(35b) Efficient Nanofiltration Separation of CO2-Derived Fructose and Hepes: An Exploratory Analysis of Parameter Optimization and Pore Properties

The production of fructose from carbon dioxide using an in vitro multi-enzyme catalytic system has significant potential to achieve carbon neutrality. However, the high cost of HEPES used as a buffer in this system and the difficulty in separating it from fructose pose significant challenges. This study aims to use nanofiltration technology to efficiently separate and recover HEPES and fructose, enabling resource recycling and reducing production costs. The influence of operating parameters such as total solution concentration, concentration ratio, pH, and temperature on the separation performance of nanofiltration membranes was investigated. Through fitting analysis using the DSPM-DE model, this study also quantitatively analyzed the pore characteristics of the nanofiltration membrane and proposed a separation mechanism: electrostatic interactions between negatively charged dissociated HEPES and the nanofiltration membrane could lead to pore swelling, thereby affecting the retention rate of fructose. The experimental results showed that the separation efficiency of HEPES and fructose can be significantly improved by optimizing the operating parameters. Furthermore, the separation experiment using spiral-wound membranes further validated the feasibility of nanofiltration for the separation of HEPES and fructose in practical applications, with the purity of the fructose solution reaching 90.22% and that of the HEPES solution reaching 92.93%. A significant highlight of this study is the proposal of a mechanism involving pore swelling of the nanofiltration membrane and the control of pore swelling by changing the operating parameters to achieve efficient separation of HEPES and fructose. This study not only provides a feasible method for the separation of HEPES and fructose, but also provides a theoretical basis and practical guidance for the design of nanofiltration separation strategies for similar systems, thus having significant scientific significance and practical value.