This work investigates the removal of various nitrophenolic compounds (ortho-nitrophenol (ONP), paranitrophenol (PNP), meta-nitrophenol (MNP), and 2,4-dinitrophenol (2,4-DNP)) from aqueous solution using hydrophobic FAU zeolites. The adsorption equilibrium of nitrophenols from aqueous solutions by FAU can be well-described using the Fowler-Guggenheim equation. The relative affinity of nitrophenols toward the FAU is dependent on the pH solution and on the pollutant solubility in water. Their sorption capacity is in the following order: ONP > 2.4-DNP > PNP > MNP. In binary mixtures, the most important parameter that governs the adsorption in zeolites seems to be the solubility of pollutants in water. Thus, the less-soluble compound (in this case, ONP) was adsorbed more easily than the other components present in the binary mixture. Finally, hydrophobic FAU zeolite seems to be an efficient adsorbent; it is able to be easily regenerated under air or by solvent leaching, through retention of these initial adsorption properties.
The adsorption of aromatic compounds (nitrophenols, nitroaniline, chlorophenols, chloroanilines) present in wastewater using dealuminated faujasite zeolite has been investigated. The adsorption capacity of faujasite zeolite depends on the pH, (the neutral form of the pollutants is more easily adsorbed into zeolite than the dissociated form), and on the solubility in water of the aromatic compounds. The adsorption capacity for a family of compounds increases with decreasing water solubility. In this study, we have shown that the pollutant acidic character enhances their adsorption into the zeolite. Thus, the changeover of phenol to aniline decreases the adsorbent−adsorbate interaction, as well as in the substitution of the NO2 group by a Cl group. The adsorption data was analyzed using the Fowler−Guggenheim isotherm. The sorption mechanism of nitrophenol in faujasite zeolite was investigated using Raman spectroscopy and through a thermodesorption kinetic study. The relative affinity of the phenolic compounds toward the surface of the dealuminated faujasite was related to the electron donor−acceptor complex formed between the basic sites on the zeolite (oxygen) and the hydrogens (acidic site) of the aromatic ring and of the phenols and anilines functions.
The influence of the morphology (microcrystals, nanocrystals, nanosponges and nanosheets) of MFI and *BEA-type zeolites on their adsorption capacities and adsorption rate of n-hexane at 25 ˚C has been investigated. The capacity of n-hexane adsorption sensitive to micro-and mesopore volume is enhanced by the use of zeolite nanocrystals or hierarchical nanoporous materials (nanosheets and nanosponges). In the case of hierarchical zeolites MFI and *BEA nanosponges, the n-hexane adsorption capacities reached values of about 790 and 693 mg/g, respectively, that are much higher than those in the corresponding microcrystals (130 and 103 mg/g, respectively). On the opposite the kinetics of nhexane adsorption are slower in nanocrystals and hierarchical zeolites compared to big crystals, due to the lower crystallinity of the zeolitic material and the nature of the probe molecule.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.