An eco-friendly method to prepare superwetting composites by modifying cotton with TA/FeIII/PDDA coatings for highly effective separations of emulsions

Abstract

Separating oil/water mixtures and emulsions is an important global topic. Accordingly, it is imperative to prepare superwetting materials for the efficient separation of oily wastewater. Herein, we report an eco-friendly method for preparing multifunctional superwetting cotton-based materials without using organic solvents. Pristine cotton was modified with tannic acid (TA)/ferric ion (FeIII)/poly(diallyldimethylammonium chloride) (PDDA) coatings to form TA/FeIII/PDDA@cotton. The as-prepared TA/FeIII/PDDA@cotton exhibited superhydrophilicity (both in air and underoil), underwater superoleophobicity, and underoil water sorption property, and could be applied for both surfactant-stabilized oil-in-water (SOW) and water-in-oil (SWO) emulsion separations possessing excellent separation performance. The separation fluxes of the SOW and SWO emulsions were 38,600 and 246,000 L m−2 h−1 bar−1, respectively. The oil content in all SOW emulsion filtrates was <20 ppm, and the oil purities in all SWO emulsion filtrates were >99.96 wt%. In addition, our TA/FeIII/PDDA@cotton could be successfully used for the separation of dye-containing aqueous solutions and dye-spiked emulsions. Because of the outstanding separation performance of the oil/water mixtures and emulsions, the as-prepared TA/FeIII/PDDA@cotton exhibited remarkable potential for practical applications.