Plastic waste for frost mitigation: A bio-inspired approach to enhance soil resilience and carbon sequestration

Abstract

This study investigates the use of waste plastic coated with biogenic carbon as a functional material for soils susceptible to frost heave and freeze-thaw. Our bio-inspired approach draws inspiration from ice-binding proteins (IBPs) found in polar organisms, using principles of surface science to develop carbon-coated oil-treated plastic granules (C-OTPG) aimed at lowering the freezing point in frost-susceptible geomaterials. We hypothesize that C-OTPG can effectively mimic the function of IBPs by disrupting ice nucleation and crystal growth through interactions among C-OTPG's functional groups, water, and the siliceous substrate. This innovative strategy seeks to bolster the resilience of geomaterials in cold climates while repurposing waste materials for sustainable applications. By integrating nature's solutions with modern engineering, we aim to create more durable and environmentally friendly materials. Evaluation experiments used a Linkam Peltier LTS120 thermoelectrical cooling device and bright-field microscopy to measure freezing temperatures and thawing temperatures and to assess the ice-inhibition properties of both silt and fine sand treated with C-OTPG. We found that for silt, C-OTPG treatment reduced the freezing point by up to 39 % and increased thermal hysteresis by up to 65 %, while for fine sand, the freezing point was reduced by up to 52 % and thermal hysteresis increased by up to 38 %. Calculations using density functional theory show strong hydrogen bonding and polar interactions between biogenic carbon and water molecules, preventing movement of water to the frost front and disrupting the formation of ice crystals. Additionally, biogenic carbon competes for adsorption sites on silica surfaces of sand and silt, while “capping” water molecules already on a silica surface inhibiting ice formation. This study highlights the potential of bio-inspired solutions to stabilize frost-susceptible soils while promoting resource conservation and environmental sustainability.