Editorial

4 pages, 463 KiB

Open AccessEditorial

Special Issue: Smart Nanomaterials for Environmental Remediation

by Won San Choi

Materials 2021, 14(1), 143; https://doi.org/10.3390/ma14010143 - 31 Dec 2020

Cited by 1 | Viewed by 1505

Nanomaterials that can be reversibly or irreversibly changed in structures and properties by the influence of external chemical and physical stimuli are defined as smart nanomaterials [...] Full article

(This article belongs to the Special Issue Smart Nanomaterials for Environmental Remediation)

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Research

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16 pages, 2734 KiB

Open AccessArticle

An Active Absorbent for Cleanup of High-Concentration Strong Acid and Base Solutions

by Nara Han, Sol Park, Byung Kwon Kaang, Wooree Jang, Hye Young Koo and Won San Choi

Materials 2019, 12(20), 3389; https://doi.org/10.3390/ma12203389 - 17 Oct 2019

Cited by 3 | Viewed by 1988

Abstract

There is significant interest in developing novel absorbents for hazardous material cleanup. Iron oxide-coated melamine formaldehyde sponge (MFS/IO) absorbents with various IO layer thicknesses were synthesized. Various other absorbents were also synthesized and compared to evaluate the absorption capability of the MFS/IO absorbents [...] Read more.

There is significant interest in developing novel absorbents for hazardous material cleanup. Iron oxide-coated melamine formaldehyde sponge (MFS/IO) absorbents with various IO layer thicknesses were synthesized. Various other absorbents were also synthesized and compared to evaluate the absorption capability of the MFS/IO absorbents for strong acid (15%, v/v) and base (50%, m/m) solutions. Specifically, absorbent and solution drop tests, dust tests, and droplet fragment tests were performed. Among the various absorbents, MFS/IO absorbents possessing a needlelike surface morphology showed several unique characteristics not observed in other absorbents. The MFS/IO absorbents naturally absorbed a strong base solution (absorption time: 0.71–0.5 s, absorption capacity: 10,000–34,000%) without an additional external force and immediately absorbed a strong acid solution (0.31–0.43 s, 9830–10,810%) without absorption delay/overflow during absorbent and solution drop tests, respectively. The MFS/IO absorbents were also demonstrated to be ideal absorbents that generated fewer dust particles (semiclass 1 (ISO 3) level of 280 piece/L) than the level of a clean room (class 100). Furthermore, the MFS/IO absorbents were able to prevent the formation of droplet fragments and solution overflow during the solution drop test due to their unique surface morphology and extremely high absorption speed/capacity, respectively. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Environmental Remediation)

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13 pages, 2156 KiB

Open AccessArticle

The Preliminary Study of Water-Retention Related Properties of Biochar Produced from Various Feedstock at Different Pyrolysis Temperatures

by Koji Kameyama, Teruhito Miyamoto and Yukiyoshi Iwata

Materials 2019, 12(11), 1732; https://doi.org/10.3390/ma12111732 - 28 May 2019

Cited by 54 | Viewed by 4272

Abstract

Physicochemical properties of biochar, which are used as a soil amendment material in agricultural fields, are different depending on biomass feedstock and pyrolysis processes. In this study, we evaluated the influence of feedstock type and pyrolysis temperature on the water-retention related properties of [...] Read more.

Physicochemical properties of biochar, which are used as a soil amendment material in agricultural fields, are different depending on biomass feedstock and pyrolysis processes. In this study, we evaluated the influence of feedstock type and pyrolysis temperature on the water-retention related properties of biochar. Wood-chips [cedar (CE) and cypress (CY)]; moso bamboo (MB); rice husk (RH); sugarcane bagasse (SB); poultry manure (PM) and agricultural wastewater sludge (WS) were each pyrolysed at 400, 600 and 800 °C with a retention time of two hours. Scanning electron microscopy micrographs (SEM), hydrophobicity indices, pore-size distribution measured by mercury-intrusion porosimetry, water-retention curves (WRCs) and plant-available water capacities (AWCs) of the biochars were measured to evaluate their potentials as soil-amendment materials for improving soils’ water-retention. As the pyrolysis temperature was increased, the hydrophobicity index decreased. On the other hand, pyrolysis temperature did not affect the distribution of micrometre-range pores, which are useful for plant-available water, of biochars. The AWCs of the biochars formed from CE, CY and SB were greater than those produced from other feedstocks, at 600 and 800 °C. Therefore, we can suggest that the biochars derived from wood-chips (CE and CY) and SB have greater potential for enhancing soils’ water-retention. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Environmental Remediation)

