Biomimetic hydrophobic plastic foams with aligned channels for rapid oil absorption

Although many oil absorption materials have been developed, it still remains a great challenge to achieve rapid absorption and efficient recovery. Over the past decade, research has focused on the development of freeze casting technology using water as a solvent. The materials prepared by this method have poor water resistance and are difficult to apply to oil absorption in aqueous environments. Here, an organic solvent freeze casting strategy is proposed to fabricate ultralight hydrophobic plastic foams with aligned channel structures. Through microscopy in situ observation, we revealed the growth morphology of ice crystals during directional freezing process. Moreover, aligned porous foams with various channel sizes are fabricated by regulating the cooling rate. We found that organic solvent-assisted freeze casting can enhance the hydrophobicity of the matrix material. These aligned porous foams exhibit excellent liquid absorption performance, with high absorption speed and large absorption capacity over a wide viscosity range. This approach has general applicability and can be used to tailor a wide variety of engineering plastic-based aligned porous foams, as long as they can dissolve in organic solvents.

Hydrophobic Porous Polypropylene with Hierarchical Structures for Ultrafast and Highly Selective Oil/Water Separation

Recently, various porous absorbents have been developed and the in situ vacuum/pump-assisted continuous separation process has proven to be the most efficient technique to utilize those absorbents for oil spill cleanup. However, to achieve a high oil removal throughput, a high pumping pressure and/or large absorbent pore sizes are required, which would compromise the selectivity of oil/water separation, as water may penetrate the absorbent beyond a critical external pressure. In this work, this challenge has been circumvented by employing hierarchically porous polypropylene (PP) with controlled pore sizes generated from a tricontinuous heterophase polymer blend system. As compared to unimodal pores, the incorporation of the secondary smaller pores significantly enhances the oil removal throughput by up to 4-5 times without the necessity of raising the pumping pressure or increasing the diameter of the primary pores, which in turn, prevents compromising the oil/water separation selectivity.