A novel cationic polyelectrolyte microsphere for ultrafast and ultra-efficient removal of heavy metal ions and dyes

Abstract Dyes and heavy metal ions contamination have caused serious hazards to human and environmental health. Thus, effective removal of dyes and heavy metal ions is urgently needed. Herein, a novel cationic polyelectrolyte microsphere (CCQM) has been successfully fabricated via facile chemical crosslinking and emulsification method. CCQM with lower crystallinity, higher specific surface area, pore volume, thermal stability and surface charges, displayed better adsorption abilities than pure chitosan microsphere (PCM). These superior characteristics of CCQM provided ultrafast adsorption rate (within 4 min) and ultra-efficient adsorption capacity to anionic dyes and heavy metal ions (1500 mg g−1 for Congo red (CR) and 179.4 mg g−1 for Methyl orange (MO), 687.6 mg g−1 for Cu (Ⅱ) and 398.8 mg g−1 for Fe (III)), which were far better than most of the reported absorbents. The adsorptions of dyes and heavy metal ions on CCQM could be modeled using Langmuir, Pseudo-second order rate equation and Fickian diffusion laws’ equation, and the adsorption capacities were still satisfactory even under harsh conditions. The interference studies were performed and Cu2+ could be preferentially adsorbed by CCQM due to the smaller steric hindrance. The adsorption mechanism was unveiled that the cation exchange, chelating effect, proton exchange and complex formation mainly contributed to the ultrafast and ultra-efficient removal of heavy metal ions, while electrostatic interaction and hydrogen bonding led to the removal of dyes. In addition, CCQM with superb recyclability (within 10% loss after five cycles), antibacterial viability and biodegradability (165 days), could be used as the filler in filled column to purify wastewater. These results indicated that CCQM exhibited appealing application prospects for the treatment of various wastewaters.