Applied Clay Science最新文献_第4页

Synergistic antibacterial material of cetylpyridinium/Cu2+/sepiolite and its application in thermoplastic polyurethane films 十六烷基吡啶/Cu2+/沸石的协同抗菌材料及其在热塑性聚氨酯薄膜中的应用

IF 5.3 2区地球科学 Q2 CHEMISTRY, PHYSICAL

Applied Clay Science

Pub Date : 2024-10-20 DOI: 10.1016/j.clay.2024.107604

Xiaoyu Zhang , Chunquan Li , Liqiu He , Yujiao Zhang , Fang Yuan , Shuilin Zheng , Zhiming Sun

Seeking non-antibiotic solutions against bacterial infections has become a global priority. Therefore, this work employs sepiolite as the carrier to load cetylpyridinium (CP⁺) and Cu²⁺, constructing a CP⁺/Cu²⁺/sepiolite (PCS) system with excellent antibacterial and application properties. Sepiolite, serving as a micro-container for storing antibacterial agents, enhances their thermal stability and realizes their “burst + sustained” release. Antibacterial agents improve the organic compatibility of sepiolite and provide a synergistic antibacterial effect. With the released antibacterial agents and contact inactivation effect, PCS at 10 mg/L and 75 mg/L achieve 100 % inactivation of Staphylococcus aureus and Escherichia coli within 120 min, respectively. Furthermore, the sepiolite carrier with an intact fibrous structure facilitates the loading-release and antibacterial activity of agents in PCS. The obtained PCS disperses uniformly in thermoplastic polyurethane and binds tightly with it, improving its mechanical properties. Film of ST-10wt%PCS with 10 wt% PCS inactivates 100 % of Staphylococcus aureus and 93.0 % of Escherichia coli in 4 h, while exhibiting superior elongation at break (263 %) and tensile strength (35 MPa) compared to the pure film (242 % and 30 MPa). Thus, it is evident that the resulting PCS holds promise for the direct use or manufacture of functional products to combat bacterial infections.

寻求非抗生素的细菌感染解决方案已成为全球的当务之急。因此，本研究采用海泡石作为载体，负载十六烷基吡啶鎓（CP+）和Cu2+，构建了具有优异抗菌和应用特性的CP+/Cu2+/海泡石（PCS）系统。作为储存抗菌剂的微容器，海泡石提高了抗菌剂的热稳定性，实现了 "爆发+持续 "释放。抗菌剂改善了海泡石的有机相容性，提供了协同抗菌效果。在释放抗菌剂和接触灭活效应的作用下，10 mg/L 和 75 mg/L 的 PCS 可分别在 120 分钟内 100%地灭活金黄色葡萄球菌和大肠杆菌。此外，具有完整纤维结构的海泡石载体有利于 PCS 中药剂的负载释放和抗菌活性。获得的 PCS 能均匀地分散在热塑性聚氨酯中，并与之紧密结合，从而改善其机械性能。与纯薄膜（242% 和 30 兆帕）相比，含有 10 wt% PCS 的 ST-10wt%PCS 薄膜可在 4 小时内灭活 100% 的金黄色葡萄球菌和 93.0% 的大肠杆菌，同时显示出更高的断裂伸长率（263%）和拉伸强度（35 兆帕）。因此，由此产生的 PCS 显然有望直接用于或制造抗细菌感染的功能性产品。

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引用次数: 0

Predicting the diffusion of CeEDTA− and CoEDTA2− in bentonite using decision tree hybridized with particle swarm optimization algorithms 利用决策树混合粒子群优化算法预测膨润土中 CeEDTA- 和 CoEDTA2- 的扩散情况

IF 5.3 2区地球科学 Q2 CHEMISTRY, PHYSICAL

Applied Clay Science

Pub Date : 2024-10-20 DOI: 10.1016/j.clay.2024.107596

Zhengye Feng, Jiaxing Feng , Junlei Tian, Xiaoqiong Shi, Dongchen Shao, Tao Wu, Qiang Shen

