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A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Energy and Catalysis".

Deadline for manuscript submissions: closed (1 December 2022) | Viewed by 29945

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Special Issue Editors

Dr. Michael Arkas

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Institute of Nanoscience and Nanotechnology, NCSR “Demokritos”, 15310 Athens, Greece
Interests: dendritic polymers; xerogels; water purification; liquid crystals; metal nanoparticle catalysts; antimicrobial coatings
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Prof. Dr. Ioannis Pashalidis

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Environmental & Radioanalytical Chemistry Lab, Department of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
Interests: (radio)toxic inorganic species; bioactive chelating ligands; natural organic matter; metal oxides; mineral surfaces; lanthanides; actinides; humic acids; biomass by-products; pollutant monitoring on ground and sea waters; water purification; plant fibres
Special Issues, Collections and Topics in MDPI journals

Dr. Dimitrios A. Giannakoudakis

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Guest Editor

Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland
Interests: physicochemical, structural, optical, and surface chemistry features of nanostructured materials; photocatalysis; mechanochemistry; ultrasound; sonophotochemistry; interfacial phenomena in catalysis; detoxification of toxic vapors; biomass valorization; selective oxidation processes; adsorptive air and water remediation; materials chemistry; MOFs and metal oxides nanocomposites; activated carbons; graphite/graphite oxide; graphitic carbon nitride polymer; semiconductor nanocatalysts; carbon quantum dots
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Dr. Ioannis P. Anastopoulos

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Radioanalytical and Environmental Chemistry Group, Department of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
Interests: wastewater treatment; adsorption; soil pollution; heavy metals; dyes; pharmaceuticals; climate change; composting
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The interdisciplinary character of nanotechnology has empowered diverse scientific partnerships aiming to discover solutions to major contemporary problems. As water resources continue to be polluted, the need to conceive novel improved antipollution methods is becoming increasingly critical. In parallel, advanced nanoscale materials with far-reaching potential have been developed in order to promote the catalytic and photocatalytic degradation of pollutants as well as chemical reactions such as advanced oxidation processes (AOPs). The concept of employing nanomaterials is not new; existing in a variety of forms including nanospheres, nanomembranes, nanotubes, and nanofibers, they exhibit unique separation and catalytic properties and constitute solutions that prevail compared with their conventional counterparts. Particular emphasis has been placed on the assembly of composite systems combining organic compounds, metals, ceramics, and carbon nanomaterials. They can combine high surface areas permitting optimum adsorption and catalytical performance with high stability and recyclability. Their superior mechanical and chemical characteristics render them ideal alternatives for optimized performance efficiency, cost-effectiveness, and ease of preparation. In this Special Issue, recent trends will be introduced in a comprehensive presentation of the methods adopted for their synthesis, the broad spectrum of applications, and future developments.

The aim of this Special Issue, entitled “Nanoscale Materials for Water Purification and Catalysis”, is to present a collection of original and innovative papers (original research articles, short communications, and reviews) describing recent trends and developments in the synthesis and physicochemical characterization of nanomaterials or nanocomposites for adsorptive and/or (photo)catalytic environmental remediation applications.

Dr. Michael Arkas
Prof. Dr. Ioannis Pashalidis
Dr. Dimitrios A. Giannakoudakis
Dr. Ioannis P. Anastopoulos
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Nanomaterials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

nanotubes
membranes
nanoparticles
nanofibers
nanospheres
photocatalysis
electrocatalysis
pollutant adsorption
separation
composite materials
organic–inorganic hybrid
ceramic materials
filtration
metal nanoparticles
quantum dots
synthesis methods
theoretical studies
water and wastewater treatment

Published Papers (12 papers)

