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Adsorption Kinetics of cationic Polyelectrolytes studied with Stagnation Point Adsorption Reflectometry and Quartz Crystal Microgravimetry
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0001-8622-0386
2008 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 14, 7329-7337 p.Article in journal (Refereed) Published
Abstract [en]

The effects of charge density, pH, and salt concentration on polyelectrolyte adsorption onto the oxidized surface of silicon wafers were studied using stagnation point adsorption reflectometry and quartz crystal microgravimetry. Five different polyelectrolytes-cationic polyacrylamides of four charge densities and one cationic dextran-were examined. The adsorption kinetics was characterized using each technique, and the adsorption kinetics observed was in line with the impinging jet theory and the theory for one-dimensional diffusion, respectively. The polyelectrolyte adsorption increased with pH as an effect of the increased silica surface charge. A maximum in the saturation adsorption for both types of polyelectrolytes was found at 10 mM NaCl concentration. A significant adsorption also occurred at I M NaCl, which indicated a significant nonionic contribution to the adsorption mechanism. The fraction of solvent in the adsorbed layer was determined to be 70-80% by combining the two analysis techniques. This indicated a loose structure of the adsorbed layer and an extended conformation at the surface, favoring loops and tails. However, considering the solution structure with a hydrodynamic diameter larger than 100 nm for the CPAM and a thickness of the adsorbed layer on the order of 10 nm, the results showed that the adsorption is accompanied by a drastic change in polymer conformation. Furthermore, this conformation change takes place on a time scale far shorter than seconds.

Place, publisher, year, edition, pages
2008. Vol. 24, no 14, 7329-7337 p.
Keyword [en]
Charge density; Concentration (process); Curve fitting; Electrolytes; Fluid dynamics; Fluid mechanics; Glucose; Nonmetals; Oxide minerals; pH effects; Polyelectrolytes; Polymers; Powders; Quartz; Reflection; Reflectometers; Silica; Silicate minerals; Silicon; Silicon compounds; Silicon wafers; Sodium alloys; Surface charge
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-6014DOI: 10.1021/la800198eISI: 000257468300042Scopus ID: 2-s2.0-47949120059OAI: oai:DiVA.org:kth-6014DiVA: diva2:10585
Note
QC 20100719. Uppdaterad från manuskript till artikel (20100719).Available from: 2006-06-21 Created: 2006-06-21 Last updated: 2010-07-20Bibliographically approved
In thesis
1. Polyelectrolyte adsorption on oppositely charged surfaces - Conformation and adsorption kinetics
Open this publication in new window or tab >>Polyelectrolyte adsorption on oppositely charged surfaces - Conformation and adsorption kinetics
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [sv]

Denna avhandling presenterar experimentella studier av polyelektrolytadsorption på motsatt laddade ytor, där substrat av både kiseloxid och blekt barrsulfatmassa har använts. Ett huvudsakligt syfte med denna forskning var att karaktärisera konformationen hos adsorberade skikt av katjonisk polyakrylamid (CPAM) i jämförelse med katjonisk dextran (Cdextran) och relatera denna information till inbindningskapaciteten av kolloidal kiselsyra. Ett andra syfte i denna avhandling var att studera kinetiken för sekventiell adsorption av polyamidamin epiklorhydrin (PAE) och karboxymetyl cellulosa (CMC) på massafibrer och att bestämma adsorptionsisotermer för deponering av polyelektrolyter skikt för skikt på massafibrer.

Adsorptionen av CPAM på kiseloxidytor studeras med stagnationspunkts-reflektometri och kvartskristalls-mikrogravimetri för att bestämma adsorptionskinetiken och mättnadsadsorptionens beroende av polyelektrolytens laddningstäthet, pH och NaCl koncentration. Konformationen hos adsorberade skikt av CPAM och Cdextran bestämdes både före och efter sekundär tillsats av kolloidal kiselsyra (CS) och adsorptionen av CS kvantifierades också som funktion av yttäckningen av polyelektrolyt.

Resultaten indikerar att laddningstätheten hos CPAM kontrollerar den adsorberade mängden på kiseloxidytor vid låga NaCl koncentrationer. Både adsorptionen av CPAM och Cdextran på kiseloxid visades vara effektiv i NaCl koncentrationer upp till 1 M, vilket indikerar ett signifikant bidrag av icke-jonisk interaktion mellan polyelektrolyterna och kiseloxid. Adsorptionen av CS var högre på föradsorberad CPAM än Cdextran. Konformationen hos de adsorberade skikten efter tillsats av CS sågs expandera signifikant för skikt baserade på CPAM medan skikt av Cdextran vid låga salthalter verkade återta sin konformation efter en temporär expansion.

