Ion Exchange Research Articles

Synthesis of 2,4-D/LHD hybrid nanocomposite using different aging times

Different aging times (1, 2, 4, and 18 h) were used to intercalate the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) into the layered double hydroxide (ZnAl-LDH) using the coprecipitation method to form the 2,4-D/LDH hybrid nanocomposite. The XRD and FTIR results demonstrated that the herbicide was introduced into the layered structure of the LDH, forming an organic-inorganic crystalline nanohybrid in very short aging times, such as one h. The herbicide molecules introduced into the LDH-ZnAl produced an increase in basal spacing, a decrease in crystallinity, and changes in the morphology and particle size of the nanohybrid. The release kinetics obeyed the pseudo-second-order model, and the herbicide release mechanism was done via ion exchange. The analysis of the nanohybrids after herbicide release confirmed the insertion of carbonate anions via ion exchange into the lamellar structure of the LDH by decreasing the basal spacing.

Heart Failure: A Deficiency of Energy—A Path Yet to Discover and Walk

Heart failure is a complex syndrome and our understanding and therapeutic approach relies mostly on its phenotypic presentation. Notably, the heart is characterized as the most energy-consuming organ, being both a producer and consumer, in order to satisfy multiple cardiac functions: ion exchange, electromechanical coordination, excitation–contraction coupling, etc. By obtaining further knowledge of the cardiac energy field, we can probably better characterize the basic pathophysiological events occurring in heart disease patients and understand the metabolic substance changes, the relationship between the alteration of energy production/consumption, and hence energetic deficiency not only in the heart as a whole but in every single cardiac territory, which will hopefully provide us with the opportunity to uncover the beginning of the heart failure process. In this respect, using (a) newer imaging techniques, (b) biomedicine, (c) nanotechnology, and (d) artificial intelligence, we can gain a deeper understanding of this complex syndrome. This, in turn, can lead to earlier and more effective therapeutic approaches, ultimately improving human health. To date, the scientific community has not given sufficient attention to the energetic starvation model. In our view, this review aims to encourage scientists and the medical community to conduct studies for a better understanding and treatment of this syndrome.

In Situ Potentiometric Monitoring of Nitrate Removal from Aqueous Solution by Activated Carbon and Ion Exchange Resin

A nitrate selective electrode was used for real-time in situ potentiometric monitoring of a batch nitrate removal process using activated carbon and ion exchange resin. A plasticized polymeric membrane consisting of polyvinyl chloride, 2-nitrophenyl octyl ether and tridodecyl methyl ammonium chloride was incorporated into an ion-selective electrode body. First, the dynamic potential response of the electrode to nitrate was investigated. Two commercial activated carbons with different physical properties were then tested. Nitrate removal with these carbons was monitored potentiometrically using several nitrate concentrations. The extreme turbidity of the solutions was not a drawback during potentiometric monitoring of the process, which is a clear advantage over other methods such as optical monitoring. The potential versus time recordings were converted into nitrate concentration versus time plots, which were evaluated with different adsorption kinetic models. A pseudo-second order kinetic model for nitrate adsorption on both activated carbons was found to fit the experimental data very well. The values of the kinetic parameters were very different between the two activated carbons. The proposed methodology was also satisfactorily applied to the study of nitrate removal by an ion exchange resin. In this case, the experimental results clearly follow a pseudo-first order kinetic model. Potential applications of the proposed methodology for monitoring nitrate removal in real water samples are discussed.