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22 pages, 7173 KiB

Open AccessEditor’s ChoiceArticle

Comparative Study of the U(VI) Adsorption by Hybrid Silica-Hyperbranched Poly(ethylene imine) Nanoparticles and Xerogels

by Michael Arkas, Konstantinos Giannakopoulos, Evangelos P. Favvas, Sergios Papageorgiou, George V. Theodorakopoulos, Artemis Giannoulatou, Michail Vardavoulias, Dimitrios A. Giannakoudakis, Konstantinos S. Triantafyllidis, Efthalia Georgiou and Ioannis Pashalidis

Nanomaterials 2023, 13(11), 1794; https://doi.org/10.3390/nano13111794 - 02 Jun 2023

Cited by 3 | Viewed by 1422

Abstract

Two different silica conformations (xerogels and nanoparticles), both formed by the mediation of dendritic poly (ethylene imine), were tested at low pHs for problematic uranyl cation sorption. The effect of crucial factors, i.e., temperature, electrostatic forces, adsorbent composition, accessibility of the pollutant to the dendritic cavities, and MW of the organic matrix, was investigated to determine the optimum formulation for water purification under these conditions. This was attained with the aid of UV-visible and FTIR spectroscopy, dynamic light scattering (DLS), ζ-potential, liquid nitrogen (LN₂) porosimetry, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Results highlighted that both adsorbents have extraordinary sorption capacities. Xerogels are cost-effective since they approximate the performance of nanoparticles with much less organic content. Both adsorbents could be used in the form of dispersions. The xerogels, though, are more practicable materials since they may penetrate the pores of a metal or ceramic solid substrate in the form of a precursor gel-forming solution, producing composite purification devices. Full article

(This article belongs to the Special Issue Nanoscale Materials for Water Purification and Catalysis)

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15 pages, 4064 KiB

Open AccessArticle

Evaluation of Photocatalytic Performance of Nano-Sized Sr_0.9La_0.1TiO₃ and Sr_0.25Ca_0.25Na_0.25Pr_0.25TiO₃ Ceramic Powders for Water Purification

by Aleksandra Jovanoski Kostić, Nikola Kanas, Vladimir Rajić, Annu Sharma, Subramshu S. Bhattacharya, Stevan Armaković, Maria M. Savanović and Sanja J. Armaković

Nanomaterials 2022, 12(23), 4193; https://doi.org/10.3390/nano12234193 - 25 Nov 2022

Cited by 1 | Viewed by 1329

Abstract

Water pollution is a significant issue nowadays. Among the many different technologies for water purification, photocatalysis is a very promising and environment-friendly approach. In this study, the photocatalytic activity of Sr_0.9La_0.1TiO₃ (SLTO) and Sr_0.25Ca_0.25Na_0.25Pr_0.25TiO₃ (SCNPTO) nano-sized powders were evaluated by degradation of pindolol in water. Pindolol is almost entirely insoluble in water due to its lipophilic properties. The synthesis of the SCNPTO was performed using the reverse co-precipitation method using nitrate precursors, whereas the SLTO was produced by spray pyrolysis (CerPoTech, Trondheim Norway). The phase purity of the synthesized powders was validated by XRD, while HR-SEM revealed particle sizes between 50 and 70 nm. The obtained SLTO and SCNPTO powders were agglomerated but had relatively similar specific surface areas of about 27.6 m² g⁻¹ and 34.0 m² g⁻¹, respectively. The energy band gaps of the SCNPTO and SLTO were calculated (DFT) to be about 2.69 eV and 3.05 eV, respectively. The photocatalytic performances of the materials were examined by removing the pindolol from the polluted water under simulated solar irradiation (SSI), UV-LED irradiation, and UV irradiation. Ultra-fast liquid chromatography was used to monitor the kinetics of the pindolol degradation with diode array detection (UFLC–DAD). The SLTO removed 68%, 94%, and 100% of the pindolol after 240 min under SSI, UV-LED, and UV irradiation, respectively. A similar but slightly lower photocatalytic activity was obtained with the SCNPTO under identical conditions, resulting in 65%, 84%, and 93% degradation of the pindolol, respectively. Chemical oxygen demand measurements showed high mineralization of the investigated mixtures under UV-LED and UV irradiation. Full article

