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Dynamics of flocculation of lignocellulosic hydrolyzates by polymers / L. Rakesh Yasarla in Industrial & engineering chemistry research, Vol. 51 N° 19 (Mai 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 19 (Mai 2012) . - pp. 6847-6861 Titre : Dynamics of flocculation of lignocellulosic hydrolyzates by polymers Type de document : texte imprimé Auteurs : L. Rakesh Yasarla, Auteur ; Bandaru V. Ramarao, Auteur Année de publication : 2012 Article en page(s) : pp. 6847-6861 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Flocculation Résumé : Pretreatment of lignocellulosic materials involves the solubilization of heniicelluloses, small portions of the lignin, and such components. The hemicellulose solutions are hydrolyzed for downstream fermentation into biofuels or biomaterials. Hydrolyzates produced by pretreatment contain significant colloidal material that is anionically charged. Many of the compounds that are present in the hydrolyzates are inhibitory to fermentation and interfere with downstream separations. The flocculation of this colloidal material makes separations easier by sedimentation and can reduce the fouling tendencies of membranes. It can also reduce the toxicity of the hydrolyzates to fermentation micro-organisms. We studied the dynamics of flocculation of lignocellulosic hydrolyzates with a variety of flocculating agents: electrolytes (alum) and polymers (PEI, pDADMAC, CPAM). It was found that trivalent cations were the most effective suspension destabilizers among the electrolytes, while the cationic polymers could cause flocculation and also redispersion depending on their dosage levels. Flocculation reduced the hydrolyzates' turbidity from > 10000 to under 20. With PEI and pDADMAC, flocculation occurred rapidly when the zeta potential of the colloid was close to zero showing that charge neutralization is the significant destabilizing mechanism. At higher dosages, redispersion occurred indicating that patching is also important in flocculation. Flocculation by PEI was sensitive to pH (from hydrolyzate pH of 3 to 8) with increased dosage necessary at higher pH values. The cationicity of PEI is reduced at higher pH which results in loss of its effectiveness. On the other hand, the zeta potential was largely unaffected with CPAM dosage indicating the dominance of bridging flocculation. Floc sizes ranged up to 3 mm, depending on flocculant dose and pH. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25900238 [article] Dynamics of flocculation of lignocellulosic hydrolyzates by polymers [texte imprimé] / L. Rakesh Yasarla, Auteur ; Bandaru V. Ramarao, Auteur . - 2012 . - pp. 6847-6861. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 19 (Mai 2012) . - pp. 6847-6861 Mots-clés : Flocculation Résumé : Pretreatment of lignocellulosic materials involves the solubilization of heniicelluloses, small portions of the lignin, and such components. The hemicellulose solutions are hydrolyzed for downstream fermentation into biofuels or biomaterials. Hydrolyzates produced by pretreatment contain significant colloidal material that is anionically charged. Many of the compounds that are present in the hydrolyzates are inhibitory to fermentation and interfere with downstream separations. The flocculation of this colloidal material makes separations easier by sedimentation and can reduce the fouling tendencies of membranes. It can also reduce the toxicity of the hydrolyzates to fermentation micro-organisms. We studied the dynamics of flocculation of lignocellulosic hydrolyzates with a variety of flocculating agents: electrolytes (alum) and polymers (PEI, pDADMAC, CPAM). It was found that trivalent cations were the most effective suspension destabilizers among the electrolytes, while the cationic polymers could cause flocculation and also redispersion depending on their dosage levels. Flocculation reduced the hydrolyzates' turbidity from > 10000 to under 20. With PEI and pDADMAC, flocculation occurred rapidly when the zeta potential of the colloid was close to zero showing that charge neutralization is the significant destabilizing mechanism. At higher dosages, redispersion occurred indicating that patching is also important in flocculation. Flocculation by PEI was sensitive to pH (from hydrolyzate pH of 3 to 8) with increased dosage necessary at higher pH values. The cationicity of PEI is reduced at higher pH which results in loss of its effectiveness. On the other hand, the zeta potential was largely unaffected with CPAM dosage indicating the dominance of bridging flocculation. Floc sizes ranged up to 3 mm, depending on flocculant dose and pH. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25900238

