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12 pages, 3494 KiB

Open AccessFeature PaperArticle

Computational Study of the Adsorption of Phosphates as Wastewater Pollutant Molecules on Faujasites

by Luis Fernando Capa-Cobos, Ximena Jaramillo-Fierro and Silvia González

Processes 2021, 9(10), 1821; https://doi.org/10.3390/pr9101821 - 14 Oct 2021

Cited by 9 | Viewed by 2557

Abstract

The adsorption of sodium dihydrogen phosphate (NaH₂PO₄) onto X- and Y-type faujasite zeolites was computationally studied using the Density Functional Theory (DFT) method. The structures were modeled using the Materials Studio software. The Si/Al ratios for the X- and [...] Read more.

The adsorption of sodium dihydrogen phosphate (NaH₂PO₄) onto X- and Y-type faujasite zeolites was computationally studied using the Density Functional Theory (DFT) method. The structures were modeled using the Materials Studio software. The Si/Al ratios for the X- and Y-type zeolite models were 1.2 and 2.5, respectively. The central pore of the zeolite provided a more favorable coordination for adsorbing NaH₂PO₄. Full molecular optimization and adsorption energy calculations were performed using the VASP code. The adsorption was more effective on zeolite Y, with an adsorption energy of 161 kJ/mol, compared to the zeolite X system, with an adsorption energy of 31.64 kJ/mol. This calculated value for X-type faujasite was found in the interval of the adsorption energy of H₂PO₄⁻ on hydrated Fe oxide (94.4 kJ/mol) and modified polyether sulfone (22.5 kJ/mol), and the calculated adsorption energy of the molecule on Y-type faujasite coincides with the reported value for this adsorbate on Mg/Ca-modified biochar structures. The molecular conformations of the adsorbate on the two studied models are very different, so the difference between the adsorption energy values of each type of zeolite model is comprehensible. On the one hand, the oxygen atoms of the molecule formed a bidentate complex with the hydrogen atoms of the pore in the X-type faujasite model, and the O-H distance was 1.5 Ǻ. On the other hand, an adsorbed oxygen atom of the phosphate was placed on a hydrogen atom at site II of the Y-type faujasite zeolite, and two of the hydrogen atoms of the phosphate were placed on the oxygen atoms. The Bader analysis results indicated that the negative charge of the phosphate anions was delocalized on the zeolites protons. The hydroxy groups of the phosphate form bonds between their hydrogen atoms and the oxygen atoms of the zeolite porous structure; therefore, we concluded that these sites have an alkaline character. The aim of this study was to include a computational analysis of possible phosphate adsorption mechanisms in faujasite zeolites that can be confirmed by experimental tests, and hence contribute to the generation of new technologies for capturing pollutant molecules in wastewater. The results are in agreement with the experimental information concerning the influence of pH on the adsorption activity of phosphate adsorption on zeolites. Full article

(This article belongs to the Special Issue Advances in Nanomaterials for Selective Adsorption)

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15 pages, 1860 KiB

Open AccessFeature PaperArticle

An Insight into the Separation of 1,2-Propanediol, Ethylene Glycol, Acetol and Glycerol from an Aqueous Solution by Adsorption on Activated Carbon

by Jorge Fortea, Lucía García, Joaquín Ruiz, Miriam Oliva and Jesús Arauzo

Processes 2021, 9(8), 1438; https://doi.org/10.3390/pr9081438 - 19 Aug 2021

Cited by 2 | Viewed by 2643

Abstract

Glycerol conversion processes such as aqueous phase reforming and hydrogenolysis generate value-added compounds highly diluted in water. Because distillation is a high energy demand separation step, adsorption could be an attractive alternative to recover these chemicals. Adsorption isotherms of 1,2-propanediol, acetol, ethylene glycol [...] Read more.