The diffusion of radionuclide anionic complexes in bentonite barriers is of great concern in assessing the safety of repositories for high-level radioactive waste due to their high diffusivity. This study investigated the diffusion behaviors of CeEDTA⁻ (as surrogate to ²⁴¹AmEDTA⁻ and ²³⁹PuEDTA⁻) and CoEDTA²⁻ (as surrogate to ⁶⁰CoEDTA²⁻) in compacted bentonite using a through-diffusion method, a multi-porosity model (MP), and various decision tree algorithms hybridized with Particle Swarm Optimization (PSO). The algorithms included PSO-Light Gradient Boosting Machine (LightGBM), PSO-Categorical Gradient Boosting (CatBoost), PSO-EXtreme Gradient Boosting (XGBoost), and PSO-Random Forest (RF). The effective diffusion coefficients of these species in compacted Wyoming bentonite were determined utilizing the through-diffusion method to assess the reliability of machine learning (ML) models. The accuracy of cross validation ranked as follows: PSO-LightGBM (R_CV² = 0.91) > PSO-XGBoost (R_CV² = 0.86) > PSO-CatBoost (R_CV² = 0.85) > PSO-RF (R_CV² = 0.81). Shapley additive explanation (SHAP) and feature importance (FI) with PSO-LightGBM identified the ion diffusion coefficient in water, total porosity, and rock capacity factor as the top three features. The MP model confirmed the reliability of partial dependence plots (PDP) method, highlighting the good interpretability of ML models. This work provides an accurate, generalizable, and interpretable ML method for analyzing the adsorptive radionuclide anionic complexes diffusion in bentonite barriers.

由于高扩散性，放射性核素阴离子复合物在膨润土屏障中的扩散是评估高放射性废物贮存库安全性的一个重要问题。本研究采用贯通扩散法、多孔模型（MP）以及与粒子群优化（PSO）混合的各种决策树算法，研究了 CeEDTA-（作为 241AmEDTA- 和 239PuEDTA- 的替代物）和 CoEDTA2-（作为 60CoEDTA2- 的替代物）在压实膨润土中的扩散行为。这些算法包括 PSO-轻梯度提升机（LightGBM）、PSO-分类梯度提升（CatBoost）、PSO-极端梯度提升（XGBoost）和 PSO-随机森林（RF）。利用贯通扩散法测定了这些物种在压实怀俄明膨润土中的有效扩散系数，以评估机器学习（ML）模型的可靠性。交叉验证的准确性排名如下：PSO-LightGBM（RCV2 = 0.91）；PSO-XGBoost（RCV2 = 0.86）；PSO-CatBoost（RCV2 = 0.85）；PSO-RF（RCV2 = 0.81）。使用 PSO-LightGBM 的 Shapley 加性解释（SHAP）和特征重要性（FI）确定了水中离子扩散系数、总孔隙度和岩石容重系数为前三个特征。MP 模型证实了部分依存图 (PDP) 方法的可靠性，凸显了 ML 模型的良好可解释性。这项工作为分析膨润土屏障中吸附性放射性核素阴离子复合物扩散提供了一种准确、可推广和可解释的 ML 方法。

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引用次数: 0

ZIF-8/magadiite layered silicate heterostructure for battery-type supercapacitors 用于电池型超级电容器的 ZIF-8/方镁石层状硅酸盐异质结构

IF 5.3 2区地球科学 Q2 CHEMISTRY, PHYSICAL

Applied Clay Science

Pub Date : 2024-10-18 DOI: 10.1016/j.clay.2024.107594

Wemerson D.C. Santos , Jhonatam P. Mendonça , Mayara M. Teixeira , Alan S. de Menezes , Alex Rojas , Marco A.S. Garcia , Ana C.S. Alcântara

