Modelling atrazine sorption in carbon-rich substrates: a case study

Background: The use of carbonaceous materials for environmental remediation is attractive due to low expense and high sorption capacity. However, their efficiency in contaminant removal is affected by substrate composition and sorption mechanism. Objective: This study investigated atrazine sorption and desorption in three carbon-rich substrates. Data were evaluated considering isotherm models and sorbent chemical composition. Methods: Sorption was performed by the batch equilibrium method with three substrates obtained from pig slurry composting with different proportions (w/w) of charcoal fines (CF): CF0, CF9 (9% CF), and CF18 (18% CF). The substrates were characterized by elemental analysis, C-13 NMR CP/MAS spectroscopy. The Freundlich and Dubinin-Radushkevich (DRK) models better fitted the sorption data (0.96>R-2>0.81), followed by Temkin (0.95>R-2>0.76). Charcoal addition to composting substrates increased carbon content and the aromaticity in the order CF010 mg L-1), and the desorption Kf values were greater than the respective sorption values. Conclusions: Atrazine sorption in the tested C-rich substrates is not governed by the carbon content or aromaticity. The low sorption reversibility implies a low atrazine mobility from the tested substrates and suggests their potential for herbicide removal in the environment.