Editorial

3 pages, 188 KiB

Open AccessEditorial

Novel Adsorbents and Adsorption Methods for Pollutant Removal

by Yuezhou Wei, Yan Wu and Xinpeng Wang

Toxics 2023, 11(12), 954; https://doi.org/10.3390/toxics11120954 - 23 Nov 2023

Viewed by 775

Over the past few decades, with the rapid growth of the global population and economy, the increasing levels of various pollutants such as heavy metals, radionuclides, and organic/inorganic/biological toxins from various industries and human activities, which diffuse into aspects of the environment such [...] Read more.

Over the past few decades, with the rapid growth of the global population and economy, the increasing levels of various pollutants such as heavy metals, radionuclides, and organic/inorganic/biological toxins from various industries and human activities, which diffuse into aspects of the environment such as the atmosphere, soil, and natural water, have posed a serious threat to human health and the environment [...] Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

Research

Jump to: Editorial, Review

14 pages, 4466 KiB

Open AccessArticle

Radiation Resistance and Adsorption Behavior of Aluminum Hexacyanoferrate for Pd

by Yueying Wen, Yan Wu and Lejin Xu

Toxics 2023, 11(4), 321; https://doi.org/10.3390/toxics11040321 - 29 Mar 2023

Cited by 1 | Viewed by 1024

Abstract

Irradiation resistance is important for adsorbents used in radioactive environments such as high-level liquid waste. In this work, a silica-based composite adsorbent (KAlFe(CN)₆/SiO₂) was synthesized and γ-irradiated from 10 to 1000 kGy. The angles of the main X-ray diffraction [...] Read more.

Irradiation resistance is important for adsorbents used in radioactive environments such as high-level liquid waste. In this work, a silica-based composite adsorbent (KAlFe(CN)₆/SiO₂) was synthesized and γ-irradiated from 10 to 1000 kGy. The angles of the main X-ray diffraction peaks slightly decreased with the increase in irradiation dose, and a minor decomposition of CN⁻ occurred after irradiation to 1000 kGy, indicating that the KAlFe(CN)₆/SiO₂ adsorbent could preserve structural integrity with a dose below 100 kGy. In 1 to 7 M HNO₃, the adsorption ability of the irradiated KAlFe(CN)₆/SiO₂ remained performant, with a higher K_d than 1625 cm³ g⁻¹. The adsorption equilibrium of Pd(II) in 3 M HNO₃ was attained within 45 min before and after irradiation. The maximal adsorption capacity Q_e of the irradiated KAlFe(CN)₆/SiO₂ on Pd(II) ranged from 45.1 to 48.1 mg g⁻¹. A 1.2% relative drop in Q_e was observed after 100 kGy irradiation, showing that γ-irradiation lower than 100 kGy insignificantly affected the adsorption capacity of KAlFe(CN)₆/SiO₂. Calculating and comparing the structures and free energies of different adsorption products via the density functional theory (DFT) method showed that KAlFe(CN)₆/SiO₂ was more inclined to completely adsorb Pd(II) and spontaneously generate Pd[AlFe(CN)₆]₂. Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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11 pages, 1728 KiB

Open AccessArticle

Advection–Dispersion Behavior for Simulation of H-3 and Pu-238 Transport in Undisturbed Argillaceous Shale of a Near-Surface Repository

by Yunfeng Shi, Song Yang, Enhui Wu, Longjiang Wang, Wenjie Chen, Weijia Xiong, Yanna Zhang, Aiming Zhang and Bing Lian

Toxics 2023, 11(2), 124; https://doi.org/10.3390/toxics11020124 - 27 Jan 2023

Cited by 1 | Viewed by 929

Abstract

In this study, a column experiment was employed to evaluate the nuclide migration behavior in the surrounding rock medium of a near-surface disposal site in China and to investigate the advection–dispersion behavior of tritium (H-3) and plutonium-238 (Pu-238) in highly weathered argillaceous shale. [...] Read more.

