Novel Fluorescent Nanocellulose Hydrogel Based on Nanocellulose and Carbon Dots for Detection and Removal of Heavy Metal Ions in Water

Water is an important raw material in the food production process. Maintaining the quality and safety of water is very important in the food field. In this study, a simple novel fluorescent nanocellulose hydrogel (FNH) was prepared for the detection and removal of heavy metals (Fe(3+) and Pb(2+)) in aqueous solutions based on carbon dots (CDs). The CDs were grafted onto the carboxylated nanocellulose (CNC) by the EDC/NHS coupling method, and then the nanocellulose (NC), CNC, and FNH were characterized by FTIR analysis. The effect of adsorption environment on FNH adsorption capacity was also investigated. After carboxylation and grafting of CDs, the adsorption capacity of nanocellulose to Fe(3+) and Pb(2+) was greatly improved, and it was also allowed to make fast visual responses to Fe(3+) as an optical sensor to determine the concentration of Fe(3+) through the visual signal. Static adsorption experiment demonstrated that the removal rate of Fe(3+) and Pb(2+) by FNH exceeded 69.4% and 98.2%, and the adsorption capacity amount reached 98.3 mg/g and 442.0 mg/g. At the same time, due to the fluorescence quenching effect of Fe(3+), FNH could also be used for the detection of Fe(3+) concentration in aqueous solution, and the limit of detection (LOD) could reach 62.5 mg/L.