Competitive Cations Research Articles

MER Zeolite with Remarkable Pb2+ and Cd2+ Removal Capability Cost-Effectively Synthesized from Postprocessed Natural Stellerite.

MER zeolite, a low-silica zeolite with an 8-membered ring aluminosilicate framework, has been recognized as a promising material in sorption, separation, and ion-exchange applications. Herein, we developed a cost-effective and rapid method to convert parent zeolite H-STI, which was derived from natural stellerite, into MER zeolite through interzeolite conversion with a crystallization time of 8 h. This MER zeolite exhibits high efficiency in removing Pb2+ and Cd2+ from simulated heavy metal wastewater over a pH range of 3-8. It also shows excellent selectivity in the presence of competitive cations, including Na+, K+, Ca2+, Mg2+, Zn2+, Cu2+, and Co2+. At 25 °C, with a MER-S dosage of 1/3000 g·mL-1 for Pb2+ and 1/500 g·mL-1 for Cd2+, the removal efficiencies were 99.7 and 99.9%, respectively. The distribution coefficients were 1097 L·g-1 for Pb2+ and 550 L·g-1 for Cd2+, and the sorption capacities reached 513 mg·g-1 for Pb2+ and 171 mg·g-1 for Cd2+, indicating that the product MER zeolite is one of the highest sorbents for Pb2+ and Cd2+ reported for zeolitic materials. The sorption for Pb2+ and Cd2+ both follows the chemisorption-dominated mechanism, driven by the ion-exchange process between the K+ in the channels MER-S and the Pb2+ or Cd2+ in solution. This work highlights the potential of rapidly synthesized MER zeolite for the effective removal of heavy metal cations, emphasizing its performance and practical applicability.

A Terbium‐Based MOF as Fluorescent Probe for Selective Sensing of Nitrobenzene and Fe3+

AbstractA three‐dimensional metal‐organic framework named as [TbL(OH)2](COOH)3 ⋅ (solvent)x (Tb‐MOF), was successfully obtained by using Tb(NO3)3 ⋅ 6H2O and 1,1′,1′′‐(2,4,6‐trimethylbenzene‐1,3,5‐triyl)tris(methylene)‐tris(4‐carboxy‐pyridinium)tribromide (H3LBr3) as raw materials. A series of fluorescence detection experiments demonstrate that Tb‐MOF shows a fluorescence quenching effect on NB. Moreover, Tb‐MOF also exhibits a very fast fluorescence quenching response to trace Fe3+ ions, which is unaffected by the existence of other competitive metal cations. The linear curve between the fluorescence intensity of Tb‐MOF and the concentration of Fe3+ was plotted by the fluorescence titration experiments data. The calculated LOD for Fe3+ ions is 2.86×10−6 M. Therefore, based on the characteristics of Tb‐MOF, it can be regarded as a luminescent sensor for detecting NB and Fe3+. We have also explored the quenching mechanism of Tb‐MOF as a fluorescent sensing material.

Effects of Successive Top-Dressing Application of Lime on a Sweet Cherry Orchard in Southern Chile

Annual top-dressing application of agricultural lime is a common practice in fruit orchards on acidic soils in southern Chile, which could result in surface over-liming and base imbalances. A trial was performed in a cherry orchard with an 8-year history of surface liming to evaluate the effectiveness of lime materials in neutralizing acidity in the soil profile and the effect on the tree nutritional status. No-lime (NL), calcitic (AgL), hydrated (HL), and liquid (LL) lime treatments were applied on soil surface at commercial rates, and soil acidity variables were measured at depths of 0–5, 5–10, and 10–20 cm in samples collected at 0, 15, 30, 60, and 225 days after application. Tree nutritional status was evaluated through foliar analysis. Top-dressing application of AgL was ineffective in ameliorating subsoil acidity at depths >5 cm, even in high-rainfall conditions. HL did not exhibit greater alkalinity mobility compared to AgL, although it had a faster but shorter-lived reaction. At the manufacturer-recommended rates, LL application was ineffective. After 8 years of top-dressing liming with AgL, a significant stratification of soil pH, Al, and Ca was observed. However, foliar concentration of bases did not reflect the surface Ca accumulation in soil, discarding an antagonistic cation competition for tree uptake.

