Studies on the mechanism of hydrolysis and polymerization of aluminum salts in aqueous solution: correlations between the “Core-links” model and “Cage-like” Keggin-Al13 model

Bi, Shuping; Wang, Chenyi; Cao, Qing; Zhang, Caihua

doi:10.1016/j.ccr.2003.11.001

Cited by 223 publications

(150 citation statements)

References 89 publications

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“…After being dosed into solution, Al 3+ tends to hydrolyze and polymerize immediately, and the formation of Al species such as bimomer, oligimer, Al polymer, sol/gel besides monomer Al as Al (OH) n (3Àn)+ (n = 0-2) occurs [14]. The presence of fluoride complicates the reactions greatly [13].…”

Section: Proposed Mechanism Of Fluoride Removal By Different Al Speciesmentioning

confidence: 99%

“…First, polymeric Al species exhibits higher positive charge than monomeric Al does [14] and shows stronger attraction towards fluoride. On the other hand, the average charge density carried by each Al atom of polymeric Al is lower as compared to monomeric Al [14]. Consequently, Al polymer with high polymerization degree tends to consume relatively small amount of OH À or fluoride ions to achieve charge neutralization of fluoride.…”

Section: Proposed Mechanism Of Fluoride Removal By Different Al Speciesmentioning

confidence: 99%

“…At elevated pH the OH À competition effect also occurs to inhibit fluoride removal and to release the complexed fluoride. In comparison to monomeric Al, polymeric Al shows net structure, and fluoride may attach onto inner-and outer-side of polymeric Al [14]. The outside fluoride is attached by ionic exchange and charge neutralization and is easy to be replaced by OH À .…”

Section: Proposed Mechanism Of Fluoride Removal By Different Al Speciesmentioning

confidence: 99%

“…Additionally, Al-F complexation also affects the hydrolysis of Al salts and their distribution and transformation afterwards. On the other hand, the hydrolysis of Al salts tends to form a series of Al species with different structures, charges, and polymerization character [14], and the diversity of Al species possibly impacts the interaction between fluoride and different Al species thereafter. PACl as polymeric species of Al salt shows superiority in removing particulate and organics as compared to traditional monomeric Al such as AlCl 3 , and PACl exhibits inherent advantages less independence on pH [15], less alkalinity consumption [16], and less sludge production [17].…”

Section: Introductionmentioning

confidence: 99%

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Coagulation behaviors of aluminum salts towards fluoride: Significance of aluminum speciation and transformation

Lan

Gong

et al. 2016

Separation and Purification Technology

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a b s t r a c tThis study investigates the effects of aluminum (Al) and F interactions on the coagulation behaviors of Al salts, i.e., AlCl 3 and polymer aluminum chloride (PACl) at different basicity (B) towards fluoride. These coagulants achieve the optimum fluoride removal over pH 6-7, and PACl exhibits higher removal efficiency than AlCl 3 does over pH 4-9. The removal of fluoride is positively correlated with the content of either Al 13 or Al b in Al-based coagulants over pH 4-9 and increases in the order: PACl 2 > PACl 1 > AlCl 3 . As for PACl, the increased B from 0 to 2.4 improves fluoride removal owing to the elevated ratios of Al b . However, at further increased B to 2.8, the formation of colloidal Al species

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Section: Proposed Mechanism Of Fluoride Removal By Different Al Speciesmentioning

confidence: 99%

Section: Proposed Mechanism Of Fluoride Removal By Different Al Speciesmentioning

confidence: 99%

Section: Proposed Mechanism Of Fluoride Removal By Different Al Speciesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Coagulation behaviors of aluminum salts towards fluoride: Significance of aluminum speciation and transformation

Lan

Gong

et al. 2016

Separation and Purification Technology

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“…So it has received the most attention (Bi et al, 2004;Gao et al, 2005 27 Al nuclear magnetic resonance (NMR) spectra about twenty years ago (Akitt and Farthing, 1981;Fu and Nazar, 1991). But its structure and stoichiometry were not determined, until 2000 it was characterized by Allouche et al (2000) and Rowsell and Nazar (2000) using X-ray diffraction and in situ 27 Al NMR.…”

Section: Introductionmentioning

confidence: 99%

Study on the hydrolysis/precipitation behavior of Keggin Al13 and Al30 polymers in polyaluminum solutions

Chen

Luan

Jia

et al. 2009

Journal of Environmental Management

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a b s t r a c tThe hydrolysis/precipitation behaviors of Al 3þ , Al 13 and Al 30 under conditions typical for flocculation in water treatment were investigated by studying the particulates' size development, charge characteristics, chemical species and speciation transformation of coagulant hydrolysis precipitates. The optimal pH conditions for hydrolysis precipitates formation for AlCl 3 , PAC Al13 and PAC Al30 were 6.5-7.5, 8.5-9.5, and 7.5-9.5, respectively. The precipitates' formation rate increased with the increase in dosage, and the relative rates were AlCl 3 [ PAC Al30 > PAC Al13 . The precipitates' size increased when the dosage increased from 50 mM to 200 mM, but it decreased when the dosage increased to 800 mM. The Zeta potential of coagulant hydrolysis precipitates decreased with the increase in pH for the three coagulants. The isoelectric points of the freshly formed precipitates for AlCl 3 , PAC Al13 and PAC Al30 were 7.3, 9.6 and 9.2, respectively. The Zeta potentials of AlCl 3 hydrolysis precipitates were lower than those of PAC Al13 and PAC Al30 when pH > 5.0. The Zeta potential of PAC Al30 hydrolysis precipitates was higher than that of PAC Al13 at the acidic side, but lower at the alkaline side. The dosage had no obvious effect on the Zeta potential of hydrolysis precipitates under fixed pH conditions. The increase in Zeta potential with the increase in dosage under uncontrolled pH conditions was due to the pH depression caused by coagulant addition. Al-Ferron research indicated that the hydrolysis precipitates of AlCl 3 were composed of amorphous Al(OH) 3 precipitates, but those of PAC Al13 and PAC Al30 were composed of aggregates of Al 13 and Al 30 , respectively. Al 3þ was the most un-stable species in coagulants, and its hydrolysis was remarkably influenced by solution pH. Al 13 and Al 30 species were very stable, and solution pH and aging had little effect on the chemical species of their hydrolysis products. The research method involving coagulant hydrolysis precipitates based on Al-Ferron reaction kinetics was studied in detail. The Al species classification based on complex reaction kinetic of hydrolysis precipitates and Ferron reagent was different from that measured in a conventional coagulant assay using the Al-Ferron method. The chemical composition of Al a , Al b and Al c depended on coagulant and solution pH. The Al b measured in the current case was different from Keggin Al 13 , and the high Al b content in the AlCl 3 hydrolysis precipitates could not used as testimony that most of the Al 3þ was converted to highly charged Al 13 species during AlCl 3 coagulation.

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2010

Surface Complexation Modeling

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Studies on the mechanism of hydrolysis and polymerization of aluminum salts in aqueous solution: correlations between the “Core-links” model and “Cage-like” Keggin-Al13 model

Cited by 223 publications

References 89 publications

Coagulation behaviors of aluminum salts towards fluoride: Significance of aluminum speciation and transformation

Coagulation behaviors of aluminum salts towards fluoride: Significance of aluminum speciation and transformation

Study on the hydrolysis/precipitation behavior of Keggin Al13 and Al30 polymers in polyaluminum solutions

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