abstract
This work explores the stabilization effect of a sulfonated tannin (black wattle extract) on water-suspended alpha-alumina particles. Results showed that first additions lead to particle agglomeration. A minimum of 0.5 wt% tan-nin (relative to the alumina content) is required to cover the whole particle surface. Suspensions regain stability at ca. 1.0 wt% tannin (ca.1 mg tannin/m2 alumina surface area), due to a high negative zeta-potential (-60 mV, pH = 8.0). Both zeta-potential and particle hydrodynamic diameter are then close to those in electrostatically dispersed alumina particles. Changes in ionic strength cause changes in zeta-potential and hydrodynamic diameter but hardly affect the tannin adsorption. The electrosteric stabilization results from the repulsion provided by the-15 nm thick adsorbed tannin layer (steric effect) and the enveloping electric double layer, which remains sensitive to the suspension ionic strength (electrostatic effect). Changes in hydrodynamic diameter can be used to infer the electric double layer thickness. (c) 2022 Elsevier B.V. All rights reserved.
keywords
DODECYL-SULFATE; ADSORPTION; SURFACE; POLYELECTROLYTES; SUSPENSIONS; STABILITY; MASS; C-13; H-1; NMR
subject category
Engineering
authors
Webber, J; Zorzi, JE; Segadaes, AM; Mantas, PQ; Cruz, RCD
our authors
Ana Maria B C Segadães
Retired Professoracknowledgements
Authors acknowledge the financial support received from CAPES Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (PDSE 88881.135911/2016-01). Other general funding from CNPq - Conselho Nacional de Desenvolvimento Cientifico e Tecnologico and the Secretaria de Desenvolvimento Economico, Ciencia e Tecnologia do Estado do Rio Grande do Sul (SDECT/RS) is gratefully appreciated.