Effective removal of tetracycline from aqueous solution using biochar prepared from pine bark: isotherms, kinetics and thermodynamic analyses

Abstract

ABSTRACT In recent years, there are many concerns about the potential risks of contamination of emerging compounds in water resources and their adverse effects on human health and the environment. Today, the production and use of drug compounds for the treatment of human and animal diseases is increasing. The aim of this study was to investigate the effect of the biosorbent prepared from pine bark on the removal of tetracycline from aqueous solutions. In this study, the effect of various variables including pH (2–12), adsorbent dose (1–2 g)), tetracycline concentration (50–500 mg/L), contact time (10–120 min)) and temperature (10–50°C) as well as the structural properties of biochar were examined. The isotherms, kinetics and thermodynamics of the adsorption process were also evaluated. The residual concentration of tetracycline after adsorption by DR5000 spectrophotometer of the Hack Company at 292 wavelengths was read. Using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) methods, it was found that the biochar structure has many pores for adsorption and also has functional groups including hydroxyl, carbonyl and amine, which increases the adsorption capacity. Maximum removal of tetracycline (89.5%) was achieved in 15 minutes, pH 5.1 and dose 1 g. In this study, the removal efficiency of tetracycline increased with increasing temperature and adsorbent dose and decreased with increasing contaminant concentration. The adsorption isotherm of tetracycline at maximum adsorption capacity (58.47 mg/g) is consistent with the Langmuir model and the adsorption kinetics follows the pseudo- second order model. According to the results of this study, it was found that biochar produced from pine bark is a cheap and efficient adsorbent in the removal of tetracycline antibiotic and can be used to remove this antibiotic in hospital wastewaters.