Enhanced coagulation with polyaluminum chlorides: Role of pH/Alkalinity and speciation

Yan, Mingquan; Wang, Dongsheng; Yu, Jianfeng; Ni, Jinren; Edwards, Marc; Qu, Jiuhui

doi:10.1016/j.chemosphere.2008.01.019

Cited by 165 publications

(80 citation statements)

References 22 publications

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“…As shown in Fig. 6, the effect of pH on DOC removal by HPAC and PACl as coagulant is less than metal salts because polymeric aluminum species pre-formed in HPAC and PACl are less affected by pH [14,19], especially for HPAC. The HPAC results are likely due to the nature of the polymerized Al species but also the presence of the synthetic cationic polymer which would not be affected by pH so should improve NOM removal relative to the standard PACl.…”

Section: Strategies For Nom Removalmentioning

confidence: 95%

“…Many researchers have found that for high pH water with lower alkalinity, the NOM is removed more efficiently [13,14]. LW is of lower alkalinity than YW and the NOM in it was removed more efficiently.…”

Section: Seasonal Variation Of Coagulation Featurementioning

confidence: 99%

“…PACl, one form of inorganic polymer flocculant, contains high level of charged polymeric Al hydrolysis products through pre-hydrolysis. The pre-formed medium polymer species (Al b ) are highly stable, even after being dosed into a high alkalinity and pH water [14,19]. The performance of PACls in the treatment of high alkalinity water was investigated.…”

Section: Coagulant Optimizationmentioning

confidence: 99%

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Natural organic matter (NOM) removal in a typical North-China water plant by enhanced coagulation: Targets and techniques

Yan

Wang²,

Ni³

et al. 2009

Separation and Purification Technology

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a b s t r a c tSeasonal coagulation objectives for a typical North-China water treatment plant with micro-polluted and high alkalinity source waters are proposed in this paper. These are based on a yearlong data collection period where raw water characteristics, trihalomethanes formation potential (THMFP) and coagulation features were investigated using a jar test procedure, resin absorption and ultrafiltration fractionations. Three approaches beyond simply increasing the coagulant dose were used to achieve optimized coagulation. One is coagulation by adjusting the pH of the raw water when metal salt coagulants (FeCl 3 and AlCl 3 ) are used. At pH levels of about 5.0 for FeCl 3 and about 5.8 for AlCl 3 , the highest removal of natural organic matter (NOM) was obtained, which is twice that without pH control. The second is enhanced coagulation through coagulant optimization based on raw water characteristics. A high efficient composite polyaluminum chloride (HPAC) coagulant was developed for the water taking the advantages of polyaluminum chloride (PACl) and other additives. HPAC exhibited 30% more efficiency than AlCl 3 , FeCl 3 and polyaluminum chloride (PACl) in dissolved organic carbon (DOC) removal and was also very effective in turbidity removal. The third is enhanced softening with coagulant addition. Higher removal of NOM is achieved by enhanced softening with coagulant addition conditions as compared with conventional coagulation at natural pH. Especially with PACl addition, it can enhance the formation of Mg(OH) 2 precipitate and remove NOM efficiently at a relatively lower pH range (pH < 10). By this approach, the pH for enhanced softening can be decreased significantly into a practical operation pH range for high-hardness water at a treatment plant.

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Section: Strategies For Nom Removalmentioning

confidence: 95%

Section: Seasonal Variation Of Coagulation Featurementioning

confidence: 99%

Section: Coagulant Optimizationmentioning

confidence: 99%

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Natural organic matter (NOM) removal in a typical North-China water plant by enhanced coagulation: Targets and techniques

Yan

Wang²,

Ni³

et al. 2009

Separation and Purification Technology

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“…According to the analysis method of ferron colorimetric and 27 Al nuclear magnetic resonance, Al species are usually divided into monomeric species (e.g., Al(OH) 2 + , Al 2 (OH) 2 4+ , Al 3 (OH) 4 5+ ), medium polymer species (i.e., AlO 4 Al 12 (OH) 24 (H 2 O) 12 7+ , Al 13 ), and colloidal or solid species [28][29][30]. Previous studies indicated that with high positive charge and strong binding ability [31][32][33], both pre-formed and in-situ formed Al 13 polymer are the most active species in Al based coagulants responsible for coagulation [21,34,35]. Thus, researchers paid more attention to the regulatory method of Al 13 formation and subsequent efficiency enhancement during CC process.…”

