Copper binding to soil fulvic and humic acids: NICA-Donnan modeling and conditional affinity spectra

Conditional affinity spectrum underlying NICA isotherm provides practical insight into the characteristics of metal ions binding to HS at constant environmental conditions. The distributions of binding affinity for bound species are estimated. Carboxylic groups make the main contributions to Cu binding to HS. For JLHA with relatively high amount of carboxylic groups, the occupation of phenolic type sites by Cu can be negligible. Phthalate-type structure is more probable for Cu binding to JLHA. There is a non-negligible amount of phenolic-Cu on JGHA, which increases the chance of forming more stable complexes.156