Aggregation behavior and mechanism of kaolin particles suspension in the presence of Xanthan gum and Fe(III)

Abstract

Aggregation is an economical and widely existing method to in fine particles dewatering, but the mechanism of composite applications of inorganic coagulants/flocculants remains unclear. In this work, the aggregation process of kaolin particles using Fe(III) and xanthan gum (XG) was investigated by settling testing. The results shows that the combination XG and Fe(III) was effective in the flocculation of kaolin, which due to the self-assembly multilayers built onto the surface of kaolin. Further, density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) analyses were performed to detect the flocculation mechanism. It was found that [Fe(Ⅲ)(OH)]2+, [Fe(Ⅲ)(H2O)6]3+ and [Fe(Ⅲ)(OH)2]+ were the dominant species, which could complex with the XG on kaolin surface by the Fe-O adsorption site. However, the precipitate Fe(OH)3(s) covered on the kaolin surface is difficult to combine XG by coordination reaction under alkaline conditions. The research elucidated a new insight into of composite applications of inorganic coagulants and flocculants which could expand our knowledge of aggregation process, further define the relationship between coagulation and flocculation for enhancing colloidal particle settling in practical application.