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Research on Green Adsorbents
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Research on Green Adsorbents

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Green Chemistry".

Deadline for manuscript submissions: closed (31 July 2023) | Viewed by 15600

Special Issue Editors

Prof. Dr. Małgorzata Wiśniewska

E-Mail Website
Guest Editor
Department of Radiochemistry and Environmental Chemistry, Institute of Chemical Sciences, Faculty of Chemistry, Maria Curie-Sklodowska University in Lublin, M. Curie-Sklodowska Sq. 3, 20-031 Lublin, Poland
Interests: polymer adsorption; heavy metal; dyes; surfactants; simultaneous removal; multicomponent systems; separation methods; wastewater purification; electrokinetic properties; metal oxides; activated carbons; zeolites; minerals; composites; coagulation-flocculation
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Piotr Nowicki

E-Mail Website
Guest Editor
Department of Applied Chemistry, Faculty of Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 8, 61-614 Poznań, Poland
Interests: biochars; activated carbons; preparation and modification of carbonaceous adsorbents; utilization of waste materials; adsorption from gas phase, water and wastewater purification

Special Issue Information

Dear Colleagues,

We are pleased to announce a Special Issue of Molecules entitled “Research on Green Adsorbents”.

Recently, there has been a significant increase in interest in materials, technologies and processes that would be ecologically justified. This includes, above all, the production of various types of adsorbents from waste materials or biomass, the development of more environmentally friendly technologies that reduce the consumption of chemical reagents and the generation of waste, the production of biofuels, biocatalysis and the use of biosensors, and the use of various substances of natural origin. All these trends can be successfully implemented based on a wide range of available experimental techniques that allow for the detailed characterization of the physicochemical properties of these types of systems. This approach is closely related to modern development strategies currently being introduced in many areas of human activity.

On the other hand, the continuous development of civilization means that various dangerous substances are depleted into water sources, which very often do not undergo microbiological decomposition. This applies mainly to inorganic nitrogen and phosphorus compounds, a whole range of organic substances (such as dyes, pesticides, aromatic and aliphatic hydrocarbons, phenols, polymers, surfactants), heavy metals and pharmacological substances, primarily from the group of antibiotics, non-steroidal anti-inflammatory drugs and hormones. The procedures used in water and wastewater treatment processes should therefore be focused on modern technological solutions that are environmentally friendly.

We are pleased to invite you to submit scientific articles, reviews and short communications discussing the latest developments in the synthesis and application of green adsorbents (among others, biochars, activated carbons, ordered mesoporous carbons; zeolites, hydroxyapatites, minerals, oxides and different kinds of composites). The investigation of their usage in wastewater treatment, air purification, energy storage, catalysis, drug delivery systems, medical biosensors and cosmetic products design as well as in agriculture is extremely important in the context of the development of innovative technologies.

Prof. Dr. Małgorzata Wiśniewska
Prof. Dr. Piotr Nowicki
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. Molecules 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 2700 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

  • green technologies
  • innovative adsorbents
  • hazardous substances removal
  • water filtration and purification
  • wastewater treatment
  • air purification
  • soil remediation
  • bioactive adsorbents

Published Papers (16 papers)

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Editorial

Jump to: Research, Review

7 pages, 195 KiB  
Editorial
Research on Green Adsorbents
by Małgorzata Wiśniewska and Piotr Nowicki
Molecules 2024, 29(8), 1855; https://doi.org/10.3390/molecules29081855 - 19 Apr 2024
Viewed by 344
Abstract
Adsorption processes play a crucial role in air purification, wastewater treatment, soil remediation technologies, noble metals recovery, and long-term energy storage systems [...] Full article
(This article belongs to the Special Issue Research on Green Adsorbents)

