Hydrothermal process development for the treatment of crocidolite asbestos waste

2019 ◽  
Vol 37 (9) ◽  
pp. 914-924
Author(s):  
CT Nzogo Metoule ◽  
S Delaby ◽  
JH Ferrasse ◽  
O Boutin
Keyword(s):  
Electron Microscopy ◽  
Supercritical Water ◽  
Process Development ◽  
Batch Reactor ◽  
Hydrothermal Process ◽  
Ultrapure Water ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Electron Microscopy Analysis ◽  
First Results

The asbestos-containing waste management is a public health topic for countries which have used this mineral. Treatment of chrysotile (white asbestos), a phyllosilicate from serpentine, crocidolite (blue asbestos, first results on this kind of asbestos), one of the five asbestos varieties of amphibole family and asbestos-containing waste conversion process is proposed by using hydrothermal treatment in supercritical water. All samples were treated in an Inconel Batch Reactor. The treatment durations range is from 1 to 6 hours, temperatures range is from 400°C to 750°C, mass concentration range is from 0.02 to 170 mg. mL−1 and pressures are higher than 23 MPa. Ultrapure water is used for sample preparation. This ultrapure water is used to monitor mineral leaching on the aqueous phase and to avoid particle cross-contamination. Transmission electron microscopy analyses were carried out to check the presence or not of asbestos phase. According to these analyses, the best conditions of conversion were 1 hour and 0.02 mg. mL−1 for chrysotile, 3 hours and 0.02 mg. mL−1 for crocidolite and 1 hour and 20 mg. mL−1 for asbestos-containing waste, at T = 750°C. Supercritical water conditions were maintained during the whole treatment. The X-ray diffraction showed that the main phases present after treatments were riebeckite and magnetite (crocidolite), forsterite and enstatite (chrysotile), and calcite, spurrite and gehlenite (asbestos-containing waste). Finally, a scanning electron microscopy analysis was performed to monitor morphological fibre change. The elongated structure, partially fragmented, was found in all samples.

scholarly journals A comparative study on the VOCs sensing behaviors of various ZnO nanostructures

2020 ◽  
Vol 9 (4) ◽  
pp. 117-122
Author(s):  
Vuong Nguyen Minh ◽  
Dung Dinh Tien ◽  
Hieu Hoang Nhat ◽  
Nghia Nguyen Van ◽  
Truong Nguyen Ngoc Khoa ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Hierarchical Structure ◽  
Hydrothermal Process ◽  
Zno Nanostructures ◽  
X Ray Diffraction ◽  
Wet Chemical Method ◽  
Electrospinning Technique ◽  
Transmission Electron ◽  
Volatile Organic ◽  
Wet Chemical

The volatile organic compounds (VOCs) sensing layers were studied using ZnO nanomaterials with different morphologies including hierarchical nanostructure (ZnO-H), nanorods (ZnO-NRs), commercial nanoparticles (ZnO-CNPs) and wet chemical synthesized nanoparticles (ZnO-HNPs). ZnO hierarchical structure was fabricated by an electrospinning technique followed by hydrothermal process. ZnO vertical nanorods structure was fabricated by hydrothermal method, while ZnO nanoparticles based sensors were prepared from commercial powder and wet chemical method. The morphology and properties of the fabricated samples were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). VOCs sensing responses toward acetone, ethanol and methanol with respect to altered ZnO nanostructureswas systematically compared at different working temperatures. The enhanced response at low working temperatures induced by theopen space hierarchical structure was observed. The VOCs sensing mechanisms of the ZnO nanostructures based sensing layer were also explained and discussed in detail. 

scholarly journals Selective Synthesis of Manganese/Silicon Complexes in Supercritical Water

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Jiancheng Wang ◽  
Zhaoliang Peng ◽  
Bing Wang ◽  
Lina Han ◽  
Liping Chang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Supercritical Water ◽  
Silica Sand ◽  
Hydroxyl Groups ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Silicon Materials ◽  
Manganese Salts ◽  
Silicon Sources

A series of manganese salts (Mn(NO3)2, MnCl2, MnSO4, and Mn(Ac)2) and silicon materials (silica sand, silica sol, and tetraethyl orthosilicate) were used to synthesize Mn/Si complexes in supercritical water using a tube reactor. X-ray diffraction (XRD), X-ray photoelectron spectrometer (XPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were employed to characterize the structure and morphology of the solid products. It was found that MnO2, Mn2O3, and Mn2SiO4could be obtained in supercritical water at 673 K in 5 minutes. The roles of both anions of manganese salts and silicon species in the formation of manganese silicon complexes were discussed. The inorganic manganese salt with the oxyacid radical could be easily decomposed to produce MnO2/SiO2and Mn2O3/SiO2. It is interesting to found that Mn(Ac)2can react with various types of silicon to produce Mn2SiO4. The hydroxyl groups of the SiO2surface from different silicon sources enhance the reactivity of SiO2.