In this study, a column experiment was employed to evaluate the nuclide migration behavior in the surrounding rock medium of a near-surface disposal site in China and to investigate the advection–dispersion behavior of tritium (H-3) and plutonium-238 (Pu-238) in highly weathered argillaceous shale. A reasonable numerical model was selected to fit the experimental breakthrough curves (BTCs) and to obtain the relevant migration parameters. The results show the following: (1) the internal structure of the highly weathered argillaceous shale exhibited heterogeneity, and the nuclide migration BTC showed characteristics of a “curve peak moving forward” and a “tail curve trailing”; (2) compared with other models, the stream tube mode could better fit the BTCs and obtain the average dispersion coefficient <D>, average distribution coefficient <K_d>, and other parameters; (3) compared to the results of the batch experiment, the distribution coefficient K_d obtained from the column experiment was smaller than that obtained from the batch experiment, which is speculated to be due to the influence of contact time and the contact area between the nuclide and the medium. Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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14 pages, 4428 KiB

Open AccessArticle

Potential Application of Discarded Natural Coal Gangue for the Removal of Tetracycline Hydrochloride (TC) from an Aqueous Solution

by Hongyou Wan, Chen Wang, Lin Gong, Xinfeng Zhu, Jingwei Yan, Jiajia Lu and Wei Zhang

Toxics 2023, 11(1), 20; https://doi.org/10.3390/toxics11010020 - 26 Dec 2022

Cited by 2 | Viewed by 1290

Abstract

The generation and accumulation of discarded coal gangue (CG) have severe environmental impacts. CG can adsorb other pollutants in the aquatic environment. However, previous studies have not assessed whether CG can adsorb the emerging contaminant tetracycline hydrochloride (TC). Here, discarded CG taken from [...] Read more.

The generation and accumulation of discarded coal gangue (CG) have severe environmental impacts. CG can adsorb other pollutants in the aquatic environment. However, previous studies have not assessed whether CG can adsorb the emerging contaminant tetracycline hydrochloride (TC). Here, discarded CG taken from a mine was pretreated by crushing, cleaning, and sieving and subsequently applied to the adsorption of TC. The adsorption studies were carried out by batch equilibrium adsorption experiments. Our findings indicated that the adsorption behavior could be accurately described using the quasi-first order kinetic and Langmuir adsorption isotherm models, indicating that monolayer adsorption was the main mechanism mediating the interaction between CG and TC. The adsorption process was classified as a thermodynamic endothermic and spontaneous reaction, which was controlled by chemical and physical adsorption, including electrostatic interaction and cation exchange. The pH of the solution had a great influence on the TC adsorption capacity of GC, with higher adsorption occurring in acidic environments compared to alkaline environments. This was attributed to the changes in CG Zeta potential and TC pKa at different pH conditions. Collectively, our findings demonstrated the potential applicability of discarded CG for the adsorption of TC and provided insights into the adsorption mechanisms. Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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19 pages, 8028 KiB

Open AccessArticle

Evaluation of Heavy Metal Removal of Nanoparticles Based Adsorbent Using Danio rerio as Model

by Antony V. Samrot, Muthiah Bavanilatha, Sivasuriyan Krithika Shree, Mahendran Sathiyasree, Jayaram Vanjinathan, Nagarajan Shobana, Rajendran Thirugnanasambandam, Chandrasekaran Kumar, Samraj Wilson, Deenadhayalan Rajalakshmi, Lawrence Xavier Noel Richard Prakash and Ram Singh Sanjay Preeth

Toxics 2022, 10(12), 742; https://doi.org/10.3390/toxics10120742 - 30 Nov 2022

Cited by 5 | Viewed by 2053

Abstract

Nanoparticles are potential candidates for wastewater treatment especially for the removal of heavy metals due to their strong affinity. Many biopolymers are used as adsorbents and encapsulation of nanoparticle onto them can increase their efficiency. In this study, SPIONs, alginate, and SPIONs incorporated [...] Read more.

Nanoparticles are potential candidates for wastewater treatment especially for the removal of heavy metals due to their strong affinity. Many biopolymers are used as adsorbents and encapsulation of nanoparticle onto them can increase their efficiency. In this study, SPIONs, alginate, and SPIONs incorporated on alginate beads have been synthesized and characterized both microscopically and spectroscopically. These were then used for the removal of chromium metal and the percentage of removal was evaluated using a batch adsorption study. The percent removal of chromium using SPIONs, alginate and alginate–SPIONs beads were recorded to be 93%, 91% and 94%, respectively. The adsorption of chromium using SPIONs and alginate–SPIONs beads followed the Tempkin isotherm, whereas adsorption of chromium metal by alginate beads was found to be homogeneous in nature and followed the Langmuir isotherm with an R² value of 0.9784. An in-vivo study using Danio rerio as a model organism was done to examine the toxicity and the removal efficiency of the samples. It was observed that chromium water treated with alginate–SPIONs beads, which were removed after water treatment showed less damage to the fishes when compared to SPIONs and alginate beads treated with chromium water where the SPIONs and alginate beads were not removed after the treatment period. Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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11 pages, 2824 KiB