Research

Jump to: Editorial, Review

16 pages, 2747 KiB  
Article
Production of Mineral-Carbon Composites and Activated Carbons as a Method of Used Gear Oil, Ashes, and Low-Quality Brown Coals Management
by Małgorzata Wiśniewska, Amanda Sadłowska, Karolina Herda, Teresa Urban and Piotr Nowicki
Molecules 2023, 28(19), 6919; https://doi.org/10.3390/molecules28196919 - 03 Oct 2023
Cited by 1 | Viewed by 876
Abstract
The main objective of this study was to assess the usefulness of the low-quality brown coal, ash obtained as a result of its combustion, as well as used gear oil for the production of mineral-carbon adsorbents. The adsorbents were characterized in terms of [...] Read more.
The main objective of this study was to assess the usefulness of the low-quality brown coal, ash obtained as a result of its combustion, as well as used gear oil for the production of mineral-carbon adsorbents. The adsorbents were characterized in terms of textural parameters, acidic-basic character of the surface, mineral matter contribution to the structure, as well as their suitability for drinking water purification. Adsorption tests were carried out against two synthetic dyes—methylene blue and methyl orange. In order to understand the nature of the organic pollutants adsorption, the effect of the initial dye concentration, temperature, and pH of the system as well as the phase contact time were investigated. The obtained mineral-carbon composite and activated carbons significantly differed not only in terms of the elemental composition and chemical character of the surface (from slightly acidic to strongly alkaline), but also showed a very diverse degree of specific surface development (from 21 to 656 m2/g) and the type of porous structure generated (from micro/mesoporous to typically mesoporous). Adsorption tests showed that the efficiency of organic dye removal from aqueous solutions primarily depends on the type of the adsorbent and adsorbate applied, and, to a lesser extent, on the temperature and pH of the system. In turn, kinetic studies have shown that the sorption of dyes on such materials is consistent with a pseudo-second-order kinetics model, regardless of the type of adsorbed dye. Full article
(This article belongs to the Special Issue Research on Green Adsorbents)
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18 pages, 6179 KiB  
Article
Synthesis and Characterization of Phosphorus-Containing Sorbent for Basic Dye Removal
by Monika Wawrzkiewicz, Sławomir Frynas and Beata Podkościelna
Molecules 2023, 28(18), 6731; https://doi.org/10.3390/molecules28186731 - 21 Sep 2023
Cited by 1 | Viewed by 713
Abstract
A new phosphorus-containing sorbent was prepared by copolymerizing ethylene glycol dimethacrylate (EGDMA) and trimethylvinyl silane (TMVS) with diphenylvinylphoshine oxide (DPVO). It was characterized and applied in the removal of cationic dyes such as C.I. Basic Yellow 2 (BY2), C.I. Basic Blue 3 (BB3) [...] Read more.
A new phosphorus-containing sorbent was prepared by copolymerizing ethylene glycol dimethacrylate (EGDMA) and trimethylvinyl silane (TMVS) with diphenylvinylphoshine oxide (DPVO). It was characterized and applied in the removal of cationic dyes such as C.I. Basic Yellow 2 (BY2), C.I. Basic Blue 3 (BB3) and C.I. Basic Red 46 (BR46) using the batch method. Spectroscopic analysis indicated that the phosphinoyl group was introduced into the sorbent structure. Equilibrium adsorption data were fitted to the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models. The Freundlich model is the most suitable to describe the adsorption of BB3 (the Freundlich constant kF = 32.3 mg1−1/nL1/n/g) and BY2 on the sorbent (13.8 mg1−1/nL1/n/g), while the Langmuir model is the most adequate to describe the adsorption of BR46 (the monolayer capacity Q0 = 2.7 mg/g). The kinetics of the dye adsorption follows the assumptions of the pseudo-second-order (the rate constants k2 = 0.087 ÷ 0.738 g/mg min) model rather than pseudo-first-order or intraparticle diffusion. The presence of Na2SO4 and cationic surfactant in the aqueous solutions inhibited dye retention by the DPVO–EGDMA–TMVS. Adsorbent regeneration efficiency does not exceed 60% using 1 M NaCl and 1 M HCl solutions in the presence of 50% v/v methanol. Full article
(This article belongs to the Special Issue Research on Green Adsorbents)
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18 pages, 2747 KiB  
Article
Adsorption of Methyl Red and Methylene Blue on Carbon Bioadsorbents Obtained from Biogas Plant Waste Materials
by Robert Wolski, Aleksandra Bazan-Wozniak and Robert Pietrzak
Molecules 2023, 28(18), 6712; https://doi.org/10.3390/molecules28186712 - 20 Sep 2023
Cited by 8 | Viewed by 1327
Abstract
In this study, biocarbon was obtained from the waste material corn digest. Carbon adsorbents were obtained by physical activation of the precursor with CO2. Detailed physicochemical characterization of the biocarbon was carried out using low-temperature nitrogen adsorption/desorption, Boehm titration, zero-charge point [...] Read more.
