A sustainable reinforced-concrete-structured sponge for highly-recyclable oil adsorption

A reinforced-concrete-structured sponge based on amino-terminated polydimethylsiloxane (PDMS) and carboxyl carbon nanotubes (CCNTs) is synthesized, without any templates or coatings. The covalent bonding of PDMS and CCNTs generate amide groups which provide considerable hydrogen bonds. The synergistic effect of dynamic hydrogen bonds and flexible PDMS chains contribute to the high elasticity, while CCNTs affect the stress. The compressive and tensile stress-train curves both overlap with the first curves during multiple load-release cycles, at the compressive strain of 80% and the tensile strain of 100%, respectively. The amount of CCNTs determines the porosity, and significantly affects the hydrophobicity. The sponge is applied to static oil adsorption, oil/water emulsion separation and oil-spill treatment. Due to the high elasticity and anti-fatigue performance, the sponge can be repeatedly regenerated using a simple squeezing method. The adsorption capacity still reaches 99.45% after 30 adsorption–desorption cycles. The weight, morphology and hydrophobicity of the sponge maintain unchanged, either. The simulation of oil-spill treatment demonstrates that the sponge can also work efficiently under dynamic conditions. The high elasticity, recyclability and stability propose the sponge to be a promising material for oily-water treatment in complex circumstances.