Research on the Adsorption Performance of Zeolites for Dimethyl Ether

The purification and removal of polar impurities in olefin feedstocks is crucial for downstream deep processing, and adsorption is the main method for deep purification of such impurities. This article takes dimethyl ether, a typical oxygen-containing compound impurity in MTOs, as a polar impurity molecule, and LTA and FAU topological zeolites as research objects. The influence of zeolite topology, morphology, skeleton silicon–aluminum (Si/Al) ratio, and ion type on the adsorption and removal of trace dimethyl ether was investigated by XRD, SEM, XRF, and nitrogen adsorption–desorption methods. The FAU topological zeolites show a better adsorption performance for dimethyl ether owing to their larger specific surface area and unobstructed pores compared with LTA zeolites. Among FAU topological zeolites, the NaX zeolite a with lower framework silica–alumina ratio has the highest adsorption capacity for dimethyl ether. Magnesium ion exchange on NaX zeolites (MgNaX) reduce the specific surface area and adsorption capacity of the NaX zeolite. However, after forming with alumina as a binder, the adsorption capacity of the MgNaX–Al2O3 adsorbent is about 13% higher than that of the NaX–Al2O3 adsorbent without Mg ion exchange. This may be due to the decomposition of residual organic Mg salts in the Mg ion exchange samples during high-temperature calcination, resulting in a larger specific surface area for the formed adsorbent. Further characterization of NH3–TPD and CO2–TPD shows that Mg ion exchange weakens the acid–base active sites on the adsorbent surface. The reduction in acid–base sites reduces the occurrence of side reactions such as polymerization and isomerization caused by the exothermic adsorption of olefins on adsorbents. Repeated adsorption data show that the formed adsorbent has excellent regeneration–adsorption performance.

Sorption-desorption of rare earth metal cations by ferromanganese crusts of Govorov’s guyote of the Magellanic Mountains of the Pacific Ocean

The article presents the results of experimental studies on the sorption and desorption of rare earth metal (REM) cations by cobalt-rich ferromanganese crusts (CMC) of Govorov’s guyot. It has been established that the sorption of REM cations occurs on the ore minerals KMK – Fe-vernadite, vernadite, Mn-feroxygite, goethite. The crusts are characterized by a high exchange capacity – 1.78–3.57 mg-eq/g, which increases in a series: (Dy Gd Lu Sm Nd Y, La Eu) Ce. The sorption of REM cations proceeds by an ion exchange equivalent irreversible mechanism. The exchange complex of ore minerals consists of Na+, K+, Ca2+, Mg2+ cations, which contribute 97‒98% to their total capacity. The crusts are characterized by the group sorption of REM cations from multicomponent aqueous solutions of metal salts. The selectivity of ore manganese and ferruginous minerals of crusts to REM cations is significantly higher than to the main cations of ocean water. From experimental data on the desorption of sorbed REM cations with NaCl solution, their irreversible absorption by ore minerals follows, and the strengthening of the chemical bond of sorbed REM cations with the main structural elements of these minerals over time. An important property of ore minerals, primarily manganese minerals, is their chemical and structural stability in aqueous solutions of electrolytes. This suggests the repeated use of ferromanganese crusts as sorbents of REM cations.

Unveiling Biodiesel Production: Exploring Reaction Protocols, Catalysts, and Influential Factors

AbstractAn environmentally responsible and sustainable replacement for finite fossil fuels is biodiesel. Because of its amazing qualities, biodiesel is becoming more and more popular as a renewable fuel around the globe. The many approaches, feedstocks, catalysts, comparison standards, reaction kinetics, final product analysis, and final product characterization of biodiesel are covered in this review article. Researchers have used a variety of techniques to produce biodiesel throughout history, with transesterification emerging as the most effective approach in more recent times. Numerous studies on biodiesel feedstock and catalysts to produce high biodiesel yields have been published; nevertheless, it should be highlighted that the type of feedstock must be considered while choosing a catalyst. The review paper highlights the significance of several parameters that are crucial to the manufacture of biodiesel, without which achieving a high yield would be challenging. The literature has also discussed the limitations and advantages of different catalysts, and scientists are currently working to identify the ideal catalyst within certain optimal parameters for the manufacture of biodiesel. Homogeneous reaction‐based biodiesel synthesis has a number of drawbacks, though, such as water content, a laborious purification procedure, and a low tolerance for free fatty acids. To address these issues, scientists have started investigating heterogeneous reactions involving solid catalysts. A large pore network, a moderate‐to‐high density of strong acid sites, a hydrophobic surface, and the ability to control surface hydrophobicity to avoid deactivation are all desirable characteristics of an ideal solid catalyst. Ion exchange resins, sulfated oxides, heterogeneous base catalysts, boron group‐based heterogeneous catalysts, alkaline earth metal oxides, mixed metal oxides, alkali metal oxides, heterogeneous catalysts derived from waste materials, and different approaches to biodiesel synthesis that employ enzymes, carbon‐based heterogeneous catalysts, and ionic liquids as catalysts are among the categories of catalysts that can be used in the production of biodiesel. The finest benchmarks to compare the quality of biodiesel with European and American Society for Testing Material standards. For detailed characterization of the finished product, gas chromatography and nuclear magnetic resonance are the most effective methods.