I den andra delen av avhandlingen studerades sekventiell adsorption av PAE och CMC på massafibrer. Adsorptionsisotermer skikt för skikt på avkryllad massa visade att PAE adsorberade i större mängd än CMC, både i hänseende av massa och laddning. Adsorptionen av PAE var signifikant långsammare än CMC och adsorptionstiden till 90% av mättnadsadsorptionen bestämdes till 3 respektive 1 minut. Zetapotentialen för kryll bestämdes för adsorption av de två första polyelektrolytskikten och resultaten tydde på att kryllmaterialet omladdade inom en minut efter tillsatserna av polyelektrolyt. Reflektometriförsök inom sekventiell adsorption av PAE och CMC på kiseloxid antydde att den låga molekylviktsfraktionen av PAE störde uppbyggnaden av polyelektrolyt-multiskikten.

Abstract [en]

This thesis presents experimental studies of polyelectrolyte adsorption on oppositely charged surfaces, where substrates of both silica and bleached softwood kraft pulp were used. A major aim of this research was to characterise the conformation of adsorbed layers of cationic polyacrylamide (CPAM), in comparison to cationic dextran (Cdextran), and relate this information to the binding capacity of colloidal silica. A second aim in this thesis was to study the kinetics of the sequential adsorption of polyamide epichlorohydrine (PAE) and carboxymethyl cellulose (CMC) on pulp fibres, and to determine the adsorption isotherms for the layer-by-layer deposition of polyelectrolytes on pulp fibres.

The adsorption of CPAM on silica surfaces was studied using stagnation point adsorption reflectometry and quartz crystal microgravimetry to determine its adsorption kinetics as well as the dependencies of polyelectrolyte charge densities, pH, and NaCl concentration on saturation adsorption. The conformation of adsorbed layers of CPAM and Cdextran, analysed in terms of amount of water and layer thickness, was determined both before and after the secondary adsorption of colloidal silica (CS), and the adsorption of CS was also quantified as a function of the surface coverage of the polyelectrolyte.

Results indicate that the charge density of CPAM controlled the amount of the polyelectrolyte adsorbed on silica surfaces at low NaCl concentrations. The adsorption of both CPAM and Cdextran on silica was shown to be effective at up to 1 M NaCl concentrations, which indicates that non-ionic interactions between the polyelectrolytes and silica contribute significantly. CS adsorption was higher on pre-adsorbed CPAM than on Cdextran. The conformation of the adsorbed layer after CS addition was seen to expand significantly in CPAM-based layers, while the Cdextran layer appeared to restore its conformation after a temporary expansion at low salt concentrations.

In the second part of the thesis, the sequential adsorption of PAE and CMC on pulp fibres was determined using the polyelectrolyte titration technique. Layer-by-layer adsorption isotherms derived on fractionated pulp showed that PAE adsorbed in higher amounts than CMC did, both in terms of adsorbed mass and adsorbed charge. The adsorption of PAE was significantly slower compared to CMC, and the adsorption times required to reach 90% of the saturation adsorption were 3 and 1 min, respectively. The zeta potential of pulp fines was determined for the adsorption of the two first polyelectrolyte layers, and data indicated that the fines recharge within one minute after the polyelectrolyte additions. Reflectometry experiments regarding the sequential adsorption of PAE and CMC on silica indicated that the low-molecular-weight fraction of PAE disturbed the formation of polyelectrolyte multilayers.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 43 p.
Series
Trita-FPT-Report, ISSN 1652-2443 ; 2006:14
Keyword
Polyelectrolyte adsorption, adsorption kinetics, adsorption isotherms, conformation, bridging, stagnation point adsorption reflectometry, quartz crystal microgravimetry, polyelectrolyte titration, cationic polyacrylamide, cationic dextran, colloidal silica, silica surfaces, pulp
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-4059 (URN)
Presentation
2006-06-15, STFI-salen, STFI-Packforsk, Drottning Kristinas väg 61, Stockholm, 10:00
Supervisors
Note
QC 20101112Available from: 2006-06-21 Created: 2006-06-21 Last updated: 2010-11-12Bibliographically approved
2. Dynamic and Equilibrium Properties of Adsorbed Polyelectrolyte Layers
Open this publication in new window or tab >>Dynamic and Equilibrium Properties of Adsorbed Polyelectrolyte Layers
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Place, publisher, year, edition, pages
Stockholm: KTH, 2008. 66 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:25
Keyword
adsorption; cellulose; conformation; flocculation; kinetics; model surfaces; polyelectrolytes; pulp fibres; Quartz Crystal Microbalance with Dissipation; silicon oxide; Stagnation Point Adsorption Reflectometry
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-4697 (URN)978-91-7178-938-9 (ISBN)
Public defence
2008-04-25, STFI-salen, STFI-Packforsk, Drottning Kristinas väg 61, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100720Available from: 2008-04-18 Created: 2008-04-18 Last updated: 2010-07-20Bibliographically approved

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