International Journal of Molecular Sciences

Editorial

8 pages, 256 KiB

Open AccessEditorial

Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants

by Thomas Dippong

Int. J. Mol. Sci. 2023, 24(1), 330; https://doi.org/10.3390/ijms24010330 - 25 Dec 2022

Viewed by 1067

Abstract

Water is a scarce resource with a close and intricate nexus with energy [...] Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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18 pages, 5773 KiB

Open AccessArticle

Effects of Acidic Environments on Dental Structures after Bracket Debonding

by Cristina Iosif, Stanca Cuc, Doina Prodan, Marioara Moldovan, Ioan Petean, Mîndra Eugenia Badea, Sorina Sava, Andrada Tonea and Radu Chifor

Int. J. Mol. Sci. 2022, 23(24), 15583; https://doi.org/10.3390/ijms232415583 - 9 Dec 2022

Cited by 10 | Viewed by 2087

Abstract

Brackets are metallic dental devices that are very often associated with acidic soft drinks such as cola and energy drinks. Acid erosion may affect the bonding between brackets and the enamel surface. The purpose of this study was to investigate the characteristics of [...] Read more.

Brackets are metallic dental devices that are very often associated with acidic soft drinks such as cola and energy drinks. Acid erosion may affect the bonding between brackets and the enamel surface. The purpose of this study was to investigate the characteristics of brackets’ adhesion, in the presence of two different commercially available drinks. Sixty human teeth were divided into six groups and bonded with either resin-modified glass ionomer (RMGIC) or resin composite (CR). A shared bond test (SBS) was evaluated by comparing two control groups with four other categories, in which teeth were immersed in either Coca-Cola^TM or Red Bull^TM energy drink. The debonding between the bracket and enamel was evaluated by SEM. The morphological aspect correlated with SBS results showed the best results for the samples exposed to artificial saliva. The best adhesion resistance to the acid erosion environment was observed in the group of teeth immersed in Red Bull^TM and with brackets bonded with RMGIC. The debonded structures were also exposed to Coca-Cola^TM and Red Bull^TM to assess, by atomic force microscopy investigation (AFM), the erosive effect on the enamel surface after debonding and after polishing restoration. The results showed a significant increase in surface roughness due to acid erosion. Polishing restoration of the enamel surface significantly reduced the surface roughness that resulted after debonding, and inhibited acid erosion. The roughness values obtained from polished samples after exposure to Coca-Cola^TM and Red Bull^TM were significantly lower in that case than for the debonded structures. Statistical results evaluating roughness showed that Red Bull^TM has a more erosive effect than Coca-Cola™. This result is supported by the large contact surface that resulted after debonding. In conclusion, the prolonged exposure of the brackets to acidic drinks affected the bonding strength due to erosion propagation into both the enamel–adhesive interface and the bonding layer. The best resistance to acid erosion was obtained by RMGIC. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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20 pages, 2726 KiB

Open AccessArticle

Photocatalytic Performance of Undoped and Al-Doped ZnO Nanoparticles in the Degradation of Rhodamine B under UV-Visible Light:The Role of Defects and Morphology

by Alessandra Piras, Chiara Olla, Gunter Reekmans, An-Sofie Kelchtermans, Dries De Sloovere, Ken Elen, Carlo Maria Carbonaro, Luca Fusaro, Peter Adriaensens, An Hardy, Carmela Aprile and Marlies K. Van Bael

Int. J. Mol. Sci. 2022, 23(24), 15459; https://doi.org/10.3390/ijms232415459 - 7 Dec 2022

Cited by 21 | Viewed by 2860

Abstract

Quasi-spherical undoped ZnO and Al-doped ZnO nanoparticles with different aluminum content, ranging from 0.5 to 5 at% of Al with respect to Zn, were synthesized. These nanoparticles were evaluated as photocatalysts in the photodegradation of the Rhodamine B (RhB) dye aqueous solution under [...] Read more.

Quasi-spherical undoped ZnO and Al-doped ZnO nanoparticles with different aluminum content, ranging from 0.5 to 5 at% of Al with respect to Zn, were synthesized. These nanoparticles were evaluated as photocatalysts in the photodegradation of the Rhodamine B (RhB) dye aqueous solution under UV-visible light irradiation. The undoped ZnO nanopowder annealed at 400 °C resulted in the highest degradation efficiency of ca. 81% after 4 h under green light irradiation (525 nm), in the presence of 5 mg of catalyst. The samples were characterized using ICP-OES, PXRD, TEM, FT-IR, ²⁷Al-MAS NMR, UV-Vis and steady-state PL. The effect of Al-doping on the phase structure, shape and particle size was also investigated. Additional information arose from the annealed nanomaterials under dynamic N₂ at different temperatures (400 and 550 °C). The position of aluminum in the ZnO lattice was identified by means of ²⁷Al-MAS NMR. FT-IR gave further information about the type of tetrahedral sites occupied by aluminum. Photoluminescence showed that the insertion of dopant increases the oxygen vacancies reducing the peroxide-like species responsible for photocatalysis. The annealing temperature helps increase the number of red-emitting centers up to 400 °C, while at 550 °C, the photocatalytic performance drops due to the aggregation tendency. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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21 pages, 5169 KiB

Open AccessArticle

One-Step Synthesis of Nitrogen-Doped Porous Biochar Based on N-Doping Co-Activation Method and Its Application in Water Pollutants Control

by Yingjie Su, Yuqing Shi, Meiyi Jiang and Siji Chen

Int. J. Mol. Sci. 2022, 23(23), 14618; https://doi.org/10.3390/ijms232314618 - 23 Nov 2022

Cited by 12 | Viewed by 2038

Abstract

In this work, birch bark (BB) was used for the first time to prepare porous biochars via different one-step methods including direct activation (BBB) and N-doping co-activation (N-BBB). The specific surface area and total pore volume of BBB and N-BBB were 2502.3 and [...] Read more.

