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10 pages, 6465 KiB

Open AccessArticle

Mullite Stabilized Palmitic Acid as Phase Change Materials for Thermal Energy Storage

by Xiaobin Gu, Peng Liu, Liang Bian, Lihua Peng, Yungui Liu and Huichao He

Minerals 2018, 8(10), 440; https://doi.org/10.3390/min8100440 - 10 Oct 2018

Cited by 19 | Viewed by 3518

In this paper, mullite was adopted in order to absorb Palmitic Acid (PA) via a direct impregnation method. The prepared PA/mullite form-stable phase change materials (FSPCM) were systematically characterized by the Leakage Test (LT), Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), [...] Read more.

In this paper, mullite was adopted in order to absorb Palmitic Acid (PA) via a direct impregnation method. The prepared PA/mullite form-stable phase change materials (FSPCM) were systematically characterized by the Leakage Test (LT), Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Differential Scanning Calorimeter (DSC), Thermogravimetry (TG) and Cooling Curve Method (CCM). The results indicated that, among these composites with different mass fractions of PA, the sample with the 32 wt % Palmitic Acid has the best properties without any leakage. The enthalpy of 32%PA/68%mullite FSPCM is 50.8 J/g for melting process, and 58.3 J/g for solidifying process. The phase change point of 32%PA/68%mullite FSPCM is 64.1 °C for melting and 58.7 °C for solidifying. The heat storage efficiency of the PA/mullite FSPCM was enhanced considerably by adding mullite. The leakage and thermal properties of PA/mullite FSPCM were discussed and the performance of the FSPCM has been apparently improved. Full article

(This article belongs to the Special Issue Mineral Materials)

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15 pages, 5020 KiB

Open AccessArticle

Fabrication of Novel Cyanuric Acid Modified g-C₃N₄/Kaolinite Composite with Enhanced Visible Light-Driven Photocatalytic Activity

by Zhiming Sun, Fang Yuan, Xue Li, Chunquan Li, Jie Xu and Bin Wang

Minerals 2018, 8(10), 437; https://doi.org/10.3390/min8100437 - 7 Oct 2018

Cited by 27 | Viewed by 4658

Abstract

A novel kind of cyanuric-acid-modified graphitic carbon nitride (g-C₃N₄)/kaolinite (m-CN/KA) composite with enhanced visible light-driven photocatalytic performance was fabricated through a facile two-step process. Rhodamine B (RhB) was taken as the target pollutant to study the photocatalytic performance of [...] Read more.

A novel kind of cyanuric-acid-modified graphitic carbon nitride (g-C₃N₄)/kaolinite (m-CN/KA) composite with enhanced visible light-driven photocatalytic performance was fabricated through a facile two-step process. Rhodamine B (RhB) was taken as the target pollutant to study the photocatalytic performance of the synthesized catalysts. It is indicated that the cyanuric acid modification significantly enhanced photocatalytic activity under visible light illumination in comparison with the other reference samples. The apparent rate constant of m-CN/KA is almost 1.9 times and 4.0 times those of g-C₃N₄/kaolinite and bare g-C₃N₄, respectively. The superior photocatalytic performance of m-CN/KA could be ascribed, not only to the generation of abundant pore structure and reactive sites, but also to the efficient separation of the photogenerated electron-hole pairs. Furthermore, the possible photocatalytic degradation mechanism of m-CN/KA was also presented in this paper. It could be anticipated that this novel and efficient, metal-free, mineral-based photocatalytic composite has great application prospects in organic pollutant degradation. Full article

(This article belongs to the Special Issue Mineral Materials)

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14 pages, 4051 KiB

Open AccessArticle

Halloysite Nanotubes as an Effective and Recyclable Adsorbent for Removal of Low-Concentration Antibiotics Ciprofloxacin

by Rongqing Cheng, Haipeng Li, Zhiliang Liu and Chunfang Du

Minerals 2018, 8(9), 387; https://doi.org/10.3390/min8090387 - 5 Sep 2018

Cited by 33 | Viewed by 4381

Abstract

In this work, halloysite nanotubes (HNTs) without modification were used as an efficient adsorbent to explore its natural adsorption capability, which showed excellent adsorption ability for low-concentration ciprofloxacin (CIP). The physicochemical properties of HNTs before and after adsorption were investigated by several characterization [...] Read more.

