Rheological, electrokinetic, and morphological characterization of alginate-bentonite biocomposites

We prepared biocomposite gel dispersions involving sodium alginate (Na-Alg) and calcium bentonite (Ca-B) with various solid concentrations and characterized their rheological, electrokinetic, and morphological properties. The flow properties, such as the apparent and plastic viscosities, shear stress, and yield value point, changed with increasing clay dosage. The viscosities of the homogeneous dispersions were represented by the Herschel-Bulkley model. The ζ-potential results were examined in the light of different characterization methods (X-ray diffraction, Fourier transform infrared spectroscopy, and atomic force microscopy) to understand the interactions between the Na and Ca ions of the alginate biopolymer and bentonite clay. A plausible structural model for the alginate-bentonite composite gel, known as the egg-box model, is proposed. The presence of Ca ions in the Ca-B partially crosslinked Na-Alg may be regarded as an excellent example of a self-assembling process.