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11 pages, 15894 KiB

Open AccessArticle

Effect of Potassium Ions on the Formation of Mixed-Valence Manganese Oxide/Graphene Nanocomposites

by Wooree Jang, Dae-Young Jeon, Youn-Sik Lee and Hye Young Koo

Materials 2019, 12(8), 1245; https://doi.org/10.3390/ma12081245 - 16 Apr 2019

Cited by 3 | Viewed by 3013

Abstract

One-pot synthesis of mixed-valence manganese oxide (MnO_x)/potassium ion-doped reduced graphene oxide (rGO) composites for efficient electrochemical supercapacitors is introduced. Using manganese nitrate and potassium permanganate as co-precursors for the MnO_x and by directly annealing the rGO without tedious purification steps, [...] Read more.

One-pot synthesis of mixed-valence manganese oxide (MnO_x)/potassium ion-doped reduced graphene oxide (rGO) composites for efficient electrochemical supercapacitors is introduced. Using manganese nitrate and potassium permanganate as co-precursors for the MnO_x and by directly annealing the rGO without tedious purification steps, as described herein, MnO_x/rGO composites with a high specific capacitance of 1955.6 F g⁻¹ at a current density of 1 A g⁻¹ are achieved. It is found that the presence of potassium ions helps in the development of mixed-valence MnO_x on the surface of the rGO. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Environmental Remediation)

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13 pages, 2564 KiB

Open AccessArticle

One-Step Synthesis of Environmentally Friendly Superhydrophilic and Superhydrophobic Sponges for Oil/Water Separation

by Yo Seph Lee, Yong Taek Lim and Won San Choi

Materials 2019, 12(7), 1182; https://doi.org/10.3390/ma12071182 - 11 Apr 2019

Cited by 22 | Viewed by 3761

Abstract

Environmentally friendly superhydrophilic and superhydrophobic sponges were synthesized using a one-step approach for oil/water separation. A superhydrophilic or superhydrophobic sponge (MFS/CC-DKGM or MFS/CC-PDMS) was synthesized by one-step coating of melamine formaldehyde sponge (MFS) with a mixture of calcium carbonate (CC) rods and deacetylized [...] Read more.

Environmentally friendly superhydrophilic and superhydrophobic sponges were synthesized using a one-step approach for oil/water separation. A superhydrophilic or superhydrophobic sponge (MFS/CC-DKGM or MFS/CC-PDMS) was synthesized by one-step coating of melamine formaldehyde sponge (MFS) with a mixture of calcium carbonate (CC) rods and deacetylized Konjac glucomannan (DKGM) [or polydimethylsiloxane (PDMS)]. The MFS/CC-PDMS showed excellent absorption capacity, which reached 52–76 g/g following immersion into various types of oil/water mixtures. Furthermore, the MFS/CC-DKGM and MFS/CC-PDMS exhibited excellent water- and oil-flux performances, which reached 4,702 L/m² h and 19,591 L/m² h, respectively, when they were used as filters. The MFS/CC-DKGM and MFS/CC-PDMS maintained their wettability characteristics relatively well after the chemical, thermal, and mechanical stability tests. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Environmental Remediation)

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11 pages, 5799 KiB

Open AccessArticle

Ag₂S Quantum Dots Based on Flower-like SnS₂ as Matrix and Enhanced Photocatalytic Degradation

by Wenhua Zhao, Zhiqiang Wei, Long Ma, Jiahao Liang and Xudong Zhang

Materials 2019, 12(4), 582; https://doi.org/10.3390/ma12040582 - 15 Feb 2019

Cited by 32 | Viewed by 4575

Abstract

Ag₂S quantum dots were dispersed on the surface of SnS₂ nanoflowers forming a heterojunction via in-situ ion exchange to improve photocatalytic degradation of RhB. All samples exhibit the hexagonal wurtzite structure. The size of Ag₂S@SnS₂ composites are [...] Read more.