In this work, halloysite nanotubes (HNTs) without modification were used as an efficient adsorbent to explore its natural adsorption capability, which showed excellent adsorption ability for low-concentration ciprofloxacin (CIP). The physicochemical properties of HNTs before and after adsorption were investigated by several characterization techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), N₂ adsorption–desorption analysis, X-ray diffractometer (XRD), and zeta potential analysis. The influences of temperature, initial CIP concentration, adsorbent dosage, and pH value on CIP adsorption performance were also studied. The kinetics analysis revealed that CIP adsorption on HNTs was a kind of monolayer adsorption process and followed a pseudo-second-order rate equation. The zeta potential result indicated that electrostatic interaction between HNTs and CIP molecules was possibly responsible for the adsorption performance. Moreover, HNTs showed no apparent loss in CIP adsorption capability after five cycles, exhibiting potential applications in wastewater treatment. Full article

(This article belongs to the Special Issue Mineral Materials)

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13 pages, 8588 KiB

Open AccessArticle

Selective Fabrication of Barium Carbonate Nanoparticles in the Lumen of Halloysite Nanotubes

by Jing Ouyang, Dawei Mu, Yi Zhang, Huaming Yang and Steven L. Suib

Minerals 2018, 8(7), 296; https://doi.org/10.3390/min8070296 - 11 Jul 2018

Cited by 12 | Viewed by 4533

Abstract

Barium carbonate (BaCO₃) materials with the controllable morphology of nanoparticles were selectively loaded into the lumen halloysite nanotubes (abbreviated as Hal) by a urease assisted catalytic implementation strategy. The Hal mineral was pre-treated through leaching by hydrochloric acid (abbreviated as A-Hal), [...] Read more.

Barium carbonate (BaCO₃) materials with the controllable morphology of nanoparticles were selectively loaded into the lumen halloysite nanotubes (abbreviated as Hal) by a urease assisted catalytic implementation strategy. The Hal mineral was pre-treated through leaching by hydrochloric acid (abbreviated as A-Hal), resulting in increased defect sites and zeta potential. The negatively charged urease was loaded inside the positively charged A-Hal lumen, and then through the decomposition of urea catalyzed by urease to produce carbonate ions and ammonia. When Ba²⁺ diffused in, BaCO₃ particles were selectively synthesized in the lumen of A-Hal, the pore channels of A-Hal effectively controlled the growth and aggregation of BaCO₃ nanocrystals and their geometrical morphology. The obtained BaCO₃/A-Hal-T was characterized by transmission electron microscopy, Fourier transformation infrared spectroscopy and X-ray diffraction, differential scanning calorimetry-thermogravimetry (DSC-TG). The BaCO₃/A-Hal-T may provide a candidate for potential applications. Full article

(This article belongs to the Special Issue Mineral Materials)

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13 pages, 3816 KiB

Open AccessArticle

Distribution and Characteristics of Nanotubular Halloysites in the Thach Khoan Area, Phu Tho, Vietnam

by Bui Hoang Bac, Nguyen Tien Dung, Luong Quang Khang, Khuong The Hung, Nguyen Van Lam, Do Manh An, Phan Viet Son, Tran Thi Van Anh, Doan Van Chuong and Bui Thanh Tinh

Minerals 2018, 8(7), 290; https://doi.org/10.3390/min8070290 - 8 Jul 2018

Cited by 13 | Viewed by 5309

Abstract

Two types of halloysite collected from the upper (UPS) and lower (LOS) zones of a weathered pegmatite profile in the Thach Khoan area, Phu Tho were defined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy [...] Read more.

Two types of halloysite collected from the upper (UPS) and lower (LOS) zones of a weathered pegmatite profile in the Thach Khoan area, Phu Tho were defined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), thermal analysis (TG and DTG), and N₂ adsorption-desorption isotherms. XRD analysis showed that halloysite and kaolinite coexist in samples of size fractions <2 µm. Semi-quantitative analysis by XRD after formamide (FA) treatment indicated that the halloysite contents are approximately 81% and 93% in UPS and LOS samples, respectively. The results of SEM and TEM analyses showed that while short halloysite type is mainly distributed in the upper zone, long halloysite type occurs primarily in the lower zone of the weathered pegmatite profile. The length of short halloysite ranging from 250 to 750 nm is most popular, accounting for 47.2% of halloysites in the UPS sample. Meanwhile, long halloysites which have the length of 750–1250 nm are dominant in the LOS sample with 69.9%. In addition, short halloysites with outer diameter of >100 nm constitute 79.1% of halloysites in the UPS sample while long halloysites with outer diameter of 50–100 nm make up 74.2% of halloysites in LOS sample. Specific surface areas are 15.7434 and 22.0211 m²/g and average pore sizes are 18.9837 and 17.0281 nm for the UPS and LOS samples, respectively. The analysis implies that although forming under same natural geographical and climatic conditions, halloysites at different depths in the weathered pegmatite profile may have different morphological and other properties. Full article

(This article belongs to the Special Issue Mineral Materials)