(This article belongs to the Special Issue Nanoscale Materials for Water Purification and Catalysis)

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13 pages, 42223 KiB

Open AccessArticle

Surfactant-Modified CdS/CdCO₃ Composite Photocatalyst Morphology Enhances Visible-Light-Driven Cr(VI) Reduction Performance

by Wen-Yi Wang, Tian Sang, Yan Zhong, Chao-Hao Hu, Dian-Hui Wang, Jun-Chen Ye, Ni-Ni Wei and Hao Liu

Nanomaterials 2022, 12(21), 3923; https://doi.org/10.3390/nano12213923 - 07 Nov 2022

Cited by 1 | Viewed by 1395

Abstract

The surfactant modification of catalyst morphology is considered as an effective method to improve photocatalytic performance. In this work, the visible-light-driven composite photocatalyst was obtained by growing CdS nanoparticles in the cubic crystal structure of CdCO₃, which, after surfactant modification, led to the formation of CdCO₃ elliptical spheres. This reasonable composite-structure-modification design effectively increased the specific surface area, fully exposing the catalytic-activity check point. Cd²⁺ from CdCO₃ can enter the CdS crystal structure to generate lattice distortion and form hole traps, which productively promoted the separation and transfer of CdS photogenerated electron-hole pairs. The prepared 5-CdS/CdCO₃@SDS exhibited excellent Cr(VI) photocatalytic activity with a reduction efficiency of 86.9% within 30 min, and the reduction rate was 0.0675 min⁻¹, which was 15.57 and 14.46 times that of CdS and CdCO₃, respectively. Finally, the main active substances during the reduction process, the photogenerated charge transfer pathways related to heterojunctions and the catalytic mechanism were proposed and analyzed. Full article

(This article belongs to the Special Issue Nanoscale Materials for Water Purification and Catalysis)

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21 pages, 4038 KiB

Open AccessArticle

Activated Carbon/ZnFe₂O₄ Nanocomposite Adsorbent for Efficient Removal of Crystal Violet Cationic Dye from Aqueous Solutions

by Tahani Saad Algarni, Amal M. Al-Mohaimeed, Abdel-Basit Al-Odayni and Naaser A. Y. Abduh

Nanomaterials 2022, 12(18), 3224; https://doi.org/10.3390/nano12183224 - 16 Sep 2022

Cited by 15 | Viewed by 1548

Abstract

The aim of this study was to investigate the potential advantage of ZnFe₂O₄-incorporated activated carbon (ZFAC), fabricated via a simple wet homogenization, on the removal of cationic dye crystal violet (CV) from its aqueous solutions. The as-prepared ZFAC nanocomposite was characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), nitrogen adsorption, scanning electron microscope (SEM), thermogravimetric analysis (TGA), and ultraviolet–visible (UV–Vis). Batch adsorption operating conditions such as the pH (3–11), CV concentration (25–200 ppm), ZFAC dose (10–50 mg), temperature (23–45 °C), and contact time were evaluated. The results indicate pH-dependent uptake (optimum at pH 7.2) increased with temperature and CV concentration increase and decreased as adsorbent dose increased. Modeling of experimental data revealed better fit to the Langmuir than Freundlich and Temkin isotherms, with maximum monolayer capacities (Q_m) of 208.29, 234.03, and 246.19 mg/g at 23, 35, and 45 °C, respectively. Kinetic studies suggest pseudo-second order; however, the intra-particle diffusion model indicates a rate-limiting step controlled by film diffusion mechanism. Based on the thermodynamic parameters, the sorption is spontaneous (−ΔG°), endothermic (+ΔH°), and random process (+ΔS°), and their values support the physical adsorption mechanism. In addition to the ease of preparation, the results confirm the potential of ZFAC as a purifier for dye removal from polluted water. Full article

(This article belongs to the Special Issue Nanoscale Materials for Water Purification and Catalysis)

