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23 pages, 4364 KiB

Open AccessArticle

Preparation of Quaternary Ammonium Separation Material based on Coupling Agent Chloromethyl Trimethoxysilane (KH-150) and Its Adsorption and Separation Properties in Studies of Th(IV)

by Zheng Wang, **que Wu, Meichen Liu, **aoqiang Zhao, Haichao Wang, **angfu Meng and **aofei Zhang

Molecules 2024, 29(13), 3031; https://doi.org/10.3390/molecules29133031 - 26 Jun 2024

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Abstract

In this research, the authors studied the synthesis of a silicon-based quaternary ammonium material based on the coupling agent chloromethyl trimethoxysilane (KH-150) as well as its adsorption and separation properties for Th(IV). Using FTIR and NMR methods, the silicon-based materials before and after [...] Read more.

In this research, the authors studied the synthesis of a silicon-based quaternary ammonium material based on the coupling agent chloromethyl trimethoxysilane (KH-150) as well as its adsorption and separation properties for Th(IV). Using FTIR and NMR methods, the silicon-based materials before and after grafting were characterized to determine the spatial structure of functional groups in the silicon-based quaternary ammonium material SG-CTSQ. Based on this, the functional group grafting amount (0.537 mmol·g⁻¹) and quaternization rate (83.6%) of the material were accurately calculated using TGA weight loss and XPS. In the adsorption experiment, the four materials with different grafting amounts showed different degrees of variation in their adsorption of Th(IV) with changes in HNO₃ concentration and NO₃⁻ concentration but all exhibited a tendency toward anion exchange. The thermodynamic and kinetic experimental results demonstrated that materials with low grafting amounts (SG-CTSQ₁ and SG-CTSQ₂) tended to physical adsorption of Th(IV), while the other two tended toward chemical adsorption. The adsorption mechanism experiment further proved that the functional groups achieve the adsorption of Th(IV) through an anion-exchange reaction. Chromatographic column separation experiments showed that SG-CTSQ has a good performance in U-Th separation, with a decontamination factor for uranium in Th(IV) of up to 385.1, and a uranium removal rate that can reach 99.75%. Full article

(This article belongs to the Special Issue Adsorbent Material for Water Treatment)

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23 pages, 4085 KiB

Open AccessArticle

Characterization and Performance of Peanut Shells in Caffeine and Triclosan Removal in Batch and Fixed-Bed Column Tests

by Cristina E. Almeida-Naranjo, Mayra Frutos, Victor H. Guerrero and Cristina Villamar-Ayala

Molecules 2024, 29(12), 2923; https://doi.org/10.3390/molecules29122923 - 19 Jun 2024

Viewed by 343

Abstract

Peanut shells’ adsorption performance in caffeine and triclosan removal was studied. Peanut shells were analyzed for their chemical composition, morphology, and surface functional groups. Batch adsorption and fixed-bed column experiments were carried out with solutions containing 30 mg/L of caffeine and triclosan. The [...] Read more.

Peanut shells’ adsorption performance in caffeine and triclosan removal was studied. Peanut shells were analyzed for their chemical composition, morphology, and surface functional groups. Batch adsorption and fixed-bed column experiments were carried out with solutions containing 30 mg/L of caffeine and triclosan. The parameters examined included peanut shell particle size (120–150, 300–600, and 800–2000 µm), adsorbent dose (0.02–60 g/L), contact time (up to 180 min), bed height (4–8 cm), and hydraulic loading rate (2.0 and 4.0 m³/m²-day). After determining the optimal adsorption conditions, kinetics, isotherm, and breakthrough curve models were applied to analyze the experimental data. Peanut shells showed an irregular surface and consisted mainly of polysaccharides (around 70% lignin, cellulose, and hemicellulose), with a specific surface area of 1.7 m²/g and a pore volume of 0.005 cm³/g. The highest removal efficiencies for caffeine (85.6 ± 1.4%) and triclosan (89.3 ± 1.5%) were achieved using the smallest particles and 10.0 and 0.1 g/L doses over 180 and 45 min, respectively. Triclosan showed easier removal compared to caffeine due to its higher lipophilic character. The pseudo-second-order kinetics model provided the best fit with the experimental data, suggesting a chemisorption process between caffeine/triclosan and the adsorbent. Equilibrium data were well-described by the Sips model, with maximum adsorption capacities of 3.3 mg/g and 289.3 mg/g for caffeine and triclosan, respectively. In fixed-bed column adsorption tests, particle size significantly influenced efficiency and hydraulic behavior, with 120–150 µm particles exhibiting the highest adsorption capacity for caffeine (0.72 mg/g) and triclosan (143.44 mg/g), albeit with clogging issues. The experimental data also showed good agreement with the Bohart–Adams, Thomas, and Yoon–Nelson models. Therefore, the findings of this study highlight not only the effective capability of peanut shells to remove caffeine and triclosan but also their versatility as a promising option for water treatment and sanitation applications in different contexts. Full article