Glycerol conversion processes such as aqueous phase reforming and hydrogenolysis generate value-added compounds highly diluted in water. Because distillation is a high energy demand separation step, adsorption could be an attractive alternative to recover these chemicals. Adsorption isotherms of 1,2-propanediol, acetol, ethylene glycol and glycerol onto activated carbon were determined by batch adsorption experiments. These isotherms were fitted slightly better to the Freundlich equation than to the Langmuir equation. Acetol is the compound with the highest adsorption at concentrations smaller than 1 M. Properties of the adsorbate such as the −OH group number, chain length, molecular size and dipole moment, besides characteristics of the adsorbent such as the surface area, oxygen and ash content, are considered to explain the observed results. Moreover, adsorption experiments were performed with mixtures of compounds and it was determined that the molar amount adsorbed is less than predicted from the adsorption isotherms of the individual compounds treated separately. In addition, the influence of the activated carbon thermal pre-treatment temperature on the adsorption capacity has been studied, the optimum being 800 °C. An analysis of the influence of the activated carbon characteristics showed that the most important parameters are the total pore volume and the ash content. Full article

(This article belongs to the Special Issue Advances in Nanomaterials for Selective Adsorption)

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23 pages, 2383 KiB

Open AccessFeature PaperArticle

Nano-Adsorbents for Cobalt Removal from Wastewater: A Bibliometric Analysis of Research Articles Indexed in the Scopus Database

by Charikleia Prochaska and George Gallios

Processes 2021, 9(7), 1177; https://doi.org/10.3390/pr9071177 - 6 Jul 2021

Cited by 13 | Viewed by 3822

Abstract

In this study, a combined technique of bibliometric and social network analysis was applied on research articles, related to the application of nano-adsorbents for cobalt removal from wastewater, published in Scopus database up to 2020. The results revealed that the first relative research [...] Read more.

In this study, a combined technique of bibliometric and social network analysis was applied on research articles, related to the application of nano-adsorbents for cobalt removal from wastewater, published in Scopus database up to 2020. The results revealed that the first relative research article appeared in the Scopus database in the year 2002. The total output of research articles reached 214 in the year 2020. Published research articles of the years 2014–2020, added up to 83.6% of total articles. King Saud University of Saudi Arabia, Chinese Academy of Science, and LUT University of Finland were found to serve as the gatekeepers who control information flows in the network of the most prolific institutions, while cooperation between China, Saudi Arabia, and United States was also identified. On average, the most prolific authors cooperated with five others, while the top 10 cited publications appeared to represent a sparse and weakly interconnected network of co-authors. Graphene oxide was the most prominent nano-adsorbent among the top 10 cited publications, and their respective co-citations network visualization helped in capturing the value of certain citations to the evolution of the research on the topic, putting thus scientific work impact assessment to a different perspective. Full article

(This article belongs to the Special Issue Advances in Nanomaterials for Selective Adsorption)

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8 pages, 592 KiB

Open AccessArticle

Stability of Plasma Protein Composition in Dried Blood Spot during Storage

by Kristina A. Malsagova, Alexander A. Stepanov, Arthur T. Kopylov, Dmitry V. Enikeev, Natalia V. Potoldykova, Alexander A. Izotov, Tatyana V. Butkova and Anna L. Kaysheva

Processes 2020, 8(11), 1500; https://doi.org/10.3390/pr8111500 - 20 Nov 2020

Cited by 5 | Viewed by 3616

Abstract

Dried blood spot (DBS) technology has become a promising utility for the transportation and storage of biological fluids aimed for the subsequent clinical analysis. The basis of the DBS method is the adsorption of the components of a biological sample onto the surface [...] Read more.

