Otimização da produção de carbonos mesoporosos utilizando metassilicato de sódio como template: aplicação na adsorção de ciprofloxacina

Abstract

The growing number of pollutants released into the environment increases the need for products that help mitigate the impacts caused by them. With that in mind, materials and methods that support the reverse pollution process have been studied and stabilize the activity of these pollutants. In addition to the need for materials with excellent performance, one must also consider their economic feasibility for use on an industrial scale, which is strongly dependent on an accessible and simple production route. Thus, this work aimed at producing and characterizing mesoporous carbons, with application in removing ciprofloxacin in aqueous solutions. The solid was produced using the "hard templating" technique, after the process of impregnating the carbonic precursor in the template, pyrolysis was performed in a nitrogen atmosphere, with a flow of 100 mL min−1 of N2, at a heating rate of 5 °C min−1 until reaching 800 °C, where it remained for 1 hour. After carbonization, different leaching agents (NaOH, HCl and water) were tested for the template removal, wherein it was possible to use water as the leaching agent, giving a higher suntentability to the material’s synthesis route. For the best mesoporous carbon, tests were carried out to remove the antibiotic ciprofloxacin (CIP). Complementary analyzes were carried out to verify the physical-chemical, textural, and morphological properties through analyses such as: N2 physisorption, thermogravimetry (TGA/DTG), scanning electron microscopy coupled with elemental composition analysis (SEM-EDS), zero charge point (pHPCZ) and Fourier transform infrared spectroscopy (FTIR). The adsorption equilibrium results indicated that the model that best fitted the data was the Langmuir model, with high affinity 𝐾𝐿 (1.374, 1.554 and 1.705 L g−1), indicating a monolayer adsorption system and the homogeneous intraparticle diffusion model in the sites indicated that the mass transfer is the rate-limiting step for the global adsorption kinetics. In general, the mesoporous carbons (CM) showed desirable adsorbent properdies, reaching values of 𝑞𝑚𝑎𝑥 = 55.6, 57.9 and 59.0 mg g−1, for concentrations of 50, 100 and 200 mg L−1, respectively. In addition, it presented very interesting textural-morphological characteristics, mainly due to its simplified synthesis route following "green chemistry"principles.