Kinetics of metal exchange reaction of Cu(II)-poly(vinyl alcohol) complex with Ca(II)-ethylenediamine-N,N,N′,N′-tetraacetic acid in aqueous solution

The kinetics of the metal exchange reaction between the Cu(II)-poly(vinyl alcohol) complex (Cu(II)-PVA) and Ca(II)-ethylenediamine-N,N,N′,N′-tetraacetic acid (Ca(II)-EDTA) were studied by mixing both solutions in a spectrophotometer at pH 9.7–11.0, at μ = 0.10(KNO₃) and at 25°C. The reaction is initiated by the formation of unstable Cu(II)-H-PVA by the attack of H⁺ to Cu(II)-PVA, and while both ligand exchange and metal exchange steps occur, the latter may be rate-determining. The kinetic expression of this reaction was determined as -dCu(II)-PVA]/dt = kCu(II)-PVA] H⁺] PVA]/Ca(II)-EDTA], where k = k₁ + k′₂H⁺], k₁ = 3.85 × 10^?2 sec^?1, k₂ = k′₂ · K^?H_Cu(II)-H-PVA 9.59 × 10⁵ 1 mol^?1 sec^?1.