Open AccessArticle

Separation of Minor Actinides from High-Level Liquid Waste Using Novel Silica-Based Butyl-BTP Adsorbents

by Tianjiao Jiang, Shunyan Ning, Tao Yu, Ji Wang, Yuezhou Wei, Yan Wu, Hui He, Fangqiang Chen and Qingsong Wang

Toxics 2022, 10(12), 741; https://doi.org/10.3390/toxics10120741 - 30 Nov 2022

Cited by 1 | Viewed by 1376

Abstract

To separate the long-lived minor actinides (MA = Am, Cm) from high-level liquid waste (HLLW), we have been studying an advanced separation process via selective adsorption that uses minimal amounts of organic solvent and compact equipment. The process consists of two separation columns [...] Read more.

To separate the long-lived minor actinides (MA = Am, Cm) from high-level liquid waste (HLLW), we have been studying an advanced separation process via selective adsorption that uses minimal amounts of organic solvent and compact equipment. The process consists of two separation columns packed with a CMPO (octyl(phenyl)-N,N-diisobutylcarbamoyl-methyl phosphine oxide) adsorbent for elemental group separation and a soft-donor named the R-BTP (2,6-bis-(5,6-dialkyl-1,2,4-triazine-3-yl) pyridine) adsorbent for the isolation of MA from lanthanides (Ln). In this work, the effects of nitrate ion (NO₃⁻) on the adsorption behavior of Am(III) and a typical fission product Ln(III) onto the isoBu-BTP/SiO₂-P adsorbent were studied experimentally. Then, the desorption properties of the adsorbed element were examined using different eluting agents. A hot test for the separation of MA from the fission product Ln in a genuine MA containing effluent from the irradiated MOX-fuel treatment process was carried out using a nBu-BTP/SiO₂-P packed column. It was found that the separation factor between Am(III) and Ln(III)-FP is over 100 in the measured 0.5–4 M NO₃⁻. The adsorbed elements could be effectively eluted off using a complexing agent such as DTPA or pure water. Complete separation between MA and Ln was achieved in the column results, indicating that the proposed MA separation process is feasible in principle. Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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13 pages, 3692 KiB

Open AccessArticle

Fabrication of a Ternary Nanocomposite g-C₃N₄/Cu@CdS with Superior Charge Separation for Removal of Organic Pollutants and Bacterial Disinfection from Wastewater under Sunlight Illumination

by Malik Imran Afzal, Sammia Shahid, Sana Mansoor, Mohsin Javed, Shahid Iqbal, Othman Hakami, El Sayed Yousef, Foziah F. Al-Fawzan, Eslam B. Elkaeed, Rami Adel Pashameah, Eman Alzahrani and Abd-ElAziem Farouk

Toxics 2022, 10(11), 657; https://doi.org/10.3390/toxics10110657 - 29 Oct 2022

Cited by 12 | Viewed by 1705

Abstract

The synthesis of a photo-catalyst with a narrow bandgap and efficient capability to degrade contaminants in the presence of sunlight is currently challenging but exciting. In this work, an efficient photocatalytic ternary nanocomposite g-C₃N₄/Cu@CdS has been synthesized successfully by [...] Read more.

The synthesis of a photo-catalyst with a narrow bandgap and efficient capability to degrade contaminants in the presence of sunlight is currently challenging but exciting. In this work, an efficient photocatalytic ternary nanocomposite g-C₃N₄/Cu@CdS has been synthesized successfully by using the co-precipitation method. The synthesized composite was then characterized by SEM, XRD studies, EDX analysis, and ultra-violet-visible (UV-VIS) spectroscopy. The catalytic efficiency for the methylene blue (MB) dye and drug degradation (ciprofloxacin) was assessed by UV-visible absorption spectra. Gram-positive and Gram-negative bacteria were used to test the fabrication composite’s antibacterial properties. Various compositions (1%, 3%, 5%, 7%, and 9%) of/Cu@CdS nanocomposite (NCs) and 20%, 30%, 40%, 50%, and 60% of g-C₃N₄ NCs were prepared. Results reveal that 5%Cu@CdS and 40%g-C₃N₄5%Cu@CdS showed maximum antibacterial activity and photocatalytic degradation of dye and drug. The X-ray pattern showed no remarkable change in doped and pristine CdS nanoparticles (NPs). The efficient photocatalytic degradation activity of the fabricated ternary nanocomposite against MB dye and ciprofloxacin an antibiotic drug makes it a viable contender for solving environmental problems. Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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13 pages, 2782 KiB

