Hierarchical porous poly( l -lactic acid)/SiO 2 nanoparticles fibrous membranes for oil/water separation

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Hierarchical porous poly(L-lactic acid)/SiO2 nanoparticles fibrous membranes for oil/water separation Zihan Lu1

1

, Qasim Zia1, Jinmin Meng1, Ting Liu1, Jun Song1, and Jiashen Li1,*

Department of Materials, The University of Manchester, Manchester M13 9PL, UK

Received: 19 May 2020

ABSTRACT

Accepted: 17 August 2020

A two-step strategy has been developed to introduce silica nanoparticles into highly porous poly(L-lactic acid) (PLLA) nanofibers. Silica nanoparticles (SiNPs) were firstly synthesized and then modified to be hydrophobic. After PLLA/ SiNPs composite fibrous membranes were electrospun and collected, they were re-crystallized by acetone at room temperature for a few minutes. With the rearrangement of PLLA chains, the nano-/micro-electrospun fibres were transformed from non-porous ones to be porous ones with high surface area. Consequently, SiNPs that were completely covered by PLLA before acetone treatment showed up at the fibre surface. Higher PLLA crystallization also enhanced the Young’s modulus and tensile strength (420 and 8.47 MPa) of the composite membrane. However, incorporation of SiNPs into porous PLLA membranes reduced their modulus and tensile strength (280.66 and 5.92 MPa), but an increase in strain to fracture (80.82%) was observed. Scanning electron microscopy (SEM), focused ion beam SEM, transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction were applied to confirm the presence of SiNP in PLLA fibres. The presence of SiNPs inside and outside fibres enhances the hydrophobicity of PLLA/SiNPs nano-fibrous membrane as the water contact angle is greater than 150°. The oil absorption of these porous composite membranes was also tested using four different oils, which can reach the highest absorption capacity when the weight ratio of PLLA and SiNPs is 1:1. The flux of prepared membranes was investigated, and results indicated that SiNPs-loaded membrane effectively enhanced the flux (5200 Lm-2 h-1).

Published online: 2 September 2020

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The Author(s) 2020

Handling Editor: Yaroslava Yingling.

Address correspondence to E-mail: [email protected]

https://doi.org/10.1007/s10853-020-05115-2

J Mater Sci (2020) 55:16096–16110

Introduction The realizing of promise of nanotechnology is dependent on efficient technology for producing nanosized objects which should be prevented from aggregating into larger objects. The optical, catalytic or electrical properties of nanoparticles are different from those of the bulk material [1]. Appropriate strategies are necessary to keep nanoparticles apart and avail nanoparticles properties over long time duration. Functional nanoparticles that are incorporated within fibres are an important topic in electrospinning research [2]. Electrospinning is a versatile technology to fabricate ultrafine polymer fibres with diameters ranging from micron to nano-scale [3–7]. Thanks to the small diameter of nano-/micro-fibres, the electrospun fibres and fibrous membranes possess very high surface area and have a wide range o