By a in situ co-precipitation approach was created a novel heterostructured material by assembling the ZIF-8 zeolitic imidazolate framework on unmodified magadiite layered silicate (Na-MAG). ZIF-8 was successfully associated with the Na-MAG, as demonstrated by the Rietveld refinement, which also revealed the existence of two phases in the heterostructure. In addition to SEM and thermal analysis, ¹³C and ²⁹Si NMR and FT-IR investigations also corroborate the formation of a new compound. Nitrogen adsorption-desorption isotherms indicated a notable increase in surface area to 842 m²/g and enhanced pore volume for the heterostructure, suggesting its potential for enhanced energy storage capabilities. Electrochemical analyses, such as Galvanostatic Charge-Discharge (GCD) tests and Cyclic Voltammetry (CV) studies, indicated a distinct hybrid electrochemical behavior integrating capacitive and Faradaic battery-type processes was identified by the CV study. Based on the GCD curves, the specific charge capacities showed that ZIF-8/Na-MAG outperformed its separate components, particularly at lower current densities, achieving a capacity of 291.3 mAh g⁻¹ at 1 A g⁻¹. Charge balancing calculations and CV curves demonstrated this supercapacitor's balanced and effective functioning, highlighting the potential of these materials in high-performance energy storage applications.

通过原位共沉淀法，在未改性的麦饭石层状硅酸盐（Na-MAG）上组装了 ZIF-8 锆石咪唑框架，从而创造出了一种新型异质结构材料。通过里特维尔德细化，ZIF-8 与 Na-MAG 成功地结合在一起，这也揭示了异质结构中两相的存在。除了 SEM 和热分析外，13C 和 29Si NMR 以及 FT-IR 研究也证实了一种新化合物的形成。氮吸附-解吸等温线表明，异质结构的表面积显著增加到 842 m2/g，孔隙体积增大，这表明它具有增强能量存储能力的潜力。电化学分析，如 Galvanostatic Charge-Discharge (GCD) 测试和循环伏安法 (CV) 研究表明，CV 研究确定了电容和法拉第电池类型过程的独特混合电化学行为。根据 GCD 曲线，比电荷容量显示 ZIF-8/Na-MAG 的性能优于其单独成分，尤其是在较低的电流密度下，在 1 A g-1 的条件下可达到 291.3 mAh g-1。充电平衡计算和 CV 曲线证明了这种超级电容器的平衡和有效功能，凸显了这些材料在高性能储能应用中的潜力。

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引用次数: 0

Blocking endogenous phosphorus release in sediments by a hydrotalcite mixture synthesized with natural sepiolite and discarded cans 用天然海泡石和废弃易拉罐合成的水滑石混合物阻止沉积物中内源性磷的释放

IF 5.3 2区地球科学 Q2 CHEMISTRY, PHYSICAL

Applied Clay Science

Pub Date : 2024-10-17 DOI: 10.1016/j.clay.2024.107599

Fulong Cheng , Jie Pan , Changxin Zhao , Wei Li , Yuting Peng , Zuo Zhang , Yanjuan Lin , Guowen Chen

Pure hydrotalcite (LDH) materials prepared from chemical reagents have been investigated as solid-phase phosphorus (P) inactivation materials (SPIM) to manage endogenous P loading in sediments. However, the efficacy and mechanism of LDH mixtures prepared by natural minerals and solid wastes in controlling sediment P release are unclear. Therefore, a Ca/Mg-Al-LDH (CMA-LDH) material was synthesized using sepiolite and cans, and its efficacy, mechanism, and ecological impact in controlling sediment P release were investigated. CMA-LDH-p was prepared as a control material using pure chemical reagents. The CMA-LDH and CMA-LDH-p were both composed of hydrotalcite and hydrocalumite. The maximum P adsorption capacity of CMA-LDH was 123.01 mg/g, comparable to that of CMA-LDH-p. The adsorbed P by CMA-LDH was mostly in the stable P form, accounting for 87.2 % of the total P. The adsorption capacity and immobilization ability of CMA-LDH for P were superior to other reported LDH-based SPIM. Both the CMA-LDH addition and capping successfully blocked sediment P release under anaerobic conditions. Passivation of mobile P in the sediment and DGT-labile P in the interstitial water was critical to preventing sediment P release by the CMA-LDH addition. The CMA-LDH capping inhibited sediment P release through the effective adsorption of CMA-LDH on DGT-labile P at the sediment/overlying water interface. The CMA-LDH addition and capping affected the abundance of microbial communities associated with iron and sulfur cycling, which might affect the stability of endogenous P. These results confirmed that CMA-LDH addition and capping treatments were effective methods for managing sediment P loading.

