Modelagem fenomenológica da adsorção de atrazina em biocarvões de casca de arroz

Abstract

Atrazine is one of the most applied herbicides worldwide, and it is used to remove weed in agricultural crops, although, alternatives are required to remove it from the environment because its toxicity. Adsorption in biochars has been recognized as an efficient technique to remove organic contaminants. In this study, two biochars, produced from rice husk at different pyrolysis temperatures (400 and 700 ºC), were compared for atrazine adsorption ability. The biochars were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), characteristics of Brunauer-Emmett-Teller (BET). Kinetic and equilibrium experimental data were obtained for both biochars to evaluate Langmuir, Freundlich and BET isotherms, as well as kinetics by intraparticle diffusion. The characterization by BET and SEM analysis of biochars showed higher porosity for the biochar produced at the highest studied temperature; Pore sizes for biofilms were small (15 Å), favoring the atrazine adsorption process. The equilibrium data show that the adsorption process is propitious, and the Langmuir isotherm could describe well the system for biochar at 400 °C, while Freundlich isotherm did it at 700 °C. The results showed some positive effect caused by pyrolysis temperature, which has indicated the highest experimental adsorption capacity of the studied herbicide by biochar when produced at 700 ºC, and the rice husk biochar was considered an efficient material on atrazine removal from aqueous media. Based on the kinetic data, different equilibrium times were obtained for both biochars. Thus, in order to describe kinetic adsorption data for biochars, a phenomenological model based on intraparticle diffusion was applied, and the model fitted well to those data for each biochar.