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10 pages, 4029 KiB

Open AccessArticle

MoSe₂/Montmorillonite Composite Nanosheets: Hydrothermal Synthesis, Structural Characteristics, and Enhanced Photocatalytic Activity

by Xiaoyu Li and Kang Peng

Minerals 2018, 8(7), 268; https://doi.org/10.3390/min8070268 - 26 Jun 2018

Cited by 48 | Viewed by 5512

Abstract

MoSe₂/montmorillonite composite nanosheets were successfully synthesized by a facile hydrothermal method, and the photocatalytic activities of the samples were evaluated by the decoloration of Rhodamine B. The structural characterizations indicate that the MoSe₂ nanosheets grow uniformly on the surface of [...] Read more.

MoSe₂/montmorillonite composite nanosheets were successfully synthesized by a facile hydrothermal method, and the photocatalytic activities of the samples were evaluated by the decoloration of Rhodamine B. The structural characterizations indicate that the MoSe₂ nanosheets grow uniformly on the surface of montmorillonite with interface interaction, and the active sites on the nanosheet edges are exposed. Montmorillonite can inhibit the agglomeration of MoSe₂ nanosheets, improve the hydrophilicity and dispersibility of composites, and provides a larger surface area and more reactive sites for photocatalytic reaction. MoSe₂/montmorillonite possesses the highest adsorption properties and photocatalytic abilities, and the overall decoloration rate is up to 98.2% after visible light irradiation for 45 min. The assembly of montmorillonite could enhance the photocatalytic ability of MoSe₂, and the possible photocatalytic reaction mechanism of MoSe₂/montmorillonite for Rhodamine B was explored. MoSe₂/montmorillonite has potential applications in the photodegradation of organic dyes in the wastewater. Full article

(This article belongs to the Special Issue Mineral Materials)

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13 pages, 2328 KiB

Open AccessArticle

Preparation of Mullite-Silica Composites Using Silica-Rich Monophasic Precursor Obtained as a Byproduct of Mineral Carbonation of Blast-Furnace Slag

by Kyungsun Song, Wonbaek Kim, Chang-Yul Suh, Jun-Hwan Bang and Ji-Whan Ahn

Minerals 2018, 8(5), 219; https://doi.org/10.3390/min8050219 - 22 May 2018

Cited by 11 | Viewed by 5033

Abstract

Previously, mineral carbonation of blast-furnace slag was carried out to sequestrate CO₂ and attain pure CaCO₃ crystals. In this process, amorphous silica-alumina nanoparticles were obtained as a byproduct. In this study, the crystallization of these nanoparticles on calcination at various temperatures [...] Read more.

Previously, mineral carbonation of blast-furnace slag was carried out to sequestrate CO₂ and attain pure CaCO₃ crystals. In this process, amorphous silica-alumina nanoparticles were obtained as a byproduct. In this study, the crystallization of these nanoparticles on calcination at various temperatures in air was examined using TGA-DTA, XRD, MAS-NMR spectroscopy, and FT-IR spectroscopy. The precursor nanoparticles (Si:Al = 78:22 mol %) were prepared using the solution extracted from blast-furnace slag (BFS) with acetic acid at room temperature. The XRD analysis showed that the initial amorphous state was retained up to 800 °C, and decomposition to amorphous silica and mullite started after calcination at 950 °C. At temperatures between 1150 °C and 1250 °C, amorphous silica crystalized to cristobalite, which eventually melted to glassy silica at 1500 °C. The mullite crystals initially adopted a metastable tetragonal phase and transformed to a stable, needle-like orthorhombic phase at higher temperatures. ²⁷Al MAS-NMR spectroscopy revealed that octahedrally coordinated Al was favored up to a temperature of 800 °C as a result of the dehydration process and transformed into tetrahedrally coordinated Al at higher temperatures. A microstructural examination revealed that the initially randomly-oriented mullite developed into stable, needle-like grains owing to anisotropic grain growth in the presence of a glass phase at high temperatures. This study suggests that the recycling of BFS can be exploited for the procurement of a mullite-type ceramic material. Full article

(This article belongs to the Special Issue Mineral Materials)

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15 pages, 5497 KiB

Open AccessArticle

Surface-Modified Garnet Particles for Reinforcing Epoxy Composites

by Yiming Jiang, Fengping Xu, Kun Liu and Qiming Feng

Minerals 2018, 8(5), 217; https://doi.org/10.3390/min8050217 - 19 May 2018

Cited by 4 | Viewed by 4727

Abstract

The present study investigated the tribological performance of epoxy (EP) matrix composites enhanced with natural garnet. The garnet was surface-modified with sodium stearate for optimal performance. Composites comprising different contents and particle sizes of modified garnet (MG) were prepared with a mixture of [...] Read more.

