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Titre :
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Coagulation of bentonite suspension by polyelectrolytes or ferric chloride : floc breakage and reformation (2010)
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Auteurs :
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E. Barbot, Auteur ;
P. Dussouillez, Auteur ;
J. Y. Bottero, Auteur
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Type de document :
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Article : texte imprimé
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Dans :
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Chemical engineering journal (Vol. 156 N° 1, Janvier 2010)
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Article en page(s) :
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pp. 83-91
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Note générale :
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Génie Chimique
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Langues :
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Anglais
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Index. décimale :
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660
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Tags :
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Coagulation Flocculation Ferric chloride Polyelectrolytes Shear stress Laser granulometry
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Résumé :
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Coagulation process usually involves different hydrodynamic conditions, in particular when it is followed by a filtration step. In this study, coagulation performance was investigated under a wide range of shear stress. Floc behaviour was followed in-line by laser granulometry to determine size distribution and structure. Synthetic suspension of bentonite in tap water was used as a reference for mineral solids in surface water. Three cationic polymers (polyamine based and polyDADMAC) and ferric chloride were tested using different coagulation reactor geometries. Jar-test indicated coagulation performance under mild hydrodynamic conditions and Taylor–Couette reactors were used to create shear stresses up to 8 Pa. Flocs formed with ferric chloride are not able to grow under middle shear stress like 1.5 Pa. On the contrary, polyelectrolytes lead to large flocs, dense (Df = 2.6) and resistant to shear stress. A qualitative comparison of floc resistance to shear depending on hydrodynamic conditions and coagulant type is given through the calculation of the strength factor. Fractal dimension measurements indicate a mechanism of particle erosion when flocs are subjected to a higher shear stress in Taylor–Couette reactor. Floc re-growth is also investigated, and breakage appears to be non-reversible regardless of coagulant and conditions experimented.
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DEWEY :
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660
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ISSN :
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1385-8947
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En ligne :
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http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFJ-4XF840K-1&_user=6909337&_coverDate=01%2F01%2F2010&_alid=1262973641&_rdoc=27&_fmt=high&_orig=search&_cdi=5228&_sort=r&_docanchor=&view=c&_ct=31&_acct=C000070790&_version=1&_urlVersion=0&_userid
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