Experimental studies on the desorption of adsorbed sodium poly(acrylic acid) from crude kaolin particles

AbstractBackground ntrolled stability and fluidity of highly concentrated kaolin dispersion is a crucial problem when kaolin is used in industry due to the charge heterogeneity of its surface. To solve the common industrial problems of dispersions prepared at high solid loadings in terms of their rheological behavior, some organic and inorganic dispersing agents have to be added into the system to modify the particle surfaces. ive tion and desorption behaviors of sodium poly(acrylic acid) (NaPAA) on the surface of kaolin particles were investigated to elucidate the adsorption mechanism of the PAA–kaolin dispersion system within the scope of the rheology and the colloidal stability. We also investigated the structural changes in the kaolin particles due to the extraction of Si4+ and Al3+ ions when a dispersing agent was used. dispersions were prepared using NaPAA, and investigated in terms of the adsorption and desorption behaviors, the rheological and the electrokinetic properties and the extracted Al3+ and Si4+ ions from the particles. s ected, PAA was strongly adsorbed on the positively charged alumina sites of the particles. According to the results obtained in the experiments of adsorption density, viscosity, ζ-potential and the dissolution of metal ion measurements for the adsorption/desorption, a strong and irreversible adsorption was observed between PAA and the surface of the kaolin surface, indicating the existence of unbreakable chemical bonds. This is due to the adsorption of negatively charged carboxylic acid groups (–COO−) from the PAA onto the positive alumina sites on the edges of the kaolin surface by electrostatic attraction. Due to the negative charge, no adsorption was observed on the silica surface of the particles within the working pH range of 5.3 to 8.4. sion sorption mechanism of PAA–kaolin interaction is attributed to chemical adsorption with the formation of chemical bonds between the charged carboxylic acid groups (–COO−) of the polymer and the alumina sites on the edges of the kaolin.