Humic acid potentiometric response patterns: out-of-equilibrium properties and species distribution modeling

Abstract

Background: Negentropy and entropy fluctuations, which are concepts of out-of-equilibrium thermodynamics, were considered in the development of a simple potentiometric titration method for the study of natural complex systems, in this case humic acids. Results: The method allows, besides the obtainment of traditional titration curves, the observation of response patterns for the out-of-equilibrium evolution throughout the titration pH range, at each point of the titration. Also, two humic acid species distribution models are proposed and interpreted. Conclusions: The obtained potentiometric out-of-equilibrium response patterns (graphical method) are correlated with the negentropic organizational/structural properties of the sample and provide information on its relation with the natural environment.

Revealing the effect of anion exchange resin conditioning on the pH and natural organic matter model compounds removal mechanisms

“…As model compound for the HS fraction, humic acid (HA) (technical grade, Sigma Aldrich) was selected. It is a mixture of complex aromatic molecules having different functional groups of which the carboxylic acid (pK a 4.7) and phenolic functionalities (pK a 10.0) are the most abundant, resulting in a negative charges molecule at slightly acid to basic pH [49][50][51].…”

Erratum to: Humic acid potentiometric response patterns: out-of-equilibrium properties and species distribution modeling

“…After the publication of the original article [1], we noticed that Figs. 1-4 were ordered incorrectly and the figure captions did not correspond to the correct figures.…”