由化学试剂制备的纯水滑石（LDH）材料已被研究用作固相磷（P）失活材料（SPIM），以管理沉积物中的内源磷负荷。然而，天然矿物和固体废弃物制备的 LDH 混合物在控制沉积物磷释放方面的功效和机制尚不清楚。因此，研究人员利用海泡石和罐头合成了一种 Ca/Mg-Al-LDH （CMA-LDH）材料，并研究了它在控制沉积物 P 释放方面的功效、机理和生态影响。使用纯化学试剂制备了 CMA-LDH-p 作为对照材料。CMA-LDH 和 CMA-LDH-p 均由水滑石和氢铝土组成。CMA-LDH 的最大 P 吸附量为 123.01 mg/g，与 CMA-LDH-p 相当。CMA-LDH 对磷的吸附容量和固定能力均优于其他已报道的基于 LDH 的 SPIM。在厌氧条件下，CMA-LDH 的添加和封盖都成功阻止了沉积物中 P 的释放。钝化沉积物中的可移动磷和间隙水中的 DGT 标记磷对防止 CMA-LDH 添加后沉积物中磷的释放至关重要。通过 CMA-LDH 在沉积物/上覆水体界面上对 DGT 标记 P 的有效吸附，CMA-LDH 封盖抑制了沉积物 P 的释放。这些结果证实了 CMA-LDH 添加和加盖处理是管理沉积物 P 负荷的有效方法。

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引用次数: 0

Compositional and textural evidences of Na-bentonite authigenesis in the Pellegrini lake deposit (Neuquen basin, Argentina) 佩莱格里尼湖矿床（阿根廷内乌肯盆地）纳-膨润土自生过程的成分和纹理证据

IF 5.3 2区地球科学 Q2 CHEMISTRY, PHYSICAL

Applied Clay Science

Pub Date : 2024-10-17 DOI: 10.1016/j.clay.2024.107598

T.B. Musso , G. Pettinari , A.B. Galán , G.A. Martinez , M. Pozo

Textural and compositional variations of Na-bentonites from the Pellegrini Lake deposit (Neuquén Basin) have been established, with special emphasis on petrographic features in order to better understand the genetic pathways in their formation. In this region, two bentonite beds named “white bentonite” and “green bentonite” are mined mainly for the oil and foundry industries. The genesis of these beds was studied using petrological (petrography, SEM and TEM), mineralogical (DRX, FT-IR, DTA-TGA, ²⁷Al MAS NMR) and geochemical (ICP-AES) data from two quarries named COR and CA. The bentonites mainly consist of Na-montmorillonite, with lesser amounts of quartz, plagioclase, potassium feldspar, illite, zeolite, barite and gypsum. Mineralogical and petrographical evidence indicates that the authigenic smectite was formed by devitrification of unstable glass shards in a shallow coastal marine environment. Green bentonite would be the result of several episodes of volcanic ash-fall input from multiple eruptions with a higher degree of alteration uppermost in the bed. In this case, the alteration would have occurred in a reducing environment as evidenced by the greenish colouration of these bentonites, the Ce anomaly and the presence of pyrite. Meanwhile, white bentonite would have formed in a less restricted environment than green bentonite, as evidenced by the existence of intercalations of silt-sized grains and a higher amount of detrital grains in the clay groundmass transported probably by fresher waters. The presence of celestine, barite, halite and gypsum indicates evaporitic conditions after smectite formation. The observed secondary gypsum and iron staining of surfaces are much later processes. Green bentonite samples indicate a trachyandesite composition of the parent material, while the white bentonite suggests a parent material most related to a rhyodacite/dacite composition showing that the characteristics of the volcanism might have changed with time.