Section: Introductionmentioning

confidence: 99%

An effective method for improving electrocoagulation process: Optimization of Al 13 polymer formation

Wang

Sun

et al. 2016

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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h i g h l i g h t s• Al 13 polymer formation in EC process are investigated.• Al 13 species fraction positively correlated with removal of turbidity and organic.• pH 5-7 and lowering j favored the formation of Al 13 polymer.• Al 13 fraction can reach more than 60% under optimal EC conditions. Keywords: Electrocoagulation Aluminum species Electrochemical parameter a b s t r a c t Al 13 polymer has been believed to be the most active species responsible for coagulation. The character of Al species distribution and the formation of Al 13 polymer in electrocoagulation (EC) process were investigated in order to provide insight into optimizing EC operation and design. The results indicated that predominant Al species shifted from monomer toward medium polymer then to larger polymer or Al(OH) (s) with increasing EC time. The in-situ Al 13 polymer could be generated in EC process, and became the dominant species during 5-15 min. In EC process, Al 13 species fraction positively correlated with the removal of turbidity and organic. The increase of pH and current density could accelerate the hydrolysis-polymerization process of Al 3+ . pH 5-7 and lowering current density favored the formation of Al 13 polymer during EC process, EC process with bipolar electrodes had a higher yield of monomeric and Al 13 species, while EC process with monopolar electrodes facilitated the formation of larger polymer or Al(OH) (s) . The content of Al 13 polymer can reach more than 60% under optimal conditions.

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“…Among many coagulants, polyaluminum chloride (PACl) is the most widely used coagulant and has been paid attention by researchers (Edzwald, 1993;Hu et al, 2006;Qu and Liu, 2004;Tang and Luan, 1995;Wang et al, 2002;Yan et al, 2008). Many studies have confirmed that the content of Al b and Al c in PACl are correlated closely to Al 13 and Al 30 , respectively (Akitt and Farthing, 1981;Chen et al, 2005;He et al, 2003;Yan et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Preparation of high concentration polyaluminum chloride with high content of Alb or Alc

Zhao¹,

Zhang²,

Luan³

et al. 2009

Journal of Environmental Sciences

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A novel membrane distillation concentration method was used to prepare high concentration polyaluminum chloride (PACl) with high content of Al b or Al c . 2.52 mol/L PACl 1 with 88% Al b and 2.38 mol/L PACl 2 with 61% Al c were successfully prepared. Three coagulants, AlCl 3 , PACl 1 and PACl 2 were investigated on their hydrolysis behavior and speciation under different conditions. The effects of pH and dilution ratio on Al species distribution were investigated by ferron assay. Experimental result showed that pH had a significant effect on Al species distribution for the three coagulants. Dilution ratio had little effects on Al b and Al c distribution in whole dilution process except the beginning for PACl 1 and PACl 2 . The results indicated that transformation of Al depends largely on their original composition. AlCl 3 was the most unstable coagulant among these three coagulants during hydrolysis process. PACl 1 and PACl 2 with significant amounts of highly charged and stable polynuclear aluminum hydrolysis products were less affected by the hydrolysis conditions and could maintain high speciation stability under various conditions.

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Enhanced coagulation with polyaluminum chlorides: Role of pH/Alkalinity and speciation

Cited by 165 publications

References 22 publications

Natural organic matter (NOM) removal in a typical North-China water plant by enhanced coagulation: Targets and techniques

Natural organic matter (NOM) removal in a typical North-China water plant by enhanced coagulation: Targets and techniques

An effective method for improving electrocoagulation process: Optimization of Al 13 polymer formation

Preparation of high concentration polyaluminum chloride with high content of Alb or Alc

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