Adsorptive removal of volatile petroleum hydrocarbons from aqueous solution by zeolite imidazole framework (ZIF-8) and iron oxide (Fe3O4) nanoparticles

Volatile petroleum hydrocarbons (VPHs), including pentane, ethylbenzene, methyl tert-butyl ether, toluene, and n-hexane, are often found on the surface and underground water due to industrial activities. As such the removal of VPHs is crucial by a vital task that requires great attention, especially in oil-rich countries. Thus, in this study, the adsorptive removals of VPHs from an aqueous solution by zeolite imidazole framework-8 (ZIF-8) and iron oxide nanoparticles (IONs) were investigated. The characterization results revealed that ZIF-8 has a higher surface area, and larger pore volume, and is more thermally stable than IONs. Fourier transform infrared spectra have found peaks corresponding to functional groups such as Zn-N, C-N, C-H, and C=N in ZIF-8 and Fe-O and hydroxyl groups in IONs confirming the successful synthesis of the adsorbents nanoparticles. Furthermore, the zeta potential values were -10 mV and -17 mV for ZIF-8 and IONs, respectively; suggesting good stability while Brunauer, Emmett, and Teller (BET) specific surface area results revealed that both adsorbents have a high surface area of 1268 m2/g for ZIF-8 and 130.8 m2/g for IONs. The optimum pH for the removal of VPHs for both adsorbents was observed to be pH 8, with the highest removal efficiency reaching 82.2% and 63.6% for ZIF-8 and IONs, respectively. Isotherm model studies revealed that the adsorption data was best fit using the Langmuir model indicating monolayer adsorption. The maximum adsorption capacities (Qm) of VPHs onto ZIF-8 was 5.51 mg/g and onto IONs was 1.459 mg/g at 45◦C, respectively. Lastly, the thermodynamic studies revealed that the reaction was endothermic, spontaneous, and had a good affinity. The results demonstrated the great potentiality of ZIF-8 application as a benchmark adsorbent for the removal of VPHs compounds. In this study for the first time, the wide matrix of VPHs was attempted to be removed from a real wastewater sample using ZIF-8 and IONs. The results designate that ZIF-8 and IONs as good adsorbents for the removal of a wide range of VPHs from a water matrix.