In this work, birch bark (BB) was used for the first time to prepare porous biochars via different one-step methods including direct activation (BBB) and N-doping co-activation (N-BBB). The specific surface area and total pore volume of BBB and N-BBB were 2502.3 and 2292.7 m²/g, and 1.1389 and 1.0356 cm³/g, respectively. When removing synthetic methyl orange (MO) dye and heavy metal Cr⁶⁺, both BBB and N-BBB showed excellent treatment ability. The maximum adsorption capacities of BBB and N-BBB were 836.9 and 858.3 mg/g for MO, and 141.1 and 169.1 mg/g for Cr⁶⁺, respectively, which were higher than most previously reported biochar adsorbents. The probable adsorption mechanisms, including pore filling, π–π interaction, H-bond interaction, and electrostatic attraction, supported the biochars’ demonstrated high performance. In addition, after five recycles, the removal rates remained above 80%, which showed the high stability of the biochars. This work verified the feasibility of the one-step N-doping co-activation method to prepare high-performance biochars, and two kinds of biochars with excellent performance (BBB and N-BBB) were prepared. More importantly, this method provides new directions and ideas for the development and utilization of other biomasses. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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16 pages, 4162 KiB

Open AccessArticle

The Synergistic Effect of Adsorption-Photocatalysis for Removal of Organic Pollutants on Mesoporous Cu₂V₂O₇/Cu₃V₂O₈/g-C₃N₄ Heterojunction

by Jian Feng, Xia Ran, Li Wang, Bo Xiao, Li Lei, Jinming Zhu, Zuoji Liu, Xiaolan Xi, Guangwei Feng, Zeqin Dai and Rong Li

Int. J. Mol. Sci. 2022, 23(22), 14264; https://doi.org/10.3390/ijms232214264 - 17 Nov 2022

Cited by 18 | Viewed by 2303

Abstract

Cu₂V₂O₇/Cu₃V₂O₈/g-C₃N₄ heterojunctions (CVCs) were prepared successfully by the reheating synthesis method. The thermal etching process increased the specific surface area. The formation of heterojunctions enhanced the visible light [...] Read more.

Cu₂V₂O₇/Cu₃V₂O₈/g-C₃N₄ heterojunctions (CVCs) were prepared successfully by the reheating synthesis method. The thermal etching process increased the specific surface area. The formation of heterojunctions enhanced the visible light absorption and improved the separation efficiency of photoinduced charge carriers. Therefore, CVCs exhibited superior adsorption capacity and photocatalytic performance in comparison with pristine g-C₃N₄ (CN). CVC-2 (containing 2 wt% of Cu₂V₂O₇/Cu₃V₂O₈) possessed the best synergistic removal efficiency for removal of dyes and antibiotics, in which 96.2% of methylene blue (MB), 97.3% of rhodamine B (RhB), 83.0% of ciprofloxacin (CIP), 86.0% of tetracycline (TC) and 80.5% of oxytetracycline (OTC) were eliminated by the adsorption and photocatalysis synergistic effect under visible light irradiation. The pseudo first order rate constants of MB and RhB photocatalytic degradation on CVC-2 were 3 times and 10 times that of pristine CN. For photocatalytic degradation of CIP, TC and OTC, it was 3.6, 1.8 and 6.1 times that of CN. DRS, XPS VB and ESR results suggested that CVCs had the characteristics of a Z-scheme photocatalytic system. This study provides a reliable reference for the treatment of real wastewater by the adsorption and photocatalysis synergistic process. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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15 pages, 3139 KiB

Open AccessArticle

Impact of Ni Content on the Structure and Sonophotocatalytic Activity of Ni-Zn-Co Ferrite Nanoparticles

by Thomas Dippong, Oana Cadar, Firuta Goga, Dana Toloman and Erika Andrea Levei

Int. J. Mol. Sci. 2022, 23(22), 14167; https://doi.org/10.3390/ijms232214167 - 16 Nov 2022

Cited by 11 | Viewed by 1518

Abstract

The structure, morphology, and sonophotocatalytic activity of Ni-Zn-Co ferrite nanoparticles, embedded in a SiO₂ matrix and produced by a modified sol-gel method, followed by thermal treatment, were investigated. The thermal analysis confirmed the formation of metal succinate precursors up to 200 °C, [...] Read more.

The structure, morphology, and sonophotocatalytic activity of Ni-Zn-Co ferrite nanoparticles, embedded in a SiO₂ matrix and produced by a modified sol-gel method, followed by thermal treatment, were investigated. The thermal analysis confirmed the formation of metal succinate precursors up to 200 °C, their decomposition to metal oxides and the formation of Ni-Zn-Co ferrites up to 500 °C. The crystalline phases, crystallite size and lattice parameter were determined based on X-ray diffraction patterns. Transmission electron microscopy revealed the shape, size, and distribution pattern of the ferrite nanoparticles. The particle sizes ranged between 34 and 40 nm. All the samples showed optical responses in the visible range. The best sonophotocatalytic activity against the rhodamine B solution under visible irradiation was obtained for Ni_0.3Zn_0.3Co_0.4Fe₂O₄@SiO₂. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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17 pages, 2351 KiB

Open AccessArticle

Size Effect in Hybrid TiO₂:Au Nanostars for Photocatalytic Water Remediation Applications

by Fangyuan Zheng, Pedro M. Martins, Joana M. Queirós, Carlos J. Tavares, José Luis Vilas-Vilela, Senentxu Lanceros-Méndez and Javier Reguera

Int. J. Mol. Sci. 2022, 23(22), 13741; https://doi.org/10.3390/ijms232213741 - 8 Nov 2022

Cited by 9 | Viewed by 2244

Abstract

TiO₂:Au-based photocatalysis represents a promising alternative to remove contaminants of emerging concern (CECs) from wastewater under sunlight irradiation. However, spherical Au nanoparticles, generally used to sensitize TiO₂, still limit the photocatalytic spectral band to the 520 nm region, neglecting [...] Read more.

