Research

16 pages, 4027 KiB

Open AccessArticle

Biosorption of Methylene Blue Dye Using Natural Biosorbents Made from Weeds

by Francisco Silva, Lorena Nascimento, Matheus Brito, Kleber da Silva, Waldomiro Paschoal and Roberto Fujiyama

Materials 2019, 12(15), 2486; https://doi.org/10.3390/ma12152486 - 05 Aug 2019

Cited by 63 | Viewed by 4144

Abstract

The purpose of this work is to make use of vegetables that, although widely found in nature, there are few applications. The weeds used here, Cyanthilium cinereum (L.) H. Rob (CCLHR) and Paspalum maritimum (PMT) found in the Amazon region of Belém state [...] Read more.

The purpose of this work is to make use of vegetables that, although widely found in nature, there are few applications. The weeds used here, Cyanthilium cinereum (L.) H. Rob (CCLHR) and Paspalum maritimum (PMT) found in the Amazon region of Belém state of Pará-Brazil, contribute to the problem of water contamination by the removal of the methylene blue dye through the biosorption process, taking advantage of other materials for economic viability and processing. The influences of parameters such as, biosorbent dose, contact time, and initial concentration of dye were examined. The characterizations were realized using SEM to verify the morphology of the material and spectroscopy in the FTIR region. As for the adsorption mechanism, the physical adsorption mechanism prevailed. The time required for the system to reach equilibrium for both biosorbents was from 50 min, following a kinetics described by the pseudo-second order model. The adsorption isotherm data for PMT were better adjusted to the Langmuir model and the biosorption capacity (

q_{m a x}

) value was (56.1798 mg/g). CCLHR was better adjusted to the Freundlich model and its maximum biosorption capacity was 76.3359 mg/g. Thus, these weed species are promising for the biosorption of methylene blue dye in effluents. Full article

(This article belongs to the Special Issue Porous Materials for Environmental Applications)

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8 pages, 5240 KiB

Open AccessArticle

Effect of High Pressure on the Reducibility and Dispersion of the Active Phase of Fischer–Tropsch Catalysts

by Simón Yunes, Miguel Ángel Vicente, Sophia A. Korili and Antonio Gil

Materials 2019, 12(12), 1915; https://doi.org/10.3390/ma12121915 - 13 Jun 2019

Cited by 3 | Viewed by 2417

Abstract

The effect of high pressure on the reducibility and dispersion of oxides of Co and Fe supported on γ-Al₂O₃, SiO₂, and TiO₂ has been studied. The catalysts, having a nominal metal content of 10 wt.%, were [...] Read more.

The effect of high pressure on the reducibility and dispersion of oxides of Co and Fe supported on γ-Al₂O₃, SiO₂, and TiO₂ has been studied. The catalysts, having a nominal metal content of 10 wt.%, were prepared by incipient wetness impregnation of previously calcined supports. After drying at 60 °C for 6 h and calcination at 500 °C for 4 h, the catalysts were reduced by hydrogen at two pressures, 1 and 25 bar. The metal reduction was studied by temperature-programmed reduction up to 750 °C at the two pressures, and the metal dispersion was measured by CO chemisorption at 25 °C, obtaining values between 1% and 8%. The physicochemical characterization of these materials was completed by means of chemical analysis, X-ray diffraction, N₂ adsorption-desorption at −196 °C and scanning electron microscopy. The high pressure lowered the reduction temperature of the metal oxides, improving their reducibility and dispersion. The metal reducibility increased from 42%, in the case of Fe/Al₂O₃ (1 bar), to 100%, in the case of Fe/TiO₂ (25 bar). Full article

(This article belongs to the Special Issue Porous Materials for Environmental Applications)

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11 pages, 2907 KiB

Open AccessArticle

CO Adsorption Performance of CuCl/Activated Carbon by Simultaneous Reduction–Dispersion of Mixed Cu(II) Salts

by Cailong Xue, Wenming Hao, Wenping Cheng, Jinghong Ma and Ruifeng Li

Materials 2019, 12(10), 1605; https://doi.org/10.3390/ma12101605 - 16 May 2019

Cited by 27 | Viewed by 4682

Abstract

CO is a toxic gas discharged as a byproduct in tail gases from different industrial flue gases, which needs to be taken care of urgently. In this study, a CuCl/AC adsorbent was made by a facile route of physically mixing CuCl₂ and [...] Read more.