Open AccessArticle

Study on the Effect of Gamma-Ray Irradiation on the Adsorption of ⁹⁹Tc and Re by a Silica-Based Pyridine Resin

by Hongji Sang, Cong Mao, Yan Wu and Yuezhou Wei

Toxics 2022, 10(11), 638; https://doi.org/10.3390/toxics10110638 - 25 Oct 2022

Cited by 3 | Viewed by 1162

Abstract

A silica-based anion exchange resin was synthesized and used to remove ⁹⁹Tc from real radioactive liquid waste. The adsorbent had a uniform particle size and exhibited good thermal stability up to 100 °C, which is promising for large-scale column experiments. In accordance [...] Read more.

A silica-based anion exchange resin was synthesized and used to remove ⁹⁹Tc from real radioactive liquid waste. The adsorbent had a uniform particle size and exhibited good thermal stability up to 100 °C, which is promising for large-scale column experiments. In accordance with the chemical similarity with Tc, Re was used as a surrogate in this study. The N 1s high-resolution XPS spectra of the adsorbent before and after the adsorption of Re indicated that the ion exchange reaction was the controlling mechanism in the process. After γ-ray irradiation, the changing trend of the K_d was consistent, which showed that the competitive adsorption of NO₃⁻ led to a decrease in K_d. The adsorption capacity for the Re decreased slightly from 35.8 to 31.9 mg/g with the increase in the absorbed dose from 0 to 50 kGy. The separation and recovery of Re and the coexisting ions were achieved by chromatographic separation experiments, and the recovery percentage of Re was 86%. In real radioactive liquid waste, N3/SiO₂ exhibited good selectivity toward ⁹⁹Tc over the coexisting metals, namely, ⁹⁰Sr, ¹³⁷Cs, ²⁴¹Am, and U, and the decontamination efficiency of ⁹⁹Tc attained 65%. Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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13 pages, 6593 KiB

Open AccessArticle

Highly Selective Adsorption of ⁹⁹TcO₄⁻/ReO₄⁻ by a Novel Polyamide-Functionalized Polyacrylamide Polymer Material

by Ben Qin, Yanqin Hu, Meiying Xie, Liyan Xue, Chunfa Liao and Fan Yang

Toxics 2022, 10(10), 630; https://doi.org/10.3390/toxics10100630 - 21 Oct 2022

Cited by 1 | Viewed by 1430

Abstract

The treatment of radioactive wastewater is one of the major problems in the current research. With the development of nuclear energy, the efficient removal of ⁹⁹TcO₄⁻ in radioactive wastewater has attracted the attention of countries all over the world. In [...] Read more.

The treatment of radioactive wastewater is one of the major problems in the current research. With the development of nuclear energy, the efficient removal of ⁹⁹TcO₄⁻ in radioactive wastewater has attracted the attention of countries all over the world. In this study, a novel functional polyamide polymer p-(Amide)-PAM was synthesized by the two-step method. The experimental results show that p-(Amide)-PAM has good adsorptive properties for ⁹⁹TcO₄⁻/ReO₄⁻ and has good selectivity in the nitric acid system. The kinetics of the reaction of p-(Amide)-PAM with ⁹⁹TcO₄⁻/ReO₄⁻ was studied. The results show that p-(Amide)-PAM has a fast adsorption rate for ⁹⁹TcO₄⁻/ReO₄⁻, the saturated adsorption capacity reaches 346.02 mg/g, and the material has good reusability. This new polyamide-functionalized polyacrylamide polymer material has good application prospects in the removal of ⁹⁹TcO₄⁻ from radioactive wastewater. Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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14 pages, 19770 KiB

Open AccessArticle

Study on Tritium and Iodine Species Transport through Porous Granite: A Non-Sorption Effect by Anion Exclusion

by Yunfeng Shi, Song Yang, Wenjie Chen, Weijia Xiong, Aiming Zhang, Zhixiang Yu, Bing Lian and Chuan-Pin Lee

Toxics 2022, 10(9), 540; https://doi.org/10.3390/toxics10090540 - 16 Sep 2022

Cited by 5 | Viewed by 1436

Abstract

The safety of deep geological repositories is important in the disposal of high-level radioactive waste (HLW). In this study, advection–dispersion experiments were designed to build a transport model through a calibration/validation process, and the transport behavior of tritiated water (HTO) and various iodine [...] Read more.