TiO₂:Au-based photocatalysis represents a promising alternative to remove contaminants of emerging concern (CECs) from wastewater under sunlight irradiation. However, spherical Au nanoparticles, generally used to sensitize TiO₂, still limit the photocatalytic spectral band to the 520 nm region, neglecting a high part of sun radiation. Here, a ligand-free synthesis of TiO₂:Au nanostars is reported, substantially expanding the light absorption spectral region. TiO₂:Au nanostars with different Au component sizes and branching were generated and tested in the degradation of the antibiotic ciprofloxacin. Interestingly, nanoparticles with the smallest branching showed the highest photocatalytic degradation, 83% and 89% under UV and visible radiation, together with a threshold in photocatalytic activity in the red region. The applicability of these multicomponent nanoparticles was further explored with their incorporation into a porous matrix based on PVDF-HFP to open the way for a reusable energy cost-effective system in the photodegradation of polluted waters containing CECs. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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18 pages, 6257 KiB

Open AccessArticle

Preparation of a Z-Type g-C₃N₄/(A-R)TiO₂ Composite Catalyst and Its Mechanism for Degradation of Gaseous and Liquid Ammonia

by Jiaming Zhu, Zuohua Liu, Hao Wang, Yue Jian, Dingbiao Long and Shihua Pu

Int. J. Mol. Sci. 2022, 23(21), 13131; https://doi.org/10.3390/ijms232113131 - 28 Oct 2022

Cited by 2 | Viewed by 1491

Abstract

In this study, an (A-R)TiO₂ catalyst (ART) was prepared via the sol–gel method, and g-C₃N₄ (CN) was used as an amendment to prepare the g-C₃N₄/(A-R)TiO₂ composite catalyst (ARTCN). X-ray diffraction (XRD), scanning electron microscopy [...] Read more.

In this study, an (A-R)TiO₂ catalyst (ART) was prepared via the sol–gel method, and g-C₃N₄ (CN) was used as an amendment to prepare the g-C₃N₄/(A-R)TiO₂ composite catalyst (ARTCN). X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, N₂ adsorption–desorption curves (BET), UV–Vis diffuse absorption spectroscopy (UV–Vis DRS), and fluorescence spectroscopy (PL) were used to evaluate the structure, morphology, specific surface area, optical properties, and photocarrier separation ability of the catalysts. The results showed that when the modifier CN content was 0.5 g, the dispersion of the ARTCN composite catalyst was better, with stronger light absorption performance, and the forbidden band width was smaller. Moreover, the photogenerated electrons in the conduction band of ART transferred to the valence band of CN and combined with the holes in the valence band of CN, forming Z-type heterostructures that significantly improved the efficiency of the photogenerated electron-hole migration and separation, thus increasing the reaction rate. Gaseous and liquid ammonia were used as the target pollutants to investigate the activity of the prepared catalysts, and the results showed that the air wetness and initial concentration of ammonia had a great influence on the degradation of gaseous ammonia. When the initial concentration of ammonia was 50 mg/m³ and the flow rate of the moist air was 0.9 mL/min, the degradation rate of gaseous ammonia by ARTCN-0.5 reached 88.86%, and it had good repeatability. When the catalytic dose was 50 mg and the initial concentration of NH₄⁺ was 100 mg/L, the degradation rate of liquid ammonia by ARTCN-0.5 was 71.60% after 3 h of reaction, and small amounts of NO₃⁻ and NO₂⁻ were generated. The superoxide anion radical (·O₂⁻) and hydroxyl radical (·OH) were the main active components in the photocatalytic reaction process. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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12 pages, 2643 KiB

Open AccessArticle

Spark Plasma Sintering-Assisted Synthesis of Bi₂Fe₄O₉/Bi₂₅FeO₄₀ Heterostructures with Enhanced Photocatalytic Activity for Removal of Antibiotics

by Zhifei Liu, Yaqi Tan, Xuefeng Ruan, Jing Guo, Wei Li, Jiajun Li, Hongyu Ma, Rui Xiong and Jianhong Wei

Int. J. Mol. Sci. 2022, 23(20), 12652; https://doi.org/10.3390/ijms232012652 - 21 Oct 2022

Cited by 12 | Viewed by 1871

Abstract

Bismuth ferrite-based heterojunction composites have been considered as promising visible-light responsive photocatalysts because of their narrow band gap structure; however, the synthetic methods reported in the literature were usually time-consuming. In this study, we report a facile and quick preparation of bismuth ferrite-based [...] Read more.

Bismuth ferrite-based heterojunction composites have been considered as promising visible-light responsive photocatalysts because of their narrow band gap structure; however, the synthetic methods reported in the literature were usually time-consuming. In this study, we report a facile and quick preparation of bismuth ferrite-based composites by the hydrothermal method, combined with spark plasma sintering (SPS), a technique that is usually used for the high-speed consolidation of powders. The result demonstrated that the SPS-assisted synthesized samples possess significant enhanced photoelectric and photocatalytic performance. Specifically, the SPS650 (sintered at the 650 °C for 5 min by SPS) exhibits a 1.5 times enhancement in the photocurrent density and a 3.8 times enhancement in the tetracycline hydrochloride photodegradation activity than the unmodified bismuth ferrite samples. The possible influence factors of SPS on photoelectric and photocatalytic performance of bismuth ferrite-based composites were discussed carefully. This study provides a feasible method for the facile and quick synthesis of a highly active bismuth ferrite-based visible-light-driven photocatalyst for practical applications. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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24 pages, 6442 KiB

Open AccessArticle

One-Step Carbonization Synthesis of Magnetic Biochar with 3D Network Structure and Its Application in Organic Pollutant Control

by Xiaoxin Chen, Jiacheng Lin, Yingjie Su and Shanshan Tang

Int. J. Mol. Sci. 2022, 23(20), 12579; https://doi.org/10.3390/ijms232012579 - 20 Oct 2022

Cited by 13 | Viewed by 2196

Abstract

In this study, a magnetic biochar with a unique 3D network structure was synthesized by using a simple and controllable method. In brief, the microbial filamentous fungus Trichoderma reesei was used as a template, and Fe³⁺ was added to the culture process, [...] Read more.

