coefficients (Kd) from literature, calculated at aqueous equilibrium concentration of 1 ± 0.3 µg/L under comparable experimental conditions. On average, Kd of AC and BC exceeded 107 L/kg for PFAS with C-F bonds > 7, unlike other adsorbents with Kd < 107. This trend holds for C-F bonds ≥ 4. Cyclodextrins, polymer-based adsorbents and resins outperform AC and BC for C-F bonds < 4. For AC and BC, Kd follows the order PFOS>PFOA>PFBS>PFBA, with adsorption increasing with increasing point of zero charge of the adsorbent. For AC and BC, as well as cyclodextrins, Kd values were related to PFAS hydrophobicity and steric properties. Additionally, adsorption was influenced by head group type, non-fluorinated carbon atoms, and the presence of oxygen and/or chlorine in the PFAS. No clear relationship was found for the other adsorbents. Adsorption prediction using a Random Forest Regressor and literature data was feasible for AC and BC, but not for other adsorbents. Cyclodextrins outperform AC and BC for removing PFAS across varying mobilities from water, whereas AC and BC are superior for low mobility PFAS. To support further data use all data and code used are freely available, following FAIR data principles.

Sorption of zinc chloride complexes from acid-based solutions by using anionic resins: process optimization and modelling

The sorption of zinc chloride ions from hydrochloric acid-based solutions using anionic resins was investigated. A two-stage experiment was planned. In the first stage, parameter optimization was performed using the Taguchi experimental optimization approach for type of anionic resins, initial Zn (II) ion concentration, resin dose, agitation rate, and temperature and time of the process as process parameters. According to the signal—to—noise ratio values calculated with the larger better-quality feature; the optimum parameter levels were determined as chloride form resin, 10 g/L, 1200 mg/L, 200 rpm and 35 °C and 90 min, respectively. Under optimum operating conditions, the sorption capacity of the resin for zinc chloride complex ions was 46.52 mg/g. The energy dispersive X-Ray analyses confirmed that zinc chloride complexes bind to the resin’s surfaces. In the second step, equilibrium and kinetic tests were performed under the optimum parameters. The tests results were compared with six equilibrium isotherm models with 2 or more parameters and four kinetic models. The non-linear solution approach was applied for all models. Langmuir isotherm and the general order models were the best fit. The values of KL\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${K}_{L}$$\\end{document} and qm,L\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${q}_{m,L}$$\\end{document} for the Langmuir model were 2.15*10–3 L/g and 66.08 mg/g, respectively. The kinetic model can be given by an equation of order 3.26. Accordingly, kn\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${k}_{n}$$\\end{document} and qe,n\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${q}_{e,n}$$\\end{document} were 2.18*10–5 min/(g mg)2.26 and 60.03 mg/g, respectively. The process mechanism was a typical chemical sorption. According to the results of desorption tests conducted using 1 M HCl, the desorption efficiency was 65%.

Coordination structures and stabilities of Am(III) adsorption complexes at kaolinite(0 0 1)-water interface

Understanding the structures and stabilities of actinide species is crucial for comprehending the sorption mechanisms at mineral–water interfaces. However, the relevant molecular-level fundamental aspects of actinide coordination chemistry at the mineral–water interface remain unclear. We herein conduct a systematic theoretical study of coordination structures and adsorption energies of Am3+ and Am(OH)2+ sorption complexes at the kaolinite(001)-water interface by integrating static density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations. Computational results show that stable outer- and inner-sphere adsorption complexes are respectively formed through hydrogen bonding and coordinate bonding with surface aluminol groups. The most stable inner-sphere species are predicted to be tridentate surface complexes with an eight-folded coordination structure in the first coordination sphere of Am(III). This work deepens the understanding of Am(III) adsorption and complexation behaviors at the mineral–water interface, providing essential insights for actinide migration in natural environments and nuclear waste disposal. The synergy between static DFT calculations for initial screening and AIMD simulations for comprehensive dynamic analysis in this work enhances the efficiency and accuracy of theoretical predictions for actinide environmental chemistry and can be helpful for the broader research fields of geochemistry and environmental science.