The safety of deep geological repositories is important in the disposal of high-level radioactive waste (HLW). In this study, advection–dispersion experiments were designed to build a transport model through a calibration/validation process, and the transport behavior of tritiated water (HTO) and various iodine species (iodide: I⁻ and iodate: IO₃⁻) was studied on a dynamic compacted granite column. Breakthrough curves (BTCs) were plotted under various flow rates (1–5 mL/min). BTCs showed that the non-sorption effect by anion exclusion was observed only in I⁻ transport because the retardation factor (R) of I⁻ was lower than that of HTO (R = 1). Moreover, equilibrium and nonequilibrium transport models were used and compared to identify the mobile/immobile zones in the compacted granite column. The anion exclusion effect was influenced by the immobile zones in the column. The non-sorption effect by anion exclusion (R < 1) was only observed for I⁻ at 5.0 ± 0.2 mL/min flow rate, and a relatively higher Coulomb’s repulsive force may be caused by the smaller hydration radius of I⁻(3.31 Å) than that of IO₃⁻(3.74 Å). Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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16 pages, 13475 KiB

Open AccessArticle

Performance and Mechanism of As(III/V) Removal from Aqueous Solution by Fe₃O₄-Sunflower Straw Biochar

by Yuling Zhao, Hao Shi, Xin Tang, Daihong Kuang, Jinlong Zhou and Fangyuan Yang

Toxics 2022, 10(9), 534; https://doi.org/10.3390/toxics10090534 - 11 Sep 2022

Cited by 4 | Viewed by 1805

Abstract

Humans and ecosystems are severely damaged by the existence of As(III/V) in the aquatic environment. Herein, an advanced Fe₃O₄@SFBC (Fe₃O₄-sunflower straw biochar) adsorbent was fabricated by co-precipitation method with sunflower straw biochar (SFBC) prepared at [...] Read more.

Humans and ecosystems are severely damaged by the existence of As(III/V) in the aquatic environment. Herein, an advanced Fe₃O₄@SFBC (Fe₃O₄-sunflower straw biochar) adsorbent was fabricated by co-precipitation method with sunflower straw biochar (SFBC) prepared at different calcination temperatures and different SFBC/Fe mass ratios as templates. The optimal pH for As(III/V) removal was investigated, and Fe₃O₄@SFBC shows removal efficiency of 86.43% and 95.94% for As(III) and As(V), respectively, at pH 6 and 4. The adsorption effect of calcining and casting the biochar-bound Fe₃O₄ obtained at different temperatures and different SFBC/Fe mass ratios were analyzed by batch experiments. The results show that when the SFBC biochar is calcined at 450 °C with an SFBC/Fe mass ratio of 1:5, the adsorption of As(III) and As(V) reaches the maximum, which are 121.347 and 188.753 mg/g, respectively. Fe₃O₄@SFBC morphology, structure, surface functional groups, magnetic moment, and internal morphology were observed by XRD, FTIR, SEM, TEM, and VSM under optimal working conditions. The material shows a small particle size in the range of 12–14 nm with better magnetic properties (54.52 emu/g), which is suitable for arsenic removal. The adsorption mechanism of As(III/V) by Fe₃O₄@SFBC indicates the presence of chemisorption, electrostatic, and complexation. Finally, the material was used for five consecutive cycles of adsorption–desorption experiments, and no significant decrease in removal efficiency was observed. Therefore, the new adsorbent Fe₃O₄@SFBC can be efficiently used for arsenic removal in the aqueous system. Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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14 pages, 3464 KiB

Open AccessArticle

Chitosan-Modified Biochar and Unmodified Biochar for Methyl Orange: Adsorption Characteristics and Mechanism Exploration

by Nguyen Xuan Loc, Phan Thi Thanh Tuyen, Le Chi Mai and Do Thi My Phuong

Toxics 2022, 10(9), 500; https://doi.org/10.3390/toxics10090500 - 27 Aug 2022

Cited by 17 | Viewed by 2543

Abstract

In this study, shrimp shell-derived chitosan (CS) and rice husk-derived biochar (RHB) were produced; CS and RHB were then used to synthesize chitosan-modified biochar (CSBC) hydrogel beads. N₂ adsorption (77K), SEM-EDX and FT-IR techniques were used to evaluate the physicochemical properties of [...] Read more.