Ordered Mesoporous SBA-15 for Controlled Release of Water-Insolube Drug

2011 ◽  
Vol 236-238 ◽  
pp. 1873-1876 ◽  
Author(s):  
Jun Jie Tao ◽  
Yun Qiang Xu ◽  
Guo Wei Zhou ◽  
Cui Cui Wu ◽  
Hong Bin Song ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Controlled Release ◽  
Hydrothermal Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Mesoscopic Structure ◽  
Ordered Mesoporous ◽  
Adsorption Desorption ◽  
Phosphate Buffered Saline

Ordered mesoporous SBA-15 was synthesized through hydrothermal process under acidic condition. The material was characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), small-angle X-ray diffraction (SAXRD), and N2 adsorption-desorption. The results indicated that SBA-15 has 2-dimensional hexagonal p6mm mesoscopic structure and well-ordered parallel mesochannel. The as-obtained mesoporous silica was used for controlled release of water-insolube drug emodin. The loading capacity could achieve 6.64 mg/g, and the release profiles that studied in phosphate buffered saline (PBS, pH = 7.4) showed that released amount of emodin was 95.8 % after 48 h.

Hydrothermal Synthesis and Electrocatalytic Property for H2O2 Reduction of Co3O4 Nanocubes

2011 ◽  
Vol 311-313 ◽  
pp. 477-480
Author(s):  
Zhi Ai Yang ◽  
Li Jin Feng ◽  
Xia Wang ◽  
Rong Ma ◽  
Jian Ping Sun ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Hydrothermal Process ◽  
Linear Sweep Voltammetry ◽  
Average Crystallite Size ◽  
X Ray Diffraction ◽  
Linear Sweep ◽  
Electrocatalytic Property ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Electron

Subscript textThe Co3O4 nanocubes were synthesized by hydrothermal process. The products are characterized in detail by multiform techniques: scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray analysis. The results show that the products are uniform nanocubes with an average crystallite size about 20-40 nm. Electrocatalytic property of the prepared Co3O4 nanocubes was characterized by linear sweep voltammetry. LSV results indicate that Co3O4 nanocubes exhibit a remarkable electrocatalytic activity for the H2O2 reduction.

Preparation of Polyaniline Supported TiO2 Photocatalyst and its Photocatalytic Property

2011 ◽  
Vol 356-360 ◽  
pp. 524-528 ◽  
Author(s):  
Chun Ling Yu ◽  
Rui Xue Wu ◽  
Ying Huan Fu ◽  
Xiao Li Dong ◽  
Hong Chao Ma
Keyword(s):  
Electron Microscopy ◽  
Hydrothermal Process ◽  
Photocatalytic Property ◽  
Visible Spectrum ◽  
X Ray Diffraction ◽  
Visible Spectroscopy ◽  
Anthraquinone Dye ◽  
X Ray ◽  
Transmission Electron ◽  
Uv Visible

A polyaniline supported titanium dioxide photocatalyst was prepared by an impregnation-hydrothermal process and characterized by powder X-ray diffraction, transmission electron microscopy and UV-visible spectroscopy. It was found that the TiO2 nanoparticles were well dispersed on the surface of the polyaniline and the photocatalyst has a stronger absorption compared with that of pure TiO2 over the whole of the visible spectrum. The photocatalyst exhibited higher photocatalytic activity than pure TiO2 for the photodegradation of solutions of the anthraquinone dye, reactive brilliant blue KN-R, under visible light irradiation.

scholarly journals ZnO/ZnAl2O4 Nanocomposite with 3D Sphere-Like Hierarchical Structure for Photocatalytic Reduction of Aqueous Cr(VI)

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1624 ◽  
Author(s):  
Xiaoya Yuan ◽  
Xin Cheng ◽  
Qiuye Jing ◽  
Jiawei Niu ◽  
Dong Peng ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Diffuse Reflectance Spectroscopy ◽  
Uv Light ◽  
Hydrothermal Process ◽  
Three Dimensional ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Excellent Photocatalytic Activity ◽  
Potential Applications

Three dimensional (3D) ZnO/ZnAl2O4 nanocomposites (ZnnAl-MMO) were synthesized by a simple urea-assisted hydrothermal process and subsequent high-temperature calcination. The as-prepared samples and their precursors were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), and Photoluminescence spectra (PL). It was observed that the morphology of ZnnAl-MMO nanocomposites could be tuned from cubic aggregates, hierarchically flower-like spheres to porous microspheres by simply changing the molar ratio of metal cations of the starting reaction mixtures. The photocatalytic performance of ZnO/ZnAl2O4 nanocomposites in the photoreduction of aqueous Cr(VI) indicated that the as-prepared 3D hierarchical sphere-like ZnnAl-MMO nanocomposite showed excellent photocatalytic activity of Cr(VI) reduction under UV light irradiation. The results indicated that the maximum removal percentage of aqueous Cr(VI) was 98% within four hours at 10 mg/L initial concentration of Cr(VI), owing to the effective charge separation and diversion of photogenerated carriers across the heterojunction interface of the composite. Our study put forward a facile method to fabricate hierarchical ZnO/ZnAl2O4 composites with potential applications for wastewater treatment.

