Study of zinc (Zn) retention by mixtures of soil and pruning waste biochar

• Grant number: 21/08223-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2021
• End date: August 31, 2022
• Field of knowledge: Engineering - Sanitary Engineering - Environmental Sanitation
• Principal Investigator: Valéria Guimarães Silvestre Rodrigues
• Grantee: Julia Paschoal Lopreto
• Host Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil

Abstract

In Brazil and worldwide, many areas have been contaminated by inadequate disposal of mining waste containing potentially toxic metals. Among these metals, there is zinc (Zn), which is an essential element with great biological importance for plants, animals, and humans, but which becomes toxic in high concentrations. Thus, it is necessary to develop techniques (if possible at low cost and linked to the circular economy) aimed at containing the contamination. In this context, soils, due to their characteristics, can be used as adsorbents in geoenvironmental works. When the soil does not present adequate characteristics to be used in the retention of contaminants, mixtures with other materials (such as biochar, peat, compost, among others) must be studied. Therefore, the application of pruning waste biochar would be an alternative to improve the soil's adsorptive properties, aiming at Zn retention. The use of urban pruning residues as a source of biochar is directly related to the circular economy and constitutes an alternative to utilize this material which is still an issue in Brazil in terms of volume and destination. Thus, the objective of this research is to assess mixtures of biochar from urban pruning waste with a representative cambisol from the Vale do Ribeira region for Zn retention in remediation of contaminated areas or as environmental protection barriers for waste deposits. To this end, laboratory tests will be carried out in stages: (1) characterization of the mixtures in different proportions of soil and biochar, to identify the one with best results; (2) batch equilibrium tests to assess the adsorption capacity of Zn by the mixtures; (3) assessment of the phytotoxicity after Zn retention by the mixtures, analyzing effectively the improvement of soil quality. The results of this research, it is expected to contribute to the fields of geology and environmental geotechnics with a low-cost alternative for remediation of contaminated areas or for environmental protection barriers in waste deposits, both mining and industrial, and also for the management of solid municipal residues, through a new use for pruning waste and an innovative application of biochar. Few types of research have approached biochar from urban pruning waste and, in Brazil, there are no studies that assess its use as an adsorbent for potentially toxic metals. (AU)