(This article belongs to the Special Issue Adsorbent Material for Water Treatment)

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21 pages, 5930 KiB

Open AccessArticle

Conversion of Phosphogypsum into Porous Calcium Silicate Hydrate for the Removal and Recycling of Pb(II) and Cd(II) from Wastewater

by Gangan Wang, Chaoyi Chen, Junqi Li, Yuanpei Lan, **n Lin and Jiahang Chen

Molecules 2024, 29(11), 2665; https://doi.org/10.3390/molecules29112665 - 4 Jun 2024

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Abstract

The discharge of lead and cadmium wastewater, along with the pollution caused by phosphogypsum, represents a particularly urgent environmental issue. This study employed a straightforward hydrothermal method to convert phosphogypsum into porous calcium silicate hydrate (P-CSH), which was then used to remove and [...] Read more.

The discharge of lead and cadmium wastewater, along with the pollution caused by phosphogypsum, represents a particularly urgent environmental issue. This study employed a straightforward hydrothermal method to convert phosphogypsum into porous calcium silicate hydrate (P-CSH), which was then used to remove and recover Pb(II) and Cd(II) from wastewater. The adsorption capacities of P-CSH for Pb(II) and Cd(II) were notably high at 989.3 mg/g and 290.3 mg/g, respectively. The adsorption processes adhered to the pseudo-second-order kinetics model and the Langmuir isotherm model. Due to identical adsorption sites on P-CSH for both Pb(II) and Cd(II), competitive interaction occurred when both ions were present simultaneously. Additionally, the adsorption efficacy was minimally impacted by the presence of common coexisting cations in wastewater. The dominant mechanisms for removing Pb(II) and Cd(II) via P-CSH were chemical precipitation and surface complexation. Moreover, the adsorbed heavy metals were efficiently separated and reclaimed from the wastewater through a stepwise desorption process. The primary components of the residue from stepwise desorption were quartz and amorphous SiO₂. Following dissolution via pressurized alkaline leaching, this residue could be recycled for synthesizing P-CSH. This research offered a new strategy for the resourceful use of phosphogypsum and heavy metal wastewater. Full article

(This article belongs to the Special Issue Adsorbent Material for Water Treatment)

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8 pages, 2839 KiB

Open AccessArticle

Host–Guest Cocrystallization of Phenanthrene[2]arene Macrocycles Facilitating Structure Determination of Liquid Organic Molecules

by Guangchuan Ou, Yanfeng Zhang, Qiong Wang, Yingzhi Tan, Qiang Zhou and Fei Zeng

Molecules 2024, 29(11), 2523; https://doi.org/10.3390/molecules29112523 - 27 May 2024

Viewed by 489

Abstract

Single-crystal X-ray diffraction analysis has emerged as the most reliable method for determining the structures of organic molecules. However, numerous analytes, such as liquid organic molecules, pose challenges in crystallization, making their structures directly elusive via X-ray crystallography methods. Herein, we introduced the [...] Read more.

Single-crystal X-ray diffraction analysis has emerged as the most reliable method for determining the structures of organic molecules. However, numerous analytes, such as liquid organic molecules, pose challenges in crystallization, making their structures directly elusive via X-ray crystallography methods. Herein, we introduced the rapid cocrystallization of a macrocycle named phenanthrene[2]arene (PTA, host) with 15 liquid organic molecules (guests). The guest liquid organic molecules were successively cocrystallized with the aid of the PTA host. Moreover, the chemical structures of the liquid organic molecules could be determined through single-crystal X-ray diffraction analysis. PTA exhibited high adaptivity and was capable of encapsulating liquid organic molecules without forming covalent bonds or strong directional interactions. The results revealed that the adaptive crystals of PTA exhibited excellent cocrystallization capacity. Weak noncovalent interactions between the host and guest molecules were crucial for organizing the guests in an ordered pattern. Full article

(This article belongs to the Special Issue Adsorbent Material for Water Treatment)

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13 pages, 6366 KiB

Open AccessArticle

Reconstructing Kaolinite Compounds for Remarkably Enhanced Adsorption of Congo Red

by Ting Liu, **nle Li, Hao Wang, Mingyang Li, Hua Yang, Yunhui Liao, Wufei Tang, Yong Li and Fang Liu

Molecules 2024, 29(9), 2121; https://doi.org/10.3390/molecules29092121 - 3 May 2024

Viewed by 623

Abstract

Organic dyes are widely used in many important areas, but they also bring many issues for water pollution. To address the above issues, a reconstructed kaolinite hybrid compound (γ-AlOOH@A-Kaol) was obtained from raw kaolinite (Kaol) in this work. The product was then characterized [...] Read more.

