Produção e caracterização de biocarvão por pirólise de biomassa de casca de mandioca: avaliação com nutriente e contaminante

Abstract

The development of Brazilian agriculture and agribusiness is one of the main sectors responsible for the country’s economic and social growth. This development leads to a significant increase in the waste generated during the process of production and industrialization, which may cause soil and water contamination when improperly disposed. Brazil is one of the main cassava producers in the world. However, the process of obtaining products from this culture brings concern about a large amount of waste generated. In addition, the anthropogenic activities are main responsible for environmental contamination, bringing constant concerns and challenges to the scientific community. The biochar from slow pyrolysis under controlled conditions is favorable in the transformation of waste into materials that serve as soil conditioners, and/or environmental remediation. Thus, this work aimed to produce and characterize biochar from cassava peel (agro-industrial residues) under different temperature conditions and evaluate interactions with Pb(II) and Ca(II) for agricultural and environmental applications. The biochar were characterized by thermogravimetric analysis, elemental analysis, infrared spectroscopy and X-ray diffraction, in addition to determination of metallic species by microwave plasma atomic emission spectroscopy, pH and zero charge point pH. To investigate the efficiency of the interaction of biochar with contaminant (Pb) and nutrient (Ca), the influence of pH and contact time were evaluated. The elemental analysis showed the influence of the pyrolysis temperature on the biochar characteristic. There was an increase in pH, pHzpc (zero point charge), and condensed aromatic structures in biochar, due to the increase in pyrolysis temperature. Also, biochar demonstrated a Pb(II) adsorbed amount of 2.03 to 2.37 mg g–1 and a Ca(II) release amount of 0.655 to 0.765 mg g–1 . The pseudo-second order kinetic model better described the kinetic behavior of both metal ions in the investigated adsorbent, the biochar from cassava peel. Among the adsorption isotherm models, the Langmuir model better described the experimental data for Pb(II) and Ca(II) for biochar produced at lower temperatures (350 °C and 450 °C), while the Freundlich model, demonstrated better ability to describe Ca(II) adsorption for biochar produced at higher temperatures (500 °C and 550 °C). The maximum adsorption capacity of Pb(II) and Ca(II) were 37.27 mg g-1 and 16.31 mg g-1, respectively, being achieved with the biochar produced at the highest pyrolysis temperature (550 °C). The complexing capacity of the biochar was 37.60 mg g-1 to 39.11 mg g-1 for Pb(II) and from 8.66 mg g-1 to 14.21 mg g-1 for Ca(II). In this way, biochar produced from residues of cassava peel can be a viable strategy to enhance agricultural production and reduce environmental contaminants.