Zirconium-Modified Attapulgite Composite for Phosphorus Removal and Algae Control in Lake Water

Phosphorus removal is critical for effective water treatment and the prevention of eutrophication. This study focuses on the modification of attapulgite, an economical clay material, with zirconium (Zr@ATP) to enhance its phosphorus adsorption capacity. Zr@ATP was comprehensively characterized, and its phosphorus-removal mechanisms were investigated. Additionally, its performance in water treatment was evaluated using a lake water-sediment system. Zr@ATP exhibited a high surface area of 329.29 m2/g. The static adsorption experiments revealed that Zr@ATP achieved a phosphorus-removal efficiency of 95.8% at an adsorbent dosage of 5 g/L. Kinetic studies indicated that the adsorption followed a pseudo-second-order model, with the primary mechanism being chemisorption via ion exchange. Application of Zr@ATP in a lake water-sediment system resulted in an 83.6% reduction in total phosphorus. The chlorophyll concentration significantly decreased from 32.33 μg/L to 8.56 μg/L, and the algal density decreased by 84.6%, effectively inhibiting algal growth. These results suggest that Zr@ATP is a promising adsorbent for sustainable phosphorus removal and eutrophication control in aquatic environments.

Experimental and molecular dynamic simulation studies of landfill contaminated groundwater remediation by graphene oxide coated zeolite

ABSTRACT Graphene oxide (GO) has proven effective in wastewater treatment due to its capability to adsorb heavy metals and organic contaminants. Zeolite is also widely used in contaminant remediation as a reactive material in permeable reactive barrier (PRB). Experimental column flow-through tests were applied in this study to investigate the remediation ability of composite granule-graphene oxide coated zeolite (GOZ) on FA, Pb2+ and NH4 +, from municipal landfill contaminated groundwater. Microscopic characterization and molecular dynamic simulation were carried out in sequence to understand the adsorption process. The results demonstrated that GO significantly enhanced zeolite’s adsorption capacity for Pb2+ and FA by 147.5% and 164.8%, respectively, though NH4 + removal experienced a slight decrease of 25% after GO coating. The ion exchange of Pb2+ resulted in more significant partial collapse compared to NH4 + due to different effective diameter comparing with the channel size of zeolite. However, GO coating relieved the framework deformation by engaging in functional group reactions during Pb2+ adsorption. A recommended surface area coating ratio between 47.0% and 78.4% was identified, as values outside this range may lead to significant GO deformation or inefficient FA adsorption. The GO-zeolite granules displayed significant potential in remediating various contaminants while effectively preventing GO aggregation and zeolite collapse. As technological advancements reduce GO production costs, the economic feasibility of using GOZ in groundwater remediation is increasingly promising.