In this study, a magnetic biochar with a unique 3D network structure was synthesized by using a simple and controllable method. In brief, the microbial filamentous fungus Trichoderma reesei was used as a template, and Fe³⁺ was added to the culture process, which resulted in uniform recombination through the bio-assembly property of fungal hyphae. Finally, magnetic biochar (BMFH/Fe₃O₄) was synthesized by controlling different heating conditions in a high temperature process. The adsorption and Fenton-like catalytic performance of BMFH/Fe₃O₄ were investigated by using the synthetic dye malachite green (MG) and the antibiotic tetracycline hydrochloride (TH) as organic pollutant models. The results showed that the adsorption capacity of BMFH/Fe₃O₄ for MG and TH was 158.2 and 171.26 mg/g, respectively, which was higher than that of most biochar adsorbents, and the Fenton-like catalytic degradation effect of organic pollutants was also better than that of most catalysts. This study provides a magnetic biochar with excellent performance, but more importantly, the method used can be effective in further improving the performance of biochar for better control of organic pollutants. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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15 pages, 5795 KiB

Open AccessArticle

Granulation of Bismuth Oxide by Alginate for Efficient Removal of Iodide in Water

by Tae-Hyun Kim, Chihyun Seo, Jaeyoung Seon, Anujin Battulga and Yuhoon Hwang

Int. J. Mol. Sci. 2022, 23(20), 12225; https://doi.org/10.3390/ijms232012225 - 13 Oct 2022

Cited by 2 | Viewed by 2159

Abstract

The granulation of bismuth oxide (BO) by alginate (Alg) and the iodide adsorption efficacy of Alg–BO for different initial iodide concentrations and contact time values were examined. The optimal conditions for Alg–BO granulation were identified by controlling the weight ratio between Alg and [...] Read more.

The granulation of bismuth oxide (BO) by alginate (Alg) and the iodide adsorption efficacy of Alg–BO for different initial iodide concentrations and contact time values were examined. The optimal conditions for Alg–BO granulation were identified by controlling the weight ratio between Alg and BO. According to the batch iodide adsorption experiment, the Alg:BO weight ratio of 1:20 was appropriate, as it yielded a uniform spherical shape. According to iodide adsorption isotherm experiments and isotherm model fitting, the maximum sorption capacity (q_m) was calculated to be 111.8 mg/g based on the Langmuir isotherm, and this value did not plateau even at an initial iodide concentration of 1000 mg/L. Furthermore, iodide adsorption by Alg–BO occurred as monolayer adsorption by the chemical interaction and precipitation between bismuth and iodide, followed by physical multilayer adsorption at a very high concentration of iodide in solution. The iodide adsorption over time was fitted using the intraparticle diffusion model. The results indicated that iodide adsorption was proceeded by boundary layer diffusion during 480 min and reached the plateau from 1440 min to 5760 min by intraparticle diffusion. According to the images obtained using cross-section scanning electron microscopy assisted by energy-dispersive spectroscopy, the adsorbed iodide interacted with the BO in Alg–BO through Bi–O–I complexation. This research shows that Alg–BO is a promising iodide adsorbent owing to its high adsorption capacity, stability, convenience, and ability to prevent secondary pollution. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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14 pages, 2626 KiB

Open AccessArticle

Sulfonated Pentablock Copolymer Coating of Polypropylene Filters for Dye and Metal Ions Effective Removal by Integrated Adsorption and Filtration Process

by Simona Filice, Viviana Scuderi, Sebania Libertino, Massimo Zimbone, Clelia Galati, Natalia Spinella, Leon Gradon, Luciano Falqui and Silvia Scalese

Int. J. Mol. Sci. 2022, 23(19), 11777; https://doi.org/10.3390/ijms231911777 - 4 Oct 2022

Cited by 5 | Viewed by 1827

Abstract

In this work, we coated polypropylene (PP) fibrous filters with sulfonated pentablock copolymer (s-PBC) layers and tested them for the removal of cationic organic dyes, such as methylene blue (MB), and heavy metal ions (Fe³⁺ and Co²⁺) from water by [...] Read more.

In this work, we coated polypropylene (PP) fibrous filters with sulfonated pentablock copolymer (s-PBC) layers and tested them for the removal of cationic organic dyes, such as methylene blue (MB), and heavy metal ions (Fe³⁺ and Co²⁺) from water by adsorption and filtration experiments. Some of the coated filters were irradiated by UV light before being exposed to contaminated water and then were tested with unirradiated filters in the same adsorption and filtration experiments. Polymer-coated filters showed high efficiency in removing MB from an aqueous solution in both absorption and filtration processes, with 90% and 80% removal, respectively. On the other hand, for heavy metal ions (Fe³⁺ and Co²⁺), the coated filters showed a better removal performance in the filtration process than for the adsorption one. In fact, in the adsorption process, controlled interaction times allow the ionic species to interact with the surface of the filters leading to the formation and release of new species in solution. During filtration, the ionic species are easily trapped in the filters, in particular by UV modified filters, and we observed for Fe³⁺ ions a total removal (>99%) in a single filtration process and for Co²⁺ ions a larger removal with respect to the untreated filter. The mechanisms involved in the removal of the contaminants processes were investigated by characterizing the filters before and after use by means of scanning electron microscopy (SEM) combined with energy-dispersive X-ray (EDX) analysis and Fourier transform infrared spectroscopy (FT-IR). Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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12 pages, 2771 KiB

