Multicomponent Photocatalytic-Dispersant System for Oil Spill Remediation

Abstract

In the present work, the potential application of a fabricated halloysite nanotubes-Ag-TiO₂ (HNT-Ag-TiO₂) composite loaded with a binary surfactant mixture made up of lecithin and Tween 80 (LT80) in remediating oil spillages was examined. The as-prepared Ag-TiO₂ that was used in the fabrication of the HNT-Ag-TiO₂-LT80 composite was characterized by X-ray diffraction, Raman spectroscopy, UV-vis and diffuse reflectance spectroscopy, CV analyses, and SEM-EDX. The synthesized composite was also characterized by thermogravimetric analysis, Fourier-transform infrared spectroscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy. The synthesized composite was active in both the UV and visible light regions of the electromagnetic spectrum. The oil-remediating potential of the as-prepared composite was examined on crude oil, and aromatics and asphaltene fractions of crude oil. The composite was able to reduce the surface tension, form stable emulsions and smaller oil droplet sizes, and achieve a high dispersion effectiveness of 91.5%. A mixture of each of the crude oil and its fractions and HNT-Ag-TiO₂-LT80 was subjected to photodegradation under UV light irradiation. The results from the GC-MS and UV-vis analysis of the photodegraded crude oil revealed that the photocatal composite was able to photodegrade the crude oil, aromatics, and asphaltene fractions of crude oil with the formation of intermediate photodegradation products depicting that the HNT-Ag-TiO₂-LT80 has a potential as an oil spill remediation material.

Figure 1

(a) XRD Pattern of Ag-TiO₂ and HNT-Ag-TiO₂ [Note: Characteristic peaks of Halloysite (o), Anatase TiO₂ (*) and Rutile TiO₂(#).] and (b) Raman spectra of TiO₂ and Ag-TiO₂.

Figure 2

SEM-EDX of (a) HNT-Ag-TiO_2, (b) HNT-Ag-TiO₂-LT80, (c) Ag-TiO₂ and (d) TiO₂.

Figure 3

FTIR analysis of (a) TiO₂, Ag-TiO₂ and HNT and (b) HNT-Ag-TiO₂ and HNT-Ag-TiO₂-Lecithin-Tween 80 (LT 80).

Figure 4

(a) UV–vis absorption spectra (b) Optical band gap and (c) Diffuse reflectance spectra of Ag-TiO₂, TiO₂ and HNT/Ag-TiO₂.

Figure 5

CV analysis of (a) TiO₂, HNT-Ag-TiO₂, and Ag-TiO₂, (b) HNT-Ag-TiO₂-LT80 and (c) LSV results of TiO₂, Ag-TiO₂ and HNT-Ag-TiO₂.

Figure 6

Dispersion effectiveness of HNT-Ag-TiO₂-LT80 at different SOR.

Figure 7

GC-MS spectra of (a) 0 min/undegraded crude oil, (b) 30 min light irradiated crude oil, (c) 7 days light irradiated crude oil, and (d) 14 days light irradiated crude oil obtained with HNT-Ag-TiO₂-LT80.

Figure 8

GC–MS spectra of (a) 0 min/undegraded aromatic fraction of crude oil (b) 30 min light irradiated aromatic fraction of crude oil, (c) 7 days light irradiated aromatic fraction of crude oil and (d) 14 days light irradiated aromatic fraction of crude oil obtained with HNT-Ag-TiO₂-LT80.

Figure 9

GC–MS spectra of (a) 0 min undegraded asphaltene fraction of crude oil (b) 30 min light irradiated asphaltene fraction of crude oil and (c) 7 days light irradiated asphaltene fraction of crude oil obtained with HNT-Ag-TiO₂-LT80.