Particulate Science and technology
V. Onen and M. Gocer
In this study, the sedimentation behavior of bentonite (Na and Ca bentonite) suspensions with different swelling potentials was investigated with single and combined coagulation and flocculation methods. The samples exhibited a negative surface charge over a broad pH range and had a relatively high suspension stability. Al2(SO4)3, FeCl3, MgCl2, CaCl2, and NaCl were used as coagulants. All coagulants have provided sedimentation efficiencies higher than 85% with Ca bentonite suspension, but only 22% efficiency was seen with Na bentonite suspensions. The effectiveness of coagulants increased with higher ionic values of the metal salts. Versus monovalent cations, multivalent cations had a greater influence on the zeta potential of the samples. Higher coagulant concentrations enhance the conductivities of the suspensions. In flocculation, anionic (A-150), cationic (C-521) and nonionic (N-100) flocculants were used. For a Ca bentonite suspension, all flocculants have 98% efficiency. The anionic flocculant was more efficient than cationic and nonionic ones for Na bentonite suspension. The dual-flocculation of cationic and anionic flocculant combinations and pre-destabilization via coagulants of Na bentonite suspension were also studied. Better flocculation performance was achieved with these combined methods.