The present study investigated the tribological performance of epoxy (EP) matrix composites enhanced with natural garnet. The garnet was surface-modified with sodium stearate for optimal performance. Composites comprising different contents and particle sizes of modified garnet (MG) were prepared with a mixture of EP and MG. The sodium stearate-bonded garnet and EP formed a stable structure. Tribological performance was measured by a ball-on-plate apparatus under permanent dry sliding conditions and a wear track was obtained by an optical profilometer. The wear mechanism was explored by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) images. Wear test results showed that the coefficient of friction for all EP/MG composites decreased compared with that for neat epoxy. The results also indicated that the addition of MG can evidently improve the tribological properties of EP matrix composites. Full article

(This article belongs to the Special Issue Mineral Materials)

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12 pages, 4084 KiB

Open AccessArticle

Structure Simulation and Host–Guest Interaction of Histidine-Intercalated Hydrotalcite–Montmorillonite Complex

by Chen-Xi Wang, Min Pu, Pei-Huan Zhang, Yang Gao, Zuo-Yin Yang and Ming Lei

Minerals 2018, 8(5), 198; https://doi.org/10.3390/min8050198 - 7 May 2018

Cited by 6 | Viewed by 3955

Abstract

The structures of histidine intercalated hydrotalcite–montmorillonite complex (His–LDHs–MMT) were studied using the DMol3 code, GGA/PW91 function, and DND basis set of the density functional theory (DFT). The geometries of His–LDHs–MMT were optimized, and their electronic properties were calculated. The results showed that the [...] Read more.

The structures of histidine intercalated hydrotalcite–montmorillonite complex (His–LDHs–MMT) were studied using the DMol3 code, GGA/PW91 function, and DND basis set of the density functional theory (DFT). The geometries of His–LDHs–MMT were optimized, and their electronic properties were calculated. The results showed that the structure of the complex can be seen as that the quaternary ammonium group of histidine was adsorbed on the oxygen of MMT lamella, and its oxygen on the carboxylic acid anion was combined with the hydrogen atoms of the LDHs lamella. It was determined that the interaction mainly consisted in hydrogen bonding and electrostatic force. The average binding energies per histidine of His–LDHs and His–MMT were about −65.89 and −78.44 kcal/mol, respectively. The density of states of the complexes showed that the 2p orbitals of oxygen were dominant, and the 1s orbit of hydrogen near the Fermi level indicate the formation of hydrogen bonds in the complex. The charge density data displayed the density field of histidine carboxylic acid anion overlapped with that of hydrotalcite layer, indicating that a strong hydrogen bond interaction existed between histidine and hydrotalcite layer. The analysis of the electrostatic potential of complex indicated that the electrostatic interaction between histidine and MMT is obviously stronger than that of LDHs. The simulated XRD spectra showed the special diffraction peaks of LDHs and MMT layer in the complex. Full article

(This article belongs to the Special Issue Mineral Materials)

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8 pages, 14033 KiB

Open AccessArticle

Lauric Acid Hybridizing Fly Ash Composite for Thermal Energy Storage

by Dawei Xu, Huaming Yang, Jing Ouyang, Yi Zhang, Liangjie Fu and Deliang Chen

Minerals 2018, 8(4), 161; https://doi.org/10.3390/min8040161 - 16 Apr 2018

Cited by 17 | Viewed by 4405

Abstract

Fly ash includes different mineral phases. This paper reported on the preparation of a novel lauric acid (LA)/fly ash (FA) composite by vacuum impregnation as a form-stable phase change material (PCM) for thermal energy, and especially investigated the effect of the hydrochloric acid-treated [...] Read more.

Fly ash includes different mineral phases. This paper reported on the preparation of a novel lauric acid (LA)/fly ash (FA) composite by vacuum impregnation as a form-stable phase change material (PCM) for thermal energy, and especially investigated the effect of the hydrochloric acid-treated fly ash (FAh) on the thermal energy storage performance of the composites. The morphology, crystalline structure, and porous textures of the samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), X-ray fluorescence (XRF), and differential scanning calorimetry (DSC). The results indicated that hydrochloric acid treatment was beneficial to the increase of loading capacity and crystallinity of LA in the LA/FAh composite, which caused an enhanced thermal storage capacity with latent heats for melting and freezing of LA/FAh (80.94 and 77.39 J/g), higher than those of LA/FA (34.09 and 32.97 J/g), respectively. Furthermore, the mechanism of enhanced thermal storage properties was investigated in detail. Full article

(This article belongs to the Special Issue Mineral Materials)

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