In this study, biocarbon was obtained from the waste material corn digest. Carbon adsorbents were obtained by physical activation of the precursor with CO2. Detailed physicochemical characterization of the biocarbon was carried out using low-temperature nitrogen adsorption/desorption, Boehm titration, zero-charge point (pHpzc) and iodine number. In addition, the sorption capacity of the biocarbon agents towards an aqueous solution of methylene blue and methyl red was determined, and the kinetics of the adsorption process were determined. The biocarbon adsorbents were characterized by an average developed specific surface area covering the range from 320 to 616 m2/g. The sorption capacity of the biocarbon adsorbents against methylene blue ranged from 40 mg/g to 146 mg/g, and for methyl red it covered the range from 31 mg/g to 113 mg/g. It was shown that the efficiency of organic dye removal by the obtained biocarbons depends on the initial concentration of the adsorbate solution, its mass, shaking rate, adsorbent–adsorbate contact time and temperature. The results obtained from the Langmuir and Freundlich kinetic models showed that the Langmuir model is the most suitable model for describing the adsorption of the studied pollutants on biocarbon. In turn, the adsorption kinetics of dyes is described according to the pseudo-second-order model. Adsorption studies also showed that as the process temperature increases, the removal efficiency of methylene blue and methyl red increases. Full article
(This article belongs to the Special Issue Research on Green Adsorbents)
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19 pages, 3767 KiB  
Article
A Green Approach to Obtaining Glycerol Carbonate by Urea Glycerolysis Using Carbon-Supported Metal Oxide Catalysts
by Karolina Ptaszyńska, Anna Malaika, Klaudia Kozigrodzka and Mieczysław Kozłowski
Molecules 2023, 28(18), 6534; https://doi.org/10.3390/molecules28186534 - 09 Sep 2023
Cited by 1 | Viewed by 972
Abstract
The results of sustainable and selective synthesis of glycerol carbonate (GC) from urea and glycerol under ambient pressure using carbon-fiber-supported metal oxide catalysts are reported. Carbon fibers (CF) were prepared via a catalytic chemical vapor deposition method (CCVD) using Ni as a catalyst [...] Read more.
The results of sustainable and selective synthesis of glycerol carbonate (GC) from urea and glycerol under ambient pressure using carbon-fiber-supported metal oxide catalysts are reported. Carbon fibers (CF) were prepared via a catalytic chemical vapor deposition method (CCVD) using Ni as a catalyst and liquefied petroleum gas (LPG) as a cheap carbon source. Supported metal oxide catalysts were obtained by an incipient wetness impregnation technique using Zn, Ba, Cr, and Mg nitrates. Finally, the samples were pyrolyzed and oxidized in an air flow. The obtained catalysts (10%MexOy/CFox) were tested in the reaction of urea glycerolysis at 140 °C for 6 h under atmospheric pressure, using an equimolar ratio of reagents and an inert gas flow for NH3 removal. Under the applied conditions, all of the prepared catalysts increased the glycerol conversion and glycerol carbonate yield compared to the blank test, and the best catalytic performance was shown by the CFox-supported ZnO and MgO systems. Screening of the reaction conditions was carried out by applying ZnO/CFox as a catalyst and considering the effect of reaction temperature, molar ratio of reagents, and the mode of the inert gas flow through the reactor on the catalytic process. Finally, a maximum yield of GC of about 40%, together with a selectivity to glycerol carbonate of ~100%, was obtained within 6 h of reaction at 140 °C using a glycerol-to-urea molar ratio of 1:1 while flowing Ar through the reaction mixture. Furthermore, a positive heterogeneous catalytic effect of the CFox support on the process was noticed. Full article
(This article belongs to the Special Issue Research on Green Adsorbents)
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15 pages, 4418 KiB  
Article
Magnetic Adsorbent Fe3O4/ZnO/LC for the Removal of Tetracycline and Congo Red from Aqueous Solution
by Anjiu Zhao, Qi Tang, Yuanlong Chen, Chongpeng Qiu and Xingyan Huang
Molecules 2023, 28(18), 6499; https://doi.org/10.3390/molecules28186499 - 07 Sep 2023
Viewed by 869
Abstract
Zeolitic imidazolate frameworks (ZIFs) can be used as an adsorbent to efficiently adsorb organic pollutants. However, ZIF nanoparticles are easy to form aggregates, hampering the effective and practical application in practical adsorption. In this study, the ZIF-8 was successfully loaded onto lignocellulose (LC) [...] Read more.
Zeolitic imidazolate frameworks (ZIFs) can be used as an adsorbent to efficiently adsorb organic pollutants. However, ZIF nanoparticles are easy to form aggregates, hampering the effective and practical application in practical adsorption. In this study, the ZIF-8 was successfully loaded onto lignocellulose (LC) to further produce ZnO/LC by in situ growth method and hydrothermal treatment, and then Fe3O4 nanoparticles (Fe3O4 NPs) were loaded onto ZnO/LC to prepare magnetic Fe3O4/ZnO/LC adsorbent for removing tetracycline (TC) and congo red (CR) pollutants from aqueous solution. The adsorption properties of the adsorbent were systematically analyzed for different conditions, such as adsorbent dosage, solution pH, contact time, temperature and initial concentration. The experimental data were fitted using adsorption kinetic and isotherm models. The results showed that the pseudo-second-order model and Sips model were well fitted to the adsorption kinetic and adsorption isotherm, respectively. The adsorption capacities of TC and CR reached the maximum value of 383.4 mg/g and 409.1 mg/g in experimental conditions. The mechanism of the removal mainly includes electrostatic interaction, hydrogen bonding and π-π stacking. This novel adsorbent could be rapidly separated from the aqueous solution, suggesting its high potential to remove pollutants in wastewater. Full article