In-depth mechanistic insights into Au nanoparticles based polyurethane foams as a selective and efficient dispersive solid phase microextractor for textile dyes from water: performance and reusability study

ABSTRACT Herein, a simple, superhydrophobic, superoleeophilic and low cost microextractor Au nanparticles (Au NPs) based polyurethane (PUFs) solid platform (Au NPs/PUFs) has been developed as a promising sorbent for removal and recovery of Congo red (CR) textile dye from water bodies. The sorbent was characterised using UV-visible and SEM techniques. The procedure relied complete dye retention from the aqueous solution at pH 5.0–5.5 onto an Au NP/PUF extractor. Analytical assessments revealed that the Au NPs/PUFs combination significantly improves mass transfer of dye and enhances creation of active sites for CR retention. CR sorption by the sorbent fitted well with intra-particle diffusion and pseudo first-order kinetic models (R2 = 0.990). The enthalpy change, ΔH (37.8 kJ mol−1) indicates that dye extraction is endothermic whereas the entropy change, ΔS0 (116.6 J mol−1K−1), reveals a significant change in the entropy during dye uptake. The free energy change ΔG (3.12 kJ mol−1 at 298 K) of CR sorption indicated that the dye retention was not spontaneous at all temperatures. A twofold sorption mechanism involving absorption accompanying ‘solvent extraction’ and/or ‘weak ion exchange’, combined with surface adsorption of dye is proposed. Sorbent packed mini column demonstrated effective percent removal and recovery (101.8%) of CR from water samples using acetone or NaOH as an eluting agent. The study expands the utility of Au NPs/PUFs for reusability and spectrophotometric sensing of trace levels of CR in water. The key attention also includes integrating PUFs utility by improving the selectivity and sensing properties towards textile dyes.

Zeolites – tabletting ibuprofen with and without zeolites as an excipient

Abstract Introduction Drug delivery via the oral route is a patient and industry-preferred approach. However, maintaining plasma concentrations of the active pharmaceutical ingredient (API) within the therapeutic window can be challenging with immediate-release (IR) tablets. To avoid the plasma peaks and troughs associated with IR tablets, sustained release (SR) formulations have been investigated. Zeolites are microporous aluminosilicate minerals that represent a novel tabletting material with the potential for modifying drug release due to their unique adsorption and ion exchange properties1. Aim This study will investigate the potential for inclusion of zeolites within orally disintegrating tablets (ODTs) and assessment of their ability to modify API release. Methods In-house, 50%w/w ibuprofen (IBU)-loaded ODTs (IHODTs) were prepared from Pearlitol® Flash, magnesium (Mg) stearate and 2 different zeolites (CP814C and CP814E), incorporated at 5%w/w each, using a manual tablet press. Formulations were prepared and mixed for 10 minutes in a cube mixer prior to direct compression (DC) into tablets. Physical characteristics of the tablets were assessed by hardness and friability measurements. Tablet quality was assessed by disintegration and dissolution analysis to British Pharmacopeia (BP) standards2. Release profiles were assessed against various models to determine the effect of zeolites on the release of IBU. Formulations were further examined and characterised using scanning electron microscopy (SEM) and energy-dispersive x-ray (EDX) spectroscopy. An ethics evaluation was completed, and the study was identified as not having any ethical considerations by the University of South Wales. Results The mean weight of blank ODTs was found to be 225.3mg, with a mean thickness of 3.65mm, diameter of 8.10mm, hardness of 43.9±9.2N (mean±SD, n=5) and friability of 0.2±0.2% (mean±SD, n=3). The hardness of IHODTs was found to be 59.98±1.6N, reducing to 54.9±4.3N and 43.4±0.7N (mean±SD, n=3) with the inclusion of CP814C and CP814E, respectively. The friability of IHODTs containing zeolites was 1.76±0.4% and 1.91±0.9N (mean±SD, n=3), for CP814C and CP814E, respectively; conforming to BP specification2. The disintegration time for all in-house tablets, both with and without a zeolite included, was found to be an order of magnitude greater than commercial ODTs (CT) controls, but all remained within the BP specification2. The release of IBU from IHODTs and CTs showed good correlation to the first-order release model (R2 = 0.96 and 0.98, respectively), indicating IR behaviour. Similarly, the release of IBU from IHODTs containing zeolites was shown to correlate best with the first-order release model, R2 = 0.91 for CP814C and R2 = 0.90 for CP814E, respectively. SEM analysis suggested a homogeneous blend of components within IHODTs, whilst EDX analysis indicated the presence of silicon and aluminium from zeolites, and Mg and carbon from Mg stearate and IBU, respectively. Discussion / Conclusion This study investigated the effect of zeolite inclusion on the release properties of ODTs containing IBU. Although the quality of ODTs containing zeolites was not compromised, this study suggests that inclusion of a zeolite by DC only, does not significantly modify the release profile. Future studies are required to ascertain whether zeolites can achieve SR from ODTs using alternative API loading approaches, such as solvent loading1.