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18 pages, 3139 KiB

Open AccessEditor’s ChoiceArticle

Ni-Doped Ordered Nanoporous Carbon Prepared from Chestnut Wood Tannins for the Removal and Photocatalytic Degradation of Methylene Blue

by Ruby Bello, Elena Rodríguez-Aguado, Victoria A. Smith, Dmitry Grachev, Enrique Rodríguez Castellón and Svetlana Bashkova

Nanomaterials 2022, 12(10), 1625; https://doi.org/10.3390/nano12101625 - 10 May 2022

Cited by 3 | Viewed by 1564

Abstract

In this work, Ni-doped ordered nanoporous carbon was prepared by a simple and green one-pot solvent evaporation induced self-assembly process, where chestnut wood tannins were used as a precursor, Pluronic^® F-127 as a soft template, and Ni²⁺ as a crosslinking agent and catalytic component. The prepared carbon exhibited a 2D hexagonally ordered nanorod array mesoporous structure with an average pore diameter of ~5 nm. Nickel was found to be present on the surface of nanoporous carbon in the form of nickel oxide, nickel hydroxide, and metallic nickel. Nickel nanoparticles, with an average size of 13.1 nm, were well dispersed on the carbon surface. The synthesized carbon was then tested for the removal of methylene blue under different conditions. It was found that the amount of methylene blue removed increased with increasing pH and concentration of carbon but decreased with increasing concentration of methylene blue. Furthermore, photocatalytic tests carried out under visible light illumination showed that purple light had the greatest effect on the methylene blue adsorption/degradation, with the maximum percent degradation achieved at ~4 h illumination time, and that the percent degradation at lower concentrations of methylene blue was much higher than that at higher concentrations. The adsorption/degradation process exhibited pseudo second-order kinetics and strong initial adsorption, and the prepared carbon showed high magnetic properties and good recyclability. Full article

(This article belongs to the Special Issue Nanoscale Materials for Water Purification and Catalysis)

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15 pages, 5395 KiB

Open AccessArticle

Facile Synthesis of Magnetic Biochar Derived from Burley Tobacco Stems towards Enhanced Cr(VI) Removal: Performance and Mechanism

by Baihui Cui, Zhihua Chen, Feihua Wang, Zihan Zhang, Yanran Dai, Dabin Guo, Wei Liang and Yu Liu

Nanomaterials 2022, 12(4), 678; https://doi.org/10.3390/nano12040678 - 18 Feb 2022

Cited by 25 | Viewed by 1992

Abstract

In this study, ferric-loaded magnetic burley tobacco stem biochar (MBTS) was synthesized via pyrolysis to improve the removal of Cr(VI). The results showed that MBTS had an adsorption capacity of 54.92 mg Cr(VI)/g, which was about 14 times higher than raw burley tobacco stem biochar (i.e., 3.84 mg/g). According to the findings obtained, a three-step mechanism of Cr(VI) removal by MBTS was further put forward, i.e., (1) Cr(VI) exchanged with hydroxyl groups on MBTS, (2) the reduction in Cr(VI) to Cr(III) mediated by oxygen-containing groups, and (3) the chelation of produced Cr(III) with the amino groups on MBTS. FTIR spectra further revealed that C-N, C-H, and C=C groups played an important role in Cr(VI) removal. Furthermore, the adsorption equilibrium and kinetics of Cr(VI) on MBTS could better be described by the Langmuir equation and pseudo-second-order rate equation. This study clearly demonstrated that ferric-loaded biochar derived from burley tobacco stems could serve as a cost-effective magnetic adsorbent for the high-efficiency removal of soluble Cr(VI) from wastewater. Tobacco stem-adsorbed Cr(VI) realized a green path for treating waste by waste. Full article

(This article belongs to the Special Issue Nanoscale Materials for Water Purification and Catalysis)

