Synthesis and characterization of ferric@nanocellulose/nanohydroxyapatite bio-composite based on sea scallop shells and cotton stalks: adsorption of Safranin-O dye.

In the present study, four solid adsorbents were prepared via green synthesis sources, namely, nanohydroxyapatite (NHAP), nanocellulose (NC), nanocellulose/nanohydroxyapatite composite (NPC), and ferric@nanocellulose/nanohydroxyapatite composite (FNPC). Synthesis procedures were based on natural sources such as sea scallop shells and cotton stalks. All the prepared solid adsorbents were characterized by TGA, XRD, nitrogen adsorption/desorption isotherm, FTIR, pH_PZC, SEM, and TEM. FNPC exhibited a higher surface area (358.32 m²/g), mesoporous surface (pore diameter, 12.29 nm), TEM particle size of 45 nm, and the availability of various surface functional groups. Static adsorption of Safranin-O (SO) dye was investigated for all the prepared solid adsorbents under different application conditions. Maximum adsorption capacity (239.23 mg/g) was achieved by FNPC after 24 h of equilibrium time, at pH 7, 2 g/L as adsorbent dosage, and 40 ℃. Adsorption of Safranin-O onto all the samples well-fitted Langmuir, Temkin, Freundlich, Dubinin–Radushkevich, pseudo-second-order, and Elovich models. Thermodynamic and kinetic parameters proved that Safranin-O adsorption is favorable, spontaneous, endothermic, and physisorption. Desorption studies confirmed that hydrochloric acid (0.03 mol/L) achieved the maximum desorption efficiency (92.8%). Reusability of FNPC showed a decrease in the adsorption capacity after five cycles of adsorption and desorption by only 7.8%. [ABSTRACT FROM AUTHOR]