Effect of hot water extraction on hardwood kraft pulp fibers (Acer saccharum, Sugar Maple) / Gustavo V. Duarte in Industrial & engineering chemistry research, Vol. 50 N° 17 (Septembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 17 (Septembre 2011) . - pp. 9949–9959 Titre : Effect of hot water extraction on hardwood kraft pulp fibers (Acer saccharum, Sugar Maple) Type de document : texte imprimé Auteurs : Gustavo V. Duarte, Auteur ; Bandaru V. Ramarao, Auteur ; Thomas E. Amidon, Auteur Année de publication : 2011 Article en page(s) : pp. 9949–9959 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Kraft  pulp  fibers  saccharum  Sugar  maple Résumé : This study focuses on the properties of fibers obtained from the kraft pulping of pre-extracted sugar maple wood chips. Hot-water pre-extraction was carried out for different times characterized by P-factors in the range of 12 and 600 h. It was found that pre-extraction of the chips significantly accelerates delignification during Kraft pulping such that the H-factors necessary to obtain equivalent delignification (i.e., the same κ numbers) were substantially smaller than control cooks (i.e., with unextracted chips). Unbleached pulps of κ numbers of 35, 25, and 15 were prepared, and their papermaking properties were tested. The hemicellulose content of the pulps decreased with pretreatment, whereas the cellulose contents increased. Pretreatment also resulted in an increase in the pulp viscosity. The fiber lengths showed no change, but the fines content was reduced. The kink index of pre-extracted pulps showed large increases. The porosity of the cell wall also increased with extraction severity as did the mean pore size. The water retention values (WRV) also increased with extraction probably because of the increased fiber porosity. The ζ potential of the fines remained unaffected, whereas the total charge (cationic) demand of the pulps decreased with pre-extraction. There is also a significant loss of tensile and burst strengths of handsheets made with extracted pulps possibly as a consequence of the increased kink and curl index and decreased interfiber bonding ability. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie200639u [article] Effect of hot water extraction on hardwood kraft pulp fibers (Acer saccharum, Sugar Maple) [texte imprimé] / Gustavo V. Duarte, Auteur ; Bandaru V. Ramarao, Auteur ; Thomas E. Amidon, Auteur . - 2011 . - pp. 9949–9959. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 17 (Septembre 2011) . - pp. 9949–9959 Mots-clés : Kraft  pulp  fibers  saccharum  Sugar  maple Résumé : This study focuses on the properties of fibers obtained from the kraft pulping of pre-extracted sugar maple wood chips. Hot-water pre-extraction was carried out for different times characterized by P-factors in the range of 12 and 600 h. It was found that pre-extraction of the chips significantly accelerates delignification during Kraft pulping such that the H-factors necessary to obtain equivalent delignification (i.e., the same κ numbers) were substantially smaller than control cooks (i.e., with unextracted chips). Unbleached pulps of κ numbers of 35, 25, and 15 were prepared, and their papermaking properties were tested. The hemicellulose content of the pulps decreased with pretreatment, whereas the cellulose contents increased. Pretreatment also resulted in an increase in the pulp viscosity. The fiber lengths showed no change, but the fines content was reduced. The kink index of pre-extracted pulps showed large increases. The porosity of the cell wall also increased with extraction severity as did the mean pore size. The water retention values (WRV) also increased with extraction probably because of the increased fiber porosity. The ζ potential of the fines remained unaffected, whereas the total charge (cationic) demand of the pulps decreased with pre-extraction. There is also a significant loss of tensile and burst strengths of handsheets made with extracted pulps possibly as a consequence of the increased kink and curl index and decreased interfiber bonding ability. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie200639u