CO is a toxic gas discharged as a byproduct in tail gases from different industrial flue gases, which needs to be taken care of urgently. In this study, a CuCl/AC adsorbent was made by a facile route of physically mixing CuCl₂ and Cu(HCOO)₂ powder with activated carbon (AC), followed by heating at 533 K under vacuum. The samples were characterized by X-ray powder diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), N₂ adsorption/desorption, and scanning electron microscopy (SEM). It was shown that Cu(II) can be completely reduced to Cu(I), and the monolayer dispersion threshold of CuCl on AC support is 4 mmol·g⁻¹ AC. The adsorption isotherms of CO, CO₂, CH₄, and N₂ on CuCl/AC adsorbents were measured by the volumetric method, and the CO/CO₂, CO/CH₄, and CO/N₂ selectivities of the adsorbents were predicted using ideal adsorbed solution theory (IAST). The obtained adsorbent displayed a high CO adsorption capacity, high CO/N₂, CO/CH₄, and CO/CO₂ selectivities, excellent ad/desorption cycle performance, rapid adsorption rate, and appropriate isosteric heat of adsorption, which made it a promising adsorbent for CO separation and purification. Full article

(This article belongs to the Special Issue Porous Materials for Environmental Applications)

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10 pages, 1648 KiB

Open AccessArticle

Combined Effect of Pressure and Carbon Dioxide Activation on Porous Structure of Lignite Chars

by Natalia Howaniec

Materials 2019, 12(8), 1326; https://doi.org/10.3390/ma12081326 - 23 Apr 2019

Cited by 9 | Viewed by 2719

Abstract

Lignite is an important natural resource with the application potential covering present and future energy systems, including conventional power plants and gasification systems. Lignite is also a valuable precursor for the production of porous materials of tailored properties for various environmental applications, including [...] Read more.

Lignite is an important natural resource with the application potential covering present and future energy systems, including conventional power plants and gasification systems. Lignite is also a valuable precursor for the production of porous materials of tailored properties for various environmental applications, including the removal of contaminants from gaseous or liquid media. Although the lignite-based activated carbons are commercially available, various approaches to produce carbon materials of desired properties are still being reported, covering temperature, partial oxidation and chemical activation effects on surface and structural properties of these materials. Limited data is, however, available on the effects of pressure as the activation parameter in shaping the porous structure of carbonaceous materials, in particularly lignite-derived. In the study presented the combined effect of carbon dioxide activation and pressure in the range of 1–3 MPa at the temperature of 800 °C on the development of porous structure of lignite chars was reported. The study was also focused on poor-quality resources valorization by using a relatively low calorific value, low volatiles and high ash content lignite as a carbon material precursor. The results showed that the application of pressure in carbon dioxide-activation process at 800 °C results in generation of chars of comparable or higher specific surface area than the carbon materials previously received with demineralization and carbon dioxide activation of lignite. They also proved that the combined pressure and carbon dioxide activation may be effectively applied in conversion of low quality lignite into valuable porous materials. Full article

(This article belongs to the Special Issue Porous Materials for Environmental Applications)

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17 pages, 6653 KiB

Open AccessArticle

Study of Catalytic Combustion of Chlorobenzene and Temperature Programmed Reactions over CrCeOx/AlFe Pillared Clay Catalysts

by Yingnan Qiu, Na Ye, Danna Situ, Shufeng Zuo and Xianqin Wang

Materials 2019, 12(5), 728; https://doi.org/10.3390/ma12050728 - 02 Mar 2019

Cited by 10 | Viewed by 2889

Abstract

In this study, both AlFe composite pillaring agents and AlFe pillared clays (AlFe-PILC) were synthesized via a facile process developed by our group, after which mixed Cr and Ce precursors were impregnated on AlFe-PILC. Catalytic combustion of organic pollutant chlorobenzene (CB) on CrCe/AlFe-PILC [...] Read more.