Open AccessArticle

Impact of Acetate in Reduction of Perchlorate by Mixed Microbial Culture under the Influence of Nitrate and Sulfate

by Hosung Yu, Kang Hoon Lee and Jae-Woo Park

Int. J. Mol. Sci. 2022, 23(18), 10608; https://doi.org/10.3390/ijms231810608 - 13 Sep 2022

Cited by 3 | Viewed by 1791

Abstract

The biological reduction of slow degradation contaminants such as perchlorate (ClO₄⁻) is considered to be a promising water treatment technology. The process is based on the ability of a specific mixed microbial culture to use perchlorate as an electron acceptor [...] Read more.

The biological reduction of slow degradation contaminants such as perchlorate (ClO₄⁻) is considered to be a promising water treatment technology. The process is based on the ability of a specific mixed microbial culture to use perchlorate as an electron acceptor in the absence of oxygen. In this study, batch experiments were conducted to investigate the effect of nitrate on perchlorate reduction, the kinetic parameters of the Monod equation and the optimal ratio of acetate to perchlorate for the perchlorate reducing bacterial consortium. The results of this study suggest that acclimated microbial cultures can be applied to treat wastewater containing high concentrations of perchlorate. Reactor experiments were carried out with different hydraulic retention times (HRTs) to determine the optimal operating conditions. A fixed optimal HRT and the effect of nitrate on perchlorate reduction were investigated with various concentrations of the electron donor. The results showed that perchlorate reduction occurred after nitrate removal. Moreover, the presence of sulfate in wastewater had no effect on the perchlorate reduction. However, it had little effect on biomass concentration in the presence of nitrate during exposure to a mixed microbial culture, considering the nitrate as the inhibitor of perchlorate reduction by reducing the degradation rate. The batch scale experiment results illustrated that for efficient operation of perchlorate reduction, the optimal acetate to perchlorate ratio of 1.4:1.0 would be enough. Moreover, these experiments found the following results: the kinetic parameters equivalent to Y = 0.281 mg biomass/mg perchlorate, K_s = 37.619 mg/L and q_max = 0.042 mg perchlorate/mg biomass/h. In addition, anoxic–aerobic experimental reactor results verify the optimal HRT of 6 h for continuous application. Furthermore, it also illustrated that using 600 mg/L of acetate as a carbon source is responsible for 100% of nitrate reduction with less than 50% of the perchlorate reduction, whereas at 1000 mg/L acetate, approximately 100% reduction was recorded. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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20 pages, 3311 KiB

Open AccessArticle

Adjusting Some Properties of Poly(methacrylic acid) (Nano)Composite Hydrogels by Means of Silicon-Containing Inorganic Fillers

by Claudia Mihaela Ninciuleanu, Raluca Ianchiș, Elvira Alexandrescu, Cătălin Ionuț Mihăescu, Sabina Burlacu, Bogdan Trică, Cristina Lavinia Nistor, Silviu Preda, Cristina Scomoroscenco, Cătălina Gîfu, Cristian Petcu and Mircea Teodorescu

Int. J. Mol. Sci. 2022, 23(18), 10320; https://doi.org/10.3390/ijms231810320 - 7 Sep 2022

Cited by 13 | Viewed by 2328

Abstract

The present work aims to show how the main properties of poly(methacrylic acid) (PMAA) hydrogels can be engineered by means of several silicon-based fillers (Laponite XLS/XLG, montmorillonite (Mt), pyrogenic silica (PS)) employed at 10 wt% concentration based on MAA. Various techniques (FT-IR, XRD, [...] Read more.

The present work aims to show how the main properties of poly(methacrylic acid) (PMAA) hydrogels can be engineered by means of several silicon-based fillers (Laponite XLS/XLG, montmorillonite (Mt), pyrogenic silica (PS)) employed at 10 wt% concentration based on MAA. Various techniques (FT-IR, XRD, TGA, SEM, TEM, DLS, rheological measurements, UV-VIS) were used to comparatively study the effect of these fillers, in correlation with their characteristics, upon the structure and swelling, viscoelastic, and water decontamination properties of (nano)composite hydrogels. The experiments demonstrated that the nanocomposite hydrogel morphology was dictated by the way the filler particles dispersed in water. The equilibrium swelling degree (SDe) depended on both the pH of the environment and the filler nature. At pH 1.2, a slight crosslinking effect of the fillers was evidenced, increasing in the order Mt < Laponite < PS. At pH > pKa_MAA (pH 5.4; 7.4; 9.5), the Laponite/Mt-containing hydrogels displayed a higher SDe as compared to the neat one, while at pH 7.4/9.5 the PS-filled hydrogels surprisingly displayed the highest SDe. Rheological measurements on as-prepared hydrogels showed that the filler addition improved the mechanical properties. After equilibrium swelling at pH 5.4, G’ and G” depended on the filler, the Laponite-reinforced hydrogels proving to be the strongest. The (nano)composite hydrogels synthesized displayed filler-dependent absorption properties of two cationic dyes used as model water pollutants, Laponite XLS-reinforced hydrogel demonstrating both the highest absorption rate and absorption capacity. Besides wastewater purification, the (nano)composite hydrogels described here may also find applications in the pharmaceutical field as devices for the controlled release of drugs. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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15 pages, 3306 KiB