我们已经确定了佩莱格里尼湖矿床（内乌肯盆地）纳膨润土的质地和成分变化，并特别强调了岩石学特征，以便更好地了解其形成的遗传途径。该地区有两个膨润土矿床，分别被命名为 "白色膨润土 "和 "绿色膨润土"，主要用于石油和铸造业。研究人员利用名为 COR 和 CA 的两个采石场的岩石学（岩相学、扫描电镜和 TEM）、矿物学（DRX、傅立叶变换红外光谱、DTA-TGA、27Al MAS NMR）和地球化学（ICP-AES）数据对这两个膨润土床的成因进行了研究。膨润土的主要成分是钠蒙脱石，以及少量石英、斜长石、钾长石、伊利石、沸石、重晶石和石膏。矿物学和岩相学证据表明，自生铁闪长岩是由浅海环境中不稳定的玻璃碎片蜕变形成的。绿色膨润土是多次火山喷发产生的火山灰沉降物，在岩床最上层的蚀变程度较高。在这种情况下，蚀变是在还原环境中发生的，这些膨润土的绿色、Ce 异常和黄铁矿的存在都证明了这一点。与绿色膨润土相比，白色膨润土形成的环境限制较少，这从粘土基质中存在淤泥大小的夹层和较多的碎屑颗粒可以看出，这些颗粒可能是由较新鲜的水流带走的。天青石、重晶石、海绿石和石膏的存在表明了软玉形成后的蒸发条件。观察到的次生石膏和表面的铁污是更晚的过程。绿色膨润土样本表明母质成分为特斜安山岩，而白色膨润土则表明母质成分与流纹岩/英安岩最为相似，这表明火山活动的特征可能随着时间的推移而发生变化。

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引用次数: 0

Extracting hydromechanical properties of montmorillonite quasi-crystals via nanoindentation of oriented thin films 通过纳米压痕取向薄膜提取蒙脱石准晶体的水力学特性

IF 5.3 2区地球科学 Q2 CHEMISTRY, PHYSICAL

Applied Clay Science

Pub Date : 2024-10-16 DOI: 10.1016/j.clay.2024.107595

Yu-Cheng Li , Yong-Gui Chen , Li Liu , Guo-Ping Zhang , Wei-Min Ye , Qiong Wang

This paper presents the first effort to extract the hydromechanical properties of montmorillonite quasi-crystals via nanoindentation testing of highly oriented montmorillonite thin films with varying degrees of water intercalation. By preparing highly preferentially oriented montmorillonite thin films, the evolution of basal spacing, isothermal adsorption of water, microstructure, and mechanical properties of montmorillonite quasi-crystals equilibrated with different relative humidity (RH) was examined by the grazing incidence X-ray diffraction (GIXRD), sorptometry, environmental scanning electron microscopy (ESEM), and nanoindentation, respectively. Results indicate that the montmorillonite thin films exhibit depth-dependent mechanical properties across different RH. At a 40 % RH, the Young's modulus and hardness of a montmorillonite quasi-crystal consisting of ∼60 platelets are 4.85 and 0.20 GPa, which remain relatively stable upon increasing the RH to 50 % but experienced a remarkable decrease to 3.31 and 0.12 GPa when the RH reaches 65 %. Simultaneous GIXRD and isothermal adsorption results reveal the interlayer swelling as the key factor contributing to the mechanical property variation of montmorillonite quasi-crystal, while the capillarity dominates the mechanical behavior at high RH. This study shed light on the hydromechanical behavior of montmorillonite upon hydration and swelling, and paves a solid foundation for the multiscale modeling of unsaturated compacted bentonites.

本文首次尝试通过对不同插水程度的高取向蒙脱石薄膜进行纳米压痕测试来提取蒙脱石准晶体的水力学特性。通过制备高优先取向蒙脱石薄膜，采用掠入射X射线衍射（GIXRD）、吸光度法、环境扫描电子显微镜（ESEM）和纳米压痕法分别研究了在不同相对湿度（RH）下平衡的蒙脱石准晶体的基底间距、水的等温吸附、微观结构和力学性能的演变。结果表明，蒙脱石薄膜在不同相对湿度下表现出与深度相关的机械特性。在相对湿度为 40% 时，由 ∼60 个小板组成的蒙脱石准晶体的杨氏模量和硬度分别为 4.85 和 0.20 GPa，在相对湿度升高到 50% 时保持相对稳定，但当相对湿度达到 65% 时，杨氏模量和硬度分别显著下降到 3.31 和 0.12 GPa。同时进行的 GIXRD 和等温吸附结果表明，层间膨胀是导致蒙脱石准晶体力学性能变化的关键因素，而毛细管在高相对湿度下的力学行为中占主导地位。该研究揭示了蒙脱石水化膨胀时的水力学行为，为非饱和致密膨润土的多尺度建模奠定了坚实的基础。