Recovery of gold ions from thiosulfate solution using an electrogenerative process

Traditional zinc powder cementation method for recovering gold ions from thiosulfate solution has the disadvantages such as high consumption of active metal, surface passivation, and co-deposition of copper ions. The key to solving these issues is providing the necessary electrons for the reduction of Au(S2O3)23- while avoiding direct contact between zinc powder and the leaching solution. In this study, a novel electrogenerative device with ion exchange membranes separating the anode and cathode is developed for the recovery of gold ions from thiosulfate solution. The oxidation reaction of zinc electrode occurs in the anode chamber, while the reduction reaction of gold ions occurs on a platinum electrode in the cathode chamber. The optimal experimental conditions for the gold recovery are determined to be using a cation exchange membrane, with the anode solution of 0.08 M ZnSO4, pH = 6, and the cathode solution of 0.10 M Na2S2O3, 5 mM CuSO4, 0.5 M NH3·H2O, pH = 10, with an initial gold concentration of 10 mg/L. It obtains the gold recovery of 99.59 %. Compared the zinc powder cementation method with the similar gold recovery, the electrogenerative process reduces zinc consumption by 67 % and prevents the passivation on the zinc surface caused by copper, oxygen, and sulfur.

SODA LIME SILICATE GLASSES CONTAINING IRON OXIDE - IN VITRO EVALUATION

Three glasses with different iron oxide concentrations (between 5 and 8.1 mol %) were obtained in the CaO - Na2O - SiO2 - Fe2O3 system by using conventional melting-quenching technique. The amorphous nature of the synthesized materials is confirmed by X-ray diffraction analysis, XRD. The physico-chemical and structural characterization of the glasses was performed by measuring their density, refractive indices, as well as by calculating the molar volume, oxygen packing density and recording the infrared spectra by Fourier Transformed Infrared Spectroscopy, FT-IR, respectively. The glasses were evaluated in vitro by examining bone-like apatite formation on their surfaces in a simulated body fluid, SBF. The structural changes in the glasses during the in-vitro test were traced by means of FT-IR and Scanning Electron Microscopy, SEM. The solutions were examined by Inductively Coupled Plasma Optical Emission Spectroscopy, ICP-OES to determine the ion exchange between the glasses and the starting SBF and the corresponding effect on the pH was also recorded.

Acrylate reductase of an anaerobic electron transport chain of the marine bacterium shewanella woodyi

Many microorganisms are capable of anaerobic respiration in the absence of oxygen, by using different organic compounds as terminal acceptors in electron transport chain. We identify here an anaerobic respiratory chain protein responsible for acrylate reduction in the marine bacterium Shewanella woodyi. When the periplasmic proteins of S. woodyi were separated by ion exchange chromatography, acrylate reductase activity copurified with an ArdA protein (Swoo_0275). Heterologous expression of S. woodyi ardA gene (swoo_0275) in Shewanella oneidensis MR-1 cells did not result in the appearance in them of periplasmic acrylate reductase activity, but such activity was detected when the ardA gene was co-expressed with an ardB gene (swoo_0276). Together, these genes encode flavocytochrome c ArdAB, which is thus responsible for acrylate reduction in S. woodyi cells. ArdAB was highly specific for acrylate as substrate and reduced only methacrylate (at a 22-fold lower rate) among a series of other tested 2-enoates. In line with these findings, acrylate and methacrylate induced ardA gene expression in S. woodyi under anaerobic conditions, which was accompanied by the appearance of periplasmic acrylate reductase activity. ArdAB-linked acrylate reduction supports dimethylsulfoniopropionate-dependent anaerobic respiration in S. woodyi and, possibly, other marine bacteria.