Investigating the sorption behavior of selenite on commercial partially oxidized magnetite nanopowder under aerobic conditions: Characterization and mechanisms

Selenium, which belongs to essential elements, has a narrow margin between necessity and toxicity. Anthropogenic activities may lead to its elevated concentrations in aquatic ecosystems, particularly in the undesirable form of toxic selenite, due to its high environmental mobility. Hence, it is imperative to devise effective technologies to limit its potential migration through the environment. Therefore, the development and evaluation of new adsorbents for its effective removal from selenium-contaminated waters are crucial for both human health and environmental stability in affected areas. Specifically, magnetite-based nanomaterials showed promise as sorbents due to their capacity to immobile contaminants through reductive transformation or adsorption, but there is a lack of comprehensive understanding regarding the sorption mechanisms and the factors influencing the efficiency of this process. A deeper understanding of these factors is crucial for developing sustainable and efficient water treatment strategies. This study focuses on magnetite nanopowder’s sorptive properties, examining critical factors such as pH, ionic strength, and competing anions that affect selenite removal. Sorption kinetics revealed an initial rapid selenite removal followed by a slower, time-dependent phase, suggesting a complex sorption mechanism. Chemisorption was considered the primary sorptive interaction, with diffusion playing a minor role, and was best described by the pseudo-second order kinetic model. Notably, pH significantly affected sorption efficiency and the suggested sorptive mechanism. Acidic conditions favored selenite removal due to formation of inner-sphere complexes, while alkaline conditions reduced efficiency due to repulsive interactions. Equilibrium sorption data were best fitted by the Langmuir model, with maximum sorption at pH 3, indicating that acidic conditions favor selenite removal. X-ray photoelectron spectroscopy (XPS) analysis ruled out the formation of reduced selenium compounds on the magnetite nanopowder surfaces. Additionally, Mössbauer spectrometry revealed that the nanopowder is not homogeneous and contains both magnetite and maghemite phases. Ionic strength and co-occurring ions showed minimal chloride impact but significant phosphate competitiveness due to its affinity for iron oxides. In conclusion, this study sheds light on the complex selenite sorptive interactions with magnetite nanopowder, emphasizing the dominance of chemisorption, especially in acidic solutions.

Simple and complex sorption−solution isotherms for membrane polymers: A statistical thermodynamic fluctuation theory

Simple, site-specific adsorption isotherm models, such as GAB and other generalizations of BET, fit strikingly well to experimental isotherms of simple shapes for glassy and rubbery polymers. However, the structures of dense polymers do not necessarily resemble the unrestricted layer-by-layer adsorption mechanism on one type of sorption site assumed by these models. Since polymers contain micropores, sorptive likely (ad)sorbs on the internal surfaces of the free (accessible) volume voids, and dissolves in the polymer phase. While the empirical dual mode sorption model and its variants address this duality, other common models assume chiefly only one of the two mechanisms. Moreover, the simplified models do not fit complex isotherms, such as those for alcohols and poly[(trimethylsilyl)propyne] (PTMSP). The statistical thermodynamic fluctuation theory is adopted here to capture the sorption-solution duality consistently even for the complex isotherms. The statistical thermodynamic ABC isotherm derived from this theory involves the sorbate-sorbent and mono-, di-, and tri-sorbate interactions expressed by sorbate number correlations. This work shows that BET, GAB, dual-mode sorption model, Flory-Huggins, and ENSIC models are special cases of the ABC isotherm. The isotherm multiplicativity principle has been derived from the number fluctuation relationship to model complex isotherms.

Mechanistic interpretation of the sorption of terbuthylazine pesticide onto aged microplastics

Microplastics (MPs) pose a global concern due to their ubiquitous distribution. Once in the environment, they are subject to aging, which changes their chemical-physical properties and ability to interact with organic pollutants, such as pesticides. Therefore, this study investigated the interaction of the hydrophobic herbicide terbuthylazine (TBA), which is widely used in agriculture, with artificially aged polyethylene (PE) MP (PE-MP) to understand how aging affects its sorption. PE was aged by an accelerated weathering process including UV irradiation, hydrogen peroxide, and ultrasonic treatment, and aged particles were characterized in comparison to pristine particles. Sorption kinetics were performed for aged and pristine materials, while further sorption studies with aged PE-MP included determining environmental factors such as pH, temperature, and TBA concentration. Sorption of TBA was found to be significantly lower on aged PE-MP compared to pristine particles because aging led to the formation of oxygen-containing functional groups, resulting in a reduction in hydrophobicity and the formation of negatively charged sites on oxidized surfaces. For pristine PE-MP, sorption kinetics were best described by the pseudo-second-order model, while it was intra-particle diffusion for aged PE-MP as a result of crack and pore formation. Sorption followed a decreasing trend with increasing pH, while it became less favorable at higher temperatures. The isotherm data revealed a complex sorption process on altered, heterogeneous surfaces involving hydrophobic interactions, hydrogen bonding, and π-π interactions, and the process was best described by the Sips adsorption isotherm model. Desorption was found to be low, confirming a strong interaction. However, thermodynamic results imply that increased temperatures, such as those resulting from climate change, could promote the re-release of TBA from aged PE-MP into the environment. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) confirmed TBA sorption onto PE.