Dairy manure influences soil properties, plant nutrient uptake, and tuber quality in potatoes

AbstractDairy manure applications are a common practice in Idaho potato (Solanum tuberosum L.) production, however the impacts on tuber yield and quality are not well understood. Our objectives were to determine (1) how repeated dairy manure applications impact soil properties and plant nutrient uptake, and (2) how these changes influence plant nutrient interactions, tuber yield, and quality. Stockpiled dairy manure was fall‐applied over a 6‐year period to two adjacent potato production fields in Kimberly, ID. Eight treatments included application frequency (annual and biennial), manure application rate (18, 36, and 52 Mg ha−1 application−1 [dry weight basis]), fertilizer‐only, and a non‐amended control. Manure treatments were supplemented with fertilizer to prevent nutrient‐limiting conditions. Compared to fertilizer treatments, mean soil organic matter, total N, and K were greater for annual manure by 53%, 47%, and 426%, and biennial manure by 24%, 23%, and 199%, respectively. For annual applications only, mean soil nitrate, P, and electrical conductivity were greater than fertilizer treatments by 247%, 431%, and 222%, respectively. Manure promoted P and K luxury consumption with increasing application rate and frequency. Foliage Ca, Mg, Zn, Mn, and Cu correlated negatively against foliage K, potentially due to cation competition and translocation disruption. Annual applications decreased mean tuber specific gravity from 1.078 to 1.073, which may be attributed to saline‐sodic conditions and delayed maturity from late‐season N mineralization. Our findings suggest that biennial manure applications may prevent specific gravity issues. Agronomic parameters related to N, K, and soluble salts should be closely monitored in these systems.

Decoupling the air sensitivity of Na-layered oxides.

Air sensitivity remains a substantial barrier to the commercialization of sodium (Na)-layered oxides (NLOs). This problem has puzzled the community for decades because of the complexity of interactions between air components and their impact on both bulk and surfaces of NLOs. We show here that water vapor plays a pivotal role in initiating destructive acid and oxidative degradations of NLOs only when coupled with carbon dioxide or oxygen, respectively. Quantification analysis revealed that reducing the defined cation competition coefficient (η), which integrates the effects of ionic potential and sodium content, and increasing the particle size can enhance the resistance to acid attack, whereas using high-potential redox couples can eliminate oxidative degradation. These findings elucidate the underlying air deterioration mechanisms and rationalize the design of air-stable NLOs.

Implementation of Three Gallium-Based Complexes in the "Trojan Horse" Antibacterial Strategy against A. baumannii: A DFT Approach.

Microorganisms of the ESKAPE group pose an enormous threat to human well-being, thus requiring a multidisciplinary approach for discovering novel drugs that are not only effective but utilize an innovative mechanism of action in order to decrease fast developing resistance. A promising but still hardly explored implementation in the "Trojan horse" antibacterial strategy has been recognized in gallium, an iron mimicry species with no known function but exerting a bacteriostatic/bactericidal effect against some representatives of the group. The study herewith focuses on the bacterium A. baumannii and its siderophore acinetobactin in its two isomeric forms depending on the acidity of the medium. By applying the powerful tools of the DFT approach, we aim to delineate those physicochemical characteristics that are of great importance for potentiating gallium's ability to compete with the native ferric cation for binding acinetobactin such as pH, solvent exposure (dielectric constant of the environment), different metal/siderophore ratios, and complex composition. Hence, the provided results not only furnish some explanation of the positive effect of three Ga3+-based anti-infectives in terms of metal cation competition but also shed light on reported in vitro and in vivo observations at a molecular level in regard to gallium's antibacterial effect against A. baumannii.