Versatile silicate-modified hydrochar based on Scutellaria baicalensis-residue for efficiently removing heavy metal-antibiotic co-contamination and relevant bio-contaminants from wastewater

In this study, we utilized typical Chinese medicine herbal residues (CMHRs)－Scutellaria baicalensis (Scutellaria baicalensis Georgi) residue (SR), as the raw material and employed Na2SiO3 and Fe2(SO4)3 as modifying agents to fabricate a novel and multifunctional hydrochar (FeSi-SRHC), which was designed for comprehensive removal of typical contaminants such as Cu2+, Zn2+, tetracycline (TC), and ciprofloxacin (CIP), along with relevant bio-contaminants (resistant bacteria (RBs) and resistance genes (RGs)) present in wastewater. Based on the analysis of adsorption kinetics and Freundlich isotherm, it was found that FeSi-SRHC exhibited physical monolayer adsorption for Cu2+/Zn2+ while mainly chemical multilayer adsorption for TC/CIP in single-contamination system. Furthermore, Langmuir isotherm demonstrated excellent adsorption capacity of FeSi-SRHC towards Cu2+/Zn2+/TC/CIP with maximum capacities of 255.75, 265.26, 425.53, and 404.86 mg/g, respectively. In the co-contamination system, the presence of Cu2+, Zn2+, TC, and CIP exhibited varying degrees of inhibitory or promotive effects on the mutual adsorption by FeSi-SRHC. This divergence stemmed from differences in complexation intensities and concentration ratios among diverse co-existing contaminants. Based on XPS and Density Functional Theory (DFT) analyses, the adsorption process for Cu2+, Zn2+, TC, and CIP by FeSi-SRHC primarily involves pore fill, complexation reactions, ion exchange, hydrogen bonding, π-π stacking interactions, and electrostatic interactions. Bio-contaminant removal experiments revealed that the release of baicalin and wogonoside from FeSi-SRHC disrupts the structure of RBs cells and compromises the integrity of resistance plasmids. The practical application experiment showed that FeSi-SRHC displayed favorable performance for removing heavy metals, antibiotics, and bio-contaminants in actual wastewater. This study presented a “Treating waste with waste” strategy, which provided a method with low carbon, eco-friendly, and inexpensive for CMHRs resources and turning waste into treasure while proposing a idea to address the challenges associated with treating heavy metal, antibiotic, and bio-contaminant contamination in wastewater.

From Tradition to Innovation: An In-Depth Review of Manganese Removal Techniques in Water Treatment

Contamination of water is currently one of the alarming issues all around the planet. Water that is contaminated with manganese (Mn) could potentially give rise to functional and aesthetic complications. Removal of manganese is critical and often has substantial implications for the layout of treatment trains. Precipitation, ion exchange, depth filtration, oxidation, adsorption, biosorption, and biological methods are the traditional chemical, physical, and biological processes for removing Mn (II) from contaminated water. All these treatment processes have some advantages and disadvantages and are based on which the implementation of any process varies. In recent years, the use of biofiltration to eliminate manganese (Mn) from water has grown owing to the progress made in molecular techniques for studying microorganisms found in biological Mn elimination systems. This study aims to contribute to the existing research on Mn occurrence and highlight the historical and current removal strategies used in drinking water treatment. The main objective is to assist future researchers in developing more efficient technologies and clarify the subject matter.

