Functionalized adsorbents resulting from the transformation of fly ash: characterization, modification, and adsorption of pesticides

Abstract

Surfactant-modified zeolite materials are known for their good sorption properties of organic compounds from aqueous solutions. Zeolites and zeolite-carbon composites from the transformation of fly ashes can be modified to obtain functionalized sorbents of pesticides. The current knowledge regarding zeolites' modification mechanisms and sorption properties toward pesticides is still insufficient. Zeolite types A and X and zeolite-carbon composites with zeolite types A and X, obtained by the conversion of fly ashes we modified with a cationic and a nonionic surfactant. The modified materials were characterized by X-ray diffraction (XRD), infrared spectrometry (FTIR), scanning electron microscopy (SEM), thermogravimetric/ differential thermal (TG/DTA), and specific surface area and pore volume (BET) methods. We show that the presence of a cationic surfactant significantly increases the amount of the adsorbed nonionic surfactant. These features enabled the proposed adsorbent to be utilized to efficiently remove 2,4-dichlorophenoxyacetic acid (2,4-D), 2-methyl-4-chlorophenoxyacetic acid (MCPA), carbendazim, and simazine. Our experiments on pesticides adsorption indicate that 2,4-D and MCPA are the most effectively adsorbed on the cationic surfactant-modified adsorbents, while carbendazim and simazine show the highest affinity to unmodified zeolite-carbon composites. A detailed study of the adsorption of pesticides is the topic of forthcoming works.