(This article belongs to the Special Issue Research on Green Adsorbents)
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21 pages, 3187 KiB  
Article
Removal of Methylene Blue and Methyl Red from Aqueous Solutions Using Activated Carbons Obtained by Chemical Activation of Caraway Seed
by Dorota Paluch, Aleksandra Bazan-Wozniak, Agnieszka Nosal-Wiercińska and Robert Pietrzak
Molecules 2023, 28(17), 6306; https://doi.org/10.3390/molecules28176306 - 29 Aug 2023
Cited by 1 | Viewed by 852
Abstract
In this study, activated carbons were produced through the chemical activation of caraway seeds using three different activators: Na2CO3, K2CO3, and H3PO4. A 1:2 weight ratio of precursor to activator was [...] Read more.
In this study, activated carbons were produced through the chemical activation of caraway seeds using three different activators: Na2CO3, K2CO3, and H3PO4. A 1:2 weight ratio of precursor to activator was maintained in every instance. Comprehensive analyses were conducted on the resultant activated carbons, including elemental analysis, textural parameters determination, Boehm titration for surface oxygen functional groups, pH assessment of aqueous extracts, and quantification of ash content. The produced materials were subjected to adsorption tests for methylene blue and methyl red sodium salt from the liquid phase and the effects of adsorbent dosage, pH of the aqueous dye solution, process temperature, and adsorbent–adsorbate contact time on sorption capacity obtained. To characterize the adsorption model of the examined pollutants, both the Langmuir and Freundlich equations were employed. In addition, the sorption capacity of the obtained carbon materials against an iodine aqueous solution was assessed. The specific surface area of the obtained adsorbents ranged from 269 to 926 m2/g. By employing potassium carbonate to chemically activate the starting substance, the resulting activated carbons show the highest level of specific surface area development and the greatest sorption capacity against the tested impurities—296 mg/g for methylene blue and 208 mg/g for methyl red sodium salt. The adsorption rate for both dyes was determined to align with a pseudo-second-order kinetic model. The experimental adsorption data for methylene blue were well-described by the Langmuir model, whereas the Freundlich model was found to be congruent with the data pertaining to methyl red sodium salt. Full article
(This article belongs to the Special Issue Research on Green Adsorbents)
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15 pages, 1826 KiB  
Article
Ecotoxicity of Diazinon and Atrazine Mixtures after Ozonation Catalyzed by Na+ and Fe2+ Exchanged Montmorillonites on Lemna minor
by Amina Benghaffour, Abdelkrim Azzouz and David Dewez
Molecules 2023, 28(16), 6108; https://doi.org/10.3390/molecules28166108 - 17 Aug 2023
Viewed by 770
Abstract
The toxicity of two pesticides, diazinon (DAZ) and atrazine (ATR), before and after montmorillonite-catalyzed ozonation was comparatively investigated on the duckweed Lemna minor. The results allowed demonstrating the role of clay-containing media in the evolution in time of pesticide negative impact on [...] Read more.
The toxicity of two pesticides, diazinon (DAZ) and atrazine (ATR), before and after montmorillonite-catalyzed ozonation was comparatively investigated on the duckweed Lemna minor. The results allowed demonstrating the role of clay-containing media in the evolution in time of pesticide negative impact on L. minor plants. Pesticides conversion exceeded 94% after 30 min of ozonation in the presence of both Na+ and Fe2+ exchanged montmorillonites. Toxicity testing using L. minor permitted us to evaluate the change in pesticide ecotoxicity. The plant growth inhibition involved excessive oxidative stress depending on the pesticide concentration, molecular structure, and degradation degree. Pesticide adsorption and/or conversion by ozonation on clay surfaces significantly reduced the toxicity towards L. minor plants, more particularly in the presence of Fe(II)-exchanged montmorillonite. The results showed a strong correlation between the pesticide toxicity towards L. minor and the level of reactive oxygen species, which was found to depend on the catalytic activity of the clay minerals, pesticide exposure time to ozone, and formation of harmful derivatives. These findings open promising prospects for developing a method to monitor pesticide ecotoxicity according to clay-containing host-media and exposure time to ambient factors. Full article
