Uso de subprodutos de milho, soja e trigo como adsorvente de ferro e manganês em sistema aquoso

Abstract

The increased volume of agricultural by-products generated coupled with inadequate disposal of these is a growing worldwide problem. The use of these agricultural by-products is of extreme importance, since it results in the reduction of environmental impacts, preservation of the health of the population, allowing adding value to these materials supplying the economic and global needs. One of the ways of exploitation is related to the ability of some of these agricultural by-products to efficiently remove micro-contaminants in aqueous systems due to their adsorbent properties. The adsorption process is a method that promotes the removal of micro-contaminants in aqueous solutions. This work aimed to investigate the use of agricultural by - products: corn straw (PM), wheat straw (PT), soybean straw (PS) and soybean husk (CS) to produce different adsorbents to remove Fe and Mn. For each by-product investigated, two different adsorbents were used: natural (cellulose / lignin) and one modified with EDTA (ethylenediaminetetraacetic acid). After the characterization of the adsorbents by FTIR (Fourier transform infrared spectroscopy), nitrogen content, the adsorption tests were carried out to evaluate the efficiency and elemental analysis of these adsorbents in aqueous solutions of Fe and Mn. The concentration of the micro-contaminants in the solution was determined by atomic absorption spectrophotometry. Then, for the most efficient natural and modified adsorbents, the kinetic models of pseudo-first order and pseudo-second order were applied to define the order of the adsorption reaction. The results showed that the modified adsorbent obtained from the soybean hull (CSE) showed the best results in the adsorption of Fe (96%) and Mn (88%) in aqueous solution. The pseudo-second order model showed a better adjustment of the adsorption reaction for both micro-contaminants investigated. In general, the modified soybean hull proved to be an adequate adsorbent for the removal of iron and manganese, since it presented high efficiency, as evaluated in this study.