The liquid mineral- and probiotic-containing feed additives for poultry

In this study, we assessed the biocompatibility of five probiotic lactobacilli strains and characterized sapropel, bentonite, and zeolite from the deposits of Tatarstan Republic in terms of their chemical and mineral compositions, cation exchange capacities, sorption activity, and the structure of the ion exchange and sorption complexes. We also constructed a synbiotic preparation with sapropel, bentonite, and zeolite as carrier matrixes for probiotic lactobacilli and determined their viability in the preparation for two weeks. High ion-exchange and sorption properties of sapropel, bentonite, and zeolite and suitable bacterial survival rate during storage are among the main benefits of the developed poultry feed. The obtained data have a great potential for practical use in the construction of multi-strain liquid probiotics, in which probiotic lactobacilli are immobilized on mixtures of various mineral matrix carriers.

CALCULATION OF THE ELECTRODE REACTION RATE ON A GRAPHITE CATHODE OF ALUMINUM-ION BATTERY WITH 1-ETHYL-3-METHYLIMIDAZOLIUM CHLORIDE

A method for determining the rate of sorption of chloraluminate complexes on graphite material as the main cathode reaction in aluminum-ion batteries with an ionic liquid as an electrolyte is proposed in terms of classic chemical kinetics approach. The method is applied to the description of the rate of a one-electron cathode reaction that is in the case the sorption/desorption of complexes on the electrode surface with no migration in the interlayer space of graphite taken into account. The experimental part is based on the selection and providing of measurement conditions and the ratio of the components of the cell to ensure that the rate of the cathode process sets the rate of current generation of the cell. The rate of supply/removal of electrons, as participants in the reaction, thus can be directly related to the reaction rate on graphite. The point of reaching the limiting current on the polarization curve in that case corresponds the limiting rate of the chemical sorption reaction. The approach takes into account the effect of other limiting processes, such as the rate of removal/supply of electrons, the rate of removal/supply of ions to/from the electrolyte volume, and the rate of anodic dissolution/deposition of aluminum. The calculated value of the reaction rate for graphite material grade EC-02 and low-temperature ionic liquid 1-ethyl-3-methylimidazole chloride in a mixture with aluminum chloride (1 : 1.3) was calculated to be 46 µmol/cm2 · s.

Estimation and sensitivity analysis on cadmium desorption rates in soils under influence of cadmium complex sorption

Estimation and sensitivity analysis on cadmium desorption rates in soils under influence of cadmium complex sorption

Probing interfacial water structure induced by charge reversal and hydrophobicity of silica surface in the presence of divalent heavy metal ions using sum frequency generation spectroscopy

HypothesisAdsorption of divalent heavy metal ions (DHMIs) at the mineral–water interfaces changes interfacial chemical species and charges, interfacial water structure, Stern (SL), and diffuse (DL) layers. These molecular changes can be detected by probing changing orientation and hydrogen-bond network of interfacial water molecules in response to changing local charges and hydrophobicity. ExperimentsSum-frequency generation (SFG) spectroscopy was used to probe changes in vibrational resonances of interfacial OH vs. DHMI concentration and pH. SFG spectra were deconvoluted using the measured surface potential and maximum entropy method in conjunction with the electrical double-layer theory for the SL and DL structures and correlated by hydrophobicity. FindingsThree surface charge reversals (CRs) were detected at low (CR1), medium (CR2), and high (CR3) pHs. Unlike CR1, SFG signals were minimized at CR2 and CR3 for DHMIs-silica systems highlighting considerable alterations in the structure of interfacial waters due to the inner-sphere sorption of metal hydroxo complexes. SFG results showed “hydrophobic-like” stretching modes at > 3600 cm−1 for Pb-, Cu-, and Zn-treated silica. However, contact angle measurements revealed the hydrophobization of silica only in the presence of Pb(II), as confirmed by an in-depth SFG analysis of the hydrogen-bond network of the interfacial water molecules in the SL.

Complex Sorption Treatment of Industrial Waste and Production of Plastic Lubricants

Complex Sorption Treatment of Industrial Waste and Production of Plastic Lubricants

Effects of Fe3O4 nanoparticles and nano hydroxyapatite on Pb and Cd stressed rice (Oryza sativa L.) seedling