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13 pages, 2040 KiB

Open AccessArticle

N-Doped Biochar as a New Metal-Free Activator of Peroxymonosulfate for Singlet Oxygen-Dominated Catalytic Degradation of Acid Orange 7

by Ruirui Han, Yingsen Fang, Ping Sun, Kai Xie, Zhicai Zhai, Hongxia Liu and Hui Liu

Nanomaterials 2021, 11(9), 2288; https://doi.org/10.3390/nano11092288 - 02 Sep 2021

Cited by 20 | Viewed by 3330

Abstract

In this paper, using rice straw as a raw material and urea as a nitrogen precursor, a composite catalyst (a nitrogen-doped rice straw biochar at the pyrolysis temperature of 800 °C, recorded as NRSBC800) was synthesized by one-step pyrolysis. NRSBC800 was then characterized using XPS, BET, TEM and other technologies, and its catalytic performance as an activator for permonosulfate (PMS) to degrade acid orange 7 (AO7) was studied. The results show that the introduction of N-doping significantly improved the catalytic performance of NRSBC800. The NRSBC800/PMS oxidation system could fully degrade AO7 within 30 min, with the reaction rate constant (2.1 × 10 ⁻¹ min⁻¹) being 38 times that of RSBC800 (5.5 × 10⁻³ min⁻¹). Moreover, NRSBC800 not only had better catalytic performance than traditional metal oxides (Co₃O₄ and Fe₃O₄) and carbon nanomaterial (CNT) but also received less impact from environmental water factors (such as anions and humic acids) during the catalytic degradation process. In addition, a quenching test and electron paramagnetic resonance (EPR) research both indicated that AO7 degradation relied mainly on non-free radical oxidation (primarily singlet oxygen (¹O₂)). A recycling experiment further demonstrated NRSBC800’s high stability after recycling three times. Full article

(This article belongs to the Special Issue Nanoscale Materials for Water Purification and Catalysis)

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11 pages, 2090 KiB

Open AccessArticle

Improving the Performance of ZnS Photocatalyst in Degrading Organic Pollutants by Constructing Composites with Ag₂O

by Dequan Yu, Hao Fang, Peikai Qiu, Fancong Meng, Haixia Liu, Shuai Wang, Pingli Lv, Xiaoyan Cong, Qingfen Niu and Tianduo Li

Nanomaterials 2021, 11(6), 1451; https://doi.org/10.3390/nano11061451 - 30 May 2021

Cited by 14 | Viewed by 2481

Abstract

ZnS is a promising photocatalyst in water purification, whereas its low photon efficiency and poor visible-light response restrict its application. Constructing composites may help solve these problems. In this work, Ag₂O was introduced to ZnS for the first time based on their energy band characteristics to form a novel ZnS/Ag₂O composite photocatalyst. In the model reaction of degrading methylene blue, the as-designed catalyst exhibited high catalytic activity among a series of ZnS-based composite photocatalysts under similar conditions. The catalytic rate constant was up to 0.138 min⁻¹, which is 27.4- and 15.6-times higher than those of ZnS and Ag₂O. This composite degraded 92.4% methylene blue in 50 min, while the ratios were 31.9% and 68.8% for ZnS and Ag₂O. Catalytic mechanism study based on photoluminescence and radical-scavenging experiments revealed that the enhanced photocatalytic activity was attributed to the composite structure of ZnS/Ag₂O. The structure not only facilitated the separation and transmission of photogenerated carriers but also extended the light response range of the catalyst. The as-designed ZnS/Ag₂O composite is promising in degrading organic pollutants in water. Full article

(This article belongs to the Special Issue Nanoscale Materials for Water Purification and Catalysis)

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20 pages, 3843 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Uranium Removal from Aqueous Solutions by Aerogel-Based Adsorbents—A Critical Review

by Efthalia Georgiou, Grigorios Raptopoulos, Ioannis Anastopoulos, Dimitrios A. Giannakoudakis, Michael Arkas, Patrina Paraskevopoulou and Ioannis Pashalidis

