Adsorption of crude and waste diesel oil onto agar-carboxymethylcellulose-silver nanocomposite in aqueous media

Abstract

Waste containing oil is generally classified as hazardous pollutants especially aquatic environment. A new agar-CMC-silver (AG-CMC-Agnp) nanocomposite was synthesized by surface modification of cellulose (extracted from Egyptian macroalga Ulva fasciata) to carboxymethylcellulose (CMC) anchored on silver nanoparticles (Agnp), followed by agar (AG; extracted from Gelidium crinale). A batch study was applied to evaluate the efficacy of these biomaterials to remove crude and waste diesel oil from water. The optimum parameters affecting oil adsorption (oil concentration, contact time, temperature, and sorbent dose) were investigated. AG-CMC-Agnp composite shows the highest adsorption capacity with 10.95 ± 0.47 and 8.95 ± 0.54 g g−1, for removal of crude and waste diesel oil from aqueous media, respectively, with excellent recyclability for more than nine cycles. The kinetic studies indicate that diesel oil diffused into the internal layers of AG-CMC Agnp and can be fitted to a pseudo- first order (PFORE) model. Furthermore, isotherm studies were discussed using the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The result showed that adsorption of diesel oil onto AG-CMC-Agnp could be best fitted with the Langmuir model with a maximum monolayer capacity of 12.26 and 11.04 (exp. 10.95 and 8.95) mg g−1, respectively. The spectral {Infrared (IR), UV–vis and X-Ray powder diffraction (XRD)}, and scanning electronic microscopy (SEM) and transmission electron microscopy (TEM) micrographs with energy-dispersive X-ray (EDX) of AG-CMC-Agnp composite indicated that, upon adsorption, oil molecules are covering the pores on the surface.