Hexagonal boron nitride nanosheets incorporated photocatalytic polyvinylidene fluoride mixed matrix membranes for textile wastewater treatment via vacuum-assisted distillation

Abstract

Textile wastewater poses a significant environmental threat, and its treatment is one of the most demanding and challenging problems. This study investigates the feasibility of vacuum membrane distillation (VMD) for colour removal from real textile industry wastewater. Hexagonal boron nitride (h-BN) nanosheets and Zinc oxide (ZnO) nanoflowers were synthesised using a facile single-step synthesis protocol. 1% w/v ZnO nanoflowers and a varied amount of h-BN nanosheets (0–2% w/v) were impregnated in a polyvinylidene fluoride (PVDF) matrix using the phase inversion technique. The h-BN nanosheets, ZnO nanoflowers and membranes were characterised using scanning electron microscopy (SEM), Fourier transform attenuated total reflectance (FT-ATR), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). The XRD and FT-ATR spectra of the mixed matrix membranes confirmed the successful impregnation of h-BN nanosheets and ZnO nanoflowers in the PVDF matrix. The effect of various process parameters (feed temperature, feed flow rate, and degree of vacuum) on membranes' permeate flux and colour removal efficiency was studied. The M-BZ2 mixed matrix membrane having 18% PVDF+ 2% h-BN nanosheets+ 1% ZnO nanoflowers composition showed the highest flux of 12.98 kg m−2 h−1 and colour removal efficiency of > 98%. Incorporating ZnO nanoflowers in the membrane, matrix provided the membrane with a UV cleaning property. More than 95% of the initial flux was recovered after the UV treatment of the membrane surface. The SEM images confirmed successful photocatalytic degradation of dye and organic molecules from the membrane surface. The UV-treated membranes retained all characteristic bands with no significant alterations. This study established that the M-BZ2 is suitable for treating real textile wastewater with high flux and colour removal efficiency.