Ag₂S quantum dots were dispersed on the surface of SnS₂ nanoflowers forming a heterojunction via in-situ ion exchange to improve photocatalytic degradation of RhB. All samples exhibit the hexagonal wurtzite structure. The size of Ag₂S@SnS₂ composites are ~ 1.5 μm flower-like with good crystallinity. Meanwhile, the E_g of 3% Ag₂S@SnS₂ is close to that of pure SnS₂. Consequently, the 3% Ag₂S@SnS₂ composite displays the excellent photocatalytic performance under simulated sunlight irradiation with good cycling stability, compared to the pure SnS₂ and other composites. Due to the blue and yellow luminescence quenching, the photogenerated electrons and holes is effectively separated in the 3% Ag₂S@SnS₂ sample. Especially, the hydroxyl radicals and photogenerated holes are main active species. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Environmental Remediation)

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15 pages, 2955 KiB

Open AccessArticle

Synthesis, Characterization, and Modification of Alumina Nanoparticles for Cationic Dye Removal

by Thi Phuong Minh Chu, Ngoc Trung Nguyen, Thi Lan Vu, Thi Huong Dao, Lan Chi Dinh, Hai Long Nguyen, Thu Ha Hoang, Thanh Son Le and Tien Duc Pham

Materials 2019, 12(3), 450; https://doi.org/10.3390/ma12030450 - 01 Feb 2019

Cited by 76 | Viewed by 5723

Abstract

In the present study, alumina nanoparticles (nano-alumina) which were successfully fabricated by solvothermal method, were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Transmission Electron Microscopy (TEM), and Brunauer–Emmett–Teller (BET) methods. The removal of cationic dye, Rhodamine B (RhB), through adsorption [...] Read more.

In the present study, alumina nanoparticles (nano-alumina) which were successfully fabricated by solvothermal method, were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Transmission Electron Microscopy (TEM), and Brunauer–Emmett–Teller (BET) methods. The removal of cationic dye, Rhodamine B (RhB), through adsorption method using synthesized nano-alumina with surface modification by anionic surfactant was also investigated. An anionic surfactant, sodium dodecyl sulfate (SDS) was used to modify nano-alumina surface at low pH and high ionic strength increased the removal efficiency of RhB significantly. The optimum adsorption conditions of contact time, pH, and adsorbent dosage for RhB removal using SDS modified nano-alumina (SMNA) were found to be 120 min, pH 4, and 5 mg/mL respectively. The RhB removal using SMNA reached a very high removal efficiency of 100%. After four times regeneration of adsorbent, the removal efficiency of RhB using SMNA was still higher than 86%. Adsorption isotherms of RhB onto SMNA at different salt concentrations were fitted well by a two-step model. A very high adsorption capacity of RhB onto SMNA of 165 mg/g was achieved. Adsorption mechanisms of RhB onto SMNA were discussed on the basis of the changes in surface modifications, the change in surface charges and adsorption isotherms. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Environmental Remediation)

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15 pages, 5998 KiB

Open AccessArticle

Industrial Waste Treatment by ETS-10 Ion Exchanger Material

by Pierantonio De Luca, Ivano Bernaudo, Rosangela Elliani, Antonio Tagarelli, Jànos B. Nagy and Anastasia Macario

Materials 2018, 11(11), 2316; https://doi.org/10.3390/ma11112316 - 18 Nov 2018

Cited by 33 | Viewed by 4043

Abstract

The aim of this project was to study the treatment of industrial waste using ETS-10 zeolite. The pollutants that must be removed were metals sourced from zinc ferrite, a processing waste derived from the use of mineral-containing zinc. The first phase of the [...] Read more.

