Fig. 7. Model applied to Cd, Zn, and Cu competition; total concentration of each metal ion ([M]) was 2.50 x 10^–4 M and the mole ratio of Cd/Zn/Cu was 1:1:1. The background electrolyte was 0.1 M NaNO₃. The bound species considered included: monodentate Cd–carboxyl complex (CdC), bidentate Cd–carboxyl complex (CdCC), bidentate Cd–(carboxyl + phenolic hydroxyl) complex (CdC), monodentate Zn–carboxyl complex (ZnC), bidentate Zn–carboxyl complex (ZnCC), bidentate Zn–(carboxyl + phenolic hydroxyl) complex (ZnC), monodentate Cu–carboxyl complex (CuC), bidentate Cu–carboxyl complex (CuCC), and bidentate Cu–(carboxyl + phenolic hydroxyl) complex (CuC). The values of constants and parameters used were: for Cd, intrinsic stability constant for metal complexation to a monodentate carboxyl binding site (pß_int^M,C) = 0.290, intrinsic stability constant for metal complexation to a monodentate phenolic hydroxyl binding site (pß_int^M,)=4.76, proportion of carboxyl groups capable of forming bidentate chelates (P_CC) = 0.051, proportion of monodentate binding carboxyl groups capable of forming bidentate chelates to a phenolic hydroxyl group (P_C) = 0.951, and proportionality factor F_W = 0.169; for Zn,pß_int^M,C=0.969,pß_int^M,=4.52, P_CC = 0.172, P_C = 0.887, and F_W = 0.260; for Cu,pß_int^M,C=0.042, pß_int^M,=4.04, P_CC = 0.126, P_C = 0.585, and F_W = 0.397.