Quantitatively modeling of tetracycline photodegradation in low molecular weight organic acids under simulated sunlight irradiation

As the ubiquitous active components in aquatic environments, low molecular weight organic acids (LMWOAs) have a large influence on the environmental behaviors of contaminants. This research was focused on the effect of different LMWOAs including 11 aliphatic acids and 7 aromatic acids on the photodegradation kinetics of tetracycline (TC), and the development of quantitative structure-activity relationship (QSAR) model. Results showed that TC photodegradation in the presence of LMWOAs fitted pseudo-first-order photolysis kinetics, and the observed photolysis rate constant (k(obs)) varied from 0.077 to 0.331 h(-1). The QSAR model was developed by partial-least-squares (PLS) with using a sequential approach with 25 theoretical molecular descriptors. Four descriptors including E-LUMO-E-HOMO, E-LUMO, CCR and Q(max) were found to mechanistically and statistically affect k(obs). The high cross validated regression coefficient (Q(cum)(2), 0.898) and high correlation coefficient (R-2, 0.908) indicated significantly goodness-of-fit and high robustness of the model. The predicted and observed values with high agreement in the defined applicability domain featured accuracy and feasibility of model. This work provided a robust predictive method for estimating the TC photodegradation in the presence of different structures of LMWOAs.

Automated summary

The research focused on the effect of LMWOAs on the photodegradation kinetics of tetracycline and the development of a QSAR model. Results showed that TC photodegradation in the presence of LMWOAs followed pseudo-first-order kinetics, and a QSAR model with high reliability and accuracy was established by using 25 theoretical molecular descriptors.