High-efficiency and durable removal of water-in-heavy oil emulsions enabled by delignified and carboxylated basswood with zwitterionic nanohydrogel coatings

Abstract

HypothesisIt is hypothesized that grafting zwitterionic nanohydrogel (ZNG) helps to achieve anti-asphaltene properties on cellulosic substrates, thus overcoming the fouling issue of natural cellulosic materials for treating oily emulsions. It is also hypothesized that ZNG coatings enhance the water-binding affinity of the substrates, resulting in an outstanding water-removal performance on asphaltene-stabilized emulsions with long-term stability. ExperimentsA cellulosic substrate was derived from nature basswood via a sequence of delignification and carboxylation processes. The ZNG-DBS composite was then developed by esterification to covalently graft ZNGs on the inner channels of the substrate. The water-binding affinity, wettability, water-removal performance for treating water in asphaltene-stabilized emulsions were evaluated via characterizing the filtration/absorption, and anti-fouling mechanism of the ZNG-DBS. FindingsZNG coatings enhance the hydration capability of the basswood substrate, allowing it to absorb water emulsion droplets protected by asphaltenes in the oil medium without being contaminated. Moreover, superior and stable removal capabilities were achieved by using this unique material to treat asphaltenes-stabilized water-in-oil emulsions with the water residue content of <1.0 and ∼0.065 wt% via cyclic filtration and absorption tests, respectively. Our results demonstrate the successful conversion of widely accessible wood resources to functional materials with great potential in the practical treatment of oily wastewater.