Influences of pH value on the microstructure and phase transformation of aluminum hydroxide

Du, Xiaolong; Wang, Yanqin; Su, Xinghua; Li, Jiangong

doi:10.1016/j.powtec.2008.11.008

Cited by 156 publications

(77 citation statements)

References 28 publications

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“…Though all aluminas had poor crystalline structure with broad diffractogram peaks, different patterns were observed in five aluminas. In agreement with the previous study, A1, A2 and A5 were identified as amorphous aluminum hydroxide, AlOOH, and ␥-Al 2 O 3 , respectively [23]. The characteristic diffraction peaks of both AlOOH and Al(OH) 3 were recognized in the samples of A3 and A4, which indicated that A3 and A4 were the transition phase of alumina.…”

Section: Characterization Of Aluminas With Different Typessupporting

confidence: 90%

“…Different types of aluminas were prepared by the following method as reported [23]. Solution of 250 ml NaOH (100 g/L) was added into 250 ml AlCl 3 ·6H 2 O solution (200 g/L) drop by drop at room temperature.…”

Section: Preparation Of Aluminas With Different Typesmentioning

confidence: 99%

“…Alumina is formed through a dehydroxylation process of aluminium hydroxide and there are many forms of transition alumina. Aluminas prepared at different pH and calcination temperatures have different chemical composition and surface properties [22][23][24]. In the catalytic field, the studies about alumina with different phases are well conducted [25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

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Adsorption of fluoride onto different types of aluminas

Gong

Liu

et al. 2012

Chemical Engineering Journal

121

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a b s t r a c tIn this study, five aluminas were synthesized at different pH and calcination temperatures, and the surface properties and defluoridation performance of aluminas were investigated. Characterization of XRD showed that five aluminas were poorly crystallized with different phases and their anion exchange capacity and the point of zero charge varied with the species of aluminas. The batch experiments (thermodynamics, kinetics and the effect of pH) were conducted to evaluate the fluoride adsorption behavior of different aluminas. For all aluminas, both Langmiur and Freundlich models fitted the adsorption isotherms well and the calculation of thermodynamics showed that adsorption was spontaneous and endothermic; the kinetics was well described by the pseudo-second-order model and the weak acidic pH favored the fluoride adsorption. Acidity/basicity of alumina exhibited significant effect on the behaviors of adsorption and the process of ion exchange in fluoride removal. Acidic alumina exhibited higher ion exchange capacity, more positively charged surface, and better defluoridation performance (higher adsorption capacity and quicker removal of fluoride) than basic alumina. Acidic alumina also showed higher efficiency when treating natural ground water without pH adjustment. The difference in the adsorption properties was ascribed to the different exchange sites and the different behaviors of anion exchange. In the case of acidic alumina, more Cl − was exchanged with fluoride and the adsorption/release of OH − was dependent on the initial fluoride concentration. For basic alumina most of exchange sites were provided by OH − and fluoride was removed through the exchange between fluoride and OH − .

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Section: Characterization Of Aluminas With Different Typessupporting

confidence: 90%

Section: Preparation Of Aluminas With Different Typesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Adsorption of fluoride onto different types of aluminas

Gong

Liu

et al. 2012

Chemical Engineering Journal

121

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“…Characteristic bands are found at the same wave numbers as for methyl alcohol but their intensity is considerably larger. A broadening and increased intensity of the band at 660 cm −1 as compared to the initial solution is attributed to the presence of aluminum oxides [13,21,24]. The appearance of the broadened band at 1,030 cm −1 suggests the presence of the Al-OH bond [25].…”

Section: Resultsmentioning

confidence: 93%

“…Broad bands in the range of 400-800 cm −1 represent stretching vibrations of Al-O bonds for octahedral (AlO 6 ) and tetrahedral (AlO 4 ) coordination in ultra fine particles or amorphous structure of aluminum hydroxide. A broad band observed at 3,000-3,750 cm −1 originates from stretching vibrations of O-H [24]. A band at 1,640 cm −1 is related to adsorbed water.…”

Section: Resultsmentioning

confidence: 99%

Alumina-based nanoparticles obtained by anodic dissolution of Al in electrolytes with alcohol solvents

Starowicz

Stypuła

2014

J Solid State Electrochem

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In the present work, alumina-based nanoparticles were produced by an electrochemical method. Alcohols (methanol, ethanol, and propanol) containing 5 % of water and LiCl were applied as electrolytes. Sizes of the micelles in the obtained solution ranged from 200 nm to over 1 μm depending on the used alcohol. Measurements performed by ultraviolet and visible light (UV-VIS) spectroscopy indicated a presence of aluminum oxides and hydroxides in the solution. Studies using transmission electron microscopy (TEM) revealed that the obtained nanoparticles are in a form of flakes and membranes and their size is~200 nm for methanol and 50 nm for propanol. The composition of the product was characterized by the Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD). It consists of amorphous Al oxides and hydroxides as well as poorly crystallized aluminates and metallic Al.

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Synergistic effects of aluminum hydroxide, red phosphorus, and expandable graphite on the flame retardancy and thermal stability of polyethylene

Thi

Nguyen

Oanh

et al. 2020

J of Applied Polymer Sci

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The flame‐retardant low‐density polyethylene (LDPE) composites loading aluminum hydroxide (ATH), red phosphorus (RP), and expandable graphite (EG) were successfully prepared. The flame retardancy, the thermo‐oxidative stability, and the mechanical property of the composites were investigated. The synergistic effect of ATH, RP, and EG on the flame‐retardant property and thermal behavior of LDPE were observed. The limiting oxygen index value of LDPE significantly increased from 17.1% to 25.4% upon the incorporation of 15 wt.% of the mixture of three fillers with ATH:RP:EG mass ratio of 1:1:1; and this composite achieved the V‐0 classification of the UL94 vertical burning test. The thermogravimetric analysis of this composite under air atmosphere revealed that its residue weight remained 27.89% at 900°C. Furthermore, the results of tension tests indicated that the surface modification of ATH by magnesium stearate and RP by poly(methylhydrosiloxane) noticeably improved the tensile strength and the elongation of the composite.

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Influences of pH value on the microstructure and phase transformation of aluminum hydroxide

Cited by 156 publications

References 28 publications

Adsorption of fluoride onto different types of aluminas

Adsorption of fluoride onto different types of aluminas

Alumina-based nanoparticles obtained by anodic dissolution of Al in electrolytes with alcohol solvents

Synergistic effects of aluminum hydroxide, red phosphorus, and expandable graphite on the flame retardancy and thermal stability of polyethylene

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