Nowadays, Lead (Pb) and Cadmium (Cd) contamination in rice is an important worldwide environmental concern. Fe3O4 nanoparticles (Fe3O4 NPs) and Nano hydroxyapatite (n-HAP) are promising materials to manage Pb and Cd contamination. This study systematically investigated the effect of Fe3O4 NPs and n-HAP on Pb and Cd stressed rice seedlings’ growth, oxidative stress, Pb and Cd uptake and subcellular distribution in roots. Furthermore, we clarified the immobilization mechanism of Pb and Cd in the hydroponic system. Fe3O4 NPs and n-HAP could reduce Pb and Cd uptake of rice mainly through decreasing Pb and Cd concentrations in culture solution and combining with Pb and Cd in root tissues. Pb and Cd were immobilized by Fe3O4 NPs through complex sorption processes and by n-HAP through dissolution-precipitation and cation exchange, respectively. On the 7th day, 1000 mg/L Fe3O4 NPs reduced the contents of Pb and Cd in shoots by 90.4% and 95.8%, in roots by 23.6% and 12.6%, 2000 mg/L n-HAP reduced the contents of Pb and Cd in shoots by 94.7% and 97.3%, in roots by 93.7% and 77.6%, respectively. Both NPs enhanced the growth of rice seedlings by alleviating oxidative stress and upregulating glutathione secretion and antioxidant enzymes activity. However, Cd uptake of rice was promoted at certain concentrations of NPs. The subcellular distribution of Pb and Cd in roots indicated that both NPs decreased the percentage of Pb and Cd in the cell wall, which was unfavorable for Pb and Cd immobilization in roots. Cautious choice was needed when using these NPs to manage rice Pb and Cd contamination.

Sorption isotherm measurements for porous materials: A new hygroscopic method

The water sorption of materials can significantly affect their durability. While a wide range of techniques has been already introduced and implemented to measure the sorption behavior of materials, obtaining high-resolution data to describe the water sorption isotherm is still a challenging task. This is especially the case for materials with a complex sorption behavior such as concrete for which the pore structure is very complicated. The level of complexity increases when chloride is present in such structures. In this study, a hygroscopic technique is introduced to measure the sorption behavior of porous materials. By this technique, the sorption isotherm can be obtained by injecting water with a high level of control into a controlled environment where a sample is positioned. The amount of water can be added in steps resulting in high-resolution data for the sorption properties of the sample. The technique is evaluated for two porous materials: Portland cement mortar and sand-lime brick. The results are extensively compared with similar measured data available in the literature. In addition, the performance of the technique is evaluated for porous materials with initial chloride content. The results show that the present technique allows for obtaining high-resolution data in desirable ranges that is essential for materials with complicated pore structures.

Modeling diffusion and types I-V sorption of water vapor in heterogeneous systems

A sorption and diffusion model is developed using a mobile-immobile decomposition of the vapor concentration. Henry’s mode represents the mobile species which diffuses through the solid, while Langmuir and pooling modes represent possible immobilization processes that cause nonlinearities in sorption capacity. The model can simulate the five classical sorption types and can incorporate additional dynamics compared to models based on thermodynamic equilibrium. Additionally, the framework allows for discontinuities in material properties encountered in multi-material systems. The resulting non-linear coupled equations are solved by employing a finite element method to discretize in space, and a backward Euler method to discretize in time. The discretized system of equations is solved via a Newton-type iteration scheme at each time-step. Four different materials are parameterized for the model, which are then used in examples to demonstrate the model’s ability to capture complex sorption processes in multi-material systems.

Sorption of representative organic contaminants on microplastics: Effects of chemical physicochemical properties, particle size, and biofilm presence

Microplastic pollution has attracted mounting concerns worldwide. Microplastics may concentrate organic and metallic contaminants; thus, affecting their transport, fate and organismal exposure. To better understand organic contaminant-microplastic interactions, our study explored the sorption of selected polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), α-hexabromocyclododecane (α-HBCDD), and organophosphate flame retardants (OPFRs) on high-density polyethylene (HDPE) and polyvinylchloride (PVC) microplastics under saline conditions. Sorption isotherms determined varied between chemicals and between HDPE and PVC microplastics. Log Freundlich sorption coefficients (Log KF) for the targeted chemicals ranged from 2.01 to 5.27 L kg-1 for HDPE, but were significantly lower for PVC, i.e., ranging from Log KF data (2.84 – 8.58 L kg-1). Significant correlations between chemicals’ Log KF and Log Kow (octanol-water partition coefficient) indicate that chemical-dependent sorption was largely influenced by their hydrophobicity. Sorption was evaluated using three size classes (< 53, 53 – 300, and 300 – 1000 µm) of lab-fragmented microplastics. Particle size did not significantly affect sorption isotherms, but influenced the time to reach equilibrium and the predicted maximum sorption, likely related to microplastic surface areas. The presence of biofilms on HDPE particles significantly enhanced contaminant sorption capacity, indicating more complex sorption dynamics in the chemical-biofilm-microplastic system. Our findings offer new insights into the chemical-microplastic interactions in marine environment.