Ce-Fe-modified zeolite-rich tuff to remove Ba(2+)-like (226)Ra(2+) in presence of As(V) and F(-) from aqueous media as pollutants of drinking water

Open-framework hybrid zinc/tin selenide as an ultrafast adsorbent for Cs+, Ba2+, Co2+, and Ni2

Efficient adsorption of radioactive ¹³⁷Cs⁺ and ⁶⁰Co²⁺ and their decay products ¹³⁷Ba²⁺ and ⁶⁰Ni²⁺ bears significance for hazard elimination in case of nuclear emergency, which relies on the adsorption rate enhancement that takes advantages of compositional and structural optimization. Herein, we report a zinc-doped selenidostannate constructed from T2-supertetrahedral clusters, namely K_3.4(CH₃NH₃)_0.45(NH₄)_0.15Zn₂Sn₃Se₁₀·3.4 H₂O (ZnSnSe-1K). The soft Se and micro-porosity synergistically endow this material with a binding affinity to Cs⁺, Ba²⁺, Co²⁺, and Ni²⁺ ions and ultrafast kinetics with R > 97.6% in 2-60 min. In particular, ZnSnSe-1K can remove 99.34% of Cs⁺ in 2 min ⁽K_d^Cs > 1.5 × 10⁵ mL g^-1), contributing to a record rate constant k₂ of 9.240 g mg^-1 min^-1 that surpasses all metal chalcogenide adsorbents. ZnSnSe-1K exhibits good acid/base tolerance (pH = 0-12), and the adsorption capacities at neutral are 253.61 ± 9.15, 108.94 ± 25.32, 45.76 ± 14.19 and 38.49 ± 2.99 mg g^-1 for Cs⁺, Ba²⁺, Co²⁺, and Ni²⁺, respectively. The adsorption performances resist well co-existing cations and anions, and the removal rates can keep above or close to 90% even in sea water. ZnSnSe-1K is employed in continuous column and membrane filtration, both of which shows excellent elimination efficiency (R > 99%) for mixed Cs⁺, Ba²⁺, Co²⁺, and Ni²⁺. Especially, the membrane with an ultrathin (70 µm) ZnSnSe-1K layer can remove 97-100% Cs⁺ in suction filtration with a short contact time of 0.33 s. Combined with the simple synthesis, facile elution and great irradiation resistance, ZnSnSe-1K emerges as a selenide adsorbent candidate for use in environmental remediation especially that involving nuclear waste disposal.

Efficient removal of Ba2+, Co2+ and Ni2+ by an ethylammonium-templated indium sulfide ion exchanger

Removal of radioactive ¹³³Ba, ⁶⁰Co and ⁶³Ni and their nonradioactive isotopes through ion exchange method would be highly beneficial for the safe disposal of liquid industrial waste, and it also bears importance for the emergency response to nuclear accident. Herein, we report the employment of an indium sulfide [CH₃CH₂NH₃]₆In₈S₁₅ (InS-2) with exchangeable ethylammonium cations for efficient and selective uptake of Ba²⁺, Co²⁺ and Ni²⁺. The corner-sharing linkage of P1-{In₈S₁₇} clusters in InS-2 endow the layered structure with nanoscale windows, which facilitates both transfer and accommodation of the large hydrated divalent metal ions. This results in ultrafast exchange kinetics (10-20 min) and top-level exchange capacities of 211.73 mg g^-1 for Ba²⁺, 103.57 mg g^-1 for Co²⁺, and 111.78 mg g^-1 for Ni²⁺. Particularly, InS-2 achieves ultrahigh K_d values of 2.3 × 10⁵ mL g^-1 for Ba²⁺, 2.0 × 10⁵ mL g^-1 for Co²⁺ and 1.6 × 10⁵ mL g^-1 for Ni²⁺, corresponding to remarkable removal efficiencies larger than 99.4% (C₀ ~ 6 ppm). InS-2 shows high β and γ irradiation resistance, wide pH durability (pH 3-13 for Ba²⁺, pH 3-11 for Co²⁺ and Ni²⁺), and outstanding selectivity against competitor ions (e.g. Na⁺, K⁺, Mg²⁺, Ca²⁺). The InS-2-filled ion exchange column exhibits a fantastic removal effect (R > 99%) for mixed Ba²⁺, Co²⁺, Ni²⁺, as well as Sr²⁺. The ultralong column-treatment on 20000 BVs of flow reveals an affinity order of Co²⁺ > Ni²⁺ > Ba²⁺ > Sr²⁺ for InS-2, which gives deep insights into the adsorption process and interaction between competitor ions. This excellent uptake of Ba²⁺ (Ra by analogy), Co²⁺ and Ni²⁺ ions by InS-2 highlights the great potential of metal chalcogenides as a type of promising materials for minimizing contamination in complex wastewater.