Open AccessArticle

Effective Removal of Methylene Blue on EuVO₄/g-C₃N₄ Mesoporous Nanosheets via Coupling Adsorption and Photocatalysis

by Xia Ran, Li Wang, Bo Xiao, Li Lei, Jinming Zhu, Zuoji Liu, Xiaolan Xi, Guangwei Feng, Rong Li and Jian Feng

Int. J. Mol. Sci. 2022, 23(17), 10003; https://doi.org/10.3390/ijms231710003 - 2 Sep 2022

Cited by 5 | Viewed by 1799

Abstract

In this study, we first manufactured ultrathin g-C₃N₄ (CN) nanosheets by thermal etching and ultrasonic techniques. Then, EuVO₄ (EV) nanoparticles were loaded onto CN nanosheets to form EuVO₄/g-C₃N₄ heterojunctions (EVCs). The ultrathin and porous [...] Read more.

In this study, we first manufactured ultrathin g-C₃N₄ (CN) nanosheets by thermal etching and ultrasonic techniques. Then, EuVO₄ (EV) nanoparticles were loaded onto CN nanosheets to form EuVO₄/g-C₃N₄ heterojunctions (EVCs). The ultrathin and porous structure of the EVCs increased the specific surface area and reaction active sites. The formation of the heterostructure extended visible light absorption and accelerated the separation of charge carriers. These two factors were advantageous to promote the synergistic effect of adsorption and photocatalysis, and ultimately enhanced the adsorption capability and photocatalytic removal efficiency of methylene blue (MB). EVC-2 (2 wt% of EV) exhibited the highest adsorption and photocatalytic performance. Almost 100% of MB was eliminated via the adsorption–photocatalysis synergistic process over EVC-2. The MB adsorption capability of EVC-2 was 6.2 times that of CN, and the zero-orderreaction rate constant was 5 times that of CN. The MB adsorption on EVC-2 followed the pseudo second-order kinetics model and the adsorption isotherm data complied with the Langmuir isotherm model. The photocatalytic degradation data of MB on EVC-2 obeyed the zero-order kinetics equation in 0–10 min and abided by the first-order kinetics equation for10–30 min. This study provided a promising EVC heterojunctions with superior synergetic effect of adsorption and photocatalysis for the potential application in wastewater treatment. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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13 pages, 1393 KiB

Open AccessArticle

Sensitivity of the Transport of Plastic Nanoparticles to Typical Phosphates Associated with Ionic Strength and Solution pH

by Xingyu Liu, Yan Liang, Yongtao Peng, Tingting Meng, Liling Xu and Pengcheng Dong

Int. J. Mol. Sci. 2022, 23(17), 9860; https://doi.org/10.3390/ijms23179860 - 30 Aug 2022

Cited by 1 | Viewed by 1633

Abstract

The influence of phosphates on the transport of plastic particles in porous media is environmentally relevant due to their ubiquitous coexistence in the subsurface environment. This study investigated the transport of plastic nanoparticles (PNPs) via column experiments, paired with Derjaguin–Landau–Verwey–Overbeek calculations and numerical [...] Read more.

The influence of phosphates on the transport of plastic particles in porous media is environmentally relevant due to their ubiquitous coexistence in the subsurface environment. This study investigated the transport of plastic nanoparticles (PNPs) via column experiments, paired with Derjaguin–Landau–Verwey–Overbeek calculations and numerical simulations. The trends of PNP transport vary with increasing concentrations of NaH₂PO₄ and Na₂HPO₄ due to the coupled effects of increased electrostatic repulsion, the competition for retention sites, and the compression of the double layer. Higher pH tends to increase PNP transport due to the enhanced deprotonation of surfaces. The release of retained PNPs under reduced IS and increased pH is limited because most of the PNPs were irreversibly captured in deep primary minima. The presence of physicochemical heterogeneities on solid surfaces can reduce PNP transport and increase the sensitivity of the transport to IS. Furthermore, variations in the hydrogen bonding when the two phosphates act as proton donors will result in different influences on PNP transport at the same IS. This study highlights the sensitivity of PNP transport to phosphates associated with the solution chemistries (e.g., IS and pH) and is helpful for better understanding the fate of PNPs and other colloidal contaminants in the subsurface environment. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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14 pages, 16849 KiB

Open AccessArticle

Water-Tree Characteristics and Its Mechanical Mechanism of Crosslinked Polyethylene Grafted with Polar-Group Molecules

by Xiao-Xia Zheng, You-Cheng Pan and Wei-Feng Sun

Int. J. Mol. Sci. 2022, 23(16), 9450; https://doi.org/10.3390/ijms23169450 - 21 Aug 2022

Cited by 10 | Viewed by 1950

Abstract

In order to restrain electric-stress impacts of water micro-droplets in insulation defects under alternating current (AC) electric fields in crosslinked polyethylene (XLPE) material, the present study represents chemical graft modifications of introducing chloroacetic acid allyl ester (CAAE) and maleic anhydride (MAH) individually as [...] Read more.

