Conversão pirolítica de lodo de esgoto a biocarvão e seu uso na remediação de ambientes contaminados

Abstract

Sewage sludge is a waste product produced in large quantities by sewage treatment plants. Alternative solutions for the reuse of this type of waste can add value to the material and contribute to sustainable development and the environment. The aim of this study was to produce biochar from the pyrolytic conversion of sewage sludge and use it for the remediation of environments contaminated with heavy metals. In the first study, biochars (active and nonactive) were tested for their ability to remove Cr(VI) from solution. The treatment with phosphoric acid increased the adsorption capacity and resulted in the creation of functional groups (O--P+ and P-O-P) on the surface of the material. The data of adsorption isotherms (at 25˚C) were better adjusted by the SIPS model. The temperature and pH are determining physical parameters for the removal of Cr(VI), which increases at lower pH and with increasing temperature. The thermodynamic parameters indicate that the adsorption process is spontaneous and physical. In the second part of the study, we assessed the ability of remediation of sewage sludge biochar when applied as an amendment in soils from a Zn mining area, which has high contents of heavy metals (Cd, Pb and Zn). The application of sewage sludge biochar resulted in the increase of pH and electrical conductivity of the soils and decreased the Cd, Pb and Zn that are available to plants, causing higher growth and plant development compared with soils that did not receive any treatment. In this context, we conclude that the pyrolytic conversion of sewage sludge to biochar is a promising process to manage and add value to this waste, contributing yet to the preservation and environmental remediation, especially in environments contaminated by heavy metals.