Nanoporous electrospun cellulose acetate butyrate nanofibres for oil sorption
Introduction
Oily wastewater generated by industries inevitably finds its way into water bodies such as oceans, lakes and rivers, causing catastrophic damage to aquatic life and ecosystems in the long-term [1]. The existing treatment methods for oily waste water include adsorption, gravity separation, electro-coagulation, biological treatment and sedimentation in a centrifugal field [2], with adsorption being the most preferred method. Adsorption is preferred because adsorbents are cost-effective and do not cause secondary pollution. A range of materials have been investigated for oil adsorption, including sand, activated carbon, bentonite, peat, fibreglass, polypropylene, organoclay, and attapulgite [3]. The most commonly used commercial sorbent is organic synthetic polypropylene (PP). PP is commonly used due to its hydrophobic, oleophilic and buoyant nature, notable oil–water selectivity, and ease of availability. However, PP suffers from low oil sorption capacity, ranging between 15 and 30 g/g for different kinds of oils [4].
Biopolymer based sorbents for oil/water separation have not been widely investigated in the literature. Zhang et al. [5] recently reported a fluorine-free method to prepare a superhydrophobic and superoleophilic cellulose filter paper for oil/water separation. In this work, we report a facile one-step preparation of porous CAB nanofibres using electrospinning. To the best of the authors’ knowledge this is the first time that the electrospinning of porous electrospun CAB nanofibres has been reported. CAB was chosen because it is inherently hydrophobic due to the presence of butyryl chains [6]. Electrospinning was chosen as the fabrication method as it results in nanofibres with high surface area, high surface roughness (hydrophobicity), and inter-fibre porosity, all of which are beneficial for adsorption. A study on the nanofibres was done to explore their potential as oil sorbents.
Section snippets
Materials
Cellulose Acetate Butyrate (Mn ≈ 65,000) with a butyryl content of 16.5–19.0% and an acetyl content of 28.0–31.0%, acetone and dicholoromethane were purchased from Sigma Aldrich, USA. Motor oil (Magnatec, 10W-40) from Castrol, UK was used for the oil sorption test.
Electrospinning
10 wt% CAB solution was prepared at room temperature by stirring CAB in a binary solvent system consisting of dichloromethane and acetone with a volume ratio of 1:1. Electrospinning was carried out using a flow rate of 1 mL/h under an
Results and discussion
As seen in Fig. 1, the obtained nanofibres had pores on their surface; the average pore diameter was measured using ImageJ software, it was found to be in the range 65–80 nm.
The formation of nanopores can be explained using the ‘breath figures’ mechanism, which was first observed by Srinivasarao et al. [8]. In this mechanism, the rapid evaporation of the volatile solvent, in our case DCM, results in a large amount of heat being absorbed as it evaporates thereby cooling the surface of the
Conclusions
Porous CAB nanofibres were created by electrospinning in high humidity conditions. The porous, hydrophobic, oleophilic nature of the fibres makes them a viable candidate as a sustainable oil sorbent. The fibres exhibited an oil sorption capacity of 60 g/g for motor oil, which is four times higher than that of commercially used polypropylene. The high surface porosity greatly increased the surface area of the fibres, which effectively means more contact area for the oil on the sorbent thus
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
VPT acknowledges funding from the EPSRC (EP/R01650X/1).
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