Estudo da sorção do antibiótico ciprofloxacina em partículas de magnetita modificada com sílica e surfactante CTAB

Abstract

The occurrence of emerging microcontaminants has been observed in several environmental compartments as result of anthropogenic activities. Pharmaceutical substances, such as residual antimicrobials, represent potential risks to human and ecosystems health. In the context, the development of treatment techniques capable of contributing to the mitigation of these new pollutants are essential. In this research, sorption study of antibiotic Ciprofloxacin (CIP - C17H18FN3O3) into magnetic adsorbent of Fe3O4@SiO2/CTAB (Iron oxide core@shell silica and CTAB) by kinetic and isothermal adsorption essays and desorption tests (with the purpose to evaluate reuse) were performed. In the tests, three parameters considered influential to the reaction were investigated: solution pH, CIP initial concentration (in mg.L-1) and adsorbent mass (in grams). Design of Experiments (DoE) statistical tools of Full Factorial 23 and Central Composite Design (CCD) were applied to determine the optimum conditions that would induce to best results. Optimization indicated that the ideal conditions for the process would be pH equal to 4, CIP Ci concentration equal to 20 mg.L-1 and adsorbent mass equal to 0.02 grams. The research was relevant to approach the problematic of waters and soil contamination by presence of micro-quantities of Ciprofloxacin, in addition, pointed out promising data regarding the development of a new technique for the removal of CIP from water samples. The adsorbent material was able to remove about 90% of CIP initial concentration. The reaction equilibrium was relatively fast, following pseudo-second order kinetics, with 47% removal at the first minute of contact in a constant rate of 0.092 mg.g-1.min-1. The adsorption isotherm data were adjusted in Langmuir’s and Freundlich models, but, although the latter adjusted better, both presented R2 < 0.99. The graphical profile for the experimental data indicates adsorption to be favorable. The maximum adsorptive efficiency (qmax) is approximately 25.25 mg of CIP per gram of adsorbent. Positive response was also obtained for CIP desorption when absolute ethyl alcohol was used as solvent, allowing the adsorbent material to be reused for up to 6 cycles (adsorption – desorption – re-adsorption).