Study of Factors Governing Oil–Water Separation Process Using TiO₂ Films Prepared by Spray Deposition of Nanoparticle Dispersions

Abstract

Surfaces which possess extraordinary water attraction or repellency depend on surface energy, surface chemistry and nano-and microscale surface roughness. Synergistic superhydrophilic-underwater superoleophobic surfaces were fabricated by a spray deposition of nanostructured TiO 2 on stainless steel mesh substrates. The coated meshes were then used to study gravity driven oil-water separation, where only the water from the oil-water mixture is allowed to permeate through the mesh. Oil-water separation efficiencies of up to 99 % could be achieved through the coated mesh of pore sizes 50 and 100 micron, compared to no separation at all, that was observed in the case of uncoated meshes of the same material and pore sizes. An adsorbed water on the TiO 2 coated surface, formation of a water-film between 2 the wires that form the mesh and the underwater superoleophobicity of the structured surface are the key factors that contribute to the enhanced efficiency observed in oil-water separation.The nature of the oil-water separation process using this coated mesh (in which the mesh allows water to pass through the porous structure but resists wetting by the oil phase) minimizes the fouling of mesh so that the need for frequent replacement of the separating medium is reduced. This fabrication approach presented here can be applied for coating large surface areas and to develop a large-scale oil water separation facility for oil-field applications and petroleum industries.

Versatile fabrication of magnetic superhydrophobic foams and application for oil–water separation

“…Therefore, much attention was paid on developing facile methods for fast and selective removal of oils from water surface. A number of strategies have been proposed for achieving this goal, which mainly involved meshes [9][10][11][12][13], films [14,15], or membranes [16][17][18][19]. Although these previously developed materials can be effective for oil/water separation, they cannot be applied in the place of the oil spills because the polluted water should be first collected and then be filtered.…”

Purification of oily seawater/wastewater using superhydrophobic nano-silica coated mesh and sponge

“…As a result, the development of effective and inexpensive methods for oilwater separation has become an important issue in order to meet environmental and economic demands [1]. Despite the fact that many oil-water separation methods such as adhesion, membrane filtration, and absorbance have been developed and are widely used [2], achieving an energy-and cost-effective oil-water separator with high efficiency remains a great challenge. Since oil-water separation is governed by the interfacial features of the substrate, fabrication of preferential wettability materials toward oil or water is desirable and effective [3,4].…”

“…Recently, novel materials possessing both hydrophobic/oleophilic ''oil-removing'' and hydrophilic/oleophobic ''water-removing'' surfaces have been developed, with which oil or water phases spread and penetrate readily through the material, and the remaining water or oil phase is repelled [2][3][4][5][6][7][8]. For a small oil spill, oil sorbent materials are commonly used, and recent studies have focused on the preparation of superhydrophobic sponges.…”

“…However, these materials have several drawbacks such as inadequate absorption capacity, low selectivity, and poor recyclability [6]. Therefore, the gravity-driven filtration method is preferred due to the high cost-efficiency and high permeability in comparison to cumbersome and expensive absorption [2,7]. The pioneering work of Fen et al, wherein a steel mesh was spraycoated with polymer composite, was one of the first reports describing the use of superhydrophobic/superoleophilic durable substrates in the selective separation of oil and water by means of pouring-type gravity-driven approaches [8].…”

A study on the performance of self-cleaning oil–water separation membrane formed by various TiO2 nanostructures

“…In addition, the high definition FESEM image (figure 1f) revealed that the nanowire hosts were uniformly and densely covered by 200nm long and 150nm wide nanosheet structures. This incorporation of nanosheet onto nanowire form a single "heterostructure" that possesses enhanced specific surface area for mass transfer and reactive sites, which are important factors to improve the photocatalytic properties as well as oil-water separation ability [37,38]. As shown in figure S1, the thickness of a typical TiO 2 nanostructured membrane is approximately 120µm.…”