Studies of hydrolyzed aluminum chloride solutions. 1. Nature of aluminum species and composition of aqueous solutions

Soluble aluminum (Al 3+ ) may react with both ambient silica and antiscalant components to form colloidal foulants during reverse osmosis (RO) treatment. Whereas conventional treatment (coagulation/filtration/sedimentation/dual-media filtration) was being used prior to RO, aluminum sulfate (alum) and polyaluminum chloride (PACl) coagulants were evaluated at ambient pH (pH 7.8 to 7.9) and suppressed pH (pH 6.7) in an effort to lower the total aluminum to below 50 µg/L-a level previously observed to prevent RO membrane fouling. Additional tests were conducted with 5 mg/L citric acid added to the RO influent to chelate the soluble aluminum fraction. All tests were conducted with 1.5 to 2.5 mg/L chloramines present. Testing of a RO process fed with optimized alum-or PACl-coagulated water showed that PACl outperformed alum regardless of pH. Alum coagulation at ambient pH resulted in 184 to 273 µg/L total aluminum passing through the filtration process. Only by lowering the mean influent water pH to 6.7 was the mean soluble aluminum residual (45 µg/L) for alum coagulation reduced to below the 50 µg/L aluminum goal. Regardless of pH, for alum-coagulated waters, the higher aluminum carryover resulted in severe RO membrane fouling within 500 hours of operation. Only when a chelating agent (citric acid) was added to the RO feed was the loss in productivity and selectivity arrested. However, PACl consistently met the 50-µg/L goal for both total and soluble aluminum for all pH levels tested, which resulted in more stable membrane performance over time. Further research on the compatibility of PACl and polyamide membranes in the presence of chloramines is needed as data from this project suggest PACl coagulation may facilitate membrane oxidation.

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“…PACl consists of preformed polymers of varying lengths, distinct from alum that mainly consists of monomers [15]. …”

Section: E-10mentioning

confidence: 99%

Control of residual aluminum from conventional treatment to improve reverse osmosis performance

Gabelich¹,

Ishida

Gerringer³

et al. 2006

Desalination

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“…[4][5][6]. However, it can determine only a few Al species like mononuclear (Al m ), oligomers (Al 2 even Al 3 ), and tridecamer (Al 13 ).…”

Section: Introductionmentioning

confidence: 99%

Differentiation of hydroxyl-aluminum species at lower OH/Al ratios by combination of 27Al NMR and Ferron assay improved with kinetic resolution

Feng

Tang

Wang

2007

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…Il existe, en effet, de nombreuses espèces intermédiaires entre l'ion AI 3 * hydraté et le trihydroxyde d'aluminium. Différentes structures de complexes polynucléaires ont ainsi été proposées par BROSSET et al (1954), MATIJEVIC et " STRYKER (1766), HAYDEN et RUBIN (1974), BOTTERO et al (1980BOTTERO et al ( ) (1982 ainsi que par KAPOL'SKii (1987).…”

Section: Pour Pallier Ces Inconvénients Le Service Des Eaux De La VIunclassified

Modélisation mathématique du taux de coagulant dans une station de traitement d'eau

Bazer-Bachi¹,

Puech-Coste²,

Aim³

et al. 2005

rseau

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Les auteurs, après une synthèse bibliographique sur la coagulation, présentent deux modèles mathématiques reliant la dose optimale d'un coagulant, le sulfate d'aluminium, à la qualité de l'eau brute.Un premier modèle applicable aux eaux dont la turbidité est inférieure à 20 NTU tient compte de quatre variables caractéristiques de l'eau brute qui sont : la turbidité, la résistivité, la température, la teneur en matières organiques.Le second modèle, utilisable pendant les périodes de crue, intègre un cinquième descripteur : la nature de la suspension minérale.Des essais effectués sur l'usine de Clairfont, qui alimente la rive gauche de Toulouse, montrent que ces modèles sont parfaitement adaptés pour automatiser l'injection du coagulant.When the source of supply of a water treatment plant has a streaming behaviour, it is sometimes difficult to adjust correctly the coagulant dose by jar-testing alone.Following this remark, the municipal water utilities of Toulouse city (France) has decided to conduct a study on the modelisation of coagulant dose as a function of the quality of raw water.This study started first by a bibliographic survey to find the main parameters which affect the flocculation mechanisms, followed by a hydrologic study of the upper Garonne river to characterize as well as possible its behavior.This was following by a study of the influence of certain parameters on the efficiency of coagulation by aluminium sulfate on synthetic waters having characteristics close to those of the Garonne river (BAZER-BACHI, 1986). This work showed the rote of the turbidity, of the resistivity, of the temperature and of the nature of mineral suspension. It also indicated the non-linearity between the optimum coagulant dose and these parameters as well as the interactions between them.These conclusions led us to use a second degree polynomial model, as : k k kY = bo + ∑ bi Xi + ∑ bii X2i + ∑ bij Xi Xj i = 1, j = 2, i ≠ jData were collected from modified jar-test on water from the Garonne River, characterized by physico-chemical (turbidity, temperature, pH, resistivity, CEC, MES, colloid titralion, organic matters) and chemical analyses (mineralisation). As the hydrological study showed that the nature of colloid suspension changed only during storm events, the modelisation was divided in two sub-groups :- a « CALME » model, comprising four variables (turbidity, resistivity, temperature, organic matters), for low turbidity waters (below 20 NTU),- a « CRUES » a model, using a fifth parameter representative of the nature of suspension (the ratio between colloid titration and turbidity).The « CALME » model, which fitted very well, showed the primordial influence of the temperature and organic matters, and then of the turbidity. Removal of resistivity was not advisable, as this parameter showed strong interactions with turbidity and organic matters (fig. 3, 4).The « CRUES » model showed the primordial role of the turbidity followed by the temperature and then by organic matters. The tw...

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Studies of hydrolyzed aluminum chloride solutions. 1. Nature of aluminum species and composition of aqueous solutions

Cited by 422 publications

References 4 publications

Control of residual aluminum from conventional treatment to improve reverse osmosis performance

Control of residual aluminum from conventional treatment to improve reverse osmosis performance

Differentiation of hydroxyl-aluminum species at lower OH/Al ratios by combination of 27Al NMR and Ferron assay improved with kinetic resolution

Modélisation mathématique du taux de coagulant dans une station de traitement d'eau

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