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引用次数: 0

Clay minerals transformation in soil particles of Udic Ferrisols under 36-year Chinese milk vetch application in southern China 在中国南方施用中国牛奶草 36 年的乌迪克费里斯土壤颗粒中粘土矿物的转化

IF 5.3 2区地球科学 Q2 CHEMISTRY, PHYSICAL

Applied Clay Science

Pub Date : 2024-10-15 DOI: 10.1016/j.clay.2024.107593

Yulu Chen , Li Huang , Jusheng Gao , Shuo Zhao , Lei Huang , Mingjian Geng , Yangbo He , Huimin Zhang , Jing Huang

To elucidate the impact of green manure application on soil clay minerals, surface soil samples (0–20 cm) were collected from Udic Ferrisols developed from Quaternary clay sediments, under no fertilization (CK) and Chinese milk vetch (MV) application treatments, based on a 36-year long-term experiment in southern China. Synchrotron X-ray diffraction (XRD), thermogravimetric analysis (TG), ²⁷Al and ²⁹Si nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), and high-resolution transmission electron microscopy (HRTEM) were employed to investigate the composition and structural characteristics of clay minerals in soil particles (100–2000 nm and 25–100 nm). The clay minerals in the 100–2000 nm and 25–100 nm particles were mainly kaolinite and illite, containing a minor amount of vermiculite. As the particle size decreased to the nanoscale (25–100 nm), the kaolinite content increased, the vermiculite content decreased, and the crystallinity of the clay minerals weakened. Aluminum (Al) in the structure of the clay minerals mainly existed as octahedral coordinated Al (^VIAl), with a small proportion of tetrahedral coordinated Al (^IVAl) (5.8 %–18.4 %) predominantly as Q3(1Al) (where silicon (Si) in the tetrahedron was connected to three neighboring Si atoms through oxygen to form a framework structure). The abundance of ^IVAl decreased significantly with decreasing particle size, and the structure of the clay minerals gradually shifted from a 2:1 to a 1:1 type. In the 100–2000 nm particles, MV application reduced illite content and increased ^IVAl abundance. HRTEM observation revealed a transition of lattice fringes from 1.0 nm to 1.38 nm. Conversely, in the 25–100 nm particles, MV application decreased ^IVAl abundance and increased kaolinite content, with the 1.38 nm lattice fringes gradually transformed into 0.71 nm. These findings indicate that long-term MV incorporation promoted the transformation of illite to vermiculite in the 100–2000 nm particles and vermiculite to kaolinite in the 25–100 nm particles to a certain extent.

为了阐明施用绿肥对土壤粘土矿物的影响，根据在中国南方进行的一项为期 36 年的长期试验，在不施肥（CK）和施用中国牛奶菜（MV）处理下，从第四纪粘土沉积物发育而成的乌迪克费里斯土壤中采集了表层土壤样品（0-20 厘米）。采用同步辐射 X 射线衍射 (XRD)、热重分析 (TG)、27Al 和 29Si 核磁共振 (NMR)、电子顺磁共振 (EPR) 和高分辨率透射电子显微镜 (HRTEM) 研究了土壤颗粒（100-2000 nm 和 25-100 nm）中粘土矿物的组成和结构特征。100-2000 nm 和 25-100 nm 颗粒中的粘土矿物主要是高岭石和伊利石，含有少量蛭石。当粒度减小到纳米级（25-100 nm）时，高岭石含量增加，蛭石含量减少，粘土矿物的结晶度减弱。粘土矿物结构中的铝（Al）主要以八面体配位铝（VIAl）的形式存在，小部分四面体配位铝（IVAl）（5.8%-18.4%）主要以 Q3(1Al)（四面体中的硅（Si）通过氧与相邻的三个硅原子连接形成框架结构）的形式存在。随着颗粒尺寸的减小，IVAl 的丰度明显降低，粘土矿物的结构也逐渐从 2:1 型转变为 1:1 型。在 100-2000 nm 的颗粒中，MV 的应用降低了伊利石的含量，增加了 IVAl 的丰度。HRTEM 观察显示，晶格边缘从 1.0 纳米过渡到 1.38 纳米。相反，在 25-100 nm 的颗粒中，MV 的应用降低了 IVAl 的丰度，增加了高岭石的含量，1.38 nm 的晶格边缘逐渐转变为 0.71 nm。这些结果表明，在 100-2000 nm 的颗粒中，长期掺入 MV 在一定程度上促进了伊利石向蛭石的转化，在 25-100 nm 的颗粒中，促进了蛭石向高岭石的转化。

