Abstract:
CONDITION FOR PROJECT PUBLICATION. Oil production causes severe environmental impacts. This study evaluated the potential of biochars produced from local agro-industrial residues as a sustainable alternative for the remediation of these soils. Four biomasses (palm fiber, rice husk, sugarcane bagasse, and coffee husk) were selected from La Joya de los Sachas, Ecuador. The biomasses were subjected to physical and hydrothermal pretreatments, followed by pyrolysis at 400 and 500 °C. The adsorptive capacity of the biochars was initially evaluated through methylene blue adsorption tests. The outstanding biochar (derived from hydrothermally treated rice husk, HBCA) was selected for remediation experiments in soils contaminated with total petroleum hydrocarbons (TPH), including sandy loam soils contaminated with diesel and clayey soils with recalcitrant hydrocarbons and hydrocarbons from recent spills, with applications of 5, 10, and 15% (w/w) HBCA, monitoring TPH over 26 days. Methylene blue assays revealed that HBCA had the highest adsorption capacity (43 g solute/g adsorbent and 98% removal); in contaminated soils, the application of 15% HBCA resulted in a significant reduction of TPH: from 7684 mg/kg, 52% was removed in sandy loam soils; from 797 mg/kg, 19% was removed in clayey soils with recalcitrant hydrocarbons; and from 704 mg/kg, 15% was removed after 26 days, consistently outperforming the control and lower doses. Characterization of HBCA confirmed the presence of a porous structure and functional groups favorable for adsorption. Hydrothermal pretreatment followed by pyrolysis at 500 °C produced a rice husk biochar (HBCA) with exceptional properties for hydrocarbon adsorption. The results demonstrate that HBCA is a promising and low-cost adsorbent for the remediation of soils impacted by the petroleum industry in the Ecuadorian Amazon. This strategy not only valorizes agro-industrial residues for soil remediation but also offers an effective technology to overcome the limitations of conventional biological treatments in soils with persistent contaminants.