Electrospun Al2O3 hydrophobic functionalized membranes for heavy metal recovery using direct contact membrane distillation

Abstract

In this study, styrene-butadiene-styrene (SBS) was used to develop a novel functionalized electrospun membrane for the effective treatment of heavy metals in direct contact membrane distillation (DCMD) applications. Functionalization was achieved by the addition (doping) of the super hydrophobic Al2O3 nanoparticles (Al NPs) within the matrix of the membrane during electrospinning. Neat (pristine nondoped) and doped SBS membranes were tested. The performance of the SBS membranes were also compared with fabricated polyvinylidene fluoride membranes with and without doping with Al NPs. The membrane characteristics were tested via Fourier transform infrared, scanning electron microscopy, pore size, and porosity investigations. The wettability of the membranes was investigated with respect to the liquid entry pressure (LEP) and contact angle. The performance of the membranes was tested in a DCMD setting for its ability to treat water containing salt (NaCl) and heavy metals (Cr (VI), Cd, Pb) in various concentration in a single and multicomponent systems. The SBS member exhibited excellent hydrophobicity characteristics such as a high LEP (16.87 psi) and contact angle (141° ± 2°). It also had superior permeate flux rate compared to the other prepared membranes (54.4 LMH). The addition of the Al2O3 nanoparticles enhance the performance of the membranes substantially. Slight decline in the flux was observed after 14 hours of continuous operating time that could be attributed to agglomeration, adsorption, or temperature polarization effects. The SBS AL NPs membranes also demonstrated excellent flux for saline solutions of varied concentrations with 99% salt rejection.