In this study, shrimp shell-derived chitosan (CS) and rice husk-derived biochar (RHB) were produced; CS and RHB were then used to synthesize chitosan-modified biochar (CSBC) hydrogel beads. N₂ adsorption (77K), SEM-EDX and FT-IR techniques were used to evaluate the physicochemical properties of the adsorbents. A batch experiment was conducted to test the methyl orange (MO) adsorption performance of RHB and CSBC. The results showed that the MO adsorption process was strongly pH-dependent. The kinetics were well described by the pseudo-second-order and intra-particle diffusion models, assuming the chemisorption and intraparticle diffusion mechanisms govern the adsorption process. Homogeneous adsorption for MO on the surface of RHB and CSBC was also assumed since the isotherm data showed the best-fit to the Langmuir model. Under the experimental conditions of initial pH 3, dosage 0.2 g, contact time 240 min and temperature 298 K, the maximum adsorption capacity of CSBC and RHB for MO dye adsorption was 38.75 mg.g⁻¹ and 31.63 mg.g⁻¹, respectively. This result demonstrated that biochar had better performance after modification with chitosan, which provided more functional groups (i.e., −NH₂ and −OH groups) for enhanced electrostatic interactions and complexation between MO and CSBC. Overall, CSBC is an effective adsorbent for the removal of MO from aqueous solution. Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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21 pages, 6008 KiB

Open AccessFeature PaperArticle

Ecofriendly Composite as a Promising Material for Highly-Performance Uranium Recovery from Different Solutions

by Mohammed F. Hamza, Hanaa A. Abu Khoziem, Mahmoud S. Khalafalla, Walid M. Abdellah, Doaa I. Zaki, Khalid Althumayri and Yuezhou Wei

Toxics 2022, 10(9), 490; https://doi.org/10.3390/toxics10090490 - 24 Aug 2022

Cited by 9 | Viewed by 1834

Abstract

The development of new materials based on biopolymers (as renewable resources) is substantial for environmental challenges in the heavy metal and radionuclide ions removal contaminations. Functionalization of chitosan with sulfonic groups was achieved for improving the uranium sorption, not only from slightly acidic [...] Read more.

The development of new materials based on biopolymers (as renewable resources) is substantial for environmental challenges in the heavy metal and radionuclide ions removal contaminations. Functionalization of chitosan with sulfonic groups was achieved for improving the uranium sorption, not only from slightly acidic leachate, but also for the underground water. The prepared hydrogel based on chitosan was characterized by series of analysis tools for structure elucidation as FTIR spectroscopy, textural properties using nitrogen adsorption method, pH_PZC (by pH-drift method), thermogravimetric analysis (TGA), SEM, and SEM-EDX analyses. The sorption was performed toward uranium (VI) ions for adjustment of sorption performances. The optimum sorption was performed at pH 4 (prior to the precipitation pH). The total sorption was achieved within 25 min (relatively fast kinetics) and was fitted by pseudo-first order rate equation (PFORE) and resistance to intraparticle diffusion equation (RIDE). The maximum sorption capacity was around 1.5 mmol U g⁻¹. The sorption isotherms were fitted by Langmuir and Sips equations. Desorption was achieved using 0.3 M HCl solution and the complete desorption was performed in around 15 min of contact. The sorption desorption cycles are relatively stable during 5 cycles with limit decreasing in sorption and desorption properties (around 3 ± 0.2% and 99.8 ± 0.1%, respectively). The sorbent was used for removal of U from acid leachate solution in mining area. The sorbent showed a highly performance for U(VI) removal, which was considered as a tool material for radionuclides removing from aquatic medium. Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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15 pages, 4822 KiB

Open AccessArticle

Utilization of Waste Amine-Oxime (WAO) Resin to Generate Carbon by Microwave and Its Removal of Pb(II) in Water

by Chunlin He, Yun Liu, Chunhui Zheng, Yanming Jiang, Yan Liao, Jiaxin Huang, Toyohisa Fujita, Yuezhou Wei and Shaojian Ma

Toxics 2022, 10(9), 489; https://doi.org/10.3390/toxics10090489 - 23 Aug 2022

Cited by 4 | Viewed by 1158

Abstract

Utilising waste amine-oxime (WAO) resin through microwave semi-carbonization, a carbon adsorbent (CA) was obtained to remove Pb(II). After microwave treatment, the pore size of the skeleton structure, three-dimensional porous network, and lamellar pore structure of WAO was improved. The distribution coefficient (Kd) of [...] Read more.