In order to restrain electric-stress impacts of water micro-droplets in insulation defects under alternating current (AC) electric fields in crosslinked polyethylene (XLPE) material, the present study represents chemical graft modifications of introducing chloroacetic acid allyl ester (CAAE) and maleic anhydride (MAH) individually as two specific polar-group molecules into XLPE material with peroxide melting approach. The accelerated water-tree aging experiments are implemented by means of a water-blade electrode to measure the improved water resistance and the affording mechanism of the graft-modified XLPE material in reference to benchmark XLPE. Melting–crystallization process, dynamic viscoelasticity and stress-strain characteristics are tested utilizing differential scanning calorimeter (DSC), dynamic thermomechanical analyzer (DMA) and electronic tension machine, respectively. Water-tree morphology is observed for various aging times to evaluate dimension characteristics in water-tree developing processes. Monte Carlo molecular simulations are performed to calculate free-energy, thermodynamic phase diagram, interaction parameter and mixing energy of binary mixing systems consisting of CAAE or MAH and water molecules to evaluate their thermodynamic miscibility. Water-tree experiments indicate that water-tree resistance to XLPE can be significantly improved by grafting CAAE or MAH, as indicated by reducing the characteristic length of water-trees from 120 to 80 μm. Heterogeneous nucleation centers of polyethylene crystallization are rendered by the grafted polar-group molecules to ameliorate crystalline microstructures, as manifested by crystallinity increment from 33.5 to 36.2, which favors improving water-tree resistance and mechanical performances. The highly hydrophilic nature of CAAE can evidently inhibit water molecules from aggregating into water micro-droplets in amorphous regions between crystal lamellae, thus acquiring a significant promotion in water-tree resistance of CAAE-modified XLPE. In contrast, the grafted MAH molecules can enhance van der Waals forces between polyethylene molecular chains in amorphous regions much greater than the grafted CAAE and simultaneously act as more efficient crystallization nucleation centers to ameliorate crystalline microstructures of XLPE, resulting in a greater improvement (relaxation peak magnitude increases by >10%) of mechanical toughness in amorphous phase, which primarily accounts for water-tree resistance promotion. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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22 pages, 33378 KiB

Open AccessArticle

Selective Recovery of Cadmium, Cobalt, and Nickel from Spent Ni–Cd Batteries Using Adogen^® 464 and Mesoporous Silica Derivatives

by Ahmed R. Weshahy, Ahmed K. Sakr, Ayman A. Gouda, Bahig M. Atia, H. H. Somaily, Mohamed Y. Hanfi, M. I. Sayyed, Ragaa El Sheikh, Enass M. El-Sheikh, Hend A. Radwan, Mohamed F. Cheira and Mohamed A. Gado

Int. J. Mol. Sci. 2022, 23(15), 8677; https://doi.org/10.3390/ijms23158677 - 4 Aug 2022

Cited by 28 | Viewed by 3210

Abstract

Spent Ni–Cd batteries are now considered an important source for many valuable metals. The recovery of cadmium, cobalt, and nickel from spent Ni–Cd Batteries has been performed in this study. The optimum leaching process was achieved using 20% H₂SO₄, [...] Read more.

Spent Ni–Cd batteries are now considered an important source for many valuable metals. The recovery of cadmium, cobalt, and nickel from spent Ni–Cd Batteries has been performed in this study. The optimum leaching process was achieved using 20% H₂SO₄, solid/liquid (S/L) 1/5 at 80 °C for 6 h. The leaching efficiency of Fe, Cd, and Co was nearly 100%, whereas the leaching efficiency of Ni was 95%. The recovery of the concerned elements was attained using successive different separation techniques. Cd(II) ions were extracted by a solvent, namely, Adogen^® 464, and precipitated as CdS with 0.5% Na₂S solution at pH of 1.25 and room temperature. The extraction process corresponded to pseudo-2nd-order. The prepared PTU-MS silica was applied for adsorption of Co(II) ions from aqueous solution, while the desorption process was performed using 0.3 M H₂SO₄. Cobalt was precipitated at pH 9.0 as Co(OH)₂ using NH₄OH. The kinetic and thermodynamic parameters were also investigated. Nickel was directly precipitated at pH 8.25 using a 10% NaOH solution at ambient temperature. FTIR, SEM, and EDX confirm the structure of the products. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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11 pages, 3867 KiB

Open AccessArticle

Investigation of Structural, Morphological and Magnetic Properties of MFe₂O₄ (M = Co, Ni, Zn, Cu, Mn) Obtained by Thermal Decomposition

by Thomas Dippong, Erika Andrea Levei and Oana Cadar

Int. J. Mol. Sci. 2022, 23(15), 8483; https://doi.org/10.3390/ijms23158483 - 30 Jul 2022

Cited by 63 | Viewed by 2753

Abstract

The structural, morphological and magnetic properties of MFe₂O₄ (M = Co, Ni, Zn, Cu, Mn) type ferrites produced by thermal decomposition at 700 and 1000 °C were studied. The thermal analysis revealed that the ferrites are formed at up to [...] Read more.

The structural, morphological and magnetic properties of MFe₂O₄ (M = Co, Ni, Zn, Cu, Mn) type ferrites produced by thermal decomposition at 700 and 1000 °C were studied. The thermal analysis revealed that the ferrites are formed at up to 350 °C. After heat treatment at 1000 °C, single-phase ferrite nanoparticles were attained, while after heat treatment at 700 °C, the CoFe₂O₄ was accompanied by Co₃O₄ and the MnFe₂O₄ by α-Fe₂O₃. The particle size of the spherical shape in the nanoscale region was confirmed by transmission electron microscopy. The specific surface area below 0.5 m²/g suggested a non–porous structure with particle agglomeration that limits nitrogen absorption. By heat treatment at 1000 °C, superparamagnetic CoFe₂O₄ nanoparticles and paramagnetic NiFe₂O₄, MnFe₂O₄, CuFe₂O₄ and ZnFe₂O₄ nanoparticles were obtained. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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11 pages, 1604 KiB

Open AccessCommunication

Recovery of the N,N-Dibutylimidazolium Chloride Ionic Liquid from Aqueous Solutions by Electrodialysis Method

by Dorota Babilas, Anna Kowalik-Klimczak and Anna Mielańczyk

Int. J. Mol. Sci. 2022, 23(12), 6472; https://doi.org/10.3390/ijms23126472 - 9 Jun 2022

Cited by 4 | Viewed by 1667

Abstract

Ionic liquids (ILs), named also as liquid salts, are compounds that have unique properties and molecular architecture. ILs are used in various industries; however, due to their toxicity, the ILs’ recovery from the postreaction solutions is also a very important issue. In this [...] Read more.

