On the chemistry of the Keggin Al13 polymer

Hydrolyzed Al(III)-clusters. II: Speciation transformation and stability of Al13 aggregates

“…1. It can be seen that the titration curves of Al 13 solution are significantly different with those of the traditional salts [12]. Although a plateau exists still with increase of alkaline addition and OH/Al ratio (B value), the turning point of B value is delayed to a large OH/Al ratio.…”

Modified Inorganic Polymer Flocculant-PFSi: Its Preparation, Characterization and Coagulation Behavior

“…The improvement of coagulation with PACl may due to the specific characteristic of Al 13 both on its union structure and chemical behavior. Recent characterization of acid-base properties of Al 13 (Furrer et al, 1992) and coagulation behavior of PACl (Van Benschoten and Edzwald, 1990a, b;Bottero et al, 1981;Parathasarathy and Buffle, 1985;Tang and Luan, 1996) showed that Al 13 was quite stable from hydrolysis. It is interesting to note that with tetrahedral Al present in the center of the structure, the basicity of Al 13 maintain is more than 2.0.…”

An effective method for improving electrocoagulation process: Optimization of Al 13 polymer formation

“…With increasing solution pH, the net positive charge is likely to be reduced, as are the repulsive forces between individual Al 13 polymer units. This in turn could favor aggregation of units to form Al precipitates [40]. It has been also demonstrated that at more rapid rates of base injection into Al 3+ solution, less A1 13 polymer is formed, presumably to the advantage of colloidal precipitate formation [41].…”