Sustainable and efficient removal of cationic, anionic and neutral dyes from water by pre-deposited vinasse biochar membrane

Abstract

This study demonstrated a simple and sustainable approach for removing dyes from water through a new pre-deposited vinasse biochar (PDVB) membrane, which was developed by single-step deposition of vinasse biochar powder on a filter paper support via vacuum pumping. The PDVB membrane combined advantages of adsorption and membrane filtration processes in one-stage. Performance of the PDVB membranes with water-wettable surface was examined on methylene blue (as a model dye) solution as functions of pyrolysis temperature, amount of biochar on the membrane unit area, solution pH, initial concentration and temperature of dye solution in a dead-end filtration mode. The best performance (removal efficiency >99%, flux: 8017 L/(m2.h)) was obtained at a wide pH range (2−11) by using membrane (7.95 mg biochar/cm2, derived from pyrolysis of vinasse at 900 °C). Moreover, initial dye concentration and solution temperature had no considerable effect on membrane performance, which was stable even after ten cycles of filtration-regeneration by ethanol-washing. At pH 2, the membrane was also quite good at removing Congo red (anionic dye) with efficiency of 98%, which decreased when increasing pH from 2 to 11. Behavior of membrane towards dyes with different characteristics was explained by considering high surface area (756 m2/g) of the biochar and phenomenon, including aromatic stacking and electrostatic-attraction between dye molecule and biochar surface. All findings and application to a real textile industry effluent demonstrated that developed membrane was easy-to-use and sustainable material for effective treatment of water and wastewater containing dyes with different molecular weights and ionic characteristics.