Resource Recovery from Abandoned Mine Drainage Galleries via Ion Exchange: A Case Study from Freiberg Mining Area, Germany

The discharge of metal-loaded mining-influenced waters can significantly pollute downstream water bodies for many kilometers. Addressing this issue at the earliest discharge point is crucial to prevent further contamination of the natural environment. Additionally, recovering metals from these discharges and other sources of contamination can reduce the environmental impacts of mining and support the circular economy by providing secondary raw materials. This study focused on optimizing zinc recovery from mining-influenced water in the Freiberg mining region in Germany, where significant loads of zinc are released into the Elbe River. By employing pretreatment techniques, conducting 100 mL scale ion-exchange column experiments, and refining the regeneration process, we aimed to identify optimal conditions for efficient zinc removal and recovery. Initial tests showed that aminophosphonic functionalized TP 260 resin had a high affinity for aluminum, occupying 93% of the resin’s capacity, while zinc capacity was limited to 0.2 eq/L. To improve zinc recovery, selective precipitation of aluminum at pH 6.0 was introduced as a pretreatment step. This significantly increased the zinc loading capacity of the resin to 1 eq/L. Under optimal conditions, a concentrated zinc solution of 18.5 g/L was obtained with 100% recovery. Sulfuric acid proved more effective than hydrochloric acid in eluting zinc from the resin. Further analysis using SEM-EDX revealed residual acid on the resin, indicating a need for additional study on long-term resin performance and capacity variation. The research also highlighted the environmental impact of the Freiberg mining area, where three drainage galleries currently contribute nearly 85 tons of zinc annually to the Elbe River. This study underscores the feasibility of efficient zinc recovery from these point sources of pollution using advanced ion-exchange processes, contributing to circular economy efforts and environmental conservation.

Application of coniferous bark as sorbent material for per- and polyfluoroalkyl substances – A case study in Sweden

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic contaminants commonly found in drainage water from waste management facilities. Within the European Union, these facilities either treat the water locally or transfer it to wastewater treatment plants to reduce harmful emissions. However, PFAS are a broad class of compounds with varying physicochemical properties, leading to different removal efficiencies for adsorbents. Activated carbon and ion exchange resins are effective but costly, and they can become saturated with other contaminants. Therefore, this study aims to explore inexpensive, abundant alternatives for reducing PFAS concentrations in the environment. In Sweden, bark is a by-product of forestry activities, primarily used as fuel in heat and power plants. This study evaluates the ability of pine and spruce bark to remove PFAS from contaminated drainage water. Initial laboratory experiments employed liquid-to-solid ratios of 10 and 20 to assess the performance of both materials. Results indicated that pine bark exhibited better removal efficiencies, particularly when a layered column with pine bark followed by spruce bark was utilized. The overall removal efficiencies for short-chain PFAS (perfluorinated carbons: PFCA C3–C6 and PFSA C4–C5) and long-chain PFAS (PFCA > C7 and PFSA > C6) were below 20%, except for perfluorooctane sulfonic acid (PFOS), which showed reductions of 40%–80%. The pH of the treated water decreased from 7 to 4 (pine bark) and 5 (spruce bark) after treatment. In a larger-scale trial, a combination of 50% pine bark and 50% spruce bark was tested, achieving similar reductions for PFOS. Although the removal efficiencies were insufficient for exclusive treatment, these materials may be useful in specific applications targeting long-chain PFAS or in conjunction with other treatment methods.

Alkali and alkaline earth ion exchange affinity in ETS-10 toward aqueous lithium separation

Continuous ion exchange is a more sustainable alternative to current methods for removing common impurities from lithium sources. In this work, we examine ion-adsorbent interactions for Mg2+ and Ca2+ with microporous titanosilicate ETS-10, an ion exchange solid with promising performance, using experimental and computational (density functional theory, DFT) methods. Ion exchange affinity for Mg2+ and Ca2+ using the Na+-form of ETS-10 are quantified from measured equilibrium isotherms, analyzed using a modified Langmuir isotherm accounting for overall stoichiometric desorption/adsorption in the cation exchange process. The equilibrium constant for ion exchange using Na-ETS-10 is greatest for Ca and decreases in order of Mg, K, and Li, respectively. These differences in ion exchange affinity are consistent with trends in DFT-derived ion exchange energies, which account for hydration and solvation of cations using a thermochemical cycle. These equilibrium constant values and ion exchange energies suggest that exchange of Ca2+, Mg2+, and K+ using Na-ETS-10 is more favorable than that of Li+. Indeed, competitive ion exchange of equimolar aqueous mixtures of Li+ and each of K+, Mg2+, or Ca2+ demonstrate selective uptake of the non-lithium cation into the solid, thereby concentrating Li+ in the aqueous solution while removing impurity cations.

