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RESEARCH PRODUCT

Speciation of Organic Matter in Natural Waters-interaction of polyacrylates and polymethacrylates with major cation components of seawater

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Abstract The speciation of some high molecular weight polycarboxylates was studied in different ionic media. Polyacrylates here investigated ( W =2.0, 5.1 and 20.0 kDa) form weak species with alkali metal cations ( K =10 2 mol l −1 , t =25 °C, I =0 mol l −1 ) and quite stable complexes with alkaline earth metal cations ( K >10 6 mol l −1 , t =25 °C, I =0 mol l −1 ). Results are reported from experiments performed in a multicomponent electrolyte solution simulating the major composition of seawater (artificial seawater). Protonation constants in this medium are expressed as a polynomial function of S 1/2 ( S =salinity) and the sharp lowering with respect to values obtained in non-interacting aqueous tetraalkylammonium salts can be ascribed to the formation of alkali and alkaline earth cation complexes. A simplified approach, according to which the seawater salt is considered as a single 1:1 salt, was used to describe the total interacting ability of the major components of seawater towards polyacrylates. Protonation and complex formation data are reported as a function of the degree of proton dissociation and of the molecular weight: empirical equations to take into account these functions are also given.