(This article belongs to the Special Issue Research on Green Adsorbents)
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15 pages, 8713 KiB  
Article
Synthesis and Characterization of Eco-Efficient Alkali-Activated Composites with Self-Cleaning Properties for Sustainable Construction
by Agnieszka Ślosarczyk, Izabela Klapiszewska, Patryk Jędrzejczak, Weronika Jędrzejczak and Łukasz Klapiszewski
Molecules 2023, 28(16), 6066; https://doi.org/10.3390/molecules28166066 - 15 Aug 2023
Viewed by 614
Abstract
In this research, we aimed to design an eco-efficient composite based on alkali-activated materials (AAMs) with self-cleaning properties for sustainable construction. Significant emphasis was placed on determining the role of the type of precursor, the amount of sodium silicate, and the addition of [...] Read more.
In this research, we aimed to design an eco-efficient composite based on alkali-activated materials (AAMs) with self-cleaning properties for sustainable construction. Significant emphasis was placed on determining the role of the type of precursor, the amount of sodium silicate, and the addition of titanium dioxide on the rheological and mechanical properties of AAMs. An important aspect of the research was the modification of AAM with titanium dioxide to obtain the self-cleaning properties. Titanium dioxide, thanks to its photocatalytic properties, enables the reduction of organic pollutants and nitrogen oxides in the urban atmosphere and promotes the cleaning of material surfaces. Blast furnace slag (BFS) was used as the source material, which was then substituted in subsequent formulations with metakaolinite at 50% and fly ash and zeolite at 30%. The best-activated AAMs, in which blast furnace slag and its mixture with metakaolinite were used as precursors, achieved compressive strengths of 50 MPa. BFS mixtures with pozzolans were more difficult to polymerize, although their final strengths were still relatively high, in the range of 33–37 MPa. Adding titanium dioxide (T) improved the final strengths and slightly lowered the heat of hydration and spreading of the AAM mortars. The best self-cleaning properties were achieved with composites that comprised a mixture of blast furnace slag, fly ash, and 2% titanium dioxide. Full article
(This article belongs to the Special Issue Research on Green Adsorbents)
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13 pages, 6750 KiB  
Article
A New Impregnated Adsorbent for Noble Metal Ion Sorption
by Zbigniew Hubicki, Karolina Zinkowska and Grzegorz Wójcik
Molecules 2023, 28(16), 6040; https://doi.org/10.3390/molecules28166040 - 13 Aug 2023
Cited by 3 | Viewed by 738
Abstract
Noble metals (NM) such as gold, platinum, palladium, and rhodium are widely applied in the electronics and automotive industries. Thus, the search for cheap and selective sorbents for noble metals is economically justified. Nitrolite does not sorb noble metal ions. A new impregnated [...] Read more.
Noble metals (NM) such as gold, platinum, palladium, and rhodium are widely applied in the electronics and automotive industries. Thus, the search for cheap and selective sorbents for noble metals is economically justified. Nitrolite does not sorb noble metal ions. A new impregnated sorbent was prepared. The natural sorbent Nitrolite was impregnated with Aliquat 336 using a new warm impregnation method. After the impregnation process, Nitrolite adsorbed platinum(IV), palladium(II), and gold(III) ions from the chloride solutions. The values of the sorption capacity for palladium(II) and platinum(IV) ions were 47.63 mg/g and 51.39 mg/g, respectively, from the 0.1 M HCl model solution. The sorption capacity for gold(III) ions was estimated to be 73.43 mg/g from the 0.1 M HCl model solution. An exhausted catalytic converter was leached, and platinum(IV), palladium(II), and rhodium(III) were transferred to the chloride solution. The impregnated sorbent Nitrolite–Aliquat 336 was used in the investigations of the platinum(IV), palladium(II), and rhodium(III) ions’ sorption from a real solution. The impregnated sorbent Nitrolite–Aliquat 336 proved to be suitable for the recovery of platinum(IV) and palladium(II) ions, whereas rhodium ions were not sorbed from the leached solutions. Notably, 1 M thiourea in the 1 M HCl solution desorbed platinum(IV), palladium(II), and gold(III) above 94%. Full article
(This article belongs to the Special Issue Research on Green Adsorbents)
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11 pages, 3210 KiB  
Article
Plant-Waste-Derived Sorbents for Nitazoxanide Adsorption
by Artur Sokołowski, Katarzyna Jędruchniewicz, Rafał Kobyłecki, Robert Zarzycki, Krzysztof Różyło, Haitao Wang and Bożena Czech
Molecules 2023, 28(15), 5919; https://doi.org/10.3390/molecules28155919 - 07 Aug 2023
Viewed by 1115
Abstract
The increased application of drugs during the COVID-19 pandemic has resulted in their increased concentration in wastewater. Conventional wastewater treatment plants do not remove such pollutants effectively. Adsorption is a cheap, effective, and environmentally friendly method that can accomplish this. On the other [...] Read more.
