The protonation of polyacrylate in seawater. Analysis of concentration effects.
The protonation of polyacrylate (PAA, MW 2 kDa) was studied potentiometrically at 25 degrees C, in mixed electrolyte aqueous solution simulating the composition of seawater, in the salinity range 30 < or = S < or = 40. The salt composition of different solutions was varied in order to study its effect on apparent protonation constants. Results were analysed using two fairly different approaches: by simple regression analysis on a combination of concentration parameters and salinity, and by canonical correlation analysis. Unexpectedly we found that variations on protonation constants, due to the different relative component concentrations, are fairly low, revealing a sort of buffering capacity of seawater respect to protonation properties of polyacrylate (and likely for other HMW and LMW polycarboxylates). The intrinsic protonation constant of polyacrylate 2 kDa at 25 degrees C and 35 salinity is log K(H*) = log K(int) = 4.399 +/- 0.004. The use of different pH scales and standard seawater compositions is also discussed.
Battaglia
Gianluca
G
Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Università di Messina, Salita Sperone 31, I-98166, Messina (Vill. S. Agata), Italy.
Crea
Francesco
F
Crea
Pasquale
P
Silvio
Sammartano
S
D000180:Acrylic Resins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011199:Potentiometry; D012623:Seawater / Q000737:chemistry*; D013816:Thermodynamics
D000180:Acrylic Resins; C006903:carbopol 940