Tuning Octahedron Sites of CoV2O4 via Cationic Competition for Efficient Oxygen Evolution Reaction.

Doping transition metal oxide spinels with metal ions represents a significant strategy for optimizing the electronic structure of electrocatalysts. Herein, a bimetallic Fe and Ru doping strategy to fine-tune the crystal structure of CoV2O4 spinel for highly enhanced oxygen evolution reaction (OER) is presented performance. The incorporation of Fe and Ru is observed at octahedral sites within the CoV2O4 structure, effectively modulating the electronic configuration of Co. Density functional theory calculations have confirmed that Fe acts as a novel reactive site, replacing V. Additionally, the synergistic effect of Fe, Co, and Ru effectively optimizes the Gibbs free energy of the intermediate species, reduces the reaction energy barrier, and accelerates the kinetics toward OER. As expected, the best-performing CoVFe0.5Ru0.5O4 displays a low overpotential of 240mV (@10mAcm-2) and a remarkably low Tafel slope of 38.9mVdec-1, surpassing that of commercial RuO2. Moreover, it demonstrates outstanding long-term durability lasting for 72h. This study provides valuable insights for the design of highly active polymetallic spinel electrocatalysts for energy conversion applications.

Unconventional extraction of uranium from seawater through microenvironment-specific conjugated microporous poly(aniline)s

The sustainability of uranium-based nuclear energy relies on the development of quick and effective uranium adsorbents. Herein, we propose a facile post-synthetic technique by grafting amino-functional groups onto the fluorenone-functionalized conjugated microporous poly(aniline)s (CMPs) network to acquire a novel class of N decorated polymers for uranium capture. By leveraging the abundant N sites and microenvironment-containing molecular structure, CMPA-F-BDA showcases excellent UO22+ adsorption performance with fast adsorption kinetic with initial adsorption rate up to 43.78 mg g−1 min−1, Langmuir adsorption capacity of 443 mg g−1 and exceptional adsorption selectivity of Kd = 1.3 × 107 mL g−1 even in the serious presence of competitive cations. Additionally, CMPA-F-BDA could treat up to 18.5 L g−1 of low-concentration uranium solution (1 mg L−1) and actual seawater, removing 87.9% of uranium from 10 L of seawater, and has excellent reusability. This study demonstrates the bright future of CMPs for the extraction of low-concentration uranium.

Facile synthesis of magnetic intelligent sensors for the pH-sensitive controlled capture of Cr(vi).

In this work, intelligent pH-sensitive sensors (Fe3O4/RhB@PAM) for Cr(vi) detection were successfully synthesized based on polyacrylamide (PAM) and Rhodamine B (RhB) co-modified Fe3O4 nanocomposites. The characterization results indicated that the sensors had many favorable properties, including suitable size, stable crystal structure and excellent magnetic response performance (47.59 emu g-1). In addition, the fluorescence changes during the detection process indicated that Fe3O4/RhB@PAM were "ON-OFF" intelligent sensors. When the Fe3O4/RhB@PAM sensors were placed in acidic Cr(vi) solution (pH 4), PAM acted as a pH-responsive "gatekeeper" releasing RhB, and the fluorescence intensity of released RhB was weakened by the complexation of Cr(vi). Furthermore, the fluorescence changes of the magnetic sensors were remarkably specific for Cr(vi) even in the presence of other competitive cations, and the limit of detection (LOD) for Cr(vi) was lower (0.347 μM) than the value recommended by the World Health Organization (0.96 μM). All the results presented in this study showed that the Fe3O4/RhB@PAM sensors had significant potential for Cr(vi) detection in acidic environmental samples.

