Materials

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2 pages, 169 KiB

Open AccessEditorial

Editorial for the Special Issue on “Fundamentals of Adsorbents–Synthesis, Characterization, Properties, and Application”

by Durga Parajuli

Materials 2022, 15(6), 2122; https://doi.org/10.3390/ma15062122 - 14 Mar 2022

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Abstract

This Special Issue covers the widely studied topic of “Adsorbents”, materials that are known to uptake ions and molecules from water or air [...] Full article

(This article belongs to the Special Issue Fundamentals of Adsorbents–Synthesis, Characterisation, Properties, and Application)

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13 pages, 2795 KiB

Open AccessArticle

Selective Adsorption of Potassium in Seawater by CoHCF Thin Film Electrode and Its Electrochemical Desorption/Regeneration

by Nan Zhang, Tohru Kawamoto, Hiroshi Watanabe, Yong Jiang, Zhenya Zhang, Zhongfang Lei and Durga Parajuli

Materials 2021, 14(13), 3592; https://doi.org/10.3390/ma14133592 - 27 Jun 2021

Cited by 1 | Viewed by 2267

Abstract

Cobalt Hexacyanoferrate (CoHCF) was tested for the selective uptake of K from seawater and the electrochemical method was adopted for the desorption and regeneration of the material. Powder form CoHCF could adsorb about 6.5 mmol/g of K from the seawater. For the ease [...] Read more.

Cobalt Hexacyanoferrate (CoHCF) was tested for the selective uptake of K from seawater and the electrochemical method was adopted for the desorption and regeneration of the material. Powder form CoHCF could adsorb about 6.5 mmol/g of K from the seawater. For the ease of the electrochemical desorption and regeneration, CoHCF thin film was coated onto the Indium Tin Oxide (ITO) glass to obtain a CoHCF electrode. K adsorption kinetics on CoHCF thin film was found to be well fitted with the intraparticle diffusion model, which was a two-step process. Five consecutive adsorption-desorption-regeneration cycles were carried out to know the gradual decrease in the adsorption capacity owing to changes in the redox states of two metals, Co and Fe, in the material. Fourier Transform Infrared Spectroscopy (FT-IR) and Ultraviolet-Visible (UV-Vis) measurement results corresponded to the color change of CoHCF thin film, indicating the valence change of transition metals and the exchange of alkali metal cations happened on the CoHCF at different operation stages. In order to elucidate the reaction mechanism, composition of the material was analysis in the following steps: adsorption, desorption, and regeneration. It was proved that the system based on CoHCF thin film modified electrode had the potential of recovering potassium from seawater. Full article

(This article belongs to the Special Issue Fundamentals of Adsorbents–Synthesis, Characterisation, Properties, and Application)

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10 pages, 1274 KiB

Open AccessArticle

LDPE and HDPE Microplastics Differently Affect the Transport of Tetracycline in Saturated Porous Media

by Enzhu Hu, Hongbo Yuan, Yichun Du and Xijuan Chen

Materials 2021, 14(7), 1757; https://doi.org/10.3390/ma14071757 - 02 Apr 2021

Cited by 9 | Viewed by 3105

Abstract

The accumulation of microplastics (MPs) in soil and sediments may influence the penetration of contaminants into subsurface environments. However, little attention has been paid to comparing the different roles of two common polyethylene (PE) types—low-density polyethylene (LDPE) and high-density polyethylene (HDPE). In this [...] Read more.

The accumulation of microplastics (MPs) in soil and sediments may influence the penetration of contaminants into subsurface environments. However, little attention has been paid to comparing the different roles of two common polyethylene (PE) types—low-density polyethylene (LDPE) and high-density polyethylene (HDPE). In this study, the transport behaviors of tetracycline in saturated quartz sand columns in the presence and absence of these two MPs were investigated, respectively. The results showed that both types of PE MPs restrained the mobility of tetracycline at neutral conditions, while such detrimental effects were weak at acid and alkaline conditions. The degree of nonequilibrium adsorption was higher, and tetracycline transferred easier to the kinetic site for the existence of LDPE than of HDPE. The increased roughness and Brunauer-Emmett-Teller (BET) surface areas, more negative zeta potentials and the formation of oxygen function groups on the surface of MPs after UV-weathering intensified the retardation of tetracycline transport. This study revealed that the PE type and weathering should be taken into account in risk assessment, along with the solution chemistry. Full article

(This article belongs to the Special Issue Fundamentals of Adsorbents–Synthesis, Characterisation, Properties, and Application)

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19 pages, 4564 KiB

Open AccessArticle

Studies on Preparation, Characterization and Application of Porous Functionalized Glycidyl Methacrylate-Based Microspheres

by Przemysław Pączkowski and Barbara Gawdzik

Materials 2021, 14(6), 1438; https://doi.org/10.3390/ma14061438 - 16 Mar 2021

Cited by 11 | Viewed by 2296

Abstract

A one-step swelling and polymerization technique was used in the synthesis of porous glycidyl methacrylate (GMA) and ethylene glycol dimethacrylate (EGDMA) monodisperse polymeric microspheres. The polystyrene (PS) seed obtained in the dispersion polymerization was used as a shape template. The presence of epoxide [...] Read more.