The increased application of drugs during the COVID-19 pandemic has resulted in their increased concentration in wastewater. Conventional wastewater treatment plants do not remove such pollutants effectively. Adsorption is a cheap, effective, and environmentally friendly method that can accomplish this. On the other hand, maintaining organic waste is required. Thus, in this study, plant waste-derived pelletized biochar obtained from different feedstock and pyrolyzed at 600 °C was applied for the adsorption of nitazoxanide, an antiparasitic drug used for the treatment of SARS-CoV-2. The adsorption was fast and enables one to remove the drug in one hour. The highest adsorption capacity was noted for biochar obtained from biogas production (14 mg/g). The process of NTZ adsorption was governed by chemisorption (k2 = 0.2371 g/mg min). The presence of inorganic ions had a detrimental effect on adsorption (Cl−, NO3− in 20–30%) and carbonates were the most effective in hindering the process (60%). The environmentally relevant concentration of DOM (10 mg/L) did not affect the process. The model studies were supported by the results with a real wastewater effluent (15% reduction). Depending on the applied feedstock, various models described nitazoxanide adsorption onto tested biochars. In summary, the application of carbonaceous adsorbents in the pelletized form is effective in nitazoxanide adsorption. Full article
(This article belongs to the Special Issue Research on Green Adsorbents)
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15 pages, 4665 KiB  
Article
Corn Cobs’ Biochar as Green Host of Salt Hydrates for Enhancing the Water Sorption Kinetics in Thermochemical Heat Storage Systems
by Minh Hoang Nguyen, Mohamed Zbair, Patrick Dutournié, Lionel Limousy and Simona Bennici
Molecules 2023, 28(14), 5381; https://doi.org/10.3390/molecules28145381 - 13 Jul 2023
Viewed by 806
Abstract
Heat storage technologies are essential for increasing the use of solar energy in the household sector. Their development can be achieved by designing new storage materials; one way is to impregnate a porous matrix with hygroscopic salts. In this article, the possibility of [...] Read more.
Heat storage technologies are essential for increasing the use of solar energy in the household sector. Their development can be achieved by designing new storage materials; one way is to impregnate a porous matrix with hygroscopic salts. In this article, the possibility of using biochar-based composite sorbents to develop promising new heat storage materials for efficient thermal storage is explored. Biochar-based composites with defined salt loadings (5, 10, 15, and 20%) were produced by impregnating MgSO4 into a biochar matrix derived from corn cobs. The new materials demonstrated a high water sorption capacity of 0.24 g/g (20MgCC). After six successive charging-discharging cycles (dehydration/dehydration cycles), only a negligible variation of the heat released and the water uptake was measured, confirming the absence of deactivation of 20MgCC upon cycling. The new 20MgCC composite showed an energy storage density of 635 J/g (Tads = 30 °C and RH = 60%), higher than that of other composites containing a similar amount of hydrate salt. The macroporous nature of this biochar increases the available surface for salt deposition. During the hydration step, the water molecules effectively diffuse through a homogeneous layer of salt, as described by the intra-particle model applied in this work. The new efficient biochar-based composites open a low-carbon path for the production of sustainable thermal energy storage materials and applications. Full article
(This article belongs to the Special Issue Research on Green Adsorbents)
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31 pages, 4156 KiB  
Article
Synthesis, Characterization, and NH3-SCR Catalytic Performance of Fe-Modified MCM-36 Intercalated with Various Pillars
by Agnieszka Szymaszek-Wawryca, Urbano Díaz, Bogdan Samojeden and Monika Motak
Molecules 2023, 28(13), 4960; https://doi.org/10.3390/molecules28134960 - 24 Jun 2023
Cited by 1 | Viewed by 930
Abstract
Two series of MCM-36 zeolites intercalated with various pillars and modified with iron were synthesized, analyzed with respect to their physicochemical properties, and tested as catalysts for the NH3-SCR process. It was found that the characteristic MWW morphology of MCM-36 can [...] Read more.
Two series of MCM-36 zeolites intercalated with various pillars and modified with iron were synthesized, analyzed with respect to their physicochemical properties, and tested as catalysts for the NH3-SCR process. It was found that the characteristic MWW morphology of MCM-36 can be obtained successfully using silica, alumina, and iron oxide as pillars. Additionally, one-pot synthesis of the material with iron resulted in the incorporation of monomeric Fe3+ species into the framework positions. The results of catalytic tests revealed that the one-pot synthesized sample intercalated with silica and alumina was the most efficient catalyst of NO reduction, exhibiting ca. 100% activity at 250 °C. The outstanding performance of the material was attributed to the abundance of Lewis acid sites and the beneficial influence of alumina on the distribution of iron species in the zeolite. In contrast, the active centers originating from the Fe2O3 pillars improved the NO conversion in the high-temperature range. Nevertheless, the aggregated particles of the metal oxide limited the access of the reacting molecules to the inner structure of the catalyst, which affected the overall activity and promoted the formation of N2O above 300 °C. Full article