Low-Calcium, Porous, Alkali-Activated Materials as Novel pH Stabilizers for Water Media

Due to the increase of water consumption, water treatment systems become more actual and innovative materials for water treatment are welcomed. Traditionally, alkalizing agents, such as lime or caustic soda, have been employed to increase the pH levels, which induce chemical clarification of wastewater. Some innovative ideas of using low-calcium, alkali-activated materials (AAM) for this purpose have been considered previously. In this study, the low-calcium, porous, alkali-activated material (pAAM) was characterized to understand the impact of the aluminum silicate source and heat treatment on basic properties for material that might be used in water treatment systems as a softener by stabilizing the pH. The studied porous alkali-activated materials may ensure stable and long-lasting (30 days) pH (pH 10.3–11.6) in water media depending on the composition and amount of activation solution used for AAM preparation. Heat treatment does not have an impact on the mineralogical composition and structural properties of the pAAM, but it does change the leaching ability of alkalis from the material structure.

The Uptake of Hazardous Metal Ions into a High-Nuclearity Cluster-Based Compound with Structural Transformation and Proton Conduction

The discovery of novel high-nuclearity oxo-clusters considerably promotes the development of cluster science. We report a high-nuclearity oxo-cluster-based compound with acid/alkali-resistance and radiation stabilities, namely, (H₃O)₇[Cd₇Sb₂₄O₂₄(l-tta)₉(l-Htta)₃(H₂O)₆]·29H₂O (FJSM-CA; l-H₄tta = l-tartaric acid), which features a two-dimensionally anionic layer based on the largest Sb-oxo-clusters with 28-metal-ion-core [Cd₄Sb₂₄O₂₄]. It is challenging to efficiently capture Sr²⁺, Ba²⁺ (analogue of ²²⁶Ra), and [UO₂]²⁺ ions from aqueous solutions due to their high water solubility and environmental mobility, while it is unprecedented that a novel Sb-oxo-cluster-based framework material FJSM-CA can efficiently remove these hazardous ions accompanied with intriguing structural transformations. Especially, it shows fast ion-exchange abilities for Sr²⁺, Ba²⁺, and [UO₂]²⁺ (reaches equilibrium within 2, 10, and 20 min, respectively) and high exchange capacity (121.91 mg/g), removal rate R (96%), and distribution coefficient K_d^U (2.46 × 10⁴ mL/g) for uranium. Moreover, the underlying mechanism is clearly revealed, which is attributed to strong electrostatic interactions between exchanged cations and highly negative-charged frameworks and the strong affinity of (COO)^- groups for these cations. Proton conduction of the pristine and Sr²⁺, Ba²⁺, [UO₂]²⁺-loaded products was investigated. This work highlights the design of new oxo-cluster-based materials for radionuclide remediation and proton conduction performance.

Alkali-Activated Metakaolin as a Zeolite-Like Binder for the Production of Adsorbents

