Energy saving dual-mode recycling of wastewater by MWCNTs-COOK/PDA/PVA assisted composite membrane

Abstract

Membrane separation technology has been widely used for wastewater purification. However, the commonly used membrane filtration (including dead-end filtration and cross-flow filtration) and distillation are all supported by electric power. It causes great burden to environment, as the electric is still mainly come from thermal power generated from burning non-renewable resource. In this paper, we report a dual-mode functional composite membrane assisted by MWCNTs-COOK and PDA/PVA, where MWCNTs-COOK alignment layer acts as a framework to constructing water nanochannels and PDA/PVA co-deposition layer plays a role as a concrete which improved the integrity of the membrane. It achieved optimal pure water flux of 23.86 L m−2h−1 bar−1 with only 0.1 mg cm−2 of MWCNTs-COOK during cross-flow filtration. Under a light intensity of 100 mW cm2, the composite membrane obtained an average evaporation rate of 1.57 Kg m−2h−1 after 1 h due to the combination of two photothermal materials (MWCNTs-COOK and PDA). More importantly, even after working for 12 h, the membrane still kept an average evaporation rate of 1.52 Kg m−2h−1. And the rejection of organic foulant is up to 99.97 % during long time serving. This indicates that the fabricated composite membrane is prospective for generating clean water from waste solutions which contains foulant. Besides, the integration of electric-driven and solar-driven wastewater purification facilitates multi-application of separation membrane, contributes to electric power crisis, energy saving and multiple service scenarios.