(This article belongs to the Special Issue Research on Green Adsorbents)
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19 pages, 3459 KiB  
Article
Assessment of the Porous Structure and Surface Chemistry of Activated Biocarbons Used for Methylene Blue Adsorption
by Barbara Charmas, Magdalena Zięzio and Katarzyna Jedynak
Molecules 2023, 28(13), 4922; https://doi.org/10.3390/molecules28134922 - 22 Jun 2023
Cited by 11 | Viewed by 1234
Abstract
In the presented research, activated carbons from wheat bran were obtained as a result of pyrolysis and physical activation (CO2 or/and steam). In addition, the obtained materials were subjected to additional modification with superheated steam using the microwave radiation as an energy [...] Read more.
In the presented research, activated carbons from wheat bran were obtained as a result of pyrolysis and physical activation (CO2 or/and steam). In addition, the obtained materials were subjected to additional modification with superheated steam using the microwave radiation as an energy source. The detailed materials characterization was performed using low-temperature nitrogen adsorption/desorption, Raman spectroscopy, X-ray diffraction, thermal analysis (TG), Boehm’s titration, point of zero charge (pHpzc), scanning electron microscopy (SEM) and FT-IR/ATR methods. Moreover, the sorption capacity towards methylene blue (MB) was determined. The activated carbons were characterized with a well-developed surface and pore structure (SBET = 339.6–594.0 m2/g; Vp = 0.157–0.356 cm3/g). Activation in the presence of steam and additional modification with microwave radiation resulted in much better development of the porous structure (SBET = 600.4 m2/g; Vp = 0.380 cm3/g). The materials were shown to possess amorphous structure and thermal stability up to the temperatures of ~450–500 °C. They have good adsorption capacity towards MB varying from 150 mg/g to 241 mg/g depending on activation manner. The adsorption can be described by the pseudo-second order model (R2 = 0.99) and fitted to the Langmuir isotherm. Full article
(This article belongs to the Special Issue Research on Green Adsorbents)
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16 pages, 3899 KiB  
Article
Selected Textural and Electrochemical Properties of Nanocomposite Fillers Based on the Mixture of Rose Clay/Hydroxyapatite/Nanosilica for Cosmetic Applications
by Victoria Paientko, Olena I. Oranska, Volodymyr M. Gun’ko and Ewa Skwarek
Molecules 2023, 28(12), 4820; https://doi.org/10.3390/molecules28124820 - 16 Jun 2023
Cited by 3 | Viewed by 877
Abstract
In order to improve the properties and characteristics of rose clay composites with acai, hydroxyapatite (HA), and nanosilica, the systems were mechanically treated. This treatment provides the preparation of better nanostructured composites with natural and synthetic nanomaterials with improved properties. The materials were [...] Read more.
In order to improve the properties and characteristics of rose clay composites with acai, hydroxyapatite (HA), and nanosilica, the systems were mechanically treated. This treatment provides the preparation of better nanostructured composites with natural and synthetic nanomaterials with improved properties. The materials were characterized using XRD, nitrogen adsorption and desorption, particle sizing, zeta potential, and surface charge density measurements. For the systems tested in the aqueous media, the pH value of the point of zero charge (pHPZC) ranges from 8 to 9.9. However, the isoelectric point (pHIEP) values for all composites are below pH 2. This large difference between pHPZC and pHIEP is due to the complexity of the electrical double layer (EDL) and the relation of these points to different layers of the EDL. The tested samples as composite/electrolyte solutions are colloidally unstable. The toxicity level of the ingredients and release of anthocyanins as bioactive substances from acai in the composites were determined. The composites demonstrate an enhanced release of anthocyanins. There are some regularities in the characteristics depending on the type of components, morphology, and textural features of solids. The morphological, electrochemical, and structural characteristics of the components have changed in composites. The release of anthocyanins is greater for the composites characterized by minimal confined space effects in comparison with rose clay alone. The morphological, electrochemical, and structural characteristics allow us to expect high efficiency of composites as bioactive systems that are interesting for practical applications in cosmetics. Full article
(This article belongs to the Special Issue Research on Green Adsorbents)
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Review