A one-step swelling and polymerization technique was used in the synthesis of porous glycidyl methacrylate (GMA) and ethylene glycol dimethacrylate (EGDMA) monodisperse polymeric microspheres. The polystyrene (PS) seed obtained in the dispersion polymerization was used as a shape template. The presence of epoxide rings in the chemical structure of microspheres enables their post-polymerization chemical modifications involving: the Diels-Alder reaction with sodium cyclopentadienide and maleic anhydride, the reaction with 4,4′-(bismaleimido)diphenylmethane, and the thiol-Michael reaction with methacryloyl chloride and 2-mercaptopropionic acid. Changing the reaction mixture composition—the amounts of crosslinking monomer and PS seed as well as the type and concentration of porogen porous microspheres of different porous structures were obtained. Their porous structures were characterized in the dry and swollen states. The copolymers obtained from the equimolar monomers mixture modified in the above way were applied as the column packing materials and tested in the reverse-phase HPLC (High-Performance Liquid Chromatography). A few factors influencing morphology and porous structure of microspheres were studied. Full article

(This article belongs to the Special Issue Fundamentals of Adsorbents–Synthesis, Characterisation, Properties, and Application)

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20 pages, 5093 KiB

Open AccessArticle

Activation of Rubber-Seed Shell Waste by Malic Acid as Potential CO₂ Removal: Isotherm and Kinetics Studies

by Azry Borhan and Suzana Yusuf

Materials 2020, 13(21), 4970; https://doi.org/10.3390/ma13214970 - 04 Nov 2020

Cited by 17 | Viewed by 2246

Abstract

Carbon dioxide (CO₂) has been deemed a significant contributor to the climate crisis and has an impact on environmental systems. Adsorption is widely used among other technologies for carbon capture because of its many benefits. As a starting material for the [...] Read more.

Carbon dioxide (CO₂) has been deemed a significant contributor to the climate crisis and has an impact on environmental systems. Adsorption is widely used among other technologies for carbon capture because of its many benefits. As a starting material for the production of activated carbon (AC) by chemical activation using malic acid due to its biodegradable and non-toxic properties, rubber seed shell (RSS) was used as agricultural waste from rubber farming. Sample A6, which was carbonized for 120 min at a temperature of 600 °C and impregnated at a ratio of 1:2, was identified to achieve the highest surface area of 938.61 m²/g with micropore diameter of 1.368 nm, respectively. Using the fixed volumetric approach measured at 25, 50, and 100 °C, the maximum CO₂ adsorption capability reported is 59.73 cm³/g of adsorbent. Using the pseudo-first order of Lagergren, the pseudo-second order and the Elovich model, experimental data is modeled. It appears that, based on the correlation coefficient, the pseudo-first order model is aligned with the experimental findings. Furthermore, the activation energy of under 40 kJ/mol indicated a physical adsorption occurs, indicating that the RSS chemically activated with malic acid is a fascinating source of CO₂ removal requirements. Full article

(This article belongs to the Special Issue Fundamentals of Adsorbents–Synthesis, Characterisation, Properties, and Application)

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17 pages, 3759 KiB

Open AccessArticle

Surface Complexation Models of Pertechnetate on Biochar/Montmorillonite Composite—Batch and Dynamic Sorption Study

by Martin Daňo, Eva Viglašová, Michal Galamboš, Karel Štamberg and Jan Kujan

Materials 2020, 13(14), 3108; https://doi.org/10.3390/ma13143108 - 12 Jul 2020

Cited by 19 | Viewed by 2060

Abstract

The study summarizes the results of monitoring the properties of two types of sorbents, BC1 (biochar sample 1) and BC2a (biochar sample 2), prepared by pyrolysis of bamboo biomass (BC1) and as its composite with montmorillonite K10 (BC2a). The main goal was to [...] Read more.

