Coagulation with Prepolymerized Metal Salts

Enhanced coagulation with polyaluminum chlorides: Role of pH/Alkalinity and speciation

“…PACl has been found to be superior to the traditional Al-based coagulants (e.g., AlCl 3 and alum) for particulate and/or organic matter removal under some conditions in which significant amounts of high-charged polynuclear aluminum hydrolysis products (Al b ) are present (Bottero et al, 1982;Dempsey et al, 1985;Pasrthasarathy and Buffle, 1985;Edzwald, 1993;Matsui et al, 1998). In other cases, PACl does not demonstrate superior performance (Odegaard et al, 1990;Van Benschoten and Edzwald, 1990;Lind, 1994;Sinha et al, 2004) and the chemical processes determining the relative benefits are not well known.…”

Coagulation properties of an electrochemically prepared polyaluminum chloride containing active chlorine

“…Actually, these divalent metal ions may provide a buffer action to coagulation to resist the adverse effect of the by-products. The results of Dowbiggin and Singer 1) indicated that the divalent metal ions could form a bridge between the mineral particles and the polar chlorization intermediate by-products and thus these by-products along with the particles were removed by coagulation or, the divalent metal ions can form surface complex with these polar by-products thereby modifying the OM surface charge and forming a precipitates with Al coagulants. The similar results were also observed in water sample 2 ( Fig.…”

“…Comparing with the traditional Al coagulants such as alum and AlCl 3 , PACl can remove particles and organic matter (OM) with inherent advantages of less alkalinity consumption, lower cost, less sludge production, less temperature dependence, and less pH dependent [1][2][3][4] . It is known that PACl products contain cationic species, of which the most important one is Al 13 ([AlO 4 Al 12 (OH) 24 ) species [5][6][7] .…”

Coagulation behaviors of aluminum salts towards fluoride: Significance of aluminum speciation and transformation

“…On the other hand, the hydrolysis of Al salts tends to form a series of Al species with different structures, charges, and polymerization character [14], and the diversity of Al species possibly impacts the interaction between fluoride and different Al species thereafter. PACl as polymeric species of Al salt shows superiority in removing particulate and organics as compared to traditional monomeric Al such as AlCl 3 , and PACl exhibits inherent advantages less independence on pH [15], less alkalinity consumption [16], and less sludge production [17]. However, its superiority in terms of fluoride removal as compared to AlCl 3 and the mechanisms involved in has rarely been investigated.…”