Anion–Cation Competition Chemistry for Comprehensive High‐Performance Prussian Blue Analogs Cathodes

AbstractThe extensively studied Prussian blue analogs (PBAs) in various batteries are limited by their low discharge capacity, or subpar rate etc., which are solely reliant on the cation (de)intercalation mechanism. In contrast to the currently predominant focus on cations, we report the overlooked anion‐cation competition chemistry (Cl−, K+, Zn2+) stimulated by high‐voltage scanning. With our designed anion‐cation combinations, the KFeMnHCF cathode battery delivers comprehensively superior discharge performance, including voltage plateau >2.0 V (vs. Zn/Zn2+), capacity >150 mAh g−1, rate capability with capacity maintenance above 96 % from 0.6 to 5 A g−1, and cyclic stability exceeding 3000 cycles. We further verify that such comprehensive improvement of electrochemical performance utilizing anion‐cation competition chemistry is universal for different types of PBAs. Our work would pave a new and efficient road towards the next‐generation high‐performance PBAs cathode batteries.

Insights into Li+ adsorption using H2TiO3 in salt lakes with different hydrochemical types: The activity of OH groups

Adsorption-based lithium (Li) recovery from salt lakes has focused on Li+ selectivity in competitive cations and improving the adsorption capacity, but ignored the effect of different hydrochemical types on its adsorption. Herein, the adsorption behavior of Li+ was comparatively studied in carbonate-type, sulfate-type, and chloride-type salt lakes using H2TiO3 as an adsorbent. The Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy confirmed that the replacement of O–H by O-Li bond in H2TiO3 sieves drove the Li+ capture. At a salt concentration of 10 g/L, the adsorption of Li+ by H2TiO3 was in the order of SO42− (40.08 mg g−1) > Cl− (36.66 mg g−1) > CO32− (30.18 mg g−1). Thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) demonstrated that the number of activated OH groups in the three salt solutions followed the same order of adsorption capacity. The binding energy of Li+ and anion calculated by density functional theory (DFT) verified the activity of OH groups, further revealing the influence mechanism of hydrochemical types on Li+ adsorption. This study suggests that the activity of Li+ adsorption sites was affected by the specific hydrochemical types of salt lakes, providing theoretical guidance for the Li+ adsorptive recovery from different water matrices.

Ultrafast and nanomolar detection of Al3+: Furazan based fluorescent chemosensor and its practices in Smartphone, test kit, water samples and living–cell

A new fluorescent chemoprobe (SDAF) was successfully synthesized and utilized as a sensor for the recognition of Al3+ in EtOH:HEPES (3:2, v:v, pH: 7.0) media. The SDAF depicted a selective “turn–on” response at λem = 467 nm to Al3+ over competitive cations, and the SDAF–Al3+ complex had a reversible response with F−. The limit of detection (LOD) was found about at nano–molar level (28.0 nM), demonstrating the sensitivity of the chemoprobe toward Al3+. The binding stoichiometry of SDAF–Al3+ was investigated by TOF–MS, Job's plot, 1H NMR and 13C NMR methods and found as 1:1. The recognition mechanisms of SDAF for the detection of Al3+ were the –C = N isomerization and photoinduced electron transfer (PET) mechanisms, and they were confirmed by density functional theory (DFT) computation. Furthermore, the SDAF was successfully employed in living–cell bioimaging and cytotoxicity, it was also utilized in Smartphone, test–kit and natural spring water (recovery values; 89.01 %– 96.33 %)applications.

Spectroscopic properties of a fluorescent pyrene-quinoline-based bisoxime-type sensor and its application to the detection of Cu2+ ion in real water samples

Fluorescent sensors are efficient and convenient tools for metal ions analysis. Herein, a new fluorescent pyrene-quinoline-based bisoxime-type sensor PQS, possessing the monomer to excimer emission switching feature, was synthesized and the sensing ability toward Cu2+ was throughly studied. Interestingly, the blue emission of monomer PQS in dilute solution converted to the green fluorescence of excimer in aggregated state. Meanwhile, the blue fluorescence emission of sensor PQS quenched in the existence of Cu2+ with no apparent response toward other competitive cations. The plausible complexation ratio 1:1 of sensor PQS to Cu2+ was substantiated by Job's plot, mass spectrometric analysis combined with the density functional theory calculation. Furthermore, PQS coated paper strips were prepared and used for the rapid and convenient monitoring Cu2+ in a visible manner.