In this study, both AlFe composite pillaring agents and AlFe pillared clays (AlFe-PILC) were synthesized via a facile process developed by our group, after which mixed Cr and Ce precursors were impregnated on AlFe-PILC. Catalytic combustion of organic pollutant chlorobenzene (CB) on CrCe/AlFe-PILC catalysts were systematically studied. AlFe-PILC displayed very high thermal stability and large BET surface area (S_BET). After 4 h of calcination at 550 °C, the basal spacing (d₀₀₁) and S_BET of AlFe-PILC was still maintained at 1.91 nm and 318 m²/g, respectively. Large S_BET and d₀₀₁-value, along with the strong interaction between the carrier and active components, improved the adsorption/desorption of CB and O₂. When the desorption temperatures of CB and O₂ got closer to the CB combustion temperature, the CB conversion could be increased to a higher level. CB combustion on CrCe/AlFe-PILC catalyst was determined using a Langmuir–Hinshelwood mechanism. Adsorption/desorption/oxidation properties were critical to design highly efficient catalysts for CB degradation. Besides, CrCe/AlFe-PILC also displayed good durability for CB combustion, whether in a humid environment or in the presence of volatile organic compound (VOC), making the catalyst an excellent material for eliminating chlorinated VOCs. Full article

(This article belongs to the Special Issue Porous Materials for Environmental Applications)

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12 pages, 4310 KiB

Open AccessArticle

Development of a Zeolite A/LDH Composite for Simultaneous Cation and Anion Removal

by Breno Gustavo Porfírio Bezerra, Lindiane Bieseki, Djalma Ribeiro da Silva and Sibele Berenice Castellã Pergher

Materials 2019, 12(4), 661; https://doi.org/10.3390/ma12040661 - 22 Feb 2019

Cited by 8 | Viewed by 4314

Abstract

Wastewater from the oil industry is a major problem for aqueous environments due to its complexity and estimated volume of approximately 250 million barrels per day. The combination of these petroleum pollutants creates risks to human health, and their removal from the environment [...] Read more.

Wastewater from the oil industry is a major problem for aqueous environments due to its complexity and estimated volume of approximately 250 million barrels per day. The combination of these petroleum pollutants creates risks to human health, and their removal from the environment is considered a major problem in the world today. Thus, this work has the objective of studying the treatment of this type of effluent through the adsorption method using the following exchange materials: cationic, anionic, their combination by a sequential method, and a composite material. Zeolite A, a layered double hydroxide (LDH), and the new composite material formed by zeolite A and LDH structures were synthesized for this study. All were used for the simultaneous treatment of cations and anions in a complex sample such as water produced from petroleum production. The composite demonstrated an excellent ability to simultaneously remove cations and anions. The results obtained after the different treatment modes of the effluent using different materials varied from 85% to 100% for the removal of cations and from 56% to 99.7% for the removal of anions. Full article

(This article belongs to the Special Issue Porous Materials for Environmental Applications)

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15 pages, 2880 KiB

Open AccessArticle

Mesoscale Anisotropy in Porous Media Made of Clay Minerals. A Numerical Study Constrained by Experimental Data

by Thomas Dabat, Arnaud Mazurier, Fabien Hubert, Emmanuel Tertre, Brian Grégoire, Baptiste Dazas and Eric Ferrage

Materials 2018, 11(10), 1972; https://doi.org/10.3390/ma11101972 - 13 Oct 2018

Cited by 10 | Viewed by 3760

Abstract

The anisotropic properties of clay-rich porous media have significant impact on the directional dependence of fluids migration in environmental and engineering sciences. This anisotropy, linked to the preferential orientation of flat anisometric clay minerals particles, is studied here on the basis of the [...] Read more.