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引用次数: 0

Synthesis of NiCuMgAl-layered double hydroxides using advanced microwave and ultrasound methods 利用先进的微波和超声波方法合成镍铜镁铝层双氢氧化物

IF 5.3 2区地球科学 Q2 CHEMISTRY, PHYSICAL

Applied Clay Science

Pub Date : 2024-10-13 DOI: 10.1016/j.clay.2024.107590

Judith Granados-Reyes, Angie C. Rueda, Yolanda Cesteros

The effect of using ultrasound vs magnetic stirring, microwaves vs conventional heating, and autoclave vs refluxing on the synthesis of NiCuMgAl-layered double hydroxides (LDH) was widely studied. The use of ultrasounds during coprecipitation resulted in lower LDH crystallinity, difficulted the incorporation of the divalent cations in the layer and led to low specific surface area and low basicity. This could be attributed to smaller crystallization nuclei formed under ultrasound; that is, more efficient agitation due to cavitation phenomena, led to less crystal growth. The use of microwaves refluxing during the aging step instead of conventional heating resulted in higher crystallinity, allowing a better incorporation of the cations in the layer, obtaining higher specific surface area and higher amount of stronger basic sites. Interestingly, the use of autoclave at higher temperature (180 °C) but at shorter time (1 h) improved the crystallinity of the LDH samples, especially in the stacking direction and applying microwaves, favoring the incorporation of the cations in the layer. Autoclave under microwaves led to higher amount of basic sites but lower surface area than autoclave by conventional heating at the same conditions. This suggests that microwaves favored a better incorporation of the hydroxyl groups into the layers and/or the appearance of surface-defective sites.

人们广泛研究了超声与磁力搅拌、微波与传统加热、高压釜与回流对合成镍铜镁铝层双氢氧化物（LDH）的影响。在共沉淀过程中使用超声波会降低 LDH 的结晶度，使二价阳离子难以融入层中，并导致低比表面积和低碱性。这可能是由于在超声波作用下形成的结晶核较小，也就是说，空化现象导致的更有效搅拌减少了晶体生长。在老化步骤中使用微波回流而不是传统的加热，可提高结晶度，使阳离子更好地融入层中，获得更高的比表面积和更多的强碱性位点。有趣的是，在较高温度（180 °C）和较短时间（1 小时）下使用高压灭菌器可以提高 LDH 样品的结晶度，特别是在堆叠方向和微波下，有利于阳离子在层中的结合。与相同条件下的传统加热高压釜相比，微波下的高压釜产生了更多的碱性位点，但表面积却更小。这表明，微波有利于羟基更好地融入层中和/或出现表面缺陷位点。

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引用次数: 0

Montmorillonite modification and chromate adsorption mechanisms of organo-montmorillonite: A multiscale study 有机蒙脱石的蒙脱石改性和铬酸盐吸附机理：多尺度研究