Jump to: Editorial, Research

29 pages, 20449 KiB  
Review
Controversial Issues Related to Dye Adsorption on Clay Minerals: A Critical Review
by Juraj Bujdák
Molecules 2023, 28(19), 6951; https://doi.org/10.3390/molecules28196951 - 06 Oct 2023
Cited by 3 | Viewed by 1600
Abstract
This critical review points out the most serious and problematic issues to be found in the literature on the adsorption of dyes on clay minerals. The introduction draws attention to the fundamental problems, namely the insufficient characterization of adsorbents, the influence of impurities [...] Read more.
This critical review points out the most serious and problematic issues to be found in the literature on the adsorption of dyes on clay minerals. The introduction draws attention to the fundamental problems, namely the insufficient characterization of adsorbents, the influence of impurities on the adsorption of dyes, and the choice of inappropriate models for the description of the very complex systems that clay minerals and their systems represent. This paper discusses the main processes accompanying adsorption in colloidal systems of clay minerals. The relationship between the stability of the colloidal systems and the adsorption of dye molecules is analyzed. The usual methodological procedures for determining and evaluating the adsorption of dyes are critically reviewed. A brief overview and examples of modified clay minerals and complex systems for the adsorption of organic dyes are summarized. This review is a guide for avoiding some faults in characterizing the adsorption of organic dyes on clay minerals, to improve the procedure for determining adsorption, to evaluate results correctly, and to find an appropriate theoretical interpretation. The main message of this article is a critical analysis of the current state of the research in this field, but at the same time, it is a guide on how to avoid the most common problems and mistakes. Full article
(This article belongs to the Special Issue Research on Green Adsorbents)
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