Biopolímero de palma forrageira aplicado a solo para impermeabilização de base de aterro sanitário

Abstract

The adoption of base liner waterproofing systems in sanitary landfills plays an important role in protecting against the environmental impacts associated with the final disposal of solid waste, especially with regard to soil and groundwater protection. However, many available soils do not meet the permeability requirements established by technical standards, highlighting the need to seek alternatives capable of improving their geotechnical characteristics. In this context, this study investigated the hydraulic behavior of a biopolymer produced from the powder of forage cactus (Opuntia ficus-indica), applied to a soil collected from the municipal dumpsite of Crateús, Ceará, as well as analyzing different biopolymer contents mixed with the soil. To this end, tests of physical characterization, permeability, free swell index (FSI), compaction, and consistency limits were carried out, aiming to understand the effects of incorporating different biopolymer contents on the geotechnical properties of the analyzed local soil. The results showed that the addition of 5% of the biopolymer produced from forage cactus increased the soil consistency limits, in addition to reducing the maximum dry unit weight (γd,max) of the local soil from 1.82 g/cm³ to 1.64 g/cm³ and increasing the optimum moisture content (OMC) from 15.0% to 18.06%. Regarding the permeability coefficient, an increase was observed, with values ranging from 2.01 × 10⁻⁷ m·s⁻¹ to 1.42 × 10⁻⁶ m·s⁻¹, which makes its use in landfill base liner layers unfeasible. With respect to the soil expansibility index, the 5% biopolymer content showed an expansion of 57%, while the sample tested with kerosene exhibited an expansion of only 25%, since, due to its apolar and low-reactivity nature, kerosene interacts minimally with both the soil and the biopolymer, thereby restricting hydration and swelling. The results obtained indicate the need for adjustments in the cactus treatment process, such as mucilage extraction and crosslinking procedures, in order to make its application feasible in compacted soil layers intended for landfill waterproofing.