The study summarizes the results of monitoring the properties of two types of sorbents, BC1 (biochar sample 1) and BC2a (biochar sample 2), prepared by pyrolysis of bamboo biomass (BC1) and as its composite with montmorillonite K10 (BC2a). The main goal was to study their applicability to the Tc (VII) separation from liquid wastes, using NH₄ReO₄ as a carrier. The research was focused on determining the sorbents surface properties (by XRF (X-ray fluorescence) method and potentiometric titration in order to determine the properties of surface groups—Chemical Equilibrium Model (CEM) and Ion Exchange Model (IExM) models were applied here). As well as monitoring Tc (VII) (+Re(VII)) sorption, especially to determine equilibrium isotherm, the influence of pH and kinetics. The subject of research was also the dynamics of sorption, including its mathematical–physical modeling. Both sorbents have good properties against Tc (VII), however BC2a, due to the presence of montmorillonite, is more advantageous in this respect. It has a higher sorption capacity and faster kinetic investigation. An important finding is that the optimal pH is 2–3, which is related not only to the protonation of surface groups (they have a positive charge), but also to the negative form of the existence of Tc (VII) and Re (VII): TcO₄⁻ and ReO₄⁻. Full article

(This article belongs to the Special Issue Fundamentals of Adsorbents–Synthesis, Characterisation, Properties, and Application)

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16 pages, 2642 KiB

Open AccessArticle

Parametric Study on Microwave-Assisted Pyrolysis Combined KOH Activation of Oil Palm Male Flowers Derived Nanoporous Carbons

by Napat Kaewtrakulchai, Kajornsak Faungnawakij and Apiluck Eiad-Ua

Materials 2020, 13(12), 2876; https://doi.org/10.3390/ma13122876 - 26 Jun 2020

Cited by 13 | Viewed by 2379

Abstract

Oil palm male flowers (PMFs), an abundant agricultural waste from oil palm plantation in Thailand, have been utilized as an alternative precursor to develop nanoporous carbons (NPCs) via microwave-assisted pyrolysis combined potassium hydroxide (KOH) activation. The influences of relevant processing variables, such as [...] Read more.

Oil palm male flowers (PMFs), an abundant agricultural waste from oil palm plantation in Thailand, have been utilized as an alternative precursor to develop nanoporous carbons (NPCs) via microwave-assisted pyrolysis combined potassium hydroxide (KOH) activation. The influences of relevant processing variables, such as activating agent ratio, microwave power, and activation time on the specific pore characteristics, surface morphology, and surface chemistry of PMFs derived nanoporous carbons (PMFCs) have been investigated to explore the optimum preparation condition. The optimum condition under a microwave radiation power of 700 W, activation holding time of 6 min, and activating agent ratio of 2:1 obtained the PMFC with the highest Brunauer–Emmett–Teller (BET) surface area and total pore volume approximately of 991 m²/g and 0.49 cm³/g, composed of a carbon content of 74.56%. Meanwhile, PMFCs have a highly microporous structure of about 71.12%. Moreover, activating agent ratio and microwave radiation power indicated a significant influence on the surface characteristics of PMFCs. This study revealed the potential of oil palm male flowers for the NPCs’ production via microwave-assisted KOH activation with a short operating-time condition. Full article

(This article belongs to the Special Issue Fundamentals of Adsorbents–Synthesis, Characterisation, Properties, and Application)

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12 pages, 2470 KiB

Open AccessArticle

Utilization of Composts for Adsorption of Methylene Blue from Aqueous Solutions: Kinetics and Equilibrium Studies

by Remigio Paradelo, Khaled Al-Zawahreh and María Teresa Barral

Materials 2020, 13(9), 2179; https://doi.org/10.3390/ma13092179 - 09 May 2020

Cited by 9 | Viewed by 2096

Abstract

Utilization of composts as low-cost adsorbents is an important application in the field of environmental remediation, but these materials have not yet been extensively used for dye removal. In this work, we have studied the characteristics of adsorption of methylene blue onto two [...] Read more.

Utilization of composts as low-cost adsorbents is an important application in the field of environmental remediation, but these materials have not yet been extensively used for dye removal. In this work, we have studied the characteristics of adsorption of methylene blue onto two composts (a municipal solid waste compost and a pine bark compost). Kinetics and equilibrium batch experiments testing the influence of adsorbent particle size, solution pH and ionic strength were performed. Both composts have a high adsorption capacity for methylene blue, similar to other low-cost adsorbents. Kinetics of adsorption followed a pseudo-first-order model, with maximum adsorption reached after a contact time of two hours. Equilibrium adsorption followed a Langmuir model in general. Reduction of particle size only increased adsorption slightly for composted pine bark. Increase in ionic strength had no effect on adsorption by municipal solid waste compost, but increased adsorption by composted pine bark. Modification of pH between 5 and 7 did not influence adsorption in any case. Overall, the results suggest that electrostatic interaction between the cationic dye and the anionic functional groups in the composts is not the only mechanism involved in adsorption. In conclusion, the use of composts for dye removal is a likely application, in particular for those composts presenting limitations for agricultural use. Full article

