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Calcium soaps in flotation deinking; Fundamental studies using surface force and coagulation techniques
YKI – Ytkemiska institutet.
YKI – Ytkemiska institutet.
1997 (English)In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 125, p. 33-46Article in journal (Refereed)
Abstract [en]

The surface force technique was shown to give useful information concerning the interaction of fatty acid flotation collectors and Ca2+ activator with a hydroxylated mica substrate at high pH. Since the surface of ink particles are enriched mainly by hydroxyl groups from natural resins, these experiments enabled some details of the fundsmental mechanisms involved in deinking flotation to be illucinated. The preliminary results (carried out at relatively low Ca2+ and fatty acid concentrations) may be summarised as follows; (a) At pH >10, the hydroxylated surface generated a long range DLVO double_x001E_layer repulsion and the electrical potential at the mica/electrolyte interface could be estimated. However, at short distances (15 Å from mica contact) a repulsive non-DLVO hydration barrier were detected due to adsorbed Na2+. (b) On addition of CaCl2, the Na2+ was exchanged by less strongly hydrated Ca2+ resulting in the elimination of the hydration forces and mica-mica contact. On addition of fatty acid, no change in the force profile was detected suggesting no Ca2+ was removal from the surface and there was no evidence of calcium soap formation in the surface region. This result implies that the Ca2+ does not induce a bridging mechanism in the presence of fatty acid (below the calcium soap precipitation level). In fact, the Ca2+ ions could only operate as bridging agents if they can specific bind to the surface as well as the carboxylated fatty acid. The "Ca2+ dehydration destabilization mechanism" was verified by coagulation studies with quartz suspensions. At higher fatty acid and Ca2+ concentrations, calcium soap was precipitated in bulk solution. It was suggested that microencapsulation of the ink particles with hydrophobic species can only occur through heterocoagulation with the bulk precipitated calcium soap particles.

Place, publisher, year, edition, pages
1997. Vol. 125, p. 33-46
Keywords [en]
Calcium soaps, coagulation, deinking, flotation, surface forces
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:ri:diva-26458OAI: oai:DiVA.org:ri-26458DiVA, id: diva2:1053460
Note
A1065Available from: 2016-12-08 Created: 2016-12-08 Last updated: 2017-11-29Bibliographically approved

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