Insights into biopolymer and humics natural organic matter removal mechanisms by anion exchange resins

ABSTRACT Biopolymer natural organic matter is linked to different issues during water treatment, such as membrane fouling, and their complete removal, is still challenging. In this work, the removal of biopolymer surrogates (uncharged dextran and anionic alginate) was investigated with weak (WBA) and strong (SBA) basic anion exchange resins. These surrogates were introduced into ultra-pure (UP) and tap water to assess the impact of a complex water matrix on their removal. Additionally, the study explored the removal of naturally occurring humic substances present in tap water. Alginate exhibited moderate removal through ion exchange with WBA and SBA resins in both water matrices. A significantly higher removal efficiency for humics was obtained through the same removal mechanism, linked to the smaller size and higher hydrophobicity of humics. SBA resins with OH– counter ions removed up to 95% of dextran from UP water by H-bonding, while ions present in tap water excluded this interaction. The lightly functionalised WBA resin SD-2 achieved a dextran removal of 50 and 60% from tap and UP water, respectively, via CH–π interactions with the resin matrix. The latter results demonstrate that resins with lower capacities are promising to optimise interactions with both the matrix and functionalities.