Lignocellulose/chitosan hybrid aerogel composited with fluorescence molecular probe for simultaneous adsorption and detection of heavy metal pollutants

Abstract

The pollution of heavy metals to aquatic ecosystem is getting more and more attention. Therefore, there is an urgent need to develop a low-cost, high-efficient, high-selective and environmental adsorbing material that can simultaneously indicate and adsorb heavy metal ions. Cellulose-based aerogel has attracted much attention due to its strong adsorption capacity, good biodegradability and cost performance. In this paper, cellulose nanofiber/chitosan/polyvinyl alcohol/lactam Rhodamine 6 G composite aerogel (CNF/CS/PVA/SRh6G) was prepared by freeze-drying technology with CNF/CS hybrid aerogel as adsorbent skeleton, SRh6G as fluorescent probe and PVA/glutaraldehyde (GA) as crosslinking agent. When the volume ratio of CNF suspension to CS solution was 10:1, as-prepared composite aerogel had a lower density (145.92 mg/cm3) and a higher specific surface area (0.04293 cm3/g). It also exhibited excellent superhydrophilicity and superoleophobicity underwater (OCA-159°), the underwater OCA of which always kept larger than 150° in the surroundings with pH of 1–14. Therefore, CNF/CS/PVA/SRh6G composite aerogel owned good acid and base resistance, which could be applied to rapid adsorption and real-time detection of metal ions (Hg2+, Ag+, Al3+, Fe3+ and Cu2+) in wastewater. CNF/CS/PVA/SRh6G composite aerogel could display obvious color and fluorescence variations under sunlight and ultraviolet light, and present the good reversibility after regeneration via base solution (pH=14). Under water, such CNF/CS/PVA/SRh6G composite aerogel showed a good compression elasticity with the maximum pressure of 26.2 N. After five cycles, the adsorption of composite aerogel still could reach up to 19 times of its own weight. Results also showed that it had remarkable durability and structural stability, indicating its broad application prospects in the field of wastewater treatment.