A downstream process for the purification and concentration of formic acid (FA) from FA/gluconic acid (GA) mixtures, obtainable by a coupled biocatalytic reaction of CO₂ reduction and glucose oxidation, has been developed. The process involved two technologies: i) a first nanofiltration (NF) step to separate FA and GA, and ii) a second reactive liquid-liquid extraction (RLLE) step to concentrate FA. The NF process, using a Synder NFX membrane, consisted of three NF steps separated into two divergent lines, named permeate and retentate pathways. The first NF was common for both pathways, resulting in a permeate strongly enriched in FA and depleted in GA, and a retentate with opposite characteristics. In the permeate pathway, this first permeate was subjected to a second NF to obtain a 99.6% pure FA permeate. In the retentate pathway, an additional NF step on the first retentate resulted in a concentrated 99.4% pure GA retentate. The final diluted FA permeate was concentrated by RLLE using tri-N-octylamine as extractant in n-octanol, and a final back-extraction with NaOH. The optimized RLLE process involved a 100-fold volume decrease and resulted in a final FA solution (as sodium formate) of 174.5 g/L, 78 times more concentrated than the feed.

从 FA/葡萄糖酸 (GA) 混合物中纯化和浓缩甲酸 (FA) 的下游工艺，可通过 CO _{2的耦合生物催化反应获得}还原和葡萄糖氧化，已被开发。该工艺涉及两种技术：i) 分离 FA 和 GA 的第一个纳滤 (NF) 步骤，以及 ii) 浓缩 FA 的第二个反应性液液萃取 (RLLE) 步骤。使用星达 NFX 膜的 NF 过程由三个 NF 步骤组成，这些步骤分为两条不同的线，称为渗透和滞留通道。第一个 NF 对这两种途径都很常见，导致渗透物富含 FA 而缺乏 GA，以及具有相反特征的渗余物。在渗透液路径中，该第一渗透液经受第二次 NF 以获得 99.6% 纯 FA 渗透液。在渗余物途径中，对第一个渗余物进行额外的 NF 步骤会产生浓缩的 99.4% 纯 GA 渗余物。最终稀释的 FA 渗透物通过 RLLE 浓缩，使用三正辛胺作为正辛醇中的萃取剂，最后用 NaOH 反萃取。优化的 RLLE 工艺体积减少了 100 倍，最终 FA 溶液（以甲酸钠形式）为 174.5 g/L，比进料浓度高 78 倍。