This work reports and describes a novel alkali-activated metakaolin as a potential binder material for the granulation of zeolites, which are widely used as CO2 adsorbents. The alkali-activated binders are zeolite-like materials, resulting in good material compatibility with zeolite-based adsorbents. A major problem during the granulation of zeolites is that their adsorption capacities decrease by about 15–20%, because typical binder materials (for example bentonite or kaolin clay) are inactive towards CO2 adsorption. A possible pathway to solve this problem is to introduce a novel binder that is also able to sorb CO2. In such a case, a binder plays a dual role, acting both as a binding material and as a sorbent. However, it is important that, alongside the adsorptive properties, a novel binder material must fulfil mechanical and morphological requirements. Thus, in this work, physical and mechanical properties of this novel binder for zeolite granulation for CO2 adsorption are studied. Alkali-activated metakaolin was found to be efficient and competitive as a binder material, when mechanical and physical properties were concerned. The compressive strengths of most of the obtained binders reported in this work are above the compressive strength threshold of 10 MPa. The future work on this novel binder will be conducted, which includes granulation-related details and the CO2 adsorptive properties of the novel binder material. Metakaolin was used as a precursor for alkali-activated binders. Binders were synthesized using varying molarity of a NaOH solution and at varying curing conditions. The final products were characterized using density measurements, compressive strength tests, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) analysis, and scanning electron microscopy (SEM).

Synthesis of ZrO2 nanoparticles on pumice and tuff for sonocatalytic degradation of rifampin

ZrO₂-pumice and ZrO₂-tuff nanocomposites were synthesized via a modified sol-gel method and used as efficient catalysts for sonocatalytic degradation of rifampin (RIF). The physico-chemical properties of the prepared catalysts were examined using XRF, SEM, EDX, FT-IR and BET analyses and compared to pure pumice and tuff samples. Subsequently, the efficacy of catalysts in degradation of RIF was assessed under various experimental conditions. Both ZrO₂-pumice and ZrO₂-tuff (1.5 g L^-1) exhibited promising catalytic activity for sonocatalytic degradation of RIF at its initial concentration of 20 mg L^-1, natural pH and under ultrasonic irradiation power of 300 W. In this condition, about 95% and 83% of RIF was removed through US/ZrO₂-pumice and US/ZrO₂-tuff processes, respectively. Furthermore, the influence of the addition of a number of scavengers, enhancers and gases on the degradation of RIF was studied. The pronounced degradation effectiveness of the catalysts under ultrasound irradiation could be assigned to their synergetic ability to produce reactive species and subsequent radical reactions. The intermediate products formed in the solution from degradation of RIF were also identified and a decomposition pathway was proposed using GC-MS, COD, TOC and IC analyses.

POMzites: A Family of Zeolitic Polyoxometalate Frameworks from a Minimal Building Block Library

We describe why the cyclic heteropolyanion [P8W48O184]40- (abbreviated as {P8W48}) is an ideal building block for the construction of intrinsically porous framework materials by classifying and analyzing >30 coordination polymers incorporating this polyoxometalate (POM) ligand. This analysis shows that the exocyclic coordination of first-row transition metals (TMs) to {P8W48} typically yields frameworks which extend through {W-O-TM-O-W} bridges in one, two, or three dimensions. However, despite the rich structural diversity of such compounds, the coordination of TMs to the {P8W48} ring is poorly understood, and therefore largely unpredictable, and had not until now been present with any structural classification that could allow rational design. Herein, not only do we present a new approach to understand and classify this new class of materials, we also present three {P8W48}-based frameworks which complement those frameworks which have previously been described. These new compounds help us postulate a new taxonomy of these materials. This is possible because the TM coordination sites of the {P8W48} ring are found, once fully mapped, to lead to well-defined classes of connectivity. Together, analysis provides insight into the nature of the building block connectivity within each framework, to facilitate comparisons between related structures, and to fundamentally unite this family of compounds. Hence we have tentatively named these compounds as "POMzites" to reflect the POM-based composition and zeolitic nature of each family member, although crucially, POMzites differ from zeolites in the modular manner of their preparation. As the synthesis of further POMzites is anticipated, the classification system and terminology introduced here will allow new compounds to be categorized and understood in the context of the established materials. A better understanding of TM coordination to the {P8W48} ring may allow the targeted synthesis of new frameworks rather than the reliance on serendipity apparent in current methods.

Enhanced arsenite immobilization via ternary layered double hydroxides and application to paddy soil remediation

A ternary CaMgFe-LDH was developed for the immobilization of aqueous arsenic from capillary water in paddy soils, with an outstanding removal performance for aqueous arsenite (As(iii)).