Organic dyes are widely used in many important areas, but they also bring many issues for water pollution. To address the above issues, a reconstructed kaolinite hybrid compound (γ-AlOOH@A-Kaol) was obtained from raw kaolinite (Kaol) in this work. The product was then characterized by X-ray diffraction (XRD), Fourier-transform infrared (ATR-FTIR), Brunauer-Emmett-Teller (BET), and scanning electron microscopy (SEM), and the absorption properties of γ-AlOOH@A-Kaol for congo red were further studied. The results demonstrated that flower-like γ-AlOOH with nanolamellae were uniformly loaded on the surface of acid-treated Kaol with a porous structure (A-Kaol). In addition, the surface area (36.5 m²/g), pore volume (0.146 cm³/g), and pore size (13.0 nm) of γ-AlOOH@A-Kaol were different from those of A-Kaol (127.4 m²/g, 0.127 cm³/g, and 4.28 nm, respectively) and γ-AlOOH (34.1 m²/g, 0.315 cm³/g, and 21.5 nm, respectively). The unique structure could significantly enhance the sorption capacity for congo red, which could exceed 1000 mg/g. The reasons may be ascribed to the abundant groups of -OH, large specific surface area, and porous structure of γ-AlOOH@A-Kaol. This work provides an efficient route for comprehensive utilization and production of Kaol-based compound materials that could be used in the field of environmental conservation. Full article

(This article belongs to the Special Issue Adsorbent Material for Water Treatment)

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28 pages, 4205 KiB

Open AccessArticle

Process Optimization and Equilibrium, Thermodynamic, and Kinetic Modeling of Toxic Congo Red Dye Adsorption from Aqueous Solutions Using a Copper Ferrite Nanocomposite Adsorbent

by Vairavel Parimelazhagan, Akhil Chinta, Gaurav Ganesh Shetty, Srinivasulu Maddasani, Wei-Lung Tseng, Jayashree Ethiraj, Ganeshraja Ayyakannu Sundaram and Alagarsamy Santhana Krishna Kumar

Molecules 2024, 29(2), 418; https://doi.org/10.3390/molecules29020418 - 15 Jan 2024

Cited by 4 | Viewed by 1874

Abstract

In the present investigation of copper ferrite, a CuFe₂O₄ nanocomposite adsorbent was synthesized using the sol–gel method, and its relevance in the adsorptive elimination of the toxic Congo red (CR) aqueous phase was examined. A variety of structural methods were [...] Read more.

In the present investigation of copper ferrite, a CuFe₂O₄ nanocomposite adsorbent was synthesized using the sol–gel method, and its relevance in the adsorptive elimination of the toxic Congo red (CR) aqueous phase was examined. A variety of structural methods were used to analyze the CuFe₂O₄ nanocomposite; the as-synthesized nanocomposite had agglomerated clusters with a porous, irregular, rough surface that could be seen using FE-SEM, and it also contained carbon (23.47%), oxygen (44.31%), copper (10.21%), and iron (22.01%) in its elemental composition by weight. Experiments were designed to achieve the most optimized system through the utilization of a central composite design (CCD). The highest uptake of CR dye at equilibrium occurred when the initial pH value was 5.5, the adsorbate concentration was 125 mg/L, and the adsorbent dosage was 3.5 g/L. Kinetic studies were conducted, and they showed that the adsorption process followed a pseudo-second-order (PSO) model (regression coefficient, R² = 0.9998), suggesting a chemisorption mechanism, and the overall reaction rate was governed by both the film and pore diffusion of adsorbate molecules. The process through which dye molecules were taken up onto the particle surface revealed interactions involving electrostatic forces, hydrogen bonding, and pore filling. According to isotherm studies, the equilibrium data exhibited strong agreement with the Langmuir model (R² = 0.9989), demonstrating a maximum monolayer adsorption capacity (q_max) of 64.72 mg/g at pH 6 and 302 K. Considering the obtained negative ΔG and positive ΔH_ads and ΔS_ads values across all tested temperatures in the thermodynamic investigations, it was confirmed that the adsorption process was characterized as endothermic, spontaneous, and feasible, with an increased level of randomness. The CuFe₂O₄ adsorbent developed in this study is anticipated to find extensive application in effluent treatment, owing to its excellent reusability and remarkable capability to effectively remove CR in comparison to other adsorbents. Full article

