Preparation of polyaniline‐ <scp>ZnO</scp> / <scp>PES</scp> mixed matrix membrane and its application in alkali recovery from pulping and papermaking black liquor

Abstract Pulping and papermaking black liquor (BL), predominantly produced during the cooking stage of the kraft or soda pulping processes, contains large amounts of organic and inorganic pollutants including lignin, hemicellulose, sodium hydroxide (NaOH), and sodium sulfide (Na 2 S). Direct discharge of this BL into the environment can cause severe ecological harm. Traditional alkali recovery processes used for pulping BL not only require significant financial investment but also fail to achieve high‐value utilization of resources such as lignin. In the present study, PANI‐ZnO particles were first successfully synthesized using the sol–gel method. These particles were then incorporated as fillers to fabricate PANI‐ZnO/PES mixed matrix membranes using the non‐solvent‐induced phase separation (NIPS) technique. In the filtration test with pulping BL, the membrane containing 0.4% PANI‐ZnO obtained the highest flux (1.17 L·m −2 ·h −1 ) and alkali recovery rate (85.71%), while the membrane containing 0.2% PANI‐ZnO showed the highest sensitivity to lignin (58.78%) and hemicellulose (28.81%). Although MMM has been used in water treatment, it is still a challenge to use it exclusively in the harsh pulping black liquor treatment environment. In this study, MMM containing PANI‐ZnO was designed specifically, and the synergistic effect was used to tolerate the high alkalinity and high organic load of black liquor. At the same time, lignin macromolecules were efficiently intercepted, and the extremely high alkali recovery rate was given priority, which was directly aimed at the core economic demand of black liquor resource recovery, which was significantly different from the traditional research path that only pursued interception rate or flux.