Estudo da adsorção de chumbo II em lignina modificada a partir do resíduo do milho

Abstract

The use of heavy metals, especially in the industrial sector, has attracted attention for the impacts generated by the use of potentially toxic metals to the environment and public health. Some species of heavy metals when launched without proper treatment can contaminate soil, subsoil and groundwater. Adsorption is a process in which a substance (adsorbate) is physically or chemically attached to the surface of the adsorbent component and currently this process can be seen as an alternative to remove toxic metals from waste of agro-industrial sectors. In this context, this project aims to conduct a study about the adsorption of lead II (Pb II) on a modified natural polymer (lignin) obtained from corn stover. The study was divided into two parts: the first corresponding to the obtaining and characterization of crosslinked adsorbent lignin Formica (LFRT) and adsorbate (heavy metal), and the second part consists in the adsorption between heavy metal and LFRT. It was used the methodology proposed by Browning (1967) to extract lignin from lignocellulosic material, where it was isolated by pulping with formic acid (CH2O2) at 80% concentration, obtaining lignin Formica (LFOR). LFOR already been crosslinked with hydrochloric acid (HCl) 37% to give the polymer adsorbent used in this study crosslinked lignin Formica (LFT). The LFRT passed by ultraviolet spectroscopy (UV-vis) for the solubility test, and was characterized by infrared spectroscopy (IR). Adsorption tests were performed with different times of contact between adsorbent and the solution of 10 mg L-1 lead II, and the final concentration of the solution was measured by atomic absorption spectrophotometry (AAS), this way becoming possible to analyze the saturation of the adsorptive system and the adsorption efficiency. The solubility test of the polymer through the absorbance of ultraviolet light at a wavelength of 280 nanometers (nm) showed that the LFRT is less soluble compared to the LFOR. This low solubility was observed in the polymer characterization by infrared spectroscopy, where it was possible to see the addition of methyl groups (−CH3OH) on the crosslinking reaction of lignin. The results obtained with atomic adsorption proved satisfactory revealing that the LFRT achieved after 3 hours the saturation of the adsorptive system and it also could remove lead II 98,87% of the initial solution. Although requiring more extensive researches and studies, the test results showed that the adsorbent polymer can be used as a possible means to remove heavy metals from agro-industrial effluents.