Utilising waste amine-oxime (WAO) resin through microwave semi-carbonization, a carbon adsorbent (CA) was obtained to remove Pb(II). After microwave treatment, the pore size of the skeleton structure, three-dimensional porous network, and lamellar pore structure of WAO was improved. The distribution coefficient (Kd) of Pb(II) onto CA is 620 mL/g, and the maximum adsorption capacity of Pb(II) is 82.67 mg/g after 20 min of WAO microwave treatment. The adsorption kinetics and adsorption isotherms conform to the quasi-second-order kinetic equation and Langmuir adsorption isotherm model, respectively. The surface of MT-WAO is negatively charged and the adsorption mechanism is mainly electrostatic interaction. Pb(II) elution in hydrochloric acid solution is more than 98%, and its recovery is high at 318 K and for 1 h. Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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17 pages, 3629 KiB

Open AccessArticle

Mineralogical Properties of a Refractory Tantalum-Niobium Slag and the Effect of Roasting on the Leaching of Uranium-Thorium

by Min Huang, Ke Hu, Xiang Li, Yun Wang, Jinbo Ouyang, Limin Zhou and Zhirong Liu

Toxics 2022, 10(8), 469; https://doi.org/10.3390/toxics10080469 - 12 Aug 2022

Cited by 5 | Viewed by 1475

Abstract

In order to realize sustainable development, it is beneficial to explore an appropriate process to recover the radionuclides contained in tantalum-niobium slag. By micro-mineralogical analysis and roasting experiments, the effect of uranium-thorium leaching from a refractory tantalum-niobium slag is investigated. The uranium and [...] Read more.

In order to realize sustainable development, it is beneficial to explore an appropriate process to recover the radionuclides contained in tantalum-niobium slag. By micro-mineralogical analysis and roasting experiments, the effect of uranium-thorium leaching from a refractory tantalum-niobium slag is investigated. The uranium and thorium content in the slag is 2.26 × 10³ mg/kg and 7.84 × 10³ mg/kg, which have large recovery value. As the surface area and pore size of the slag are very small, the leaching agent cannot fully penetrate the particles. Various methods of characterization are used to analyze the mineralogical properties of roasted slag at different temperatures. The leaching ratio of U-Th is 90.84% and 96.62% at the optimum roasting temperature of 500 °C, which are about 39% and 27% higher than original samples. The oxidants Fe³⁺, O₂ and Mn can also promote the conversion of insoluble U(IV) to soluble U(VI). Roasting reduces the content of organic C and S, thereby preventing reduction of U(VI), and increasing pore size as well as specific surface area also promote radionuclide leaching. Thus, the roasting method at 500 °C can destroy the surface wrapping structure of radionuclides, reduce the internal density of minerals, and improve uranium-thorium leaching ratio significantly. It is of great practical significance to reduce the radioactive hazard of waste tantalum-niobium slag and to strengthen the sustainable utilization of resources by suitable process improvement techniques. Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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12 pages, 2856 KiB

Open AccessFeature PaperArticle

Detection of Cd²⁺ in Aqueous Solution by the Fluorescent Probe of CdSe/CdS QDs Based on OFF–ON Mode

by Dengpeng Wang, Feng Gao, Xianran Wang, Xiaomei Ning, Kaituo Wang, Xinpeng Wang, Yuezhou Wei and Toyohisa Fujita

Toxics 2022, 10(7), 367; https://doi.org/10.3390/toxics10070367 - 03 Jul 2022

Cited by 11 | Viewed by 1639

Abstract

The detection of heavy metals in aqueous solutions has always attracted much attention from all over the world. A fluorescent probe of CdSe/CdS core-shell quantum dots (QDs) was designed to detect trace Cd²⁺ in aqueous solutions using the OFF–ON mode rapidly and [...] Read more.