Kinetic and structural constraints during glauconite dissolution: implications for mineral disposal of CO2

2008 ◽  
Vol 72 (1) ◽  
pp. 27-31 ◽  
Author(s):  
S. Fernandez-Bastero ◽  
C. Gil-Lozano ◽  
M. J. I. Briones ◽  
L. Gago-Duport
Keyword(s):  
Electron Microscopy ◽  
Batch Reactor ◽  
Bet Surface Area ◽  
Dissolution Mechanism ◽  
Structural Constraints ◽  
X Ray Diffraction ◽  
Ph Values ◽  
Transmission Electron ◽  
Ph Range

AbstractThe kinetics of glauconite dissolution have been determined in the pH range 2—10 (T = 25°C) using flow-batch reactor experiments. Besides the kinetic characteristics, the structural and textural aspects which could influence its long-term reactivity have also been characterized by means of X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and BET surface area measurements. The results from these analyses showed that glauconite follows a dual dissolution pathway which is pH-dependent, being more stable at neutral or slightly alkaline pH values. Under acidic conditions, glauconite is slightly more soluble than other ubiquitous silicates present in the marine sediments. The dissolution mechanism is incongruent at very acid pH values and tends to be congruent for intermediate and neutral ones. In addition, the results from the structural analyses suggest that the dissolution is a two-step process: the first one involves the disorder of the octahedral and tetrahedral layers, probably following a turbostratic mechanism which is evident in the XRD spectra as selective broadening of several reflections. In the second step, the dissolution of the cations from interlayer positions takes place and leads to the formation of an amorphous residue which acts as a passivating layer and reduces the reactive surface considerably. The influence of these aspects on CO2 capture via carbonation reactions is discussed.

Hydrothermal Synthesis of Zn2(MoO4)(SeO3) and Photocatalytic Applications

2013 ◽  
Vol 385-386 ◽  
pp. 16-18
Author(s):  
Yan Zhong Zhen ◽  
Dan Jun Wang ◽  
Feng Fu ◽  
Gang Lin Xue
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Hydrothermal Synthesis ◽  
Hydrothermal Process ◽  
Experimental Result ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Photocatalytic Applications ◽  
Simple Hydrothermal Process

A novel mixed metal molybdates, Zn2(MoO4)(SeO3) 1 has been synthesized by a simple hydrothermal process. Samples obtained are characterized using powder and single crystal X-ray diffraction (XRD), transmission electron microscopy (TEM). Furthermore, the photocatalytic performances of samples obtained are investigated for degradation of RhB under visible light irradiation. photocayalysis experimental result has illustrated that the compound exhibits good photocatalysis.

Shape-Controlled Synthesis of Gadolinium Oxide Nanostructure via Facile Process

2012 ◽  
Vol 182-183 ◽  
pp. 265-269
Author(s):  
Qing Zhang ◽  
Pei Wen Hao ◽  
Xin Qu ◽  
Chun Wang ◽  
Rui Xia Li
Keyword(s):  
Electron Microscopy ◽  
Hydrothermal Process ◽  
X Ray Diffraction ◽  
Hydrothermal Temperature ◽  
X Ray ◽  
Transmission Electron ◽  
Heating Treatment ◽  
Shape Controlled ◽  
Low Dimensional ◽  
Hydrolysis Of

A facile method to selectively synthesize nano-scaled Gd2O3 with different morphology such as nanosheres and nanorods has been developed in our report. The precursors GdOHCO3 can be prepared by a two-step hydrothermal process via homogeneous generation of hydroxide ions through the hydrolysis of urea, and the formation of different morphology structures were obtained under different reaction temperatures. After further heating treatment, a transformation from GdOHCO3 to cubic Gd2O3 takes place. The morphology and size of nano Gd2O3 strongly depend on that of the precursors GdOHCO3. The X-ray diffraction, transmission electron microscopy and scanning electron microscopy were employed to characterize the as-obtained low-dimensional nanostructures. And the effects of hydrothermal temperature, solvent and urea concentration on the morphologies of the products were also studied.

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