Highly fluorescent composite of boron nitride quantum dots decorated on cellulose nanofibers for detection and removal of Hg(II) ions from waste water.

To address the challenge of heavy-metal ions in wastewater, boron nitride quantum dots (BNQDs) were synthesized in-situ on rice straw derived cellulose nanofibers (CNFs) as substrate. The composite system exhibited strong hydrophilic-hydrophobic interactions, as corroborated by FTIR, integrated the extraordinary fluorescence properties of BNQDs with fibrous-network of CNFs (BNQD@CNFs) yielding a surface of 35.147 m2 g-1 of luminescent fibers. Morphological studies revealed uniform distribution of BNQDs on CNFs due to hydrogen bonding, according high thermal stability with peak degradation occurring at 347.7 °C and quantum yield of 0.45. The nitrogen-rich surface of BNQD@CNFs exhibited strong affinity for Hg(II), quenching the fluorescence intensity due to combined inner-filter effect and photo-induced electron transfer. The limit of detection (LOD) and limit of quantification (LOQ) were 4.889 nM and 11.1 5 nM, respectively. BNQD@CNFs concomitantly exhibited adsorption of Hg(II) owing to strong electrostatic interactions, confirmed by X-ray photon spectroscopy. Presence of polar BN bonds favoured 96 % removal of Hg(II) at 10 mg L-1 with maximum adsorption capacity of 314.5 mg/ g. Parametric studies corresponded to pseudo-second order kinetics and Langmuir isotherm with R2 ≈ 0.99. BNQD@CNFs exhibited recovery rate between 101.3 %-111 % for real water samples and recyclability upto 5 cycles, demonstrating high potential in wastewater remediation.