Separation of sugars and aldonic acids from aromatic compounds and short-chain organic acids is a crucial issue in various biorefinery concepts based on wood or agricultural byproducts, which can be resolved by nanofiltration. Model solutions containing up to six compounds, representing major components of biomass hydrolysates, were used to investigate interactions between the individual chemical species, with particular emphasis on the negative retention of 5-hydroxymethylfurfural (HMF) and acetic acid (AcOH).

Various factors were found to explain the negative retention of these substances in binary and multicomponent mixtures. The presence of gluconic acid led to the negative retention of AcOH due to an additional electric potential. For HMF retention, the hydration shell formed during the solvation of magnesium sulfate was determined as the main influencing factor. For the first time, the obtained results provide a mechanistic explanation for the negative retention of biomass hydrolysates. In addition, a novel methodology based on a revised concept of retention to quantitatively describe such effects in binary mixtures is provided, which can be qualitatively applied to any biomass hydrolysate. Our results are expected to make nanofiltration for the separation of biomass hydrolysates more predictable, thereby facilitating process development.

糖和醛糖酸与芳香族化合物和短链有机酸的分离是基于木材或农业副产品的各种生物精炼概念中的关键问题，可以通过纳滤来解决。使用最多包含代表生物质水解产物主要成分的六种化合物的模型溶液来研究各个化学物种之间的相互作用，尤其着重于5-羟甲基糠醛（HMF）和乙酸（AcOH）的负保留。

发现各种因素可以解释这些物质在二元和多组分混合物中的负保留率。葡糖酸的存在由于附加电势而导致AcOH的负保留。对于HMF保留，确定在硫酸镁的溶剂化过程中形成的水​​合壳是主要影响因素。所获得的结果首次为生物质水解产物的负保留提供了机理解释。另外，提供了一种基于保留的修订概念的新颖方法，以定量描述二元混合物中的这种作用，该方法可以定性地应用于任何生物质水解产物。我们的结果有望使用于生物质水解物分离的纳滤更加可预测，从而促进工艺开发。