Sepiolite Nanomaterials: Structure, Properties and Functional Applications

Tian, Guangyan; Han, Gao‐Feng; Wang, Fei; Liang, Jinsheng

doi:10.1016/b978-0-12-814533-3.00003-x

Cited by 31 publications

(33 citation statements)

References 242 publications

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“…The greater value of E 3 # compared to E 1 # and E 2 # is due to the chemical nature of the dehydroxylation, whereas dehydration is a physical process. Similar results were obtained using the intensity of the most characteristic XRD reflection of sepiolite (110) as a kinetic variable (Kiyohiro & Otsuka, 1989; Perraki & Orfanoudaki, 2008; Sarıkaya et al , 2019; Tian et al ., 2019).…”

Section: Resultsmentioning

confidence: 99%

“…The effects of heating, acid leaching and various chemical treatments on the crystal structure and properties of sepiolite have been discussed qualitatively (Serna et al , 1975; Yebra-Rodriquez et al , 2003; Yılmaz et al , 2013, Fitaroni et al , 2019). Sepiolite has been used widely in many processes, such as adsorption, catalysis, bleaching of edible oils, clarification of fruit juices, preparation of polymer nanocomposites and pharmaceutical applications (Galan, 1996; Murray, 1999; Saneeri et al , 2015, González-Santamaria, 2017; Mirzaaghaei et al , 2017; Al-Ani et al , 2018; Tian et al , 2019).…”

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confidence: 99%

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Thermal degradation kinetics of sepiolite

2020

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The kinetic parameters of the thermal degradation of sepiolite were evaluated with a new method based on thermal analysis data. Thermogravimetric/differential thermal analysis curves were recorded for the natural and preheated sepiolite samples in the temperature range 25–800°C for 4 h. The temperature-dependent height of the exothermic heat flow peak for the thermal decomposition of sepiolite located at ~850°C on the differential thermal analysis curve was taken as a kinetic variable for the thermal degradation. A thermal change coefficient was defined depending on this variable because this coefficient fit to the Arrhenius equation was assumed as a rate constant for the thermal degradation. The Arrhenius plot showed that the degradation occurs in three steps. Two of these are due to stepwise dehydration and the third originated from dehydroxylation of sepiolite. Three activation energies were obtained that increase with the increasing temperature interval of the steps.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Thermal degradation kinetics of sepiolite

2020

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“…7). The sharp decrease in the CEC (reached 69%) with subsequent increase in the temperature and a decrease in solid rate is as a result of the acid-induced partial dissolution of cations which not only occurs in the octahedral sheets but also in tetrahedral sheets; such a dissolution process began by breaking the ribbons not along the edges, but in the centre [42], resulting in most probably the conversion of the tetrahedral sheets into silanol groups. It was inferred that the CEC of Sep was eliminated by citric-acid treatment, which had the effect of progressively transforming the mineral structure into an amorphous silica-alumina.…”

Section: Effect Of Process Parametersmentioning

confidence: 99%

Modelling and Optimization of Sepiolite Activation with Citric Acid Using Factorial Experimental Design and Response Surface Methodology

Yonar

Ugwu

Sabah

2020

Silicon

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In this study, the effects of several parameters such as the acid concentration, mixing time, temperature, solid rate, and mixing rate on the specific surface area (BET) and cation exchange capacity (CEC) of sepiolite activated by citric acid were investigated using factorial experimental design and response surface methodology. While the specific surface area and cation exchange capacity of nitric acid activated sepiolite were chosen as the responses, the acid concentration, time, temperature, solid rate, and mixing rate were the process parameters. The relationship between the process parameters and the responses was obtained and used in the determination of the optimal conditions. The result showed that the specific surface area and cation exchange capacity of the acid-activated sepiolite were strongly affected by the process parameters. The optimal conditions for achieving the maximum specific surface area and minimum cation exchange capacity were 95.73°C, 8.64%, 4.99 N, 1 h, and 450 rpm for temperature, solid rate, acid concentration, activation time, and the mixing rate, respectively. The experimental and predicted values for the S BET and the CEC were obtained as 450.97 m 2 /g and 449.97 m 2 /g, and 6.79 meq/100 g and 6.86 meq/100 g, respectively. The results obtained from this study clearly indicated that the actual values were in good conformity with the predicted values as evidenced by small errors of 1.00% and 0.07% for the S BET and CEC, respectively. As a result, the S BET and CEC of the Sep activated by citric acid were strongly affected by the process parameters, especially the solid rate for the S BET and the temperature for CEC. It was found that citric-acid activated Sep had a S BET approximately 2.5 times higher than that of the untreated Sep while the CEC of Sep may be strongly eliminated by citric acid treatment. Thus, the mineral structure was progressively transformed into amorphous silica coming from the tetrahedral sheet of the generated fibrous silicates, whose S BET was larger than that of the raw Sep.

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“…Sepiolite is characterized by blocks of octahedral sheets of magnesium oxides and hydroxides between two tetrahedral silica layers. In each tunnel, the octahedral sheets are bound with two H 2 O molecules which correspond to coordinated water and are weakly bound with zeolitic water [22]. Sepiolite exhibits a needle morphology which generates a high specific surface area of 200-300 m 2 /g, lengths of 0.2-4 µm and a width of 10-30 nm and thickness of 5-10 nm [23].…”

Section: Introductionmentioning

confidence: 99%

Fire Protective Surface Coating Containing Nanoparticles for Marine Composite Laminates

Floch¹,

Chiochetta²,

Ferry³

et al. 2020

J. Compos. Sci.

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A poly(vinyl alcohol) (PVA)-based coating containing ammonium polyphosphate (APP) and sepiolite nanofillers (SP) and supported by a glass fabric was developed to fire-protect a glass-fiber-reinforced unsaturated-polyester-based (UP) polymer (GFRP). The fire behavior and thermal stability of the PVA coatings were characterized using thermogravimetric analysis (TGA) and a cone calorimeter. The coatings’ residues were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results from the cone calorimeter showed that the addition of sepiolite significantly improves the flame retardancy of PVA/APP/SP coatings. The addition of both additives promoted the formation of a cohesive layer composed of a silico-phosphate structure resulting from the reactivity between APP and SP. The fire resistance of the composite laminate protected by PVA coatings was evaluated using a cone calorimeter by measuring the temperature of the back face. Photogrammetry was used to assess the swelling of residues after heat exposure. The interaction between APP and SP in PVA coating leads to the formation of an effective thermal barrier layer. The presence of SP reduces the layer expansion but greatly decreases the backside temperature during the initial period of exposure. The effect was assigned to high thermal stability of the layer and its ability to dissipate heat by re-radiation.

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Sepiolite Nanomaterials: Structure, Properties and Functional Applications

Cited by 31 publications

References 242 publications

Thermal degradation kinetics of sepiolite

Thermal degradation kinetics of sepiolite

Modelling and Optimization of Sepiolite Activation with Citric Acid Using Factorial Experimental Design and Response Surface Methodology

Fire Protective Surface Coating Containing Nanoparticles for Marine Composite Laminates

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