Effects of competitive cations and dissolved organic matter on ammonium exchange and up-concentration properties of ion exchangers from domestic wastewater under multicycle exchange - regeneration operation

This study aimed to investigate the impact of competitive cations and dissolved organic matter (DOM) on ammonium exchange and up-concentration properties of ion exchangers for domestic wastewater treatment during the multicycle exchange - regeneration operations. Three ion exchangers, including zeolite, strong acid cation resin and 4A molecular sieve (MS), all showed good NH4+ separation and up-concentration properties in 30 exchange - regeneration cycles. The exchange capacities of zeolite, resin, and MS decreased by 8.2 %, 10.4 %, and 4.8 % in the presence of Ca2+ and Mg2+, while DOM only impaired the exchange ability of zeolite. The up-concentration factors of zeolite, resin, and MS were 5.1, 11.5, and 5.0, respectively. Isothermal tests and breakthrough curves confirmed that long-term salt regeneration slightly reduced the exchange capacity, and the presence of competitive cations and DOM shortened the breakthrough time. Elemental mass balance further demonstrated that Ca2+ and Mg2+ were easily trapped by ion exchangers and could be released into the regeneration solution, which should be precipitated to avoid accumulation for long-term cyclic operation. Morphological analysis indicated that the presence of Ca2+ and Mg2+ would cause the resin to crack. Overall, for domestic wastewater treatment, the resin exhibited the highest NH4+ capture ability and up-concentration properties with low resistance to Ca2+ and Mg2+ contamination, while silicate exchangers with a regular and compact structure had higher durability but lower up-concentration properties.

Effect of PFDS on the immobilization of Cs+ by metakaolin-based geopolymers in complex environments

Metakaolin-based geopolymers are very promising materials for improving the safety of low and intermediate level radioactive waste disposal, with respect to ordinary Portland cement, due to their excellent immobilization performance for Cs+ and superior chemical stability. However, their application is limited by the fact that the leaching behavior of Cs+ is susceptible to the presence of other ions in the environment. Here, we propose a way to modify a geopolymer using perfluorodecyltriethoxysilane (PDFS), successfully reducing the leaching rate of Cs+ in the presence of multiple competitive cations due to blocking the diffusion of water. The leachability index of the modified samples in deionized water and highly concentrated saline water reached 11.0 and 8.0, respectively. The reaction mechanism between PDFS and geopolymers was systematically investigated by characterizing the microstructure and chemical bonding of the material. This work provides a facile and successful approach to improve the immobilization of Cs ions by geopolymers in real complex environments, and it could be extended to further improve the reliability of geopolymers used in a range of applications.

Ion pair induced supramolecular assembly for development of novel pyridine 2, 6 diamide spacer acyl hydrazone-based derivatives for selective sensing of ZnCl2 and AlCl3

The work reports the development of a novel pyridine 2, 6 diamide spacer acyl hydrazone-based dual sensor H2L via two intermediates 1 and 2. The sensor as well as intermediates have been spectroscopically characterized. The structure of intermediate 1 is validated by its single crystal data analysis. As H2L bears both amide and acyl hydrazone moiety which have selective detection ability of anion and cation respectively, after rigorous characterization, the sensors are exposed to check their dual binding behavior. The results of several spectroscopic studies disclose the fact that H2L can optically and fluorometrically detect Al (III) and Zn (II) among several competitive cations and Cl− among competitive anions in semi-aqueous and aqueous medium respectively. Interestingly in a 9:1 DMSO-water medium, the probe can act as an ion pair sensor and in this medium, the probe can simultaneously detect Zn (II)/Cl- and Al (III)/Cl- forming H2L-ZnCl2, H2L-AlCl3 adduct. The 1:1 probe-analyte ion-pair binding is confirmed by NMR and mass spectral study. The Density Functional Theory (DFT) study optimizes the structures of the probe-analyte complexes. Impressively the probe has the potential to detect and quantify the Al (III) from market-available drug samples.