Dried blood spot (DBS) technology has become a promising utility for the transportation and storage of biological fluids aimed for the subsequent clinical analysis. The basis of the DBS method is the adsorption of the components of a biological sample onto the surface of a membrane carrier, followed by drying. After drying, the molecular components of the biosample (nucleic acids, proteins, and metabolites) can be analyzed using modern omics, immunological, or genomic methods. In this work, we investigated the safety of proteins on a membrane carrier by tryptic components over time and at different temperatures (+4, 0, 25 °C) and storage (0, 7, 14, and 35 days). It was shown that the choice of a protocol for preliminary sample preparation for subsequent analytical molecular measurements affects the quality of the experimental results. The protocol for preliminary preparation of a biosample directly in a membrane carrier is preferable compared to the protocol with an additional stage of elution of molecular components before the sample preparation procedures. It was revealed that the composition of biosamples remains stable at a temperature of −20 and +4 °C for 35 days of storage, and at +25 °C for 14 days. Full article

(This article belongs to the Special Issue Advances in Nanomaterials for Selective Adsorption)

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12 pages, 1751 KiB

Open AccessArticle

Simultaneous Adsorption of 4,6-Dimethyldibenzothiophene and Quinoline over Nickel and Boron Modified Gamma-Al₂O₃ Adsorbent

by Esteban Camu, Barbara Pasten, Camila Matus, Fernanda Ramirez, Juan Ojeda, Gonzalo Aguila and Patricio Baeza

Processes 2020, 8(4), 419; https://doi.org/10.3390/pr8040419 - 2 Apr 2020

Cited by 4 | Viewed by 2895

Abstract

The simultaneous adsorption of quinoline and 4,6-dimethyldibenzothiophene over adsorbents, based on alumina modified with boron and nickel under ambient temperature and pressure, was studied. The adsorbents were characterized by BET specific surface area, a potentiometric method for the determination of acid strength, electrophoretic [...] Read more.

The simultaneous adsorption of quinoline and 4,6-dimethyldibenzothiophene over adsorbents, based on alumina modified with boron and nickel under ambient temperature and pressure, was studied. The adsorbents were characterized by BET specific surface area, a potentiometric method for the determination of acid strength, electrophoretic migration, and X-ray diffraction. The results showed that the adsorbent containing nickel had better adsorption capacity than the adsorbent modified with nickel and boron, which was attributed to its greater acidity and ability to generate π-complexation between the adsorbent and the molecules. In terms of selectivity, quinoline was more adsorbed than 4,6-dimethyldibenzothiophene in all systems, due to the basic nature of quinoline. The experimental data in all cases were adjusted by three kinetic models (Yoon–Nelson, Yan and Thomas), and the regression coefficients in all models were close to one. Finally, the values of the kinetic constant obtained by the Thomas model were used to relate the adsorption capacity results. Full article

(This article belongs to the Special Issue Advances in Nanomaterials for Selective Adsorption)

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16 pages, 3681 KiB

Open AccessArticle

Preparation of Nano-Porous Carbon-Silica Composites and Its Adsorption Capacity to Volatile Organic Compounds

by Lipei Fu, Jiahui Zhu, Weiqiu Huang, Jie Fang, Xianhang Sun, Xinya Wang and Kaili Liao

Processes 2020, 8(3), 372; https://doi.org/10.3390/pr8030372 - 23 Mar 2020

Cited by 29 | Viewed by 5531

Abstract

Carbon-silica composites with nanoporous structures were synthesized for the adsorption of volatile organic compounds (VOCs), taking tetraethyl orthosilicate (TEOS) as the silicon source and activated carbon powder as the carbon source. The preparation conditions were as follows: the pH of the reaction system [...] Read more.

Carbon-silica composites with nanoporous structures were synthesized for the adsorption of volatile organic compounds (VOCs), taking tetraethyl orthosilicate (TEOS) as the silicon source and activated carbon powder as the carbon source. The preparation conditions were as follows: the pH of the reaction system was 5.5, the hydrophobic modification time was 50 h, and the dosage of activated carbon was 2 wt%. Infrared spectrum analysis showed that the activated carbon was dispersed in the pores of aerogel to form the carbon-silica composites material. The static adsorption experiments, dynamic adsorption-desorption experiments, and regeneration experiments show that the prepared carbon-silica composites have microporous and mesoporous structures, the adsorption capacity for n-hexane is better than that of conventional hydrophobic silica gel, and the desorption performance is better than that of activated carbon. It still has a high retention rate of adsorption capacity after multiple adsorption-desorption cycles. The prepared carbon-silica composites material has good industrial application prospects in oil vapor recovery, providing a new alternative for solving organic waste gas pollution. Full article