(This article belongs to the Special Issue Fundamentals of Adsorbents–Synthesis, Characterisation, Properties, and Application)

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14 pages, 5614 KiB

Open AccessArticle

Feasibility Study on the Use of Recycled Polymers for Malathion Adsorption: Isotherms and Kinetic Modeling

by Jhonatan J. Hermosillo-Nevárez, Victoria Bustos-Terrones, Yaneth A. Bustos-Terrones, Perla Marysol Uriarte-Aceves and Jesus Gabriel Rangel-Peraza

Materials 2020, 13(8), 1824; https://doi.org/10.3390/ma13081824 - 12 Apr 2020

Cited by 7 | Viewed by 2258

Abstract

In this study, the use of Polyvinylchloride (PVC) and High Density Polystyrene (HDPS) was demonstrated as an alternative for the adsorption of Malathion. Adsorption kinetics and isotherms were used to compare three different adsorbent materials: PVC, HDPS, and activated carbon. The adsorption capacity [...] Read more.

In this study, the use of Polyvinylchloride (PVC) and High Density Polystyrene (HDPS) was demonstrated as an alternative for the adsorption of Malathion. Adsorption kinetics and isotherms were used to compare three different adsorbent materials: PVC, HDPS, and activated carbon. The adsorption capacity of PVC was three times higher than activated carbon, and a theoretical value of 96.15 mg of Malathion could be adsorbed when using only 1 g of PVC. A pseudo first-order rate constant of 1.98 (1/h) was achieved according to Lagergren kinetic model. The adsorption rate and capacity values obtained in the present study are very promising since with very little adsorbent material it is possible to obtain high removal efficiencies. Phosphorous and sulfur elements were identified through Energy Dispersive X-ray (EDX) analysis and evidenced the malathion adsorption on PVC. The characteristic spectrum of malathion was identified by the Fourier Transform Infrared (FTIR) Spectroscopy analysis. The Thermogravimetric and Differential Thermal Analysis (TG/DTA) suggested that the adsorption of malathion on the surface of the polymers was mainly determined by hydrogen bonds. Full article

(This article belongs to the Special Issue Fundamentals of Adsorbents–Synthesis, Characterisation, Properties, and Application)

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14 pages, 2569 KiB

Open AccessArticle

Improvement of Manganese Feroxyhyte’s Surface Charge with Exchangeable Ca Ions to Maximize Cd and Pb Uptake from Water

by Evgenios Kokkinos, Chasan Chousein, Konstantinos Simeonidis, Sandra Coles, Anastasios Zouboulis and Manassis Mitrakas

Materials 2020, 13(7), 1762; https://doi.org/10.3390/ma13071762 - 09 Apr 2020

Cited by 9 | Viewed by 1862

Abstract

The surface configuration of tetravalent manganese feroxyhyte (TMFx) was appropriately modified to achieve higher negative surface charge density and, hence, to improve its efficiency for the removal of dissolved Cd and Pb mostly cationic species from water at pH values commonly found in [...] Read more.

The surface configuration of tetravalent manganese feroxyhyte (TMFx) was appropriately modified to achieve higher negative surface charge density and, hence, to improve its efficiency for the removal of dissolved Cd and Pb mostly cationic species from water at pH values commonly found in surface or ground waters. This was succeeded by the favorable engagement of Ca²⁺ cations onto the surface of a mixed Mn-Fe oxy-hydroxide adsorbent during the preparation step, imitating an ion-exchange mechanism between H⁺ and Ca²⁺; therefore, the number of available negatively-charged adsorption sites was increased. Particularly, the calcium coverage can increase the deprotonated surface oxygen atoms, which can act as adsorption centers, as well as maintain them during the subsequent drying procedure. The developed Ca-modified adsorbent (denoted as TMFx-Ca) showed around 10% increase of negative surface charge density, reaching 2.0 mmol [H⁺]/g and enabling higher adsorption capacities for both Cd and Pb aquatic species, as was proved also by carrying out specific rapid small-scale column tests, and it complied with the corresponding strict drinking water regulation limits. The adsorption capacity values were found 6.8 μg·Cd/mg and 35.0 μg·Pb/mg, when the restructured TMFx-Ca adsorbent was used, i.e., higher than those recorded for the unmodified material. Full article

(This article belongs to the Special Issue Fundamentals of Adsorbents–Synthesis, Characterisation, Properties, and Application)

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