Nutrient and mycoremediation of a global menace 'arsenic': exploring the prospects of phosphorus and Serendipita indica-based mitigation strategies in rice and other crops.

Serendipita indica induced metabolic reprogramming in colonized plants complements phosphorus-management in improving their tolerance to arsenic stress on multifaceted biological fronts. Restoration of the anthropic damage done to our environment is inextricably linked to devising strategies that are not only economically sound but are self-renewing and ecologically conscious. The dilemma of heavy metal (HM) dietary ingestion, especially arsenic (As), faced by humans and animals alike, necessitates the exploitation of such technologies and the cultivation of healthy and abundant crops. The remarkable symbiotic alliance between plants and 'mycorrhizas' has evolved across eons, benefiting growth/yield aspects as well as imparting abiotic/biotic stress tolerance. The intricate interdependence of Serendipita indica (S. indica) and rice plant reportedly reduce As accumulation, accentuating the interest of microbiologists, agriculturists, and ecotoxicological scientists apropos of the remediation mechanisms of As in the soil-AMF-rice system. Nutrient management, particularly of phosphorus (P), is also praised for mitigating As phytotoxicity by deterring the uptake of As molecules due to the rhizospheric cationic competition. Taking into consideration the reasonable prospects of success in minimizing As acquisition by rice plants, this review focuses on the physiological, metabolic, and transcriptional alterations underlying S. indica symbiosis, recuperation of As stress together with nutritional management of P by gathering case studies and presenting successful paradigms. Weaving together a volume of literature, we assess the chemical forms of As and related transport pathways, discuss As-P-rice interaction and the significance of fungi in As toxicity mitigation, predominantly the role of mycorrhiza, as well as survey of the multifaceted impacts of S. indica on plants. A potential strategy for simultaneous S. indica + P administration in paddy fields is proposed, followed by future research orientation to expand theoretic comprehension and encourage field-based implementation.

Build a High‐Performance All‐Solid‐State Lithium Battery through Introducing Competitive Coordination Induction Effect in Polymer‐Based Electrolyte

AbstractPolymer‐inorganic composite electrolytes (PICE) have attracted tremendous attention in all‐solid‐state lithium batteries (ASSLBs) due to facile processability. However, the poor Li+ conductivity at room temperature (RT) and interfacial instability severely hamper the practical application. Herein, we propose a concept of competitive coordination induction effects (CCIE) and reveal the essential correlation between the local coordination structure and the interfacial chemistry in PEO‐based PICE. CCIE introduction greatly enhances the ionic conductivity and electrochemical performances of ASSLBs at 30 °C. Owing to the competitive coordination (Cs+…TFSI−…Li+, Cs+…C−O−C…Li+ and 2,4,6‐TFA…Li…TFSI−) from the competitive cation (Cs+ from CsPF6) and molecule (2,4,6‐TFA: 2,4,6‐trifluoroaniline), a multimodal weak coordination environment of Li+ is constructed enabling a high efficient Li+ migration at 30 °C (Li+ conductivity: 6.25×10−4 S cm−1; tLi+=0.61). Since Cs+ tends to be enriched at the interface, TFSI− and PF6− in situ form LiF‐Li3N‐Li2O‐Li2S enriched solid electrolyte interface with electrostatic shielding effects. The assembled ASSLBs without adding interfacial wetting agent exhibit outstanding rate capability (LiFePO4: 147.44 mAh g−1@1 C and 107.41mAhg−1@2 C) and cycling stability at 30 °C (LiFePO4:94.65 %@200cycles@0.5 C; LiNi0.5Co0.2Mn0.3O2: 94.31 %@200 cycles@0.3 C). This work proposes a concept of CCIE and reveals its mechanism in designing PICE with high ionic conductivity as well as high interfacial compatibility at near RT for high‐performance ASSLBs.

