Correction to “Competitive Association of Antibiotics with a Clay Mineral and Organoclay Derivatives as a Control of Their Lifetimes in the Environment”

In the original publication, incorrect informations were given in the main text and in Figure 2 about the chemical properties of two antibiotics: the sulfamethoxazole (SMX) and trimethoprim (TRI); however, this does not change the main conclusions of the study, nor the behaviors of the adsorption of the antibiotics to the layered materials.

Figure 2.

Speciation of the SMX and TRI antibiotics used in the study. SMX and TRI are mainly anionic and cationic species at a pH = 6.5, respectively.

The sulfamethoxazole displays a pK_a couple of 6.16 and 1.97, respectively, for the strongest acidic and basic forms. Therefore, between these two pH values, SMX is neutral and not zwitterionic compound. Summarily, TRI has a neutral character (and not zwitterionic) above its pK_a = 7.16. Thus, the correct speciation diagrams in Figure 2 for SMX and TRI are given here.

At a pH 6.5 (pH of the study), SMX displays a neutral-anionic behavior with a ratio of 30/70% whereas TRI is mainly a cation (80%) with neutral species (20%). This does not affect the main trends nor conclusions of the study. Nevertheless, in their neutral forms, these antibiotics can be adsorbed onto the whole layered materials through ion–dipole interaction (with Brij_0.4-Mt, BDTA-Mt, and Na-Mt) and by weak molecular forces: van der Waals (dispersion, hydrophobic, pi-pi, ...) with the whole organoclays and starting Na-Mt.

The authors apologize for the errors in the original manuscript but it was important for us to give these important corrections.