Quaternized chitosan modified Enteromorpha prolifera cellulose as a sustainable biosorbent for highly efficient removal of microplastics.

Microplastics (MPs), as emerging global contaminants widely present in the environment, pose potential ecological and biological hazards. Current MPs removal methods are energy-intensive and cause secondary pollution, necessitating the development of efficient and environmentally friendly alternatives. Here, Enteromorpha prolifera (EP), widely distributed in the ocean, was subjected to decolorization and alkaline treatment to obtain EP cellulose (EPC) being as a framework. Subsequently, quaternized chitosan (HACC) was cross-linked onto EPC using citric acid to yield surface charge-inverted modified EPC (M-EPC), which is the first time that EPC has been modified in this way. Surprisingly, the M-EPC exhibits exceptional adsorption capacity (1135.18 mg g-1) and removal efficiency (93.6%) for MPs, attributed to the synergistic removal mechanisms involving physical interception, electrostatic interactions, and hydrogen bonding. Remarkably, M-EPC maintained significant adsorption performance under most test conditions, including varying pH levels, different types of MPs, and various salt species and concentrations. The M-EPC also shows excellent reusability and the ability to purify real water samples, while demonstrating outstanding performance in biocompatibility and degradability. Additionally, we propose a promising strategy to convert M-EPC after MPs adsorption into value-added products. This work presents an effective solution for simultaneously addressing EP pollution and MPs contamination.