Polycarbonate ultrafiltration membrane modified with Mg–Al-layered double hydroxide nanoparticles for treatment of petroleum refinery wastewater

Abstract

In this work, to improve the antifouling and separation performance of polycarbonate (PC) membranes in the petroleum refinery wastewater treatment, various amounts of magnesium–aluminum (Mg–Al)-layered double hydroxide (LDH) nanoparticles (0–2 wt%) were incorporated into PC membrane, for the first time. The Fourier transform infrared (FTIR), X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) characterizations confirmed the synthesis of Mg–Al LDH structure through the hydrothermal method, with different counter anions including nitrate (NO₃⁻) and carbonate (CO₃²⁻) presented in the interlayer spaces. The characteristics of the fabricated membranes were investigated using water contact angle and porosity analyses, FESEM and atomic force microscopy (AFM) techniques and mechanical properties. All membranes modified with Mg–Al LDH hydrophilic nanoparticles showed a lower water contact angle and higher porosity as compared to the neat PC membrane. The FESEM micrographs of the cross section of the membrane indicated that the inclusion of CO₃.Mg–Al LDH nanoparticles in the PC matrix led to the removal of the sponge-like layer of the membrane. The results of the petroleum refinery wastewater filtration experiment revealed that the irreversible fouling ratio (IFR) value decreased from 66.7% for the neat PC membrane to 10.5% and 19.1% for PC/CO₃ Mg–Al LDH-1.5 and PC/NO₃ Mg–Al LDH-1.5 nanocomposite membranes, respectively. The membrane separation performance, measured by the total organic carbon (TOC) indicated that filtrates from all nanocomposite membranes had lower TOC values compared to the neat PC membrane.

Graphical abstract