(This article belongs to the Special Issue Adsorbent Material for Water Treatment)

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17 pages, 7588 KiB

Open AccessArticle

The Physicochemical Characteristics and Heavy Metal Retention Capability of Black Liquor Lignin-Based Biochars

by Zhanghong Wang and Jiale Li

Molecules 2023, 28(23), 7694; https://doi.org/10.3390/molecules28237694 - 21 Nov 2023

Cited by 1 | Viewed by 909

Abstract

Due to its high carbon content, lignin, particularly for lignin-containing solid waste, is considered an excellent raw material for the preparation of carbon materials like biochar. To produce high-quality lignin-based biochar (LGBCs), lignin extracted from black liquor was employed to prepare biochar at [...] Read more.

Due to its high carbon content, lignin, particularly for lignin-containing solid waste, is considered an excellent raw material for the preparation of carbon materials like biochar. To produce high-quality lignin-based biochar (LGBCs), lignin extracted from black liquor was employed to prepare biochar at various pyrolysis temperatures (300~600 °C). The physicochemical properties of LGBCs were assessed using scanning electron microscopy, N₂ adsorption/desorption, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction. Furthermore, the adsorption capability and potential mechanism of LGBCs in removing Cd(II) were investigated as well. The results indicate that LGBCs produced at higher pyrolysis temperatures exhibit rougher surfaces and more developed pore structures, which facilitate the exposure of numerous active adsorption sites. The adsorption of Cd(II) by LGBCs generally follows the order of LG-300C < LG-400C < LG-500C < LG-600C. According to the Langmuir adsorption isotherm model, the theoretical maximum adsorption capacity of LG-600C for Cd(II) is calculated to be 18.54 mg/g. Adsorption mechanism analysis reveals that the complexation interaction, dependent on the surface functional groups, plays a crucial role in the adsorption of Cd(II) by LGBCs prepared at higher pyrolysis temperatures. This study demonstrates that, by controlling the pyrolysis temperature during biochar preparation, high-quality lignin-based biochar can be readily obtained. Full article

(This article belongs to the Special Issue Adsorbent Material for Water Treatment)

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Review

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22 pages, 5419 KiB

Open AccessReview

Overview of Functionalized Porous Materials for Rare-Earth Element Separation and Recovery

by Yong Peng, **xin Zhu, Yin Zou, Qingyi Gao, Shaohui **ong, Binjun Liang and Bin **ao

Molecules 2024, 29(12), 2824; https://doi.org/10.3390/molecules29122824 - 13 Jun 2024

Viewed by 366

Abstract

The exceptional photoelectromagnetic characteristics of rare-earth elements contribute significantly to their indispensable position in the high-tech industry. The exponential expansion of the demand for high-purity rare earth and related compounds can be attributed to the swift advancement of contemporary technology. Nevertheless, rare-earth elements [...] Read more.

The exceptional photoelectromagnetic characteristics of rare-earth elements contribute significantly to their indispensable position in the high-tech industry. The exponential expansion of the demand for high-purity rare earth and related compounds can be attributed to the swift advancement of contemporary technology. Nevertheless, rare-earth elements are finite and limited resources, and their excessive mining unavoidably results in resource depletion and environmental degradation. Hence, it is crucial to establish a highly effective approach for the extraction and reclamation of rare-earth elements. Adsorption is regarded as a promising technique for the recovery of rare-earth elements owing to its simplicity, environmentally friendly nature, and cost-effectiveness. The efficacy of adsorption is contingent upon the performance characteristics of the adsorbent material. Presently, there is a prevalent utilization of porous adsorbent materials with substantial specific surface areas and plentiful surface functional groups in the realm of selectively separating and recovering rare-earth elements. This paper presents a thorough examination of porous inorganic carbon materials, porous inorganic silicon materials, porous organic polymers, and metal–organic framework materials. The adsorption performance and processes for rare-earth elements are the focal points of discussion about these materials. Furthermore, this work investigates the potential applications of porous materials in the domain of the adsorption of rare-earth elements. Full article

(This article belongs to the Special Issue Adsorbent Material for Water Treatment)

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