The aim of this project was to study the treatment of industrial waste using ETS-10 zeolite. The pollutants that must be removed were metals sourced from zinc ferrite, a processing waste derived from the use of mineral-containing zinc. The first phase of the work involved the characterization of the industrial waste, zinc ferrite, in order to deepen the knowledge regarding its nature and composition. The second phase involved the removal of the metals released by the zinc ferrite in aqueous systems using the ETS-10 phase as an ion exchanger. Different chemical and physical techniques were used: plasma mass spectrometry, X-ray diffraction, scanning electron microscopy, microanalysis, and thermal analyses. A comparison between ETS-10 and commercial zeolite A performance, in the same aqueous systems, was carried out. The results showed that the metal removal efficiency of ETS-10 phase is higher than that obtained by commercial zeolite A, especially towards dangerous heavy metals such as Pb, Zn and Mn. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Environmental Remediation)

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11 pages, 2990 KiB

Open AccessArticle

Effective Degradation of Rh 6G Using Montmorillonite-Supported Nano Zero-Valent Iron under Microwave Treatment

by Wenxiu Rao, Hao Liu, Guocheng Lv, Danyu Wang and Libing Liao

Materials 2018, 11(11), 2212; https://doi.org/10.3390/ma11112212 - 07 Nov 2018

Cited by 14 | Viewed by 3272

Abstract

Nano zero-valent iron has drawn great attention for the degradation of organic dyes due to its high reactivity, large specific surface area, lightweight, and magnetism. However, the aggregation and passivation of iron nanoparticles may prohibit the wide use of it. A new composite [...] Read more.

Nano zero-valent iron has drawn great attention for the degradation of organic dyes due to its high reactivity, large specific surface area, lightweight, and magnetism. However, the aggregation and passivation of iron nanoparticles may prohibit the wide use of it. A new composite material was prepared by loading nano zero-valent iron (nZVI) on montmorillonite (MMT) to overcome the above shortcomings and it was further used for the removal of Rhodamine 6G (Rh 6G) under microwave treatment in the present work. The effects of various parameters, including the initial concentration of Rh 6G, microwave power, and pH value were investigated. The new composite material (nZVI/MMT) showed an excellent degradation ability for removing Rh 6G, and the removal amount reached 500 mg/g within 15 min. The degradation rate reached 0.4365 min⁻¹, significantly higher than most previous reports using other removal methods for Rh 6G. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Environmental Remediation)

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Review

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33 pages, 7735 KiB

Open AccessReview

2D and 3D Bulk Materials for Environmental Remediation: Air Filtration and Oil/Water Separation

by Ha-Jin Lee and Won San Choi

Materials 2020, 13(24), 5714; https://doi.org/10.3390/ma13245714 - 15 Dec 2020

Cited by 24 | Viewed by 3093

Abstract

Air and water pollution pose an enormous threat to human health and ecosystems. In particular, particulate matter (PM) and oily wastewater can cause serious environmental and health concerns. Thus, controlling PM and oily wastewater has been a great challenge. Various techniques have been [...] Read more.

Air and water pollution pose an enormous threat to human health and ecosystems. In particular, particulate matter (PM) and oily wastewater can cause serious environmental and health concerns. Thus, controlling PM and oily wastewater has been a great challenge. Various techniques have been reported to effectively remove PM particles and purify oily wastewater. In this article, we provide a review of the recent advancements in air filtration and oil/water separation using two- and three-dimensional (2D and 3D) bulk materials. Our review covers the advantages, characteristics, limitations, and challenges of air filters and oil/water separators using 2D and 3D bulk materials. In each section, we present representative works in detail and describe the concepts, backgrounds, employed materials, fabrication methods, and characteristics of 2D and 3D bulk material-based air filters and oil/water separators. Finally, the challenges, technical problems, and future research directions are briefly discussed for each section. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Environmental Remediation)

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