Mechanistic Model Advancements for Optimal Calcium Removal in Water Treatment: Integral Operation Improvements and Reactor Design Strategies

Drinking water softening has primarily prioritized public health, environmental benefits, social costs and enhanced client comfort. Annually, over 35 Gm3 of water is softened worldwide, often utilizing three main techniques: nanofiltration, ion exchange and seeded crystallization by pellet softening. However, recent modifications in pellet softening, including changes in seeding materials and acid conditioning used post-softening, have not fully achieved desired flexibility and optimization. This highlights the need of an integral approach, as drinking water softening is just one step in the drinking water treatment chain, which includes ozonation, softening, biological active carbon filtration (BACF) and sand filtration among others. In addition, pellet softening is often practiced based on operator knowledge, lacking practical key reactor performance indicators (KPIs) for efficient control. For that reason, we propose a newly and improved integral mechanistic model designed to accurately predict (1) calcite removal rates in drinking water through seeded crystallization in pellet softening reactors, (2) the saturation of the filter bed in the subsequent treatment step, (3) values for the KPIs steering the softening efficiency. Our new mechanistic model integrates insights from hydrodynamics, thermodynamics, mass transfer kinetics, nucleation and reactor engineering, focussing on critical variables such as temperature, linear velocity, pellet particle size and saturation index with respect to calcite. Our model was validated with data from the Waternet Weesperkarspel drinking water treatment plant in Amsterdam, The Netherlands, but implies universal applicability for addressing industrial challenges beyond drinking water softening. The implementation of our model proposes five effective KPIs to optimize the softening process, chemical usage, and reactor design. The advantage of this model is that it eliminates the application of numerical methods and fills a significant gap in the field by providing predictions of the carry-over (i.e., the produced CaCO3 fines leaving the fluidized bed) from water softening practices. With our model, the calcium removal rate is predicted with an average standard deviation (SD) of 40% and the consequential clogging prediction of the BACF bed with an average SD of 130%. Ultimately, our model provides crucial insights for operational management and decision-making in drinking water treatment plants, steering towards a more circular and environmentally sustainable process.

Magnetic bentonite with organic modification highly efficient for adsorption of Ce(III) and Y(III)

A simple organic magnetic adsorbent (PAA-MBent) was synthesized using 2-hydroxyphosphonylacetic acid and applied to the adsorption of Ce(III) and Y(III). It was confirmed that the phosphoryl groups could effectively regulate the homogeneous loading of magnetic particles on the bentonite during the synthesis process, and the hydroxyl and phosphoryl groups can be sufficiently used on the surface of bentonite to increase the abundance of adsorption sites, which have favorable coordination with Ce(III) and Y(III). The experimental results showed that the maximal adsorption capacity was increased to 99.11 mg/g and 65.65 mg/g for Ce(III) and Y(III), respectively, which was 2.52 and 2.91 times higher than magnetic bentonite. The adsorption behavior conformed to the Langmuir isothermal adsorption model and the pseudo-second-order kinetic model, and the adsorption of Ce(III) by PAA-MBent performed better than that of Y(III). The adsorption efficiency was affected by ionic strength and site inhibition of coexisting cations, and its adsorption selectivity was mainly disturbed by the competition of Al ions. The results after adsorption identified the key adsorption mechanisms as ion exchange, electrostatic attraction, functional group complexation, and hole filling. After five cycles, the adsorbent still exhibited good adsorption and magnetic recovery performance. These results reveal that PAA-MBent is promised to be a novel, inexpensive and effective adsorbent for the removal of Ce(III) and Y(III) from contaminated water.