Effect of polyaniline dispersibility in chitin sponge matrix controlled by hydrophilicity on microplastics adsorption

Microplastics have become an emerging threat to global ecosystems, and their efficient removal faces with serious challenges. Herein, this study introduced different hydrophilic polyaniline (PANIs) into chitin matrix to fabricate Chitin-PANIs sponge (ChPANIs) and investigated the relationship between PANIs dispersibility in chitin sponge matrix controlled by its hydrophilicity and adsorption effects on MPs. With the increase of PANIs' hydrophilicity (WCA from 153.9 degrees to 32.8 degrees), the removal efficiency of sponges to MPs increased from 84.0 % to 91.7 %. More hydrophilic PANIs can provide more contact surfaces and adsorption sites, which enhanced the electrostatic interactions to MPs and obtained excellent adsorption properties. The adsorption of MPs on ChPANIs accorded with the pseudo-first-order adsorption, suggesting that physical adsorption plays a dominant role. The adsorption process also conformed to Freundlich model, which displayed the MPs adsorption on ChPANI-PA could be multi-layer. The adsorption strength of ChPANIs was 0.7552, suggesting that it was a strong adsorbent. The ChPANIs also exhibited good mechanical properties and reusability, which its MPs removal efficiency just decreased from 91.7 % to 86.9 % during the five cycles. These findings expand the understanding of the adsorption mechanism analysis of MPs on sponge materials, and exist guiding significance for the design of adsorbed materials.