Quaternary ammonium-modified cellulose: A sustainable strategy for purifying aqueous solutions contaminated with sunset yellow dye.

This study showcases the remarkable efficacy of quaternary ammonium-modified cellulose as a highly sustainable biosorbent for removing Sunset Yellow (SY) dye from water. Detailed analysis was conducted using infrared (FTIR) spectroscopy for structural changes and Scanning Electron Microscopy (SEM) for morphological changes. A minimal yet highly effective dose of 0.05 g was identified through dedicated optimization experiments, achieving near-complete removal (99 %) of SY. The biosorbent demonstrated exceptional performance across a broad pH range (2-10), accomplishing remarkable removal within just 5 min. Langmuir modeling uncovered a monolayer sorption mechanism with a high maximum capacity (107.08 mg g-1), and thermodynamic analysis affirmed the spontaneity and favorability of the sorption process. Noteworthy is the biosorbent's impressive regeneration capabilities (up to 95 %) using 1.0 M NaOH or HCl solutions and its sustained performance over three sorption-regeneration cycles, highlighting its exceptional stability and reusability. The modified cellulose exhibited remarkable resistance to common interfering ions (chloride, nitrate, and sulfate) at 10 and 100 mg L-1 concentrations. These combined features position quaternary ammonium-modified cellulose as a promising, sustainable, and efficient option for dye wastewater treatment.