The detection of heavy metals in aqueous solutions has always attracted much attention from all over the world. A fluorescent probe of CdSe/CdS core-shell quantum dots (QDs) was designed to detect trace Cd²⁺ in aqueous solutions using the OFF–ON mode rapidly and efficiently, likely based on adsorption and desorption reactions between ethylenediaminetetraacetic acid disodium salt (EDTA) and CdSe/CdS QDs. In the OFF mode, the optical shielding function of EDTA results in fluorescence quenching owing to the strong adsorption ability of EDTA with Cd²⁺ on the sites of CdSe/CdS QDs surface. In the ON mode, the introduction of Cd²⁺ promotes the desorption of EDTA from the EDTA-CdSe/CdS QDs and restores the fluorescence intensity. There were two linear response ranges which were 0.1–20 µmol/L and 20–90 µmol/L for the EDTA-CdSe/CdS system to detect Cd²⁺. The detection limit was 6 nmol/L, and the standard deviation was below 4% for the detection of Cd²⁺ concentration in tap water. Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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13 pages, 10822 KiB

Open AccessFeature PaperArticle

Removal of the Homolog Tellurium of Polonium by SiO₂ Nanofiber Filter for Lead Alloy-Cooled Reactors

by Xujie Chen, Xiyong Chen, Xian Zeng, Yuan Zhao, Xiaoping Li, Xi Huang, Toyohisa Fujita and Xinpeng Wang

Toxics 2022, 10(6), 275; https://doi.org/10.3390/toxics10060275 - 24 May 2022

Cited by 2 | Viewed by 2073

Abstract

The lead–bismuth eutectic (LBE) can be easily activated by neutron radiation to produce the radionuclide ²¹⁰Po. It is therefore necessary to establish an effective method to remove vaporized polonium in the cover gas to prevent its release into the air in scenarios [...] Read more.

The lead–bismuth eutectic (LBE) can be easily activated by neutron radiation to produce the radionuclide ²¹⁰Po. It is therefore necessary to establish an effective method to remove vaporized polonium in the cover gas to prevent its release into the air in scenarios of reactor maintenance and coolant leakage accidents. This paper presents a SiO₂ nanofiber membrane prepared based on the electrostatic spinning and calcination process. The SiO₂ nanofiber membrane had the advantages of good flexibility, high-temperature resistance, and corrosion resistance. In the trapping experiments, the SiO₂ nanofiber membrane filters showed excellent filtration performance at 300~400 °C, and the filtration efficiencies for Te, Pb, and Bi could reach 99%, 99%, and 98%, respectively. Proper filtration temperature and gas flow rate are important to maintain high filtration efficiency. After five cycles, the SiO₂ nanofiber membrane filter still exhibited excellent cycle-use performance. In the density functional theory (DFT) calculations, PbPo and PbTe had strong interactions with amorphous SiO₂, having adhesion energies of −2.96 to −2.83 eV/molecule. Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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Review

Jump to: Editorial, Research

17 pages, 978 KiB

Open AccessFeature PaperReview

A Review of Soil Contaminated with Dioxins and Biodegradation Technologies: Current Status and Future Prospects

by Nguyen Thi Hong Nhung, Xuan-Tung Tan Nguyen, Vo Dinh Long, Yuezou Wei and Toyohisa Fujita

Toxics 2022, 10(6), 278; https://doi.org/10.3390/toxics10060278 - 24 May 2022

Cited by 15 | Viewed by 6504

Abstract

This article provides a comprehensive assessment of dioxins contaminating the soil and evaluates the bioremediation technology currently being widely used, and also offers recommendations for future prospects. Soil pollution containing dioxins is extremely toxic and hazardous to human health and the environment. Dioxin [...] Read more.

This article provides a comprehensive assessment of dioxins contaminating the soil and evaluates the bioremediation technology currently being widely used, and also offers recommendations for future prospects. Soil pollution containing dioxins is extremely toxic and hazardous to human health and the environment. Dioxin concentrations in soils around the world are caused by a variety of sources and outcomes, but the main sources are from the consequences of war and human activities. Bioremediation technology (bioaugmentation, biostimulation, and phytoremediation) is considered an optimal and environmentally friendly technology, with the goal of applying native microbial communities and using plant species with a high biomass to treat contaminated dioxins in soil. The powerful bioremediation system is the growth of microorganisms that contribute to the increased mutualistic and competitive relationships between different strains of microorganisms. Although biological treatment technology can thoroughly treat contaminated dioxins in soil with high efficiency, the amount of gas generated and Cl radicals dispersed after the treatment process remains high. Further research on the subject is required to provide stricter control over the outputs noted in this study. Full article

(This article belongs to the Special Issue Novel Adsorbents and Adsorption Methods for Pollutants Removal)

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