Colloids and Surfaces A: Physicochemical and Engineering Aspects
Boron substituted MFI-type zeolite-coated mesh for oil-water separation
Graphical abstract
Introduction
Because of the ever-increasing demand for clean water, combined with the increasing generation of industrial oily water discharge, there is a worldwide water crisis. The presence of oil in water is immediately detrimental to the environment, but also has the long term effect of damaging the self-cleaning circulatory processes of the ecological system [1]. Thus, considerable efforts are underway to obtain energy-efficient and environmentally-friendly methods for the remediation of oily contaminants. Over the past few decades, polymeric membranes have dominated the R&D landscape because of their good performance and oil rejection rates of more than 95% [[2], [3], [4], [5], [6], [7], [8], [9], [10]]. However, due to their extremely small pore sizes, large pressure gradients across these membranes are required, which translates into power consumption and a rising cost of operation. In addition, at these pressures, polymeric membranes are prone to fouling [[4], [5], [6], [7], [8], [9], [10], [11]], where the flux through the membrane rapidly declines [12,13]. Despite efforts to develop novel self-cleaning polymeric membranes, the ratio of oil droplets adsorbed onto the surfaces of such membrane is 70–90% and the ratio of oil droplets cleaned away from membrane surface is as low as 30–40% [[9], [10], [11]].
In an effort to resolve the fouling problem, super-hydrophilic polymeric materials have been coated on stainless-steel wire mesh, which allow water to pass through the mesh and reject oil [[14], [15], [16], [17], [18]]. These super-hydrophilic membranes exploit the differences in density between water and oil and the formation of a water layer on the membrane surface that acts as barrier to oil [19]. Xue et al. [14] successfully fabricated hydrogel-coated mesh to realize a 99% oil rejection rate within only a few seconds of operation, while Xiao et al. [17] synthesized super-hydrophilic polymeric materials and with oil rejection rates of 99% or better. Chen et al. [18] prepared inorganic-organic thiol-ene coated mesh with almost 100% oil rejection. The downside of polymeric coated membranes is their intolerance to corrosive solutions, such as acids and bases, organic solvents and high temperatures [12,20,21]. They are also susceptible to swelling, which detrimentally impacts molecular diffusion and the convection of water in the pores [22]. This can produce a swelling ratio in hydrogels upwards of 2.0–3.7 [23,24], thereby limiting their use in challenging environments.
Recently, researches have turned their attention to ceramic materials as an alternative to polymers. Li et al. [23] coated SiO2 on stainless steel mesh, which separated 98% kerosene from corrosive and hot water. Li’s group utilized a spray coating process for the development of ZnO-coated mesh and TiO2-coated mesh to obtain kerosene/water separation rates of 97.3% and 97.5%, respectively, over 40–50 separation cycles [25,26]. More recently, the separation efficiencies of a variety of materials coated on stainless steel mesh coating, such as zeolite [19,27], ZnO [25,28,29], TiO2 [26], Cu2S [30], CuC2O4 [31], and SiO2 [23,32] have been examined. Among these, pure-silica or high-silica zeolite are the most promising due in part to their corrosion-resistance and their chemical, mechanical, and thermal stability [[33], [34], [35]], which enables their operation under severe conditions. The IIIA ion (e.g. B3+, Al3+) can be introduced into zeolite structure in order to make use of their empty orbitals so that more hydroxyl groups can be connected, which will form more hydrogen bonds and thereby increase the hydrophilicity [36].
Herein, we demonstrate for the first time the novel fabrication of boron substituted zeolite-coated meshes that resist fouling, highly recyclable, and efficiently separate water from oil. With the substitution of B3+ ions, the zeolite mesh becomes more hydrophilic and a higher water flux. In order to evaluate the stability of the zeolite-coated mesh when operating in corrosive aqueous solutions, oil/water separation was conducted under acidic, basic, and hot-media conditions, respectively. The rejuvenation and reusability of the zeolite-coated mesh by re-calcination was also investigated. We also report on the separation efficiency as a function of oil type.
