Interactive comment on “New and extended parameterization of the thermodynamic model AIOMFAC: calculation of activity coefficients for organic-inorganic mixtures containing carboxyl,

“My only important remark is on the use of the existing UNIFAC parameters, assembled from different research groups, for describing the organic-organic and organic-water interactions. The authors have stressed the importance of fitting the organic-ion interaction parameters for all data simultaneously. Shouldn’t the same be true for the organic-organic and organic-water interactions, i.e. wouldn’t it be better to refit these parameters over a wide variety of mixtures at once? The authors point to the shortcomings of the UNIFAC model in some circumstances, even for salt-free systems, and blame this solely on the group-contribution concept. But I think there can be another reason: the fact that the UNIFAC set of interaction parameters is not obtained by an overall optimisation. It would make sense to me -if time and manpower would be no limitationto first have the optimal UNIFAC parameters for a best description of salt-free mixtures, before improving/extending the organic-ion interaction parameters. Have the authors refrained from this because of the challenge of the task, or do they think that the existing UNIFAC parameters cannot be much improved upon?”