Use of local waste for biochar production: Influence of feedstock and pyrolysis temperature on chromium removal from aqueous solutions

ARÁN, DANIELA S.; DEZA, M.; MONFERRÁN, MAGDALENA; PIGNATA, M. LUISA; HARGUINTEGUY, CARLOS A.

Integrated Environmental Assessment and Management

Wiley-Blackwell

Año: 2022 vol. 19 p. 717 - 725

Sediment enrichment with biochar, a high carbon material produced by pyrolysis of biomass, is a promising remediation strategy for heavy metal pollution. The metal immobilization capacity of biochar can be explained by its porous structure, surface functional groups, pH≥7 and cation exchange capacity. However, the effectiveness in reducing heavy metal bioavailability depends on the physicochemical characteristics of the biochar, which are highly associated with the process conditions and the feedstock. The aims of the present study were to analyze the effect of pyrolysis temperature on the properties of biochars derived from different locally available biomass materials, biochar potential to adsorb Cr, and biochar phytotoxicity in seed germination. Poultry litter, maize straw, the macrophyte Juncus imbricatus, and phytoremediation wastes from the macrophyte previously exposed to Cr were pyrolyzed into biochar at 300 and 600 °C. Biochar properties and capacity to remove Cr from the aqueous phase were determined. Finally, a germination assay was performed to evaluate biochar phytotoxicity. Biochar yield decreased with increasing pyrolysis temperature, whereas ash content and pH increased. Biochar C content and total surface area increased with temperature. Biochar Cr removal capacity improved under the highest temperature, reaching a maximum sorption value of 13.7 mg g-1 Cr at 300 oC in poultry litter biochar and of 42.6 mg g-1 Cr at 600 °C in Juncus imbricatus biochar. Despite the comparatively high heavy metal content in the biochar, the germination indexes of all biochars produced at 600 °C were higher than 80%, suggesting no phytotoxicity. Taking into account the metal sorption capacity and the phytotoxicity, biochars produced from J. imbricatus, poultry litter and phytoremediation residues at 600 °C were suitable for use in the removal of Cr from water.