Distinct coagulation mechanism and model between alum and high Al13-PACl

Wu, Xue-Bing; Ge, Xiaopeng; Wang, Dongsheng; Tang, Hongxiao

doi:10.1016/j.colsurfa.2007.04.046

Cited by 120 publications

(48 citation statements)

References 21 publications

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“…Different coagulation mechanisms occur for aluminum sulfate (alum) and PACl [16]. As a pre-hydrolyzed coagulant, PACl is becoming increasingly popular in the coagulation-flocculation process.…”

Section: Introductionmentioning

confidence: 99%

Coagulation behavior of polyaluminum chloride: Effects of pH and coagulant dosage

Ning

Zhang

Liu

et al. 2015

Chinese Journal of Chemical Engineering

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Section: Introductionmentioning

confidence: 99%

Coagulation behavior of polyaluminum chloride: Effects of pH and coagulant dosage

Ning

Zhang

Liu

et al. 2015

Chinese Journal of Chemical Engineering

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“…This kind of electro-patch coagulation differs from that of alum, with polycations adsorbing and complexing on the particle's surface rather than precipitates [13]. On the other hand, bridge-connection can also be included since aggregated Al 13 and other polymeric species formed during pre-hydrolyzation [14]. More evidence can be seen from the following floc size distribution and floc structure.…”

Section: Zeta Potential and Particle Removalmentioning

confidence: 83%

“…The prepared coagulants included conventional alum and PACl. The preparation and characterization followed the same method as our previous study reported [14]. From Table 1 and Fig.…”

Section: Silica Microspheres and Coagulantsmentioning

confidence: 99%

“…The comparative behaviors of traditional metal coagulants such as alum, versus tailor-made IPFs such as PACl, should be more clearly related to mechanism and model in both qualitative and quantitative respects, yet few papers have been published [11][12][13]. Recently, two distinct adsorption isotherms on microsphere SiO 2 at pH 6.5 have been assigned to alum and PACl with high content Al 13 , suggesting that the chemical species and their adsorptive behaviors determine the coagulation process [14]. To date, a rigorous theoretical understanding based on interaction force calculations has not been completed, even though Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and model [15,16] have long been applied to more conventional coagulation chemicals and processes.…”

Section: Introductionmentioning

confidence: 99%

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Distinct mechanisms of particle aggregation induced by alum and PACl: Floc structure and DLVO evaluation

Wang

et al. 2009

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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a b s t r a c tInteractions of silica microspheres were examined by light scattering in presence of alum and polyaluminum chloride (PACl) with various OH/Al ratios. The coagulation behaviors were investigated using different coagulant dosages at constant pH (6.5) and salt concentration (0.01 mol/L). Based on the measurement of size distribution and zeta potential, charge neutralization was proposed to be the primary coagulation step for all the coagulants while other distinct coagulation steps were also involved depending on in situ formed or preformed hydrolyzing products. Precipitate coverage and sweep flocculation were induced for alum, contrasted to polycation patch and bridge aggregation for PACl. Based on simplified DLVO theory, particle aggregation was explained in terms of interaction forces. It was demonstrated that PACl outperformed alum in particle agglomeration at lower concentration (1-2 mol/L), owing mainly to the considerable energy barrier reduction and deeper secondary minimum at longer distance induced by high positive polycations. The role of secondary minimum was found to be significant when secondary depth exceeded 12 kT. The interaction energy calculations coincided well with coagulation result for PACl, especially PACl22 with high content Al 13 . However, other interaction forces prevailed over the electrical repulsion for alum and PACl containing other aluminum species.

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“…The main differences between these products are their basicity, strength and the content of other species such as silica, calcium or even organic compounds [18][19][20]. Although the silica removal mechanism of polyaluminum coagulants is not well understood [17,21], there is a consensus in that they act by two primary coagulation mechanisms [18,22]: (1) charge neutralization of the negative particles by adsorption of positively charged dissolved aluminum species, and (2) enmeshment of particles in precipitated Al(OH) 3 .…”

Section: Introductionmentioning

confidence: 99%

Silica removal from newsprint mill effluents with aluminum salts

Latour

Miranda

Blanco

2013

Chemical Engineering Journal

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The main obstacle for the implementation of reverse osmosis (RO) in a treatment chain to reuse the effluent of a newsprint mill as fresh water is the high silica content of the water, which produces severe scaling on the membrane, thus, limiting its recovery. Coagulation is one of the preferred methods to reduce silica concentration. Five aluminum based coagulants have been tested at five dosages (500-2500 ppm) and three pHs (8.3, 9.5 and 10.5). All products showed their best efficiency at the highest dosage and pH, with the exception of alum, that was more efficient at intermediate dosages. A combination of a polyaluminum nitrate sulphate with a cationic quaternary polyamine (PANS-PA2), was the most efficient and versatile coagulant. It removed 97% of silica (5 ppm residual silica) at the optimal conditions (pH 10.5, 2500 ppm) and it was very efficient (76% silica removal) at pH 8.3, avoiding the need of any pH adjustment, and minimizing the conductivity and pH increase of the treated waters as well as obtaining some removal of the organic colloidal matter (≈25%).

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Distinct coagulation mechanism and model between alum and high Al13-PACl

Cited by 120 publications

References 21 publications

Coagulation behavior of polyaluminum chloride: Effects of pH and coagulant dosage

Coagulation behavior of polyaluminum chloride: Effects of pH and coagulant dosage

Distinct mechanisms of particle aggregation induced by alum and PACl: Floc structure and DLVO evaluation

Silica removal from newsprint mill effluents with aluminum salts

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