IF 5.3 2区地球科学 Q2 CHEMISTRY, PHYSICAL

Applied Clay Science

Pub Date : 2024-10-11 DOI: 10.1016/j.clay.2024.107592

Xueying Liu , Wei Yang , Renpeng Chen

Cetyltrimethylammonium bromide modified montmorillonite (CTMAB-Mt) demonstrates effective removal of hexavalent chromium. It is crucial to understand the mechanisms by which changes in the microstructure of montmorillonite affect its adsorption capacity. This study combines molecular dynamic simulation, microscopic detection, and column/batch tests to reconstruct the microstructure of CTMAB-Mt at various loading levels and to investigate its chromate adsorption behavior. The results indicate that the primary modification mechanism of CTMAB-Mt involves ligand binding between the head group N(CH₃)₃ of the organic modifier and the surface oxygen of the siloxane layer in the clay. Compared to capture by CTMA⁺, CrO₄²⁻ prefers to form aqueous complexes, resulting in limited enhancement of CTMAB-Mt's adsorption capacity at low loading levels (<1.00 CEC). Notably, Molecular dynamics simulations reveal that the adsorption capacity of 1.00 CTMAB-Mt is exceptionally high, reaching 7.87 mg/L. This finding is consistent with results from column and batch tests, providing a novel method for calculating the heavy metal adsorption capacity. The enhanced adsorption capacity is primarily due to electrostatic attraction and van der Waals forces between the head groups of CTMA⁺ and CrO₄²⁻. A comprehensive understanding of chromate adsorption by modified montmorillonite is essential for developing modified clay and preventing chromium pollution.

十六烷基三甲基溴化铵修饰蒙脱石（CTMAB-Mt）可有效去除六价铬。了解蒙脱石微观结构的变化对其吸附能力的影响机制至关重要。本研究结合分子动力学模拟、显微检测和柱/批试验，重建了 CTMAB-Mt 在不同负载水平下的微观结构，并研究了其铬酸盐吸附行为。结果表明，CTMAB-Mt 的主要改性机制涉及有机改性剂的头部基团 N(CH3)3 与粘土中硅氧烷层的表面氧之间的配体结合。与 CTMA+ 的捕获相比，CrO42- 更倾向于形成水性复合物，这导致 CTMAB-Mt 在低负载水平（<1.00 CEC）下的吸附容量提升有限。值得注意的是，分子动力学模拟显示，1.00 CTMAB-Mt 的吸附容量非常高，达到 7.87 mg/L。这一发现与柱测试和批量测试的结果一致，为计算重金属吸附容量提供了一种新方法。吸附能力的增强主要是由于 CTMA+ 的头部基团与 CrO42- 之间的静电引力和范德华力。全面了解改性蒙脱石对铬酸盐的吸附对开发改性粘土和防止铬污染至关重要。

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引用次数: 0

Organometallic functionalized clays for technetium immobilization 用于固定锝的有机金属功能化粘土

IF 5.3 2区地球科学 Q2 CHEMISTRY, PHYSICAL

Applied Clay Science

Pub Date : 2024-10-09 DOI: 10.1016/j.clay.2024.107588

Emily Maulden , Elizabeth Gager , An T. Ta , Rachel F. Wood , Daria Boglaienko , Juan C. Nino , Carolyn I. Pearce , Simon R. Phillpot , James E. Szecsody , Nathalie A. Wall

Nuclear waste repository designs require backfill materials to contain long-lived radionuclides, including technetium-99, present as the pertechnetate anion (TcO₄⁻) under oxic repository conditions and mobile in the environment. Bentonite has been proposed as a suitable backfill material, and it is composed of montmorillonite clay, which can be functionalized to optimize its performance for TcO₄⁻ sorption. In the current work, bentonite clay is functionalized with organic and inorganic moieties, and the impact of dual functionalization on TcO₄⁻ sorption is investigated. The results show that the ordering of the functionalization is essential and that adding metal to an organoclay improves TcO₄⁻ sorption compared to either the reverse ordering or the organic/inorganic clay alone. Furthermore, the TcO₄⁻ sorption to the organometallic clays was consistent with either chemisorption or cooperative sorption, with a multi-step mechanism determining the kinetics of sorption.

核废料贮存库设计要求回填材料能够容纳长效放射性核素，包括锝-99，锝-99 在氧化贮存库条件下以过锝酸阴离子（TcO4-）的形式存在，并可在环境中移动。膨润土被认为是一种合适的回填材料，它由蒙脱石粘土组成，可以通过功能化来优化其对 TcO4- 的吸附性能。在当前的研究中，膨润土被有机和无机分子功能化，并研究了双重功能化对 TcO4- 吸附的影响。结果表明，官能化的排序至关重要，与反向排序或单独的有机/无机粘土相比，在有机粘土中添加金属可改善对 TcO4- 的吸附。此外，有机金属粘土对 TcO4- 的吸附与化学吸附或协同吸附一致，吸附动力学由多步骤机制决定。

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引用次数: 0