(This article belongs to the Special Issue Advances in Nanomaterials for Selective Adsorption)

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Review

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26 pages, 3060 KiB

Open AccessFeature PaperEditor’s ChoiceReview

The Dark Side of Platinum Based Cytostatic Drugs: From Detection to Removal

by Yessica Roque-Diaz, Martina Sanadar, Dong Han, Montserrat López-Mesas, Manuel Valiente, Marilena Tolazzi, Andrea Melchior and Daniele Veclani

Processes 2021, 9(11), 1873; https://doi.org/10.3390/pr9111873 - 21 Oct 2021

Cited by 17 | Viewed by 4760

Abstract

The uncontrolled release of pharmaceutical drugs into the environment raised serious concerns in the last decades as they can potentially exert adverse effects on living organisms even at the low concentrations at which they are typically found. Among them, platinum based cytostatic drugs [...] Read more.

The uncontrolled release of pharmaceutical drugs into the environment raised serious concerns in the last decades as they can potentially exert adverse effects on living organisms even at the low concentrations at which they are typically found. Among them, platinum based cytostatic drugs (Pt CDs) are among the most used drugs in cancer treatments which are administered via intravenous infusion and released partially intact or as transformation products. In this review, the studies on environmental occurrence, transformation, potential ecotoxicity, and possible treatment for the removal of platinum cytostatic compounds are revised. The analysis of the literature highlighted the generally low total platinum concentration values (from a few tens of ng L⁻¹ to a few hundred μg L⁻¹) found in hospital effluents. Additionally, several studies highlighted how hospitals are sources of a minor fraction of the total Pt CDs found in the environment due to the slow excretion rate which is longer than the usual treatment durations. Only some data about the impact of the exposure to low levels of Pt CDs on the health of flora and fauna are present in literature. In some cases, adverse effects have been shown to occur in living organisms, even at low concentrations. Further ecotoxicity data are needed to support or exclude their chronic effects on the ecosystem. Finally, fundamental understanding is required on the platinum drugs removal by MBR, AOPs, technologies, and adsorption. Full article

(This article belongs to the Special Issue Advances in Nanomaterials for Selective Adsorption)

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39 pages, 4815 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Molecular Interpretation of Pharmaceuticals’ Adsorption on Carbon Nanomaterials: Theory Meets Experiments

by Daniele Veclani, Marilena Tolazzi and Andrea Melchior

Processes 2020, 8(6), 642; https://doi.org/10.3390/pr8060642 - 27 May 2020

Cited by 36 | Viewed by 6248

Abstract

The ability of carbon-based nanomaterials (CNM) to interact with a variety of pharmaceutical drugs can be exploited in many applications. In particular, they have been studied both as carriers for in vivo drug delivery and as sorbents for the treatment of water polluted [...] Read more.

The ability of carbon-based nanomaterials (CNM) to interact with a variety of pharmaceutical drugs can be exploited in many applications. In particular, they have been studied both as carriers for in vivo drug delivery and as sorbents for the treatment of water polluted by pharmaceuticals. In recent years, the large number of experimental studies was also assisted by computational work as a tool to provide understanding at molecular level of structural and thermodynamic aspects of adsorption processes. Quantum mechanical methods, especially based on density functional theory (DFT) and classical molecular dynamics (MD) simulations were mainly applied to study adsorption/release of various drugs. This review aims to compare results obtained by theory and experiments, focusing on the adsorption of three classes of compounds: (i) simple organic model molecules; (ii) antimicrobials; (iii) cytostatics. Generally, a good agreement between experimental data (e.g. energies of adsorption, spectroscopic properties, adsorption isotherms, type of interactions, emerged from this review) and theoretical results can be reached, provided that a selection of the correct level of theory is performed. Computational studies are shown to be a valuable tool for investigating such systems and ultimately provide useful insights to guide CNMs materials development and design. Full article

(This article belongs to the Special Issue Advances in Nanomaterials for Selective Adsorption)

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