Avaliação de biocarvões obtidos da acácia negra (Acacia mearnsii de Wildemann) como adsorventes na remoção de pesticidas em água

Abstract

In accordance with the principles of green chemistry, the use of recycled materials in order to become the raw materials for the same or other process, minimizes or eliminates the generation of waste, reducing the use of materials and energy in process. Usually the alternatives explored are associated to farm products as, for example, the biomass derived of plants together with agricultural waste often lignocellulosic materials. The adsorbants used in this work derived of the tannin extraction from the Acacia mearnsii de Wildemann bark were pyrolyzed, chemically treated and appointed activated biochar (AB) and magnetic biochar (MB). Characterization by FT-IR, TGA, XDR, CHN and SEM allowed to display characteristics such as, for example, the presence of compounds originating from the biomass origin, tannins (TAN) in the BM and exhausted from the bark (CE) for BA. The adsorbents were effective in removing pesticides tiacloprid (TCL) and thiamethoxam (TMX) with values of adsorption capacity q = 0.73 and 0.40 mg g-1 for BM eq = 1.02 and 0.90 mg g-1 for BA, respectively. The removal percentage values were approximately 100% for two pesticides using BA, 72% and 42% using the WB, respectively, for the pesticides TMX and TCL. The kinetic model of pseudo-second order was the one that best fitted the results with values of q (exp) closest to q (calc) and good linearity coefficients ranging from 0.976 to 0.999. The study desorption of pesticides with water was performed in order to evaluate the possibility of the withdrawal of these pesticides for possible reuse of biochars. Attempting to desorption of adsorbed pesticides in biochar no significant results, thus evidencing the strong interaction between them. Thus, the study proposes the reuse of waste from an industrial process, which is the exhausted bark, for environmental purposes, as an alternative in removing pesticides besides assign any application to tannins extracted in the same process.