Continuous preparation of polyHIPE monoliths from ionomer-stabilized high internal phase emulsions (HIPEs) for efficient recovery of spilled oils

Highlights

• HIPEs are stabilized by an ionomer from waste polystyrene foams.

• Hydrophobic polyHIPEs can be produced continuously and used directly.

• The as-prepared polyHIPEs are excellent candidates for oil spill recovery.

• Continuous collection of spilled oils with polyHIPEs has been demonstrated.

Abstract

We present a facile and continuous approach to prepare polyHIPE monoliths for efficient reclamation of spilled oils. The polyHIPE monoliths were produced from a light induced polymerization of an ionomer, namely sulfonated polystyrene stabilized high internal phase emulsions (SPS-HIPEs). The SPS-HIPEs consisted of seawater as the dispersed aqueous phase and inexpensive monomers such as butyl acrylate and tetraethyl orthosilicate (TEOS) as the continuous phase. Sulfonated polystyrene was from used foams, realizing a sustainable transformation of waste polystyrene. PolyHIPE monoliths from SPS-HIPEs (SPS-polyHIPEs) reached a high gel fraction of 93% with exposure to UV light for only 5 min, providing a possibility to produce them continuously. SPS-polyHIPEs are much greener in comparison to those from surfactant- or particles-stabilized HIPEs, and no purification is required prior to use. SPS-polyHIPE monoliths exhibit interconnected macro-porous structures, and the sizes of pores as well as pore throats can be controlled simply by the volume fraction of the dispersed phase. These monoliths are hydrophobic with a water contact angle over 140°. Excellent performances have been verified for oil spill reclamation, including high absorption capacity to a series of organic solvents or oils, high absorption rate of reaching saturated absorption in 3–5 min, a high recovery rate over 85% and a high reusability over 20 times. A continuous process has been illustrated using SPS-polyHIPEs as absorbents for oil spill recovery.

Introduction

Oil spills have attracted considerable attention, as they are one of the major issues in the current world and cause serious damages to environment, transportation and even our health [1]. Several kinds of technologies have been developed to remove the spilled oils [2]. They are bioremediation with microorganisms [3], [4] or biological agents, in situ combust [5], [6], chemical treatment with demulsifies [7] or dispersants [8], [9] and mechanical treatment with oil–water gelators [10], [11], [12], [13] or absorbents [14], [15], [16], [17], [18], [19]. Among those technologies, mechanical treatment using absorbents is the most promising, since it can remove the pollutants and reclaim the spilled oils at the same time. Therefore, the manufacture and application of absorbent are important for efficient reclamation of spilled oils.

A variety of absorbents have been investigated and fabricated for oil spill recovery [14], [15], [20], [21], [22], [23], and porous materials from emulsion templating (termed as polyHIPEs) have attracted considerable attention [16], [24], because they usually exhibit interconnected macro-porous structures which facilitate the absorption of viscous liquids such as crude oil [23], [25].

To produce polyHIPEs, stable HIPEs are required. HIPEs are traditionally stabilized by surfactants and particles. However, a careful choice of surfactant is required to avoid phase inversion of emulsions at a high volume fraction of internal phase [26] and a high concentration (up to 50% of the continuous phase) is usually needed [27], [28], [29]. Surfactants are usually removed once polyHIPEs are produced, and these used surfactant can be a new pollutant to environment. Although surfactant can be incorporated into polyHIPEs covalently, specific monomers and surfactant are needed [30]. Surface modified particle have also been reported to stabilize HIPEs and they are known as Pickering HIPEs [31], [32], but the corresponding polyHIPEs usually have closed-cell structures [32]. Moreover, the toxicity of these nanoparticles are still in dispute [33], [34]. Recently, various amphiphilic soft particles and block copolymers have been developed to stabilize HIPEs [35], [36], [37], [38]. It has demonstrated that block copolymer (as HIPE stabilizer) is not removed during the purifying process as the entanglement of block copolymer in the polyHIPEs prevents leaching of the HIPE stabilizer [38].

We focus on the preparation of HIPEs and their applications in petroleum fields [20], [21], [39], [40], [41], [42]. An ionomer, sulfonated polystyrene has been reported previously as an efficient HIPE stabilizer [41]. Herein, we report a continuous approach to prepare polyHIPEs for oil spill recovery. The polyHIPEs (SPS-polyHIPEs) was prepared by light induced polymerization of sulfonated polystyrene stabilized HIPEs (SPS-HIPEs). The sulfonated polystyrene was obtained by sulfonation of waste polystyrene, realizing a transition from trash into treasure. SPS-polyHIPEs can be produced in a few minutes, providing a possibility to manufacture them continuously. The as-prepared SPS-polyHIPE monoliths are hydrophobic with controlled morphology, and they exhibit high absorption rate, recovery rate, high reusability and recycle. Therefore, this paper shows an environment-friendly and efficient approach to prepare and apply SPS-polyHIPE monoliths for oil spill reclamation.