Visualizing and sorbing Hg(II) with a cellulose-based red fluorescence aerogel: Simultaneous detection and removal

Both sensing and removal of Hg(II) are important to environment and human health in view of the high toxicity and wide applications of mercury in industry. This study aims to develop a cellulose-based fluorescent aerogel for simultaneous Hg(II) sensing and removal via conveniently cross-linking two nanomaterials cellulose nanocrystals and bovine serum albumin-functionalized gold nanoclusters (BSA-AuNCs) with epichlorohydrin. The aerogel exhibited strong homogeneous red fluorescence at the non-edged regions under UV light due to highly dispersed BSA-AuNCs in it, and its fluorescence could be quenched by Hg(II). Through taking pictures with a smartphone, Hg(II) in the range of 0-1000 μg/L could be quantified with a detection limit of 12.7 μg/L. The sorption isotherm of Hg(II) by the aerogel followed Freundlich model with an equation of Q_e = 0.329*C_e^1/0.971 and a coefficient of 0.999. The maximum sorption capacity can achieve 483.21 mg/g for Hg(II), much higher than many reported sorbents. The results further confirmed Hg(II) strong sorption and sensitive detection are due to its complexation and redox reaction with the chemical groups in aerogels and its strong fluorescence quenching effect. Due to extensive sources and low cost, cellulose is potential to be developed into aerogels with multiple functions for sophisticated applications.