The anisotropic properties of clay-rich porous media have significant impact on the directional dependence of fluids migration in environmental and engineering sciences. This anisotropy, linked to the preferential orientation of flat anisometric clay minerals particles, is studied here on the basis of the simulation of three-dimensional packings of non-interacting disks, using a sequential deposition algorithm under a gravitational field. Simulations show that the obtained porosities fall onto a single master curve when plotted against the anisotropy value. This finding is consistent with results from sedimentation experiments using polytetrafluoroethylene (PTFE) disks and subsequent extraction of particle anisotropy through X-ray microtomography. Further geometrical analyses of computed porous media highlight that both particle orientation and particle aggregation are responsible of the evolution of porosity as a function of anisotropy. Moreover, morphological analysis of the porous media using chord length measurements shows that the anisotropy of the pore and solid networks can be correlated with particle orientation. These results indicate that computed porous media, mimicking the organization of clay minerals, can be used to shed light on the anisotropic properties of fluid transfer in clay-based materials. Full article

(This article belongs to the Special Issue Porous Materials for Environmental Applications)

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14 pages, 2904 KiB

Open AccessArticle

One-Step Hydrothermal Synthesis of Zeolite X Powder from Natural Low-Grade Diatomite

by Guangyuan Yao, Jingjing Lei, Xiaoyu Zhang, Zhiming Sun and Shuilin Zheng

Materials 2018, 11(6), 906; https://doi.org/10.3390/ma11060906 - 28 May 2018

Cited by 45 | Viewed by 5952

Abstract

Zeolite X powder was synthesized using natural low-grade diatomite as the main source of Si but only as a partial source of Al via a simple and green hydrothermal method. The microstructure and surface properties of the obtained samples were characterized by powder [...] Read more.

Zeolite X powder was synthesized using natural low-grade diatomite as the main source of Si but only as a partial source of Al via a simple and green hydrothermal method. The microstructure and surface properties of the obtained samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), wavelength dispersive X-ray fluorescence (XRF), calcium ion exchange capacity (CEC), thermogravimetric-differential thermal (TG-DTA) analysis, and N₂ adsorption-desorption technique. The influence of various synthesis factors, including aging time and temperature, crystallization time and temperature, Na₂O/SiO₂ and H₂O/Na₂O ratio on the CEC of zeolite, were systematically investigated. The as-synthesized zeolite X with binary meso-microporous structure possessed remarkable thermal stability, high calcium ion exchange capacity of 248 mg/g and large surface area of 453 m²/g. In addition, the calcium ion exchange capacity of zeolite X was found to be mainly determined by the crystallization degree. In conclusion, the synthesized zeolite X using diatomite as a cost-effective raw material in this study has great potential for industrial application such as catalyst support and adsorbent. Full article

(This article belongs to the Special Issue Porous Materials for Environmental Applications)

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9 pages, 2102 KiB

Open AccessCommunication

Spherical Activated Carbons with High Mechanical Strength Directly Prepared from Selected Spherical Seeds

by Ana Amorós-Pérez, Laura Cano-Casanova, Mohammed Ouzzine, Mónica Rufete-Beneite, Aroldo José Romero-Anaya, María Ángeles Lillo-Ródenas and Ángel Linares-Solano

Materials 2018, 11(5), 770; https://doi.org/10.3390/ma11050770 - 10 May 2018

Cited by 20 | Viewed by 4431

Abstract

In the present manuscript, the preparation of spherical activated carbons (SACs) with suitable adsorption properties and high mechanical strength is reported, taking advantage of the retention of the spherical shape by the raw precursors. An easy procedure (carbonization followed by CO₂ activation) [...] Read more.

In the present manuscript, the preparation of spherical activated carbons (SACs) with suitable adsorption properties and high mechanical strength is reported, taking advantage of the retention of the spherical shape by the raw precursors. An easy procedure (carbonization followed by CO₂ activation) has been applied over a selection of three natural seeds, with a well-defined spherical shape and thermal stability: Rhamnus alaternus (RA), Osyris lanceolate (OL), and Canna indica (CI). After the carbonization-activation procedures, RA and CI, maintained their original spherical shapes and integrity, although a reduction in diameter around 48% and 25%, respectively, was observed. The porosity of the resulting SACs could be tuned as function of the activation temperature and time, leading to a spherical activated carbon with surface area up to 1600 m²/g and mechanical strength similar to those of commercial activated carbons. Full article

(This article belongs to the Special Issue Porous Materials for Environmental Applications)

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