Nanomaterials 2023, 13(2), 363; https://doi.org/10.3390/nano13020363 - 16 Jan 2023

Cited by 8 | Viewed by 2658

Abstract

Aerogels are a class of lightweight, nanoporous, and nanostructured materials with diverse chemical compositions and a huge potential for applications in a broad spectrum of fields. This has led the IUPAC to include them in the top ten emerging technologies in chemistry for 2022. This review provides an overview of aerogel-based adsorbents that have been used for the removal and recovery of uranium from aqueous environments, as well as an insight into the physicochemical parameters affecting the adsorption efficiency and mechanism. Uranium removal is of particular interest regarding uranium analysis and recovery, to cover the present and future uranium needs for nuclear power energy production. Among the methods used, such as ion exchange, precipitation, and solvent extraction, adsorption-based technologies are very attractive due to their easy and low-cost implementation, as well as the wide spectrum of adsorbents available. Aerogel-based adsorbents present an extraordinary sorption capacity for hexavalent uranium that can be as high as 8.8 mol kg^–1 (2088 g kg^–1). The adsorption data generally follow the Langmuir isotherm model, and the kinetic data are in most cases better described by the pseudo-second-order kinetic model. An evaluation of the thermodynamic data reveals that the adsorption is generally an endothermic, entropy-driven process (ΔH⁰, ΔS⁰ > 0). Spectroscopic studies (e.g., FTIR and XPS) indicate that the adsorption is based on the formation of inner-sphere complexes between surface active moieties and the uranyl cation. Regeneration and uranium recovery by acidification and complexation using carbonate or chelating ligands (e.g., EDTA) have been found to be successful. The application of aerogel-based adsorbents to uranium removal from industrial processes and uranium-contaminated waste waters was also successful, assuming that these materials could be very attractive as adsorbents in water treatment and uranium recovery technologies. However, the selectivity of the studied materials towards hexavalent uranium is limited, suggesting further developments of aerogel materials that could be modified by surface derivatization with chelating agents (e.g., salophen and iminodiacetate) presenting high selectivity for uranyl moieties. Full article

(This article belongs to the Special Issue Nanoscale Materials for Water Purification and Catalysis)

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40 pages, 5745 KiB

Open AccessEditor’s ChoiceReview

Carbon-Based Nanocatalysts (CnCs) for Biomass Valorization and Hazardous Organics Remediation

by Dimitrios A. Giannakoudakis, Foteini F. Zormpa, Antigoni G. Margellou, Abdul Qayyum, Ramón Fernando Colmenares-Quintero, Christophe Len, Juan Carlos Colmenares and Konstantinos S. Triantafyllidis

Nanomaterials 2022, 12(10), 1679; https://doi.org/10.3390/nano12101679 - 14 May 2022

Cited by 13 | Viewed by 3745

Abstract

The continuous increase of the demand in merchandise and fuels augments the need of modern approaches for the mass-production of renewable chemicals derived from abundant feedstocks, like biomass, as well as for the water and soil remediation pollution resulting from the anthropogenic discharge of organic compounds. Towards these directions and within the concept of circular (bio)economy, the development of efficient and sustainable catalytic processes is of paramount importance. Within this context, the design of novel catalysts play a key role, with carbon-based nanocatalysts (CnCs) representing one of the most promising class of materials. In this review, a wide range of CnCs utilized for biomass valorization towards valuable chemicals production, and for environmental remediation applications are summarized and discussed. Emphasis is given in particular on the catalytic production of 5-hydroxymethylfurfural (5-HMF) from cellulose or starch-rich food waste, the hydrogenolysis of lignin towards high bio-oil yields enriched predominately in alkyl and oxygenated phenolic monomers, the photocatalytic, sonocatalytic or sonophotocatalytic selective partial oxidation of 5-HMF to 2,5-diformylfuran (DFF) and the decomposition of organic pollutants in aqueous matrixes. The carbonaceous materials were utilized as stand-alone catalysts or as supports of (nano)metals are various types of activated micro/mesoporous carbons, graphene/graphite and the chemically modified counterparts like graphite oxide and reduced graphite oxide, carbon nanotubes, carbon quantum dots, graphitic carbon nitride, and fullerenes. Full article

