An integrated Nanofiltration-Membrane Distillation (NF-MD) process for the treatment of emulsified wastewater

Abstract

ABSTRACT Membrane Distillation (MD) is an emerging separation technology that has gained considerable interest in wastewater treatment. In this work, surface-modified poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) electrospun nanofibrous membranes were investigated for their potential to recover water from emulsified wastewater in direct contact membrane distillation (DCMD) mode. The modified electrospun membranes displayed a water contact angle of 130.5 ± 2° and water flux of 4.67 LMH with 99.9% rejection even when challenged with a 25000 ppm NaCl solution. However, membrane fouling and subsequent loss of permeate quality were observed within 120 minutes when emulsified wastewater (oil: surfactant-1:10 and 1000 ppm NaCl) was used as feed. Low-pressure nanofiltration (6 bar) was reported as a pre-treatment technology with thin-film nanocomposite (TFN) membranes incorporating Nickel-Aluminum Layered Double Hydroxide (Ni-Al LDH) nanoparticle on the polyamide layer. The TFN membranes were extensively characterized, and membrane N2 (0.01 wt.% Ni-Al LDH) exhibited a pure water permeance of 2.21 LMH/bar, 68% NaCl rejection, and 97% oil rejection. The integrated NF-MD process proved to be a robust technology and could remove 100% NaCl and 98.2% TOC for up to 300 minutes of operation. The proposed integrated technology holds the further potential to be investigated further.