Adsorption and interaction studies of methylene blue dye onto agar-carboxymethylcellulose-silver nanocomposite in aqueous media

Agar-carboxymethylcellulose-silver nanoparticle (AG-CMC-AgNP) nanocomposite was fabricated from modification of cellulose (extracted from Egyptian macroalga Ulva fasciata ) to carboxymethylcellulose (CMC), with silver nanoparticles, and agar (AG; extracted from Gelidium crinale ). The characteristics of AG-CMC-AgNP were enlightened by using Fourier transform infrared (FTIR), UV–visible (UV–vis), X-ray powder diffraction (XRD), scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDX), thermogravimetric analysis (TGA), and the zero-point charge of pH (pH ZPC ) measurements. Batch sorption investigations were carried out to determine the optimum experimental conditions (pH, contact time, temperature, amount of sorbent and initial methylene blue (MB) dye concentration). The maximal adsorption capacity of AG-CMC-AgNP (50 mg) was found to be 66.68 mg g −1 , forming a monolayer of MB at 25 °C, for 150 min at pH 5.5. The adsorption of MB onto AG-CMC-AgNP strongly obeyed the Langmuir isotherm and agreed well with the pseudo-second-order reaction (PSORE) kinetic model. The thermodynamic parameters indicated a feasible, spontaneous, endothermic, and more randomness state existing at the solid–liquid interfaces. The biosorbent can be reused, but with a decrease in the amount of adsorbed MB dye after the fifth cycle. The interaction of MB adsorbed onto AG-CMC-AgNP was discussed using spectroscopic, morphological, and TGA measurements.