(This article belongs to the Special Issue Nanoscale Materials for Water Purification and Catalysis)

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44 pages, 204911 KiB

Open AccessFeature PaperReview

Catalytic Neutralization of Water Pollutants Mediated by Dendritic Polymers

by Michael Arkas, Ioannis Anastopoulos, Dimitrios A. Giannakoudakis, Ioannis Pashalidis, Theodora Katsika, Eleni Nikoli, Rafael Panagiotopoulos, Anna Fotopoulou, Michail Vardavoulias and Marilina Douloudi

Nanomaterials 2022, 12(3), 445; https://doi.org/10.3390/nano12030445 - 28 Jan 2022

Cited by 12 | Viewed by 2851

Abstract

Radially polymerized dendritic compounds are nowadays an established polymer category next to their linear, branched, and cross-linked counterparts. Their uncommon tree-like architecture is characterized by adjustable internal cavities and external groups. They are therefore exceptional absorbents and this attainment of high concentrations in their interior renders them ideal reaction media. In this framework, they are applied in many environmentally benign implementations. One of the most important among them is water purification through pollutant decomposition. Simple and composite catalysts and photo-catalysts containing dendritic polymers and applied in water remediation will be discussed jointly with some unconventional solutions and prospects. Full article

(This article belongs to the Special Issue Nanoscale Materials for Water Purification and Catalysis)

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32 pages, 2985 KiB

Open AccessReview

Differentiating Nanomaghemite and Nanomagnetite and Discussing Their Importance in Arsenic and Lead Removal from Contaminated Effluents: A Critical Review

by Juan A. Ramos-Guivar, Diego A. Flores-Cano and Edson Caetano Passamani

Nanomaterials 2021, 11(9), 2310; https://doi.org/10.3390/nano11092310 - 06 Sep 2021

Cited by 40 | Viewed by 3440

Abstract

Arsenic and lead heavy metals are polluting agents still present in water bodies, including surface (lake, river) and underground waters; consequently, the development of new adsorbents is necessary to uptake these metals with high efficiency, quick and clean removal procedures. Magnetic nanoparticles, prepared with iron-oxides, are excellent candidates to achieve this goal due to their ecofriendly features, high catalytic response, specific surface area, and pulling magnetic response that favors an easy removal. In particular, nanomagnetite and maghemite are often found as the core and primary materials regarding magnetic nanoadsorbents. However, these phases show interesting distinct physical properties (especially in their surface magnetic properties) but are not often studied regarding correlations between the surface properties and adsorption applications, for instance. Thus, in this review, we summarize the main characteristics of the co-precipitation and thermal decomposition methods used to prepare the nano-iron-oxides, being the co-precipitation method most promising for scaling up processes. We specifically highlight the main differences between both nano-oxide species based on conventional techniques, such as X-ray diffraction, zero and in-field Mössbauer spectroscopy, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism, the latter two techniques performed with synchrotron light. Therefore, we classify the most recent magnetic nanoadsorbents found in the literature for arsenic and lead removal, discussing in detail their advantages and limitations based on various physicochemical parameters, such as temperature, competitive and coexisting ion effects, i.e., considering the simultaneous adsorption removal (heavy metal–heavy metal competition and heavy metal–organic removal), initial concentration, magnetic adsorbent dose, adsorption mechanism based on pH and zeta potential, and real water adsorption experiments. We also discuss the regeneration/recycling properties, after-adsorption physicochemical properties, and the cost evaluation of these magnetic nanoadsorbents, which are important issues, but less discussed in the literature. Full article

(This article belongs to the Special Issue Nanoscale Materials for Water Purification and Catalysis)

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