Multifunctional esterified versus carbon-based cellulose acetate membranes: Structural, thermal, and fluorescence...

This work deals with developing the esterified and hybrid cellulose acetate (CA) membranes through surface esterification by long chain ester groups and incorporation of carbon nanomaterials [graphite oxide (GO) and carboxymethyl graphite oxide (CMGO)], as multifunctional platforms for Cu²⁺ detection and removal from aqueous media. FTIR and NMR analyses confirmed successful chemical modification. The modified membranes were evaluated for metal ion adsorption capacity, thermal stability, liquid crystalline behavior, as well as sensing performance using fluorescence spectroscopy and microscopy. Thermal analysis, which were interpreted through different models (Coats-Redfern, Broido, and Horowitz-Metzger models), revealed enhanced stability and a strong correlation between Cu²⁺ adsorption and reduced activation energies of degradation. The membranes of esterified CA (ECA) demonstrated high sensitivity with a detection limit of 10 ppm and adsorption capacities of 3.6-7.3 mg/g, showing the most pronounced fluorescence quenching due to efficient chelation. Polarized Optical Microscopy further indicated that Cu²⁺ disrupted the liquid crystalline order of EC; while preserving or enhancing birefringence in GO-based hybrids through coordination-induced ordering. Collectively, these results establish esterified and hybrid CA membranes as promising candidates for sustainable fluorescence-based sensing and adsorption of Cu²⁺ in wastewater treatment applications.