Section snippets
MFI seed synthesis
The detailed MFI seed synthesis steps have been described elsewhere by Kim et al. [37]. First, NaOH (99.99%, Sigma-Aldrich) was dissolved in a mixture solution of H2O and tetrapropylammonium hydroxide (TPAOH) solution (1 M, Sigma-Aldrich), followed with gradually adding SiO2 (0.2–0.3 μm powder, Sigma-Aldrich) in water bath at 80 °C to obtain clear suspension with stirring. The molar ratio of the above suspension was NaOH: H2O: TPAOH: SiO2 = 1: 131.5: 2.86: 9.42, respectively. The suspension was
Characterization of boron substituted zeolite-coated mesh
The morphology of pristine and seeded stainless steel mesh are displayed in Figs. 2(a) and 2(b). The similarity between the images is indicative of the highly conformal nature of the seed layer. Fig. 2c shows the seeded stainless steel mesh with a mesh opening of ∼100 μm. After the 17 h of hydrothermal reduction, the boron substituted zeolite crystals are uniformly distributed on the wires, indicative of the formation of a thin crystal film that is well adhered to the stainless steel mesh (Fig.
Conclusions
We demonstrated a facile fabrication method for synthesizing boron substituted zeolite-coated mesh for efficient oil/water separation. The hydrophobicity of the zeolite-coated mesh is controlled by adjusting B/Si ratio in the precursor solution. With increasing boron substitution of Si, contact angle measurements indicated an increase of the hydrophilicity of the zeolite-coated mesh. With a B/Si ratio of 0.04, the zeolite-coated mesh exhibited super-hydrophilicity and underwater
Conflicts of interest
None.
Acknowledgement
The authors gratefully acknowledge funding from Oklahoma State University. We thank the National Energy Solutions Institute – Smart Energy Source (NESI-SES) and the Technology and Business Development Program (TBDP) for partial funding of this work. We also give special thanks to Pamela Reynolds for editing the manuscript.
References (41)
- et al.
Preparation of poly (vinylidene fluoride)(pvdf) ultrafiltration membrane modified by nano-sized alumina (Al 2 O 3) and its antifouling research
Polymer
(2005) - et al.
Polyethersulfone (PES) hollow fiber ultrafiltration membranes prepared by PES/non-solvent/NMP solution
J. Membr. Sci.
(2004) - et al.
Membrane technology enhancement in oil–water separation. A review
Desalination
(2015) - et al.
Preparation and characterization of tubular ceramic membranes for treatment of oil emulsions
J. Eur. Ceram. Soc.
(2005) - et al.
Performance study of ceramic microfiltration membrane for oily wastewater treatment
Chem. Eng. J.
(2007) - et al.
Preparation and application of zeolite/ceramic microfiltration membranes for treatment of oil contaminated water
J. Membr. Sci.
(2008) - et al.
Oil–water emulsion separation using ultrafiltration membranes based on novel blends of poly (vinylidene fluoride) and amphiphilic tri-block copolymer containing carboxylic acid functional group
J. Membr. Sci.
(2015) - et al.
Separation of oil/water emulsion using Pluronic F127 modified polyethersulfone ultrafiltration membranes
Sep. Purif. Technol.
(2009) - et al.
Functionalized PSf/SiO 2 nanocomposite membrane for oil-in-water emulsion separation
Desalination
(2011) - et al.
Study of membrane compaction and its influence on ultrafiltration water permeability
J. Membr. Sci.
(1995)
Highly efficient oil/water separation and trace organic contaminants removal based on superhydrophobic conjugated microporous polymer coated devices
Chem. Eng. J.
Advanced functional polymer membranes
Polymer
Drawbacks of applying nanofiltration and how to avoid them: a review
Sep. Purif. Technol.
Facile fabrication of underwater superoleophobic SiO 2 coated meshes for separation of polluted oils from corrosive and hot water
Sep. Purif. Technol.
Superhydrophilic–underwater superoleophobic ZnO-based coated mesh for highly efficient oil and water separation
Mater. Lett.
Facile fabrication of underwater superoleophobic TiO 2 coated mesh for highly efficient oil/water separation
Colloids Surf. A
Superhydrophilic and underwater superoleophobic MFI zeolite-coated film for oil/water separation
Colloids Surf. A
Wettability behavior of special microscale ZnO nail-coated mesh films for oil–water separation
J. Colloid Interface Sci.
A novel superhydrophilic-underwater superoleophobic Cu 2 S coated copper mesh for efficient oil-water separation
Mater. Lett.
CuC 2 O 4 nanoribbons on copper mesh with underwater superoleophobicity for oil/water separation
Mater. Lett.
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