Mechanistic study of ultrafiltration membrane fouling in the separation of molecular-size characterized pulp and paper mill effluents

Persistent Link:
http://hdl.handle.net/10150/284936
Title:
Mechanistic study of ultrafiltration membrane fouling in the separation of molecular-size characterized pulp and paper mill effluents
Author:
Kommineni, Sunil
Issue Date:
1999
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The use of ultrafiltration (UF) to treat pulp mill effluents is limited by fouling of membrane surfaces and pores. In prior studies with pulp mill effluents, no efforts were made to relate the molecular-size distribution of the solute molecules to the membrane fouling mechanisms. This dissertation presents a novel protocol for obtaining certain essential size distribution parameters, such as, the average molecular weight (M(w)), average molecular number (M(n)) and heterogeneity index (HI) to describe complex industrial wastewaters including the extraction (E)-stage effluent. This novel molecular sizing protocol was verified using challenge solutions containing solutes of known molecular weight. In these tests, the measured M(w)'s were within ±5% of the expected M(w)'s. A comprehensive model to describe the UF membrane productivity during the treatment of E-stage effluent was developed. This model accounts for variations in membrane, feed water and operational variables. The feed water variables that were incorporated into the model include molecular size distribution, viscosity and concentration. Also, included in the model are the operational variables such as trans-membrane pressure and cross-flow velocity. This model predicted the fluxes for the E- and oxygenated E-stage (E₀) effluents within an error of 9%. The UF membrane fouling by E-stage effluent was quantified employing fouling potential factors. An increase in the molecular weight cut-off (MWCO) of the membranes resulted in increased irreversible fouling possibly by increased pore plugging. Lower irreversible fouling was observed for pulp mill effluents with high M(w)'s. The role of surfactants in reducing the membrane fouling was also discussed. The ratio of M(w) of feed wastewater to the MWCO of the membrane, denoted by λ, effectively represents the ratio of the average diameter of the solute molecule to the nominal diameter of the pore. Membrane rejection and fouling potentials were related to λ. The measured apparent diffusion (D) and mass transfer (k) coefficients for the E- and E₀-stage effluents across the membranes were found to confirm to D ∼ M(w)⁻⁽⁰·³³ ᵗᵒ ⁰·⁴⁸⁾ and k ∼ D⁰·⁶⁶.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Engineering, Chemical.; Engineering, Civil.; Engineering, Environmental.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Chemical and Environmental Engineering
Degree Grantor:
University of Arizona
Advisor:
Sierka, Raymond A.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleMechanistic study of ultrafiltration membrane fouling in the separation of molecular-size characterized pulp and paper mill effluentsen_US
dc.creatorKommineni, Sunilen_US
dc.contributor.authorKommineni, Sunilen_US
dc.date.issued1999en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe use of ultrafiltration (UF) to treat pulp mill effluents is limited by fouling of membrane surfaces and pores. In prior studies with pulp mill effluents, no efforts were made to relate the molecular-size distribution of the solute molecules to the membrane fouling mechanisms. This dissertation presents a novel protocol for obtaining certain essential size distribution parameters, such as, the average molecular weight (M(w)), average molecular number (M(n)) and heterogeneity index (HI) to describe complex industrial wastewaters including the extraction (E)-stage effluent. This novel molecular sizing protocol was verified using challenge solutions containing solutes of known molecular weight. In these tests, the measured M(w)'s were within ±5% of the expected M(w)'s. A comprehensive model to describe the UF membrane productivity during the treatment of E-stage effluent was developed. This model accounts for variations in membrane, feed water and operational variables. The feed water variables that were incorporated into the model include molecular size distribution, viscosity and concentration. Also, included in the model are the operational variables such as trans-membrane pressure and cross-flow velocity. This model predicted the fluxes for the E- and oxygenated E-stage (E₀) effluents within an error of 9%. The UF membrane fouling by E-stage effluent was quantified employing fouling potential factors. An increase in the molecular weight cut-off (MWCO) of the membranes resulted in increased irreversible fouling possibly by increased pore plugging. Lower irreversible fouling was observed for pulp mill effluents with high M(w)'s. The role of surfactants in reducing the membrane fouling was also discussed. The ratio of M(w) of feed wastewater to the MWCO of the membrane, denoted by λ, effectively represents the ratio of the average diameter of the solute molecule to the nominal diameter of the pore. Membrane rejection and fouling potentials were related to λ. The measured apparent diffusion (D) and mass transfer (k) coefficients for the E- and E₀-stage effluents across the membranes were found to confirm to D ∼ M(w)⁻⁽⁰·³³ ᵗᵒ ⁰·⁴⁸⁾ and k ∼ D⁰·⁶⁶.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectEngineering, Chemical.en_US
dc.subjectEngineering, Civil.en_US
dc.subjectEngineering, Environmental.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineChemical and Environmental Engineeringen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorSierka, Raymond A.en_US
dc.identifier.proquest9946812en_US
dc.identifier.bibrecord.b39915128en_US
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