Build a High-Performance All-Solid-State Lithium Battery through Introducing Competitive Coordination Induction Effect in Polymer-Based Electrolyte.

Polymer-inorganic composite electrolytes (PICE) have attracted tremendous attention in all-solid-state lithium batteries (ASSLBs) due to facile processability. However, the poor Li+ conductivity at room temperature (RT) and interfacial instability severely hamper the practical application. Herein, we propose a concept of competitive coordination induction effects (CCIE) and reveal the essential correlation between the local coordination structure and the interfacial chemistry in PEO-based PICE. CCIE introduction greatly enhances the ionic conductivity and electrochemical performances of ASSLBs at 30 °C. Owing to the competitive coordination (Cs+…TFSI-…Li+, Cs+…C-O-C…Li+ and 2,4,6-TFA…Li…TFSI-) from the competitive cation (Cs+ from CsPF6) and molecule (2,4,6-TFA: 2,4,6-trifluoroaniline), a multimodal weak coordination environment of Li+ is constructed enabling a high efficient Li+ migration at 30 °C (Li+ conductivity: 6.25×10-4 S cm-1; tLi +=0.61). Since Cs+ tends to be enriched at the interface, TFSI- and PF6 - in situ form LiF-Li3N-Li2O-Li2S enriched solid electrolyte interface with electrostatic shielding effects. The assembled ASSLBs without adding interfacial wetting agent exhibit outstanding rate capability (LiFePO4: 147.44 mAh g-1@1 C and 107.41mAhg-1@2 C) and cycling stability at 30 °C (LiFePO4:94.65 %@200cycles@0.5 C; LiNi0.5Co0.2Mn0.3O2: 94.31 %@200 cycles@0.3 C). This work proposes a concept of CCIE and reveals its mechanism in designing PICE with high ionic conductivity as well as high interfacial compatibility at near RT for high-performance ASSLBs.

Aggregation, retention and transport of γ-MnO2 nanoparticles in water-saturated porous media: Impact on the immobility of thallium

Nano-scale Mn oxides can act as effective stabilizers for Tl in soil and sediments. Nevertheless, the comprehensive analysis of the capacity of MnO2 to immobilize Tl in such porous media has not been systematically explored. Therefore, this study investigates the impact of γ-MnO2, a model functional nanomaterial for remediation, on the mobility of Tl in a water-saturated quartz sand-packed column. The mechanisms involved are further elucidated based on the adsorption and aggregation kinetics of γ-MnO2. The results indicate that higher ionic strength (IS) and the presence of ion Ca(II) promote the aggregation of γ-MnO2, resulting from the reduced electrostatic repulsion between particles. Conversely, an increase in pH inhibits aggregation due to enhanced interaction energy. γ-MnO2 significantly influences Tl retention and mobility, with a substantial fraction of γ-MnO2-bound Tl transported through the column. This might be attributed to the high affinity of γ-MnO2 for Tl through ion exchange reactions and precipitation at the surface of γ-MnO2. The mobility of Tl in the sand column is influenced by the γ-MnO2 colloids, exhibiting either inhibition or promotion depending on the pH, IS, and cation type of the solution. In solutions with higher IS and Ca(II), the mobility of Tl decreases as γ-MnO2 colloids tend to aggregate, strain, and block, facilitating colloidal Tl retention in porous media. Although higher pH reduces the mobility of individual Tl, it promotes the mobility of γ-MnO2 colloids, facilitating a substantial fraction of colloidal-form Tl. Consequently, the optimal conditions for stabilizing Tl by γ-MnO2 involve either high IS and low pH or the presence of competitive cations (e.g., Ca(II)). These findings provide new insights into Tl immobilization using MnO2- and Mn oxide-based functional materials, offering potential applications in the remediation of Tl contamination in soil and groundwater.