Spider-Web Textured Electrospun Composite of Graphene for Sorption of Hg(Ⅱ) Ions

摘要

Expunging of heavy metal ions from industrial and nuclear discarded water is of paramount importance. Accounting the feature of large surface area and porous structure of electrospun nanofibers, present investigation deals with the synthesis and characterization of electrospun cellulose-graphene nanocarbon fibers for selective speciation of Hg(Ⅱ) ions with high efficacy. The effectiveness of these nanofibers was tested in batch adsorption process for the fast uptake of Hg(Ⅱ) ions at pH 6.0 with 77% adsorption within 60 min. Cellulose-graphene nanofibers exhibits enhanced surface area of 14.86 m~2/g as compared to cellulose fibers with 5.23 m~2/g. The adsorption behaviour towards Hg(Ⅱ) was assessed using different isotherm models (Lang-muir, Freundlich, Temkin and Dubinin-Radushkevich). Evaluated values are quantified as, Langmuir constants q_(max) = 13.73 mg/g, R_L = 0.65, Freundlich constants n = 1.30, K_F = 0.15 mg/g, Temkin constant K_T = 0.074 L/g and D-R parameter q_(max) = 0.045 mol/g, ε = 2917.31. The kinetics of Hg(Ⅱ) sorption has been exemplified by pseudo first-order, pseudo second-order and Elovich model with noble regression coefficient value (R~2 = 0.99). Intra-particle diffusion model delineates the chemical interaction between metal ion and the adsorbent. Ther-modynamic studies revealed ΔG° value of -12.90 kJ/mol, signifying feasibility and spontaneity of adsorption process. With the virtuous reusable property for cyclic Hg(Ⅱ) removal (8 cycles), the newly developed cellulose-GNC fibers may hold a great promise for higher efficiency removal of Hg(Ⅱ) ion from laboratory and industrial wastes.