Assessment of Opuntia ficus-indica (L.) Mill. extracts for the removal of lead from soil: the role of CAM plant harvest phase and soil properties.

Abstract

Extensive research to date has focused on the coagulation-flocculation and biosorption properties of the invasive Opuntia ficus-indica (L.) Mill. to remove metals from water. However, no studies have reported on the use of O. ficus-indica extract as a leaching agent to remove metals from contaminated soil. In the present work, a new environmentally friendly method for lead-contaminated soil remediation is evaluated. The method involves the use of cladode extract from O. ficus-indica as a soil washing agent. This new technique can serve to mitigate against the potential deterioration of soil quality and other secondary environmental impacts that result from the use of inorganic acids and/or chelating agents. Extractions from cladodes harvested during both day and night crassulacean acidic metabolism (CAM) phases were evaluated for treatment of lead contamination in three different soils including kaolinite, montmorillonite and a field-natural soil sample. Lead removal rates, which ranged from 44 to 100%, were significantly impacted by the intrinsic properties of the soils, the leachate dosage, the plant harvest phase, and the soil washing duration. Fourier-transform infrared spectroscopy (FTIR) characterization of the leachates indicated that functional groups present in the O. ficus-indica extracts played an essential role in the removal process. Results suggest that this species possesses promising potential to be used as a sustainable basis for the abatement of lead contaminated soil.