Ionic liquids (ILs), named also as liquid salts, are compounds that have unique properties and molecular architecture. ILs are used in various industries; however, due to their toxicity, the ILs’ recovery from the postreaction solutions is also a very important issue. In this paper, the possibility of 1,3-dialkylimidazolium IL, especially the N,N-dibutylimidazolium chloride ([C₄C₄IM]Cl) recovery by using the electrodialysis (ED) method was investigated. The influence of [C₄C₄IM]Cl concentration in diluate solution on the ED efficiency was determined. Moreover, the influence of IL on the ion-exchange membranes’ morphology was examined. The recovery of [C₄C₄IM]Cl, the [C₄C₄IM]Cl flux across membranes, the [C₄C₄IM]Cl concentration degree, the energy consumption, and the current efficiency were determined. The results showed that the ED allows for the [C₄C₄IM]Cl recovery and concentration from dilute solutions. It was found that the [C₄C₄IM]Cl content in the concentrates after ED was above three times higher than in the initial diluate solutions. It was noted that the ED of solutions containing 5–20 g/L [C₄C₄IM]Cl allows for ILs recovery in the range of 73.77–92.45% with current efficiency from 68.66% to 92.99%. The [C₄C₄IM]Cl recovery depended upon the initial [C₄C₄IM]Cl concentration in the working solution. The highest [C₄C₄IM]Cl recovery (92.45%) and ED efficiency (92.99%) were obtained when the [C₄C₄IM]Cl content in the diluate solution was equal 20 g/L. Presented results proved that ED can be an interesting and effective method for the [C₄C₄IM]Cl recovery from the dilute aqueous solutions. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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15 pages, 5596 KiB

Open AccessArticle

Dependence of Structural, Morphological and Magnetic Properties of Manganese Ferrite on Ni-Mn Substitution

by Thomas Dippong, Erika Andrea Levei, Iosif Grigore Deac, Ioan Petean and Oana Cadar

Int. J. Mol. Sci. 2022, 23(6), 3097; https://doi.org/10.3390/ijms23063097 - 13 Mar 2022

Cited by 62 | Viewed by 3389

Abstract

This paper presents the influence of Mn²⁺ substitution by Ni²⁺ on the structural, morphological and magnetic properties of Mn_1−xNi_xFe₂O₄@SiO₂ (x = 0, 0.25, 0.50, 0.75, 1.00) nanocomposites (NCs) obtained by a modified [...] Read more.

This paper presents the influence of Mn²⁺ substitution by Ni²⁺ on the structural, morphological and magnetic properties of Mn_1−xNi_xFe₂O₄@SiO₂ (x = 0, 0.25, 0.50, 0.75, 1.00) nanocomposites (NCs) obtained by a modified sol-gel method. The Fourier transform infrared spectra confirm the formation of a SiO₂ matrix and ferrite, while the X-ray diffraction patterns show the presence of poorly crystalline ferrite at low annealing temperatures and highly crystalline mixed cubic spinel ferrite accompanied by secondary phases at high annealing temperatures. The lattice parameters gradually decrease, while the crystallite size, volume, and X-ray density of Mn_1−xNi_xFe₂O₄@SiO₂ NCs increase with increasing Ni content and follow Vegard’s law. The saturation magnetization, remanent magnetization, squareness, magnetic moment per formula unit, and anisotropy constant increase, while the coercivity decreases with increasing Ni content. These parameters are larger for the samples with the same chemical formula, annealed at higher temperatures. The NCs with high Ni content show superparamagnetic-like behavior, while the NCs with high Mn content display paramagnetic behavior. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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Review

Jump to: Editorial, Research

19 pages, 927 KiB

Open AccessReview

Recent Advances in the Synthesis, Characterization, and Application of Carbon Nanomaterials for the Removal of Endocrine-Disrupting Chemicals: A Review

by Ze Liao, Yang Zi, Chunyan Zhou, Wenqian Zeng, Wenwen Luo, Hui Zeng, Muqing Xia and Zhoufei Luo

Int. J. Mol. Sci. 2022, 23(21), 13148; https://doi.org/10.3390/ijms232113148 - 29 Oct 2022

Cited by 15 | Viewed by 3188

Abstract

The large-scale production and frequent use of endocrine-disrupting chemicals (EDCs) have led to the continuous release and wide distribution of these pollutions in the natural environment. At low levels, EDC exposure may cause metabolic disorders, sexual development, and reproductive disorders in aquatic animals [...] Read more.

The large-scale production and frequent use of endocrine-disrupting chemicals (EDCs) have led to the continuous release and wide distribution of these pollutions in the natural environment. At low levels, EDC exposure may cause metabolic disorders, sexual development, and reproductive disorders in aquatic animals and humans. Adsorption treatment, particularly using nanocomposites, may represent a promising and sustainable method for EDC removal from wastewater. EDCs could be effectively removed from wastewater using various carbon-based nanomaterials, such as carbon nanofiber, carbon nanotubes, graphene, magnetic carbon nanomaterials, carbon membranes, carbon dots, carbon sponges, etc. Important applications of carbon nanocomposites for the removal of different kinds of EDCs and the theory of adsorption are discussed, as well as recent advances in carbon nanocomposite synthesis technology and characterization technology. Furthermore, the factors affecting the use of carbon nanocomposites and comparisons with other adsorbents for EDC removal are reviewed. This review is significant because it helps to promote the development of nanocomposites for the decontamination of wastewater. Full article

(This article belongs to the Special Issue Recent